View Full Version : Soil substrate comparisons and testing
hey all,
Fist here's a really good "macgyver" how-to for finding the air porosity, water porosity and total porosity of soil and soil less substrates...or you could send in sample to a lab if you need very accurate results...
Determining media porosity (https://www.cannabis-world.org/cw/showpost.php?p=74303&postcount=24)
For a cheap container use the idea from the following guide...
I use a clear soda bottle
For a screen I've used a window screen cut and hot glued onto the inside rim of the mouth
Calculating total porosity, aeration porosity, and water retention of growing media or soil. (http://www.treeco.biz/Keenan/calculating%20pore%20space.htm) (bottle idea)
Hi,
OK, well the tests that person preformed did not include vermiculite (hort grade course #3 [aka "a-3"]), coco-coir, rockwool, growrocks, axis and Pro Mix Bx...so I did it for us :farm:...now we have a full list of the air porosity, water capacity/retention and water saturation of most growing material.
In this post I'll write what I found with vermiculite and grow rocks and then in the next post I'll list all the info I have found or tested so far:
axis "regular" (kiln fired diatomaceous earth)
perlite hort grade
vermiculite hort grade
coco-coir
rockwool
turface MVP
gravel
lava rock
peat
Pro Mix Bx
grow rocks (hydroton...expanded clay)
:up:
Vermiculite:
Air porosity = update soon
Water porosity = update soon
Total porosity = update soon
As long as the air porosity is above 15% you are OK with cannabis type of roots (non-fleshy). When a growing medium drops below 15% it can become anaerobic and if it does it is bad for the roots. BTW, Pro Mix Bx is rated with 12-17% air porosity...
Hydroton Grow Rocks:
Air porosity = update soon
Water porosity = update soon
Total porosity = update soon
ps...I just fixed a few of the numbers for my tests in the above post ^^^
Here the complete list
Substrate.................Air Porosity......Water porosity.....Total Porosity
(Note: These are not scientific results)
Axis.................................update soon
Coir.................................update soon
Perite (hort grade)..............update soon
Rockwool..........................update soon
Vermiculite (hort grade).......update soon
Grow Rocks (Hydroton)........update soon
Turface.............................update soon
Pro Mix Bx..........................update soon
Gravel.............................update soon
Lava rock..........................update soon
Peat................................update soon
Hi again,
and of course CEC would be good to know but it needs to be tested in a lab...In my view CEC is important but not more important than what I listed above. CEC relates to nutrient absorption/release of the substrate...
-Stone-
06-03-2008, 03:19 AM
Great info, gojo.
It was cool of you to perform more tests on the soilless mixs the info wasn't available on!
Any thoughts on how to calculate a general CEC?
Could it be as simple as running a solution of known EC/PPM through a new (unused) media, and then testing the runoff? Would the possible drop in EC be that medias' general CEC?
I know I should go researchin', but any info on how various medias' CEC changes over time through repeated waterings & ferts?
Is there a sort of buffering capacity where repeated ferting could 'max out' a medias CEC, or maybe even just lower it?
Keep up the good work, brotha.
-Stone-
hi -stone- and welcome to the forums,
It was cool of you to perform more tests on the soilless mixs the info wasn't available on!
Thanks. That's one thing I love about this site...many ppl here do interesting tests/experiments and they often share the results for the benefit of all :up: Everyone is here to help each other...never drama here :D
In terms of testing for CEC, yes, you can test at home but it's not very accurate because it depends upon levels of Ca, K and Mg...this is called "Calculation of Effective CEC" (aka "CECe", that "e" should be a sub-script).
If you want to find accurate CEC you need to send it to a lab and have them use "Determination of CEC at pH 7 with Ammonium Acetate" or preferablly "Determination of CEC at pH 7 by Sodium Saturation".
Here's some sites you should check out:
Recommended Methods for Determining Soil Cation Exchange Capacity (http://www.analytika.gr/METHODS/SOIL/cec.htm)
The cation exchange capacity of the soil (http://www.cannabase.com/cl/bcga/soil/soil.htm#The%20cation%20exchange%20capacity%20of%2 0the) by Orchard Man on the Vic High cache site.
HTH
Ah, what the hell...
Here's the Orachrd Man info I linked to, prolly a good idea to quote it here as it's not too long:
The cation exchange capacity of the soil
Posted by Orchid man on January 11, 1999 at 18:24:30
In Reply to Soil reaction (pH) nutes lock up posted by Orchid man.
When small quantities of inorganic salts, such as the soluble mineral matter of soil and commercial fertilizers, are added to water they dissociate into electrically charged units called ions. The positively charged ions (cations) such as hydrogen (H+), potassium (K+), calcium (Ca++) magnesium (Mg++), ammonium (NH4+), iron (Fe++), manganese (Mn++), and zinc (Zn++) are absorbed mostly on the negatively charged surfaces of the soil colloids (microscopic clay and humus particles) and exist only in small quantities in the soil solution. Thus, the humus-clay colloids serve as a storehouse for certain essential ions (cations). The negatively charged ions (anions), such as nitrates (N03-) phosphates (HPO4--), sulfates (SO4--), and chlorides (Cl-), are found almost exclusively in the soil solution and can therefore be leached away easily with overwatering. The roots and root hairs are in intimate contact with the soil colloidal surfaces, which are bathed in the soil solution, and therefore nutrient uptake can take place either from the soil solution or directly from the colloidal surfaces (cation exchange). The soil solution is the most important source of nutrients, but since it is very dilute its nutrients are easily depleted and must be replenished from soil particles. The solid phase of the soil, acting as a reservoir of nutrients, slowly releases them into the soil solution by the solubilization of soil minerals and organics, by the solution of soluble salts, and by cation exchange. A more dramatic increase in the nutrient content of the soil solution takes place with the addition of commercial fertilizers. As plants absorb nutrients (ions) they exchange them for other ions. For example, for the uptake of one potassium (K+) ion or one ammonium (NH4+) ion, one hydrogen (H+) ion is released into the soil solution or directly into the soil colloids by the process of cation exchange. Similarly, for the uptake of one calcium (Ca++) or one magnesium (Mg++) ion, two hydrogen (H+) ions are released by the root. Thus, as the plant absorbs these essential cations, the soil solution and the colloidal particles contain more and more hydrogen (H+) ions, which explains why the removal of cations (ammonium (NH4+) nitrogen is a good example) by crops tends to make soils acidic, i.e., having a low pH. Also, as the plant (absorbs essential anions such as nitrates (NO3-) and phosphates (HPO4-), the soil solution is enriched with more and more hydroxyl groups (OH-) and bicarbonates (HCO3-), which explains why the removal of anions (nitrate (NO3-) nitrogen is a good example) by crops tends to make soils alkaline, i.e., having a high pH.
I know I should go researchin', but any info on how various medias' CEC changes over time through repeated waterings & ferts?
Is there a sort of buffering capacity where repeated ferting could 'max out' a medias CEC, or maybe even just lower it?
Good question. Honestly I'm not sure in terms of specific substrates, I have an idea and a gut feeling but no data...I'll try to find some. For now, the best info I can provide which is usable in our situation is the Orchard Man post. I have a collection of more informational sources but I'll have to dig through them.
I have read (un-verified) info where the substrate's CEC lowers over time due to micropore and pore space reduction, substrate decomposition, water saturation, nutrient solubleization, etc, etc.
An important point in the Orchard Man post I will quote below:
The roots and root hairs are in intimate contact with the soil colloidal surfaces, which are bathed in the soil solution, and therefore nutrient uptake can take place either from the soil solution or directly from the colloidal surfaces (cation exchange).
So the CEC isn't the be all end all, especailly in terms of our horticultural purposes such as adding fresh nutrients everyday, weekly, every two weeks, etc. Though I'm not sure what the the ratios are in terms of soil solution vs. CEC for nutrient uptake by the plants.
When I have time I'll do some testing with some substrates CEC levels over time. I'll prolly test the CEC of my OD grow soilless media before I transplant into it and then I'll test it again in mid-season and then again at the end of the season.
HTH
Hey all,
Well i just found another soil admendment that looks AMAZING!!! It's called "Axis (http://www.axisplayball.com/AXIS.htm)". The Axis "regular" is the one for us, 70% of the 'regular' is around 1/8" in size :up:
Axis should be used as a replacement for perlite AND vermiculite as it offers better properties then both of those. Axis is made from kiln fired diatomaceous earth and beats the crap out of turface and doesn't float like grow rocks!
Axis will absorb 114% of it's weight in water and has a 90% water release rate with a very low tension level (eg. it's very easy for the plants to extract up to 90% of the water held within Axis, this is due to the average pore size of 1 micron.) Axis has a med/low CEC level of 27 meq/100g (aka. 27.0)...all this with an air porosity rate of 27% and a water porosity of 26%!!!
Turface on other hand will absorb around 55% it's weight in water and has a very low water release rate of around 5% and a high tension level due to the very small pore size of turface. The CEC of Turface is higher than axis, turface is around 30.0 (aka. 30 meq/100g
I've updated my list to add Axis regular...and heres a bit more information on horticultural use of Axis (http://www.epminerals.com/landscape-copy.html)
-Stone-
06-04-2008, 09:28 PM
Hey gojo,
I'm loving it her at C-W! Not only is there a lack of drama & unneeded conflict, but the info here is second to none.
I've been bouncing around from site to site since OG & first CW went down, & this site is full of In depth topics & knowledge. At first I thought the site looked small, but I've come to realize that this is mainly b/c the thousands of 'how do I water & germinate?' questions aren't adding filler. What's here is worth reading which is more than I can say for at least a large portion of a few other sites...
That Axis looks amazing!
I wonder if the DE retains its pesticide qualities after its been fired. My gut says no, mostly b/c it would just be too perfect then.
Keep up the good work,
-Stone-
purplehaze2
06-05-2008, 04:14 PM
this sites the best hands down,my brain is filled with so much knowledge ,I learn something everyday,and no drama ! stone ,take your shoes off and stay a while. welcome!
Hey all,
OK, well in my quest to understand everything I can about subatrate composition I discovered some of the results above are not accurate. For example peat should be about 20% air porosity, not 75%...the guy who did those tests screwed up by not letting the substrate fully absorb the water before draining it. His methodology error should only affect the peat as it's the only substrate he tested which required time for the water to absorb.
Unfortunately, I also made a similar error when testing the vermiculite because the directions I was following where flawed...but not to worry...now I've got much better directions for testing (the same methodology as before, just MUCH better explained :) ).
I picked up some axis regular and pine bark fines the other day...and I have to say I am VERY, VERY impressed with the axis so far...this stuff is going to change how we make our soilless mix! :farm: Axis is displaying very good water absorption and water release properties..Heck, it's wicking water to the dry peat!
P.S.
I have a bunch of more very useful info on substrate compostion/function and benchmarks for air porosity, water porosity and total porosity :up: I'll post more tomorrow when I can make it easy to understand...
I also have the CEC of all the substrates too :up: ...I'll post them tomorrow...
I'm also gonna make a new thread "CEC: What is it and why it is and is not important" tomorrow or the next day because it's so in depth it's needs it's own thread...I have all the info we need on CEC (I think) and how it changes, functions, relates to substrates, pore size, PH, etc, etc, etc...I'm pretty sure I've got it all down but I'd love some input too. After a bunch of reading, IMVHO, it turns that CEC is not overly important because of how we fertigate when growing cannabis...air porosity, water porosity and water tension are more important IMVHO.
See you soon!
nuggdigger
06-07-2008, 05:07 AM
sounds like a great idea...i googled cation exchange capacity..here are the first two hits for you..enjoy
http://en.wikipedia.org/wiki/Cation_exchange_capacity
In soil science, cation exchange capacity (CEC) is the capacity of a soil for ion exchange of positively charged ions between the soil and the soil solution.
http://microsoil.com/CEC.htm
The CEC of the soil is determined by the amount of clay and/or humus that is present. These two colloidal substances are essentially the cation warehouse or reservoir of the soil and are very important because they improve the nutrient and water holding capacity of the soil. Sandy soils with very little organic matter (OM) have a low CEC, but heavy clay soils with high levels of OM would have a much greater capacity to hold cations.
The disadvantages of a low CEC obviously include the limited availability of mineral nutrients to the plant and the soil’s inefficient ability to hold applied nutrients. Plants can exhaust a fair amount of energy (that might otherwise have been used for growth, flowering, seed production or root development) scrounging the soil for mineral nutrients. Soluble mineral salts (e.g. Potassium sulfate) applied in large doses to soil with a low CEC cannot be held efficiently because the cation warehouse or reservoir is too small.
Hey all,
I didn't forget about this thread and I'm still really interseted in providing accurate data. I tested and retested and retested but I just could not get repeatable resulsts from the same mix over two or three tests...so the tests are not up to par. I'm gonna send off samples to a lab but it's kina expensive so it will take a bit.
For now I'm using 70% permier peat and 30% axis regular...I am really impressed with the resutls so far. In my tests that mix generally was around 20 air porosity and 30-35 water porosity...but you can't relay on those results. I really like the mix so far, the axis hold much more water and doesn't migrate upward like perlite, along with a better CEC than perlite. And axis has better air porosity and lower water surface tension then vermiculite.
The plants are loving the 70/30...I transplanted from 20oz cups to 3gallon bags and in two weeks the roots filled the whole bag. Even up to the whole media surface...anywhere I touched the surface where roots just below. Honestly I haven't seen that with Pro Mix before, I doubt it's due to axis but I'm still impressed with the air porosity even when completely soaked! And the media retains it's moisture very well...I love how the axis wicks water into the peat :up:
Glomalin...
I've been thinking about how air porosity, water porosity, media particle size and PWT (Perched Water Table) changes over time due to degradation by microbes, roots and time. At first I thought (and it has been suggested) that you should not re-use a peat or coir based mix because it will break down over time and PWT will raise and things will become anaerobic...but how the hell does nature do it? And then I started thinking about glomalin, and it all become clear how we can re-use peat/coir based media without loosing a lot of air porosity. And without the PWT raising due to the 'cloging' of media particles which have been degraded in size/shape. In the absence of glomalin and hyphae[1] these particles would migrate towards the bottom of the container thus raising the PWT and lowering the air porosity.
What does all that mean? It means we can prolly re-use peat/coir based medias if they have been infected with AM (endomycorrhiza), and the AM has produced a good bit of glomalin and hyphae. Organic gardening is the first requirement so the myco's can make the glomalin. The important part is the glomalin, hyphea and roots should hold the media particles in place, preventing the rise of the PWT AND keeping the air porosity from lowering[2] due to the prevention of media particles migrating downward.
I am thinking it'd be best to plant/re-plant into a pre and post infected soilless media, for example:
mix your media and fill your containers (peat based mix is best for microbes)
you mix shouldn't have fertilizers besides rock powerders, d.lime and EWC OR compost
add earthworm castings OR compost to your media [say 2-5% of your meida]
plant your containers with pre-infected host plants symbiont to G.mosseae (G.intraradicies is a good bet, though I haven't read it's associated to hemp).
put the containers under flours or a t5 and water, keep it for a few months (1-3 is best)
at this point your media should be fully infected
cut the host plant down (don't disturb the media!)
carefully dig a hole and plant a slightly root bound cannabis plant
water and don't add ferts for 2 weeks
after two weeks you can add ferts but try to keep the P low for the next few weeks
at this point the myco's should have entered the roots and you can add higher amounts of P in your ferts
try to keep the P low all the time, don't dump P on your plants if they don't need it
harvest your cannabis (don't disturb the media)
replant with pre-infected host as before and repeat.
it's prolly best to have two sets of media in containers, while your growing in one you have the host plant in the other (eg. "cover crop")
[1]While it is a fact the PWT will rise and the media will become more anaerobic this "fact" is based upon media that hasn't (as far asa I know) been infected with AM or any fungi...this media is generally inert and chemical fertilizers are used. It is my opinion that the addition of glomalin and hyphae from AM will prevent the rise of PWT and it's associated ills in the media, even over years of use and cover cropping...
[2]air porosity may be lowered over time due to water porosity increasing from the degradation of media particles...this tends to increase the particles own water porosity...glomalin can't help us here...
Here's some good basic benchmarks:
Things to consider is that cannabis has non-fleshy roots so that means it can thrive in media with lower air porosity and higher water porosity than many fleshy rooted plants...which is why peat/coir works so well.
Outdoor media levels to retain water (eg. higher % water porosity)
Air porosity: 20-25%
This number allows for a bit of degradation, it should stay above 16-17. Once it hits 15 it can become anerobic and once it hits 12 it will become anerobic in most cases.
Water porosity: 25-35%
Total Porosity: >50%
Indoor media levels to retain air (eg. higher % air porosity)
Higher air porosity is better for roots and microbes.
Air porosity: 30-40%
Water Porosity: 15-25%
Total Porosity: >50%
Re: CEC
I didn't forget about this either...but I wanted a better understanding of it before I started a thread. Especially on how it changes over time due to media particle degradation, ph change (ex. increase the ph 1 degree can double the CEC as with sand), effects of organic fertilizers, etc, etc. Anyway, I haven't had the time to do all the background research...but I soon hope to...
I still think the CEC isn't that important...sure you want a 'good' CEC but in most media (peat, coir, perlite, vermiculte) the CEC changes as the media degrades. Another reason why I like axis, it's CEC doesn't change the way CEC does with those other amendments because axis doesn't degrade. Turface is another option but axis is superior in every way except turface has a better CEC.
Some quick CEC levels:
(per meq/100g)
I got some of this info from here (http://64.233.169.104/search?q=cache:xeGuam2Jc_QJ:www.hort.cornell.edu/department/faculty/good/growon/media/ionstbl.html+media+cation+exchange+capacity+for+va rious&hl=en&ct=clnk&cd=1&gl=us)
axis...................................27
turface..............................30
Perlite...............................1.5 - 3.5
Pine Bark...........................53.0
Vermiculite.........................82.0-150.0
Sphagnum Peat...................80.0-180.0 (according to diff sources)
Humus...............................200.0
Peat moss:Vermiculite(1:1)....141.0
Peat moss:Sand(1:1)............8.0
Peat moss:Perlite(1:3)..........11.0
Peat moss:Perlite(2:1)..........24.0
islandgrow
06-26-2008, 08:34 AM
very good information gojo! you are clearly dedicated.
So I don't completely even understand all of what is going on in this thread but what are the mixes you use??
PS: how are the airpots?
IS,
Right now I'm using 7 parts Premiere peat to 3 parts Axis "regular". Axis is kiln-fired diatomaceous earth. I use Axis to replace both vermiculite and perlite as it's superior to both and is more earth friendly. I also include biozome, azomite (micronized), d.lime and yucca extract (surfactant).
Axis info (https://www.cannabis-world.org/cw/showpost.php?p=72993&postcount=10)
https://www.cannabis-world.org/cw/showpost.php?p=74280&postcount=15
For now I'm using 70% permier peat and 30% axis regular...I am really impressed with the resutls so far. In my tests that mix generally was around 20 air porosity and 30-35 water porosity...but you can't relay on those results. I really like the mix so far, the axis hold much more water and doesn't migrate upward like perlite, along with a better CEC than perlite. And axis has better air porosity and lower water surface tension then vermiculite.
The plants are loving the 70/30...I transplanted from 20oz cups to 3gallon bags and in two weeks the roots filled the whole bag. Even up to the whole media surface...anywhere I touched the surface where roots just below. Honestly I haven't seen that with Pro Mix before, I doubt it's due to axis but I'm still impressed with the air porosity even when completely soaked! And the media retains it's moisture very well...I love how the axis wicks water into the peat
I will play with other mixes later but I think the 7:3 is a great OD mix for all the reasons I've mentioned. This winter I'm going to try this indoor mix:
5 part aged pine bark fines (screened to 1/16"-1/8")
2-3 part axis regular (screened to 1/16"-1/8")
1-2 part permiere peat
PS: how are the airpots?
I haven't tried them yet, this fall, indoor.
For outdoor I stole an idea from the "fielder bags"...see this post (https://www.cannabis-world.org/cw/showpost.php?p=73135&postcount=17)
P.S.
I really suggest you read this thread (maybe twice ;) ) because it's important stuff that is not discussed often enough or from a scientifically sound basis (I try to keep it as scientific as I am able)...
IS,
that's not to say I don't think the 7:3 (peat:axis) wouldn't be a great indoor mix too...I think it would be good. But I would prefer a higher % of air porosity if I didn't need to worry about hauling water to the plants (like in an OD grow).
I definitely think the 7:3 I'm playing with is better than Pro Mix which is approximately 80-85% peat, 10-15% vermiculite, 5-10% perlite, surfactant, d.lime, c.lime and a few micronutrients.
I'm also adding biozome, azomite (micronized), d.lime and yucca extract (surfactact) to my mix...the funny thing here is the azomite offers micronutrients and biozome offers beneficial aerobic bacteria, archaea, etc.
Biozome info (https://www.cannabis-world.org/cw/showthread.php?t=3960)
So my mix offers all that Pro Mix Bx "Mycorise" does but in a much superior manner (IMVHO that is ;) ). My mix is all organic and actually has a good mix of bacteria and archaea, not just natto spores like "Mycorise"
I also add myco's, etc, etc but that's not really part of my "mix"...
HTH
hey all,
I just noticed Cornell U. removed imortant info from there site...so I'm paste the cache version from google so it doesn't get lost. the links i posted for directions to measure porosity, etc is broken so I'll fix it in a second...but the info is pasted below...
Update: Thanks to our kindly admin/master computer guy (:up:) here is a link which leads to the:
Table of Contents (http://web.archive.org/web/20070830021606/www.hort.cornell.edu/department/faculty/good/growon/media/index.html)(and all sub-sections)
Just in case we loose the cache I'm gonna contiue copying/pasting the whole bit...
This following very good, useful and important info!!!
(1.) Porosity (http://209.85.215.104/search?q=cache:5_E3_1GCu3MJ:www.hort.cornell.edu/department/faculty/good/growon/media/porosity.html+http://www.hort.cornell.edu/department/faculty/good/growon/media/porosity.html&hl=en&ct=clnk&cd=1&gl=us)
The amount of pore space in container media is a critical physical characteristic which influences water and nutrient absorption and gas exchange by the root system. Pore space is related to the shape, size, and arrangement of media particles. Aeration porosity and water-holding capacity are two critical physical attributes of container media.
Total porosity reflects the total pore space present in growing media; it represents the percentage of the container media volume which is not occupied by solid media particles. Porosity is determined by media particle size and the extent to which the particles can be compressed. Total porosity is the sum of the aeration and water-holding porosity of media and should comprise over 50% of the container media volume.
Irrigating media to the point of saturation fills the total pore space with water. As the media drains by the force of gravity, smaller pores remain filled with water while larger pores empty and fill with air. When all water has drained from the large pores, the amount of water remaining in the medium's small pores is referred to as container capacity. Aeration porosity is comprised mainly of the large pore spaces, macropores, which drain water freely as a result of gravitational forces and remain filled with air after media saturation and drainage.
For adequate gas exchange, aeration porosity should constitute at least 15%, but ideally, 20-35% of the media volume. Water retaining micropores should comprise 20-30% of the media volume. Water held in even smaller pores is not easily extracted by the plant. Conditions under which these very small spaces are the only pores retaining water often result in some stomatal closure and wilting. As the media dries and water is available only from the smallest pores, significant wilting can occur.
For sufficient gas exchange, drainage, and water-holding capacities, the proper proportion of macropores to micropores is necessary. The type of container media mix used determines the amount of macropores and micropores in the media. In addition, the size arrangement of pores is important in the ultimate water-holding capacity of the mix. A peat-sand mix contains a greater number of large and medium sized pores than a bark-sand mix. Media containing the greatest amount of medium-sized pores has the potential to hold more readily available water.
(2.) Factors influencing porosity (http://209.85.215.104/search?q=cache:o9-edR-fY8kJ:www.hort.cornell.edu/department/faculty/good/growon/media/poros2.html+http://www.hort.cornell.edu/department/faculty/good/growon/media/poros2.html&hl=en&ct=clnk&cd=1&gl=us)
Media porosity is influenced by several factors including:
the particle size of the separate constituents,
the particle size of the media mixture, and
particle attributes.
Particle size
Media composed of large particles has a higher percentage of total porosity than a medium composed of smaller particles. Larger particle size also contributes to a greater percentage of aeration porosity than water-holding porosity.
In addition, particle size of the media mixture influences media porosity. Because media particles are various sizes, the combined volume of two or more types of media is less than the sum total of the initial volumes. Large pore spaces created by large particles are filled by smaller particles when mixed together. Mixtures containing both large and small particles have less aeration porosity, or large pore space, than media composed of only large particles.
Particle attributes
Particle attributes influence the ratio of aeration to water-holding porosity. Chemical and physical media attributes affect particle shrinkage, breakage, and compression. Decomposition, compaction, and breakage of media alter the original media porosity. As smaller media particles decrease in size and fill larger pore spaces, pore size decreases; as a result, the water-holding porosity near the container bottom increases.
Saturation of available pore space forms a perched water table. Smaller pore space reduces media drainage as water is held more tightly in the smaller pores. As the root system of the plant grows, large pore spaces become filled, decreasing media aeration porosity. Consider these factors when selecting media and monitor the media to detect any undesirable changes.
Changes in media components
Media particles undergo many changes that affect porosity. Uncomposted or improperly composted media particles such as sawdust or bark shrink as the particles deteriorate. Peat moss expands and contracts when it is subject to wetting and drying cycles. Although vermiculite compresses and breaks easily during mixing, bark and perlite withstand compression to a greater degree. The asymmetrical shape of perlite allows for large pore sizes in a mix. Sand and pumice are composed of many particle sizes; small particles often accumulate towards the bottom of the container, reducing porosity and elevating the perched water table.
Internal porosity
Some media constituents consist of internal pore spaces that affect the bulk density, water-holding and nutrient-holding capacities of container media. Water held inside pine bark can be absorbed by plants only if roots penetrate individual particles. However, if root penetration does not occur, the internal water is not available for absorption. Sphagnum peat moss and vermiculite also have high internal porosities.
(3.) DIY testing of air, water and total porosity: (http://209.85.215.104/search?q=cache:o9-edR-fY8kJ:www.hort.cornell.edu/department/faculty/good/growon/media/poros2.html+http://www.hort.cornell.edu/department/faculty/good/growon/media/poros2.html&hl=en&ct=clnk&cd=1&gl=us)
--> This is the tests that I could not get reproducible results from. While some items like perlite are easy to test, peat, coir, axis, vermiculte, etc, etc is not so easy to test accurately.
Media structure
The movement of air, water, and nutrients within media depends on the media structure, or the geometrical shape of the media, and the porosity of the media. Good media structure provides sufficient media aeration, drainage, and water necessary for plant growth.
Determining media porosity
To ensure sufficient media porosity, it is essential to determine total porosity, aeration porosity, and water-holding porosity. Porosity can be determined through the following procedure:
* With drainage holes sealed in an empty container, fill the container and record the volume of water required to reach the top of the container. This is the container volume.
* Empty and dry the plugged container and fill it with the growing media to the top of the container.
* Irrigate the container medium slowly until it is saturated with water. Several hours may be required to reach the saturation point, which can be recognized by glistening of the medium's surface.
* Record the total volume of water necessary to reach the saturation point as the total pore volume.
* Unplug the drainage holes and allow the water to freely drain from the container media into a pan for several hours.
* Measure the volume of water in the pan after all free water has completed draining. Record this as the aeration pore volume.
* Calculate total porosity, aeration porosity, and water-holding porosity using the following equations (Landis, 1990):
Total porosity = total pore volume / container volume
Aeration porosity = aeration pore volume / container volume
Water-holding porosity = total porosity - aeration porosity
(4.) Inorganic media (http://209.85.215.104/search?q=cache:fnM4taPyjigJ:www.hort.cornell.edu/department/faculty/good/growon/media/inorg.html+http://www.hort.cornell.edu/department/faculty/good/growon/media/&hl=en&ct=clnk&cd=1&gl=us)
Materials such as vermiculite, perlite, and sand represent the inorganic fraction often used in container media formulations. These materials generally increase the aeration porosity and drainage yet decrease the water-holding porosity of media. Inorganic components are usually inert materials characterized by a low cation exchange capacity.
Associated Table:
Vermiculite Grades
Vermiculite
Vermiculite is a commonly used inorganic media component which is mined in the U.S. and Africa. This mineral, comprised of an aluminum/iron/magnesium/silicate mixture, is excavated as a material composed of thin layers. Processing includes heating the vermiculite to temperatures upwards of 1000°C, which converts water trapped between the layers of the material into steam. The production of steam results in a pressure that expands the material, increasing the volume of the pieces 15 to 20 times their original size. Vermiculite is sterile because of these high heating temperatures used during processing.
Vermiculite is characterized by a high water-holding capacity as a result of its large surface area:volume ratio, a low bulk density, nearly neutral pH, and a high cation exchange capacity attributed to its platy structure. Because it compacts readily when combined with heavier materials, vermiculite is sometimes recommended more for propagating material than container media.
Vermiculite gradually releases nutrients for plant absorption; on average it contains 5-8% available potassium and 9-12% magnesium. This inorganic media component can adsorb phosphate--some of which remains in an available form for plant uptake--but cannot adsorb nitrate, chloride, or sulfate. Vermiculite can fix ammonium into a form that is not readily available for plant absorption. This fixed nitrogen is gradually transformed to nitrate by microorganisms, making it available for plant uptake.
Vermiculite is manufactured in four different grades, differentiated by particle size. Insulation grade vermiculite and that which is marketed for poultry litter (which has not been treated with water repellents) has been used with some success. Vermiculite which has been treated with water repellent, such as block fill should not be used as growing media. Because vermiculite tends to compact over time, it should be incorporated with other materials such as peat or perlite to maintain sufficient porosity. It should not be used in conjunction with sand or as the sole media component, because as the internal structure of vermiculite deteriorates, air porosity and drainage decreases (Landis, 1990).
The particle size of vermiculite influences the water-holding and aeration porosity of the material. Although grade classification is based upon particle size, each grade is represented by a range of particle sizes. Note that grades consisting of larger particle sizes have a higher aeration porosity and lower water-holding porosity than grades consisting of a smaller range of particle sizes. Properties of the four vermiculite grades are shown in an associated table.
Associated Table:
Perlite Classifications
Tip:
Perlite can retain two to four times its dry weight in water.
Perlite
A mineral of volcanic derivation, perlite is a second inorganic component which may be used in formulating container mixes.
This chemically inert material is extracted in New Zealand, the U.S., and other countries and is usually mined by scraping the earth's surface. The processing method includes a grinding and heat treatment (up to 1000‰C) which results in very lightweight, white sterile fragments. As the ore is heated, internal water escapes as steam, resulting in the expansion of the material.
Perlite has a very low cation exchange capacity, low water-holding capacity (19%), and neutral pH. The closed-cell composition of perlite contributes to its compaction resistance, enhances media drainage, and heightens the aeration porosity of peat-based media (Bilderback 1982). Because perlite contains only minute amounts of plant nutrients, liquid feeding is a practical mode of fertilization. Be aware of possible aluminum toxicity in acidic media (pH < 5).
The very low levels of fluoride perlite contains is not likely to pose plant health problems. Any soluble fluoride present in a media characterized by 6.0 < pH < 6.5 will precipitate out of the media with excess calcium from sources such as gypsum, limestone, or calcium nitrate.
Although perlite has several positive attributes, it also has drawbacks. Perlite consists of many fine fragments which, when dry, can lead to lung or eye irritation. In addition, because water clings to the surface of perlite, it may tend to float in the presence of water (Landis, 1990).
Perlite contains, on average, 47.5% oxygen, 33.8% silicon, 7.2% aluminum, 3.5% potassium, 3.4% sodium, 3.0% bound water, 0.6% iron and calcium, and 0.2% magnesium and trace elements (Perlite Institute, 1983). Although a uniform categorization of perlite does not exist, individual producers of this inorganic component assign grade levels. Perlite classifications for horticultural use are listed in an associated table. This inorganic media amendment is sometimes recommended for use only in propagation media because of its low bulk density and tendency to compact.
In comparison with sand, polystyrene, or pumice, perlite has the greatest inner total porosity. Coarse perlite is characterized by approximately 70% total porosity, 60% of which is aeration porosity. Perlite can retain two to four times its dry weight in water, which is much greater than that of sand and polystyrene, yet much less than the water-holding capacity of peat and vermiculite (Moore, 1987).
Sand
Sand has been used as an inorganic media component to add ballast to containers. Some sands contain calcium carbonate which may raise media pH undesirably. A rise in pH may lead to nutrient deficiencies, particularly of minor elements such as iron and boron. A few drops of dilute hydrochloric acid or strong vinegar may be added to sand to test for carbonates; if bubbling and fizzing result, carbonate is present as a result of carbon dioxide production. Sand used for container media should have a 6 < pH < 7. Sand maintains good drainage, a low water-holding capacity, and a high bulk density when used independently of other materials. Because of its shape and size, sand can obstruct pore spaces, decreasing drainage and aeration, instead of improving porosity. Various sand particle sizes have been recommended for container media use, including ranges of 2-3 mm or 0.05 - 0.5 mm (fine sand) in size (Landis, 1990). In addition, another recommendation suggests that 60% of the particles be within 0.25-1.0 mm range, and 97% be greater than 0.1 mm and less than 2 mm (Swanson, 1989). Uniformity coefficients assigned to sand mixtures signify the amount of sand which is within a certain size range; a coefficient < 4 is evidence of a homogeneous sand mixture (Swanson, 1989). If the correct grade of sand is used, the wettability of the media is enhanced.
Calcined clays
When fired at high temperatures, some clays, fuel ash, and shales form stable compounds that possess low bulk densities and internal porosities of 40-50%. Though calcined clays alter the physical attributes of media in a positive way, they also decrease the level of water-soluble phosphorus in the mix. Because calcined clays are characterized by a high cation exchange capacity, fertilizer application rates may need to be modified if calcined aggregates are incorporated into the media mixes (Bunt, 1988).
Pumice
Pumice is produced as volcanic lava cools; escaping steam and gas contribute to its porous nature. This alumino-silicate material contains potassium, sodium, magnesium, calcium, and slight amounts of iron. Pumice can absorb K, Mg, P, and Ca from the soil solution and render it available for plant absorption later (Bunt, 1988).
(5.) Ions (http://209.85.215.104/search?q=cache:DA7K1qkKT6MJ:www.hort.cornell.edu/department/faculty/good/growon/media/ions.html+http://www.hort.cornell.edu/department/faculty/good/growon/media/ions.html&hl=en&ct=clnk&cd=1&gl=us)
(this is a good discription of CEC but AEC is also very important as it concerns phosphate...but AEC is not discussed often at all...)
Cation exchange capacity
Cation exchange capacity (CEC) quantifies the ability of media to provide a nutrient reserve for plant uptake. It is the sum of exchangeable cations, or positively charged ions, media can adsorb per unit weight or volume. It is usually measured in milligram equivalents per 100 g or 100 cm3 (meq/100 g or meq/100 cm3, respectively).
A high CEC value characterizes media with a high nutrient-holding capacity that can retain nutrients for plant uptake between applications of fertilizer. Media characterized by a high CEC retains nutrients from leaching during irrigation. In addition, a high CEC provides a buffer from abrupt fluctuations in media salinity and pH.
Important cations in the cation exchange complex in order of adsorption strength include calcium (Ca2+) > magnesium (Mg2+) > potassium (K+) > ammonium (NH4+), and sodium (Na+). Micronutrients which also are adsorbed to media particles include iron (Fe2+ and Fe3+), manganese (Mn2+), zinc (Zn2+), and copper (Cu2+).
The cations bind loosely to negatively charged sites on media particles until they are released into the liquid phase of the media. Once they are released into the media solution, cations are absorbed by plant roots or exchanged for other cations held on the media particles.
Anion exchange capacity
Some media retains small quantities of anions, negatively charged ions, in addition to cations. However, anion exchange capacities are usually negligible, allowing anions such as nitrate (NO3-), chloride (Cl-), sulphate (SO4-), and phosphate (H2PO4-) to leach from the media.
(5a.) Cation Exchange Capacities for various growing media amendments and selected media. (http://209.85.215.104/search?q=cache:xeGuam2Jc_QJ:www.hort.cornell.edu/department/faculty/good/growon/media/ionstbl.html+http://www.hort.cornell.edu/department/faculty/good/growon/media/ionstbl.html&hl=en&ct=clnk&cd=1&gl=us)
I added axis and turface to the list...
(per meq/100g)
axis...................................27
turface..............................30
Perlite...............................1.5 - 3.5
Pine Bark...........................53.0
Vermiculite.........................82.0-150.0
Sphagnum Peat...................80.0-180.0 (according to diff sources)
Humus...............................200.0
Peat moss:Vermiculite(1:1)....141.0
Peat moss:Sand(1:1)............8.0
Peat moss:Perlite(1:3)..........11.0
Peat moss:Perlite(2:1)..........24.0
Shoot!
There are two missing pages "organic" and "density"...the organic page was real good, as was the density; but loosing the organic page is a bigger deal than the density page...
Oh well, I hope someone finds this info to be useful! :up:
c-ray
06-26-2008, 01:11 PM
thank goodness for http://archive.org
here's the rest my friend:
http://web.archive.org/web/20070830021606/www.hort.cornell.edu/department/faculty/good/growon/media/index.html
Oh yea,
A quick note on axis:
YOu need to pre-soak it to get rid of dust it has...otherwise that dust will settle in the bottom of the container and raise the PWT. I actually watched this happen while testing the porosity of axis in clear jugs...it really drove the point home of PWT and media particle size...
To pre-soak I just fill a 5 gallon bucket 1/2 way with water and dump in a bunch of axis. Then I stir it for a few minutes and scoop out the axis. All the dust is left in the water.
The axis "regular" will adsorb 114% of it's own weight in water so it can take a good bit of water to pre-soak a lot of axis.
If your growing OD and you can't use the extra water you can presoak at home and then put it in your oven on the lowest setting for a few days...this will dry it out and save you back while hauling!!!
I envision building good media as the opposite of the game "Tetris":
...You DON'T want the blocks to stack nicely...
thank goodness for http://archive.org
here's the rest my friend:
http://web.archive.org/web/20070830021606/www.hort.cornell.edu/department/faculty/good/growon/media/index.html
Nice!!! Thanks bro :cool2:
NOTE:
This is actually the 1st part, it's the "Table of Contents" (index). But I couldn't find this copy so I didn't post it...C-ray was kind enough to provide the following urls :up:
(6.) Media: Rooted in Success (http://web.archive.org/web/20070830021606/www.hort.cornell.edu/department/faculty/good/growon/media/index.html)
Understanding the general characteristics of growing media, as well as the specific attributes of the media you are using, will enable you to get the most out of your nursery. This set of pages describes the attributes of media and how to manage media for success.
Media is composed of solid, liquid, and gaseous components.
Solid materials usually constitute 33-50% of the media volume. Spaces, or pores , between the solid particles are filled with air or water. As water moves through container media, it is retained by smaller pores, but drains through larger pores.
The second fraction of the media, the liquid portion, consists of nutrients, organic materials, dissolved gases, and water.
The third media phase consists of gaseous materials including oxygen and carbon dioxide. Although media oxygen levels vary from 0-21%, a concentration of at least 12% oxygen is necessary for root initiation to occur. Roots of most plants fail to grow in a media atmosphere containing less than 3% oxygen. The carbon dioxide content of the media may range from 0.03% to 21%; however, very high carbon dioxide contents may be detrimental to plant health (Bilderback, 1982).
Understanding the attributes of each of these media components, as well as the interactions between these components, is essential for the successful operation of a nursery. The following pages describe concepts and provide illustrations of how to effectively manage your media and keep your crops rooted in success.
(7.) Media pH (http://web.archive.org/web/20070220220506/www.hort.cornell.edu/department/faculty/good/growon/media/ph.html)
Media pH is a measure of the acidity or alkalinity of a substrate, with a pH = 7 indicating a neutral pH. Measured on a logarithmic scale ranging from 0 to 14, a pH > 7 denotes alkaline media and a pH < 7 signifies acidic media. The acidity of media is determined by the concentration of hydrogen ions [H+] on media particles and in the media solution. The chemical composition of media particles, the ratio of media components in the mix, and irrigation and fertilizer practices affect the pH of growing media. Container media can increase 0.5 - 1.0 pH units during the growing season as a result of alkaline irrigation water.
Microorganism activity
The pH of organic media influences the activity of microorganisms; bacteria are more prevalent at pH > 5.5, while fungi are most active at pH < 5.5. Nitrification occurs most readily at a neutral pH, contributing to the transformation of the ammonium-nitrogen cation (NH4+) to the nitrate-nitrogen anion (NO3-); this increases the potential for nitrogen leaching from the soilless media solution.
Nutrient availability
Micronutrient availability is optimal at media 5.0 < pH < 6.5. However, because these nutrients are furnished through fertilization, pH regulation is not as crucial with container-grown nursery crops as it is with field-grown woody ornamentals. It is usually unnecessary to modify the container media to a pH greater than 6.5 for most woody plant species if sufficient levels of nutrients are available; for Ericaceous crops, the media pH should not exceed the value of 5.5.
Soluble salts
Because media is restricted to a limited container volume, ions from dissolved fertilizers and irrigation water can accumulate and contribute to high soluble salts levels in the media water extract. Media, fertilizer materials, and irrigation water sources should be selected to minimize soluble salts buildup; in addition, media solution soluble salts levels should be monitored regularly.
Consult the Cornell Cooperative Extension publication Nutrient Management: The Key to Growing Healthy Nursery Crops for additional information on soluble salts and pH management.
Buffering Capacity
Buffering capacity is the ability of media to withstand rapid pH fluctuations. Media with a high buffering capacity requires incorporation of a greater quantity of acid or base to alter the pH than media with a low buffering capacity. Media characterized by low buffering capacities include sandy mixes containing little organic matter, while media exhibiting high buffering capacities are usually composed of greater quantities of organic matter such as peat moss, bark, sawdust, composted sewage sludge, or spent mushroom compost. Select a container media with as high of a buffering capacity as possible to alleviate unexpected pH fluctuations.
Low initial fertility
Nutrient levels can be more accurately monitored in media characterized by minimal inherent nutrient value than in purchased and prepackaged media containing pre-incorporated fertilizer materials. Low initial media fertility affords the grower the opportunity to develop a fertilization program targeted towards fulfillment of the nutrient requirements associated with the developmental stage of the species in production.
Some types of media may render certain nutrients unavailable for plant uptake. Use of media such as sawdust or bark that is not adequately composted can lead to the unavailability of nitrogen for plant absorption as microorganisms break down these materials and assimilate the nitrogen for their own use. Vermiculite can inhibit absorption of phosphorus and iron; likewise, certain kinds of pine bark can eliminate iron from the media solution.
(8.) Bulk density and Physical Support (http://web.archive.org/web/20070220220606/www.hort.cornell.edu/department/faculty/good/growon/media/bulkd.html)
Media bulk density is the weight per unit volume that includes solid particles and pore spaces. Individual particles' arrangements, bulk densities, and compaction qualities contribute to the total bulk density of the media.
Bulk density often represents a good estimation of total porosity; however, since water-holding and aeration porosity are closely related to the individual particle organization and ratio of micropores to macropores, these latter two properties cannot accurately be determined by the media bulk density. Media constituents that differ in particle size have higher bulk densities as a mix, lower nutrient and water-holding capacities, and less air porosity than media composed of similar particle sizes.
Bulk density is measured in grams per cubic centimeter (g/cm3), kilograms per cubic meter (kg/m3), pounds per cubic foot (lbs/ft3), or pounds per cubic yard (lbs/yd3).
Consider dry and wet bulk density values when selecting container growing media. Dry bulk density is calculated from oven-dried media and is an important factor in media transport. Wet bulk density affects the ease of handling and shipping of irrigated container nursery crops.
Absorptive properties
Absorptive properties of media affect wet and dry bulk densities. Although peat moss has a relatively low dry bulk density, once saturated, the bulk density increases considerably. A saturated media composed of only peat moss is quite heavy.
Bulk densities determine the stability of container-grown nursery crops. The dense particle nature and high bulk density of sand provides ballast to keep top-heavy nursery crops upright in windy conditions. As a rule of thumb, mixes should weigh 40-75 lbs/ft3. As a comparison, sand weighs approximately 100-120 lbs/ft3, while soil weighs approximately 80-100 lbs/ft3 .
Physical support
Mixes should provide ballast and an environment in which the plant can establish a strong root system. The weight per unit volume of the mix and the compactibility of individual particles determine the amount of support the media will provide.
(9.) Media drainage (http://web.archive.org/web/20061021015132/www.hort.cornell.edu/department/faculty/good/growon/media/drainage.html)
Sufficient media drainage is critical for optimal plant growth. The rate at which water drains from container media depends on the pore size and cohesive and adhesive forces between the water and container media. Media depth and pore size affect the height of the perched water table which is created when water saturates media pore spaces. If coarse materials like gravel or sand are placed in the bottom of the container, the smaller pores in the media above this layer will retain water until pressure forces the liquid downward. Water accumulation above these coarse materials elevate the perched water table.
If small pores are prevalent in the bottom layer of container media, water will pass through the larger pores above this layer fairly quickly and saturate the base layer, potentially creating an atmosphere too wet for vigorous root growth (Swanson, 1989). Avoid media saturation in the upper or lower layers of the container by thoroughly mixing the media.
Drainage, or hydraulic conductivity, is the rate at which water flows through the media.
Drainage is affected by the height of the container. Containers that have identical heights but different diameters have similar drainage characteristics when the same media is used in both. In general, water retention of container media decreases as the height of the water column increases. Media in a tall container characterized by a greater depth drains more readily than the same media in a short container with a shallower media depth. Media in a short container remains wetter than the same media in a tall container because of a lack of drainage; use a deeper container to improve media drainage.
When coarse material is placed at the bottom of a container, the height of the column is shortened, altering the drainage pattern. However, addition of coarse materials to the container bottom aids in drainage by constructing larger pore spaces.
Media capacity exists when large pore spaces do not contain any free water after drainage. Water is retained only in small pore spaces by adhesive and cohesive forces. After drainage, such a situation exists in the upper portion of container media.
Water retention
As an indication of sufficient water retention, media should absorb two inches of water per hour without runoff. In addition, if one quart of water can flow through media in a one gallon container per minute, adequate drainage exists.
Container media should also have the capability to retain sufficient amounts of water for root uptake. The ability of one cubic foot of media to retain three gallons of water is indicative of sufficient media moisture retention (Swanson, 1989).
(10.) Percent base saturation (http://web.archive.org/web/20060916184035/www.hort.cornell.edu/department/faculty/good/growon/media/pctbase.html)
If I understand accurately, this has to do with CEC and AEC (eg. ions and anions, respectively) and is something we don't need to be very concerned about...I don't take it into consideration because I don't add Ca, Mg or K to my soilless mix except in the case of Ca and Mg in the form of azomite..but it's not like I add a lot of azomite to my soilless mix...
I posted some info that is relevant HERE (https://www.cannabis-world.org/cw/showpost.php?p=72949&postcount=7)
The concentration of potassium, magnesium, and calcium expressed as a percentage of the cation exchange capacity is referred to as the percent base saturation. Values for percent base saturation should be within the range of 1-5%, 10-15%, and 60-80% for potassium, magnesium, and calcium, respectively. Media nutrient analysis recommendations for the application of these nutrients are established from the ratios of potassium, magnesium, and calcium to each other in addition to the quantity of these nutrients present in the media.
(11.) Absence of pathogens and pests (http://web.archive.org/web/20060916184001/www.hort.cornell.edu/department/faculty/good/growon/media/pathogen.html)
Pathogenic fungi, non-beneficial insects, weed seeds, and some nematodes must be eliminated from media before use in container nurseries. Some materials, such as perlite and vermiculite, are already sterile as a result of elevated temperature treatment during the production process.
Certain types of media have the ability to suppress disease organisms. For example, some species of composted hardwood bark can suppress deleterious effects of Pythium, Phytophthora, and Thielaviopsis root rots, Rhizoctonia damping-off and crown rot, Fusarium wilt, and certain diseases caused by nematodes. Pythium and Phytophthora root rots have been repressed by composted pine bark, however, Rhizoctonia has not (Hoitink, 1980). Southern pine seedlings inoculated with Pythium and Fusarium had a higher death rate in a peat-vermiculite mix than in a mix that included pine bark (Pawuk, 1981). Ericaceous plants have shown significant growth increases when the primary mix component was composted hardwood bark rather than peat. Composted bark suppresses plant pathogens by:
discouraging the proliferation of pathogenic organisms,
fostering organisms antagonistic to many plant pathogens, and
exhibiting fungicidal properties (Hoitink, 1976).
Media composting
Composting reduces the presence of plant pathogens. The composting process, quantity and source of nitrogen added, and temperature of the stack affect the pathogen suppressiveness of the resultant media.
Composting also exterminates chemical inhibitors present in hardwood and some softwood barks. Because these toxic substances which are often present in fresh bark may be lethal to young plants it is important that the correct duration of time and composting temperature be employed to eliminate these materials. Antagonistic microorganisms and naturally occurring chemicals with fungicidal attributes curtail the incidence of root pathogens. In addition, the quantity of wood present in the bark influences pathogen suppression. Elevated wood contents decrease Phytophthora control; similarly, mixes containing more than 50% Canadian peat as a substitute for composted hardwood bark exhibited increased incidence of root rots (Hoitink, 1980). On the contrary, some Sphagnum peat lots can suppress root rot and damping-off caused by Pythium spp. Suppression may be attributed to the presence of antagonistic fungi in some of these peat lots (Wolffhechel, 1988).
(12.) Rewettability (http://web.archive.org/web/20061013195112/www.hort.cornell.edu/department/faculty/good/growon/media/rewet.html)
Some points worth consideration:
I use and love yucca extract as an organic, non-ionic, surfactant (I've only tried the liquid so far)
I have read that some media may reach a surfactant 'ceiling' if you will. After the use of X amount of surfactants the surfactants don't work as well. I have not data for this and I can't find the link right now either. In any case it's best to not over use surfactants as they can be phytotoxic if overused.
It's best to wet your media with a surfactant upon the very first wetting only if your media needs it. Then don't let the medium dry out to the point it becomes hydrophobic (<30% moisture) and you won't need to use a surfactant again...just don't let the surface dry out and great crusty.
Peat is a good example...I spread out the peat on a trap and then pre-wet it with yucca extract so I mix it up really good. This way the peat is already moistened when I mix it with the axis and put it in the bags. You get a much more consistent media this way and far fewer dry pockets in the media (as you would if you filled the container w/dry peat and then watered).
The ability to rewet media is important, especially for materials such as peat moss and pine bark, which tend to be hydrophobic upon drying. The wettability of pine bark is increased by composting. A wetting agent, or surfactant, may be necessary during media mixing to provide adequate moisture for plant growth; in addition, more frequent irrigation may be required. Although they enhance the wettability of media, the effectiveness of surfactants may decrease over time; in addition, some wetting agents are phytotoxic to woody plant materials.
(13.) Organic media (http://web.archive.org/web/20061011184254/www.hort.cornell.edu/department/faculty/good/growon/media/organic.html) :clap:
The major types of organic media used in container-crop horticulture are peat moss, spent mushroom compost, and bark. Other organic and inorganic additives are also often added to these media.
Associated Table:
Horticultural peat moss characteristics
Peat Moss
Peat is produced when incompletely decayed plants, including species of sedges, grasses, and mosses, accumulate under cool temperatures and conditions of decreased oxygen and nutrient levels.
Different types of peat moss vary in their degree of decomposition. Plant species, climate, and quality of water affect the distinct characteristics of peat moss. Four horticultural classifications of peat moss exist:
sphagnum,
hypnum,
reed-sedge, and
peat humus
Sphagnum peat moss
Sphagnum peat moss, derived from the genus Sphagnum, contains at least 90% organic matter on a dry weight basis. In addition, this peat moss contains a minimum of 75% Sphagnum fiber, consisting of recognizable cells of leaves and stems. Approximately 25 species of Sphagnum exist in Alberta, Canada and 335 species are present throughout the world. Sphagnum fuscum is an important species bearing many desirable traits. Sphagnum grows in northern cool regions and is also located in peat bogs found in Washington, Maine, Minnesota, and Michigan.
Many pores are present in the leaves of sphagnum; when used as growing media, as much as 93% of the water occupying this internal pore space is available for plant uptake (Peck, 1984). After draining, sphagnum peat can hold 59% water and 25% air by volume. Sphagnum is usually characterized by an acidic pH, low soluble salts content, structural integrity, and the ability to serve as a nutrient reserve (Landis, 1990).
Although peat mosses are classified into four different groups, variation may exist within any one type of peat moss. Peats of the same classification often differ notably in quality, and even peats from the same bog taken from separate layers can possess different chemical and physical properties.
Sphagnum peat moss is classified as light or dark peat, based on its color. Light peats are characterized by a large amount of internal pore space, 15-40% of the pore space comprises aeration porosity Dark sphagnum peat does not display the elasticity of light peat and is usually not as long lasting.. Dark sphagnum peat moss maintains twice the cation exchange capacity of light peats, yet does not possess as much total or aeration porosity. An associated table lists general characteristics of sphagnum peat moss.
Hypnum peat moss
Hypnum peat moss, a second category of peat, is found in the northern United States and tends to break down more quickly than sphagnum mosses. Although hypnum peat moss is usually less expensive than sphagnum peat, it may contain plant pathogens or weed seeds as a result of the conditions under which it was produced. To meet the criteria of this classification, the oven dry weight of hypnum peat must be comprised by over 90% organic matter; 50% of this must represent plant material from the genus Hypnum. Container tree seedlings should not be grown in media consisting of large quantities of hypnum peat; however, this type of peat is often used as a suitable media component for acid-intolerant crops.
Reed and sedge peat
Sedges (Carex spp.), reed grass (Phragmites), grasses, rushes, and other marsh plants are represented in this category of peat moss. An oven dry sample consists of at least 33% of these plant materials on a dry weight basis. This category of peat moss is not very suitable for growing media; it quickly decomposes, is characterized by a fine particle size and low fiber content, and is less acidic than sphagnum. Sedge peats often contain more plant nutrients than sphagnum; this results from nutrients leaching through mineral soils into the developing layers of peat. This type of peat often has a higher cation exchange capacity per unit weight, appears darker in color, and maintains a lower water-holding capacity than sphagnum peats (Landis, 1990).
Peat humus
Because the plant materials which comprise this category of peat are extensively decomposed, it is difficult to distinguish among the individual components. Peat humus, often composed of reed-sedge or hypnum peat moss, contains less than 33% peat fiber. Since it often contains clay and silt and does not increase drainage or aeration, peat humus is not usually recommended as a component for container media (Landis, 1990).
Harvesting
The texture of peat is affected by the method in which it was harvested and processed. The technique used to harvest peat depends on climate and bog characteristics, such as the presence of tree stumps in the bog. Peat is harvested from bogs by hydraulic mining or block cutting.
Peat compacts more through hydraulic mining. In this harvest method, peat is shredded and removed from the bog by dredging. The peat's aeration porosity is decreased.
Peat derived by the block-cutting method is cut in slabs as it is excavated from the bog and shredded to a coarse texture. Block-cut peat has a higher total porosity and aeration porosity and holds more available water than mined peat; however, water-holding porosity is lower in block-cut peat as opposed to mined peat(Wilson, 1985).
Spent mushroom compost
Spent mushroom compost can be incorporated to represent 25 - 50% of the mix volume. This organic material is often aged nine to twelve months before use. It is characterized by a pH > 7, high potassium, phosphorus, and salt levels, and contains adequate amounts of trace elements and calcium.
Spent mushroom compost continues to decompose and compact in the container, decreasing air pore space and increasing the water-holding capacity of the mix. Adding pine bark or perlite enhances the air porosity. Although this material has a high buffering capacity, applying iron sulfate contributes to reducing the pH (Bunt, 1988).
Warning:
Hardwood bark must be composted before use in container media.
Bark
Bark is often used as a media component to increase the air porosity within a mix. Some bark fragments contain up to 43% internal porosity, from which roots can absorb water if penetration of the particle occurs (Pokorny, 1987). Pine bark, which is acidic in nature, also has a low initial fertility-- an important characteristic of growing media. Composted bark has a higher cation exchange capacity than raw bark and represses pathogenic fungi (Hoitink, 1980).
Several bark particle sizes have been recommended for media composition. Suggested formulations for container-grown crops include:
a mix characterized by 25-33% of the pine bark particles less than 0.5mm in size;
peat moss based media containing 25-50% pine bark; or
media containing various bark particle sizes attained by using a hammermill with a screen size of 2 - 2.5 cm.
The use of bark in container media offers both advantages and disadvantages. Bark which has not been composted properly induces nitrogen deficiency problems; however, composted bark with sufficient nitrogen fertilizer added during the process should not pose this problem. Bark from alder, poplar, maple, and oak are prone to decay as a result of a high cellulose content; plants grown in media containing these barks may experience nitrogen deficiency as the constituents rapidly decompose. Because of this, it is necessary to add more supplemental nitrogen to hardwood rather than softwood bark before or during composting to preclude nitrogen deficiency (Bilderback 1982). Hardwood bark breaks down three times more quickly than softwood bark. Continued decomposition of composted hardwood bark media during the growing season increases the water-holding capacity and decreases the air porosity of the mix. In addition, hardwood bark seems to repress nematodes and root pathogens more effectively than softwood bark; fungicidal inhibitors and antagonistic organisms present in composted hardwood bark contribute to this repression. Some barks contain organic or inorganic toxins, including high levels of monoterpenes, phenols, or manganese that may prove harmful to plants. Phenolic compounds in fresh barks are especially toxic to young nursery crops. Tree species, age, time of harvest, soil type, and geographical region are factors that affect phytotoxicity. Bark derived from older trees, lower portions of the tree, or removed during winter months tends to be more phytotoxic than bark removed from younger trees, upper portions of the tree, or during spring months. In addition, obtaining bark of uniform quality and particle size is often difficult.
The characteristics of softwood and hardwood bark are quite different. Some softwood bark can be used without composting; hardwood bark must be composted before use or phytotoxicity may ensue. Aging and composting bark is usually an effective way to eradicate toxins. Fresh pine bark repels water to a greater extent than aged pine bark or composted hardwood bark; to increase the moisture content of pine bark, soak it under a sprinkler system. Although pine bark has a lower water-holding capacity than peat moss, it holds a greater amount of available water for the plant (Pokorny 1979). Avoid water stress in newly planted nursery crops by watering regularly, particularly during the 30 days after planting.
Many plant materials appear to grow well in fresh pine bark (Self and Pounders 1974). Fresh pine or softwood bark usually has an initial pH range of 4.0 - 5.0; as pine bark ages, the pH does not increase appreciably. To increase the pH of pine bark, add 4 - 15 lbs. of dolomitic limestone per cubic yard; within a few weeks the pH of the media should equilibrate to a suitable planting pH (Bilderback 1982). Aged pine bark is often favored over fresh pine bark by growers; this may be attributed to a more desirable particle size distribution in the former (Pokorny, 1975).
Recently harvested hardwood bark is usually characterized by a pH of 5.2 - 5.5. Lime should not be added to hardwood bark mixes; as the bark ages or is composted, the pH may exceed 7.0 as a result of the natural calcium content of the bark. To avoid magnesium deficiency in hardwood bark mixes, incorporate one pound of magnesium sulfate into each cubic yard of mix. If a bark-sand mix is desired, add a low pH sand to decrease the pH of composted hardwood bark media (Bilderback, 1982).
Peat additives
Additives incorporated into young sphagnum peat tend to decrease the total porosity of the media. For example, the addition of fine sand to young sphagnum peat appreciably decreases media aeration porosity and total pore space. Research results indicate that the addition of polyacrylamide gel to young sphagnum peat increases the water-holding porosity but decreases the aeration porosity of the media. Addition of a wetting agent to the peat contributes to the ease of drainage and reduces the surface tension, increasing media air porosity (Wilson, 1985).
Other organic media
Sawdust, wood chips, spent mushroom compost, rice hulls, and bark may be used for container media. Compost wood residues, including sawdust, before using as a growing media. Because of the high carbon to nitrogen ratio (C:N) of these materials, it may be necessary to add nitrogen during composting. This will help prevent nitrogen deficiency and phytotoxicity. Because hardwood sawdust decomposes more quickly than pine sawdust, approximately 1% more nitrogen by weight is required to compost the former material (Mastalerz, 1977). Although aged sawdust requires less nitrogen for decomposition, incorporation of nitrogen is essential for complete adjustment of the C:N ratio prior to mixing and potting. Keep in mind that phytotoxicity may result from treating wood with preservatives; consequently, avoid using these materials.
Chemical properties of sawdust vary widely. Sawdust from walnut, redwood, western redcedar, or incense-cedar may contain substances toxic to plants; even sawdust derived from different tree species within a genus may contain varying levels of toxins. High salt concentrations present in sawdust derived from trees harvested in seaboard regions can be harmful to plants; inconsistent particle size may pose a problem in the formulation of uniform media (Landis, 1990). Trial media components on a small scale to ensure compatibility with establishment of healthy nursery crops before incorporating them into the mix for large scale use.
(14.) Plastics: Foam Materials (http://web.archive.org/web/20061018235532/www.hort.cornell.edu/department/faculty/good/growon/media/plastic.html)
Expanded polystyrene flakes
This chemically neutral material may be used with other types of media amendments, such as peat, to enhance the physical properties of a mix. Because of its large size and closed pore structure, polystyrene can improve the aeration porosity of media while decreasing its water-holding capacity. Expanded polystyrene flakes should not be sterilized with steam, chloropicrin, or methyl bromide.
Because of their inability to attract nutrients, it may be necessary to begin a liquid fertilization program sooner than normal when using polystyrene flakes in a mix. This material tends to float during irrigation and cling to other materials and surfaces during blending (Bunt, 1988).
Urea-formaldehyde foam resins
This low bulk density material, composed of an open arrangement of pores, can imbibe 50-70% of its volume in water. This material contains 30% nitrogen by weight, which it gradually releases as the resins slowly decompose. Because of the slow rate of urea-formaldehyde resin decay, the nitrogen contained in this substance does not contribute measurably to available nitrogen for plant use. Freshly produced urea-formaldehyde foam resins may contain less than 2.5% formaldehyde which should be thoroughly evaporated before incorporating the foam resins into container mixes. In addition, this media amendment lacks any other nutrients, is characterized by a pH near 3.0, and often comprises 20 - 50% of the mix volume (Bunt, 1988).
Polyurethane foam
A porous material of low bulk density, polyurethane foam can absorb 70% of its volume in water. This material is characterized by a pH near 7.0, offers no nutritive value to the plant, is not prone to decay, and is available in flake form for use in container media. It has been suggested that this material either be heated to 100‰C for 120 minutes or be rinsed in ethanol followed by water to ensure any phytotoxic substances are eliminated from the foam before use (Bunt, 1988).
Phenolic resin foam
Phenolic resin foam manifests similar attributes as polyurethane foams, but has a greater bulk density.
(15.) Mix formulations (http://web.archive.org/web/20061027075906/www.hort.cornell.edu/department/faculty/good/growon/media/mixes.html)
University of California
University of California mixes consist of five distinct material combinations comprised of either peat, sand, or both components to which any of six fertilizer formulations may be incorporated. Three popular mix formulations are the University of California mixes C, D, and E. UC Mix C, composed of 50% peat and 50% sand by volume, is widely used in the container nursery industry. Mix D consists of 75% peat moss and 25% sand by volume and UC Mix E consists of 100% peat. Steam sterilization of these mixes is suggested (Bunt, 1988).
Cornell Peat-lite mixes
Developed at Cornell University, these mixes consist of peat and perlite or peat and vermiculite to which various fertilizer formulations may be added. Peat-lite Mix A consists of 50% sphagnum peat and 50% vermiculite by volume. Peat-lite Mix B consists of 50% sphagnum peat and 50% perlite by volume. Keep in mind that these mixes may be too light for outdoor use. A non-ionic wetting agent may be incorporated into the Cornell Peat-lite mixes first by adding the wetting agent to a small amount of vermiculite and then working it into the mix. Alternatively, the wetting agent may be used at the rate of 85cm3 per 30-60 liters of water to moisten each cubic meter of mix (Bunt, 1988).
Other mixes, such as the Pennsylvania State and Oklahoma State University mixes are also available. The Penn State mix is based on sphagnum peat; the Oklahoma State University mix contains 3 parts ground pine bark: 1 part peat: 1 part sand by volume. Various fertilizer formulations have been recommended for addition to these mixes (Landis, 1990).
(16.) Custom mixing (http://web.archive.org/web/20060916184040/www.hort.cornell.edu/department/faculty/good/growon/media/custom.html)
Correct media mixing is imperative for successful nursery crop production. Uniformity of the mix is essential to avoid potential drainage, aeration, and plant growth problems. The formation of aggregates in the media, enhanced by the addition of water, helps maintain mix homogeneity (Bartok, 1985). Peat, when lightly squeezed, should dribble water slightly if properly moistened. Perlite and vermiculite may be moistened with water to alleviate dust, but other container mix ingredients should remain dry. For greater ease of blending peat-based media in a mixer, incorporate dry components into moistened peat (Bartok, 1985).
When mixing media, uniform quantities of materials should be added to produce a consistent, final product from batch to batch. Different mixing techniques result in varying degrees of product uniformity. Using a shredder may result in unwanted separation of heavier components and a rotary tiller may not mix the bottom layer of constituents. However, drum, concrete, and bin mixers achieve mixture homogeneity through a rolling action (Bartok, 1985).
Mixing can be accomplished by blending in batches or through a continuous flow process. Blending in batches, by hand, or in a mixer produces a defined amount of media. Continuous flow systems are suitable for producing large quantities of media. As an alternative to mechanical mixing, media can be blended on a sanitary pad with hand tools--up to 6 cubic feet of media can be blended at one time using this method. When blending ingredients by hand, all media constituents should first be mounded on top of each other. The stack should be thoroughly turned and moistened during blending to facilitate the wettability of the media.
When machine mixing, a variety of options are available. With a belt mixer, each constituent is fed onto a conveyor, where it is transported into a revolving receptacle for blending with other media components. Paddle mixers combine ingredients in a stationary drum; paddles affixed to the inside of the drum stir media constituents together (Landis, 1990). Small batches can be blended in mobile cement or mortar mixers with 3-6 cubic foot capacities or in modified concrete mixing trucks with 5-11 cubic yard capacities. Single batch mixers can yield 0.25 to 12 yd3 of mixed media per hour, while continuous flow media blending procedures can produce up to 50 cubic yards per hour (Bartok, 1985). Other machinery such as soil shredders, grinders, and auger mixers are not recommended for media mixing because of the extensive particle deterioration that results from these processes (Judd, 1984). It is important that aseptic conditions be preserved during mixing; all media constituents should remain sterile from start to finish.
Mixing duration
The duration of mixing is critical for the formation of a successful product. Overmixing organic matter like peat may result in a mix that is too finely ground, leading to compaction and decreasing aeration and drainage. When mixing peat and vermiculite, separate fibers should remain distinguishable and these materials should maintain some resiliency. When mixing by machine, ensure mixing time is not excessive. Overfilling the mixer, blending when the components are too wet, or mixing too long may result in an undesirable product. Many mechanical mixers require only three or four minutes to sufficiently blend materials when filled to 75% capacity (Whitcomb, 1988). A blending time of two to four minutes works well when using drum or hopper mixers (Bartok, 1985), but mixing media longer than five minutes has been shown to diminish particle size (Landis, 1990).
Consider many additional factors when deciding upon mixing methods and equipment. The location of equipment should allow for ease of media blending and storage. Small mobile mixers, large stationary mixers, and continuous flow operations have different space requirements. Energy demands should be considered, as electric or gas powered engines are available. Smaller mixers usually operate on 2-3 horsepower, while larger machines may require 5-10 horsepower (Bartok, 1985). Other machinery which may be incorporated into the mixing system includes wetting attachments, steam pasteurizing injectors, and screens to sift out clumps of media.
Consider all costs
When producing custom mixed media, be aware of all costs involved with the processes. Keep in mind that blended media may shrink up to 25% by volume when water is added; factors such as duration of blending, quantity of water added, and the structural stability of the media constituents affect the volume loss of final product. Weigh the cost of purchasing commercially produced media against the cost of custom producing a comparable volume. Factor in shrinkage, subsequent loss of raw materials, and consider labor costs before deciding to custom mix media (Kusey, 1989).
Avoid over-compaction
Overcompaction of container media detrimentally affects crop growth. In addition to decreasing total porosity which affects aeration and drainage, media compaction also inhibits root growth. Media compaction may be expressed in symptoms such as browning of roots, leaf drop, foliar chlorosis, and necrosis. Symptoms resembling nutrient deficiency, drought stress, or overwatering may also be attributed to compaction. Media compaction inhibits adequate nutrient absorption, often resulting in iron chlorosis and other maladies. In addition, roots in compacted media are more vulnerable to pathogen attack as a result of the stress of compaction (Landis, 1990).
Product and shipping costs of prepackaged, commercially prepared media may initially be high; however, long term success with plant production, substrate uniformity, and freedom from pests may outweigh the initial purchasing costs (Bilderback, 1982). Product inconsistency and poor quality of some custom mixed media contribute to grower costs during the growing season. Initial costs associated with custom media mixing can be increased by poor plant health or required weeding as a result of improper media sterilization. Evaluate the possible consequences and concealed expenses of custom mixing before deciding to follow such a course of action. Nursery size, availability of media constituents, and mixing equipment are all factors affecting the decision to custom mix media or use prepackaged commercially prepared media.
Combining media components
When deciding which media components to include in a custom mix, keep in mind the aeration and nutrient requirements of the specific crops to be grown. Individual characteristics of media components do not necessarily have an additive effect when combined into a mix. Media porosity is determined by particle size and distribution of the individual components in relation to one another.
(17.) Preplant incorporation of materials (http://web.archive.org/web/20060916183918/www.hort.cornell.edu/department/faculty/good/growon/media/preplant.html)
Fertilizers
Because ideal container media is characterized by low inherent fertility, it is necessary to carefully develop a fertilization program that will fulfill the specific nutrient requirements of the nursery crops. Factors such as plant age, species, and time of year affect nutrient requirements of many nursery crops. To avoid elemental deficiencies or toxicities, fertilize with adequate nutrient concentrations and incorporate fertilizers uniformly. Base nutrient management programs on media analysis results and recommendations. Consider any inherent media nutrient supplying power when formulating a nutrient management program. See the other documents in the resource Nutrient Management: The Key to Growing Healthy Nursery Crops for more information.
Surfactants
Surfactants are chemical agents that enhance the wettability of organic materials such as pine bark and peat moss. Some wetting agents may be harmful to woody plants; researchers have found that application of surfactants at some of the suggested rates may result in plant phytotoxicity. Consult the following references for more information: Ward et. al, 1987; Whitcomb, 1988; Barnett and Brissette, 1986; Barnett, 1977; and Pokorny, 1979.
Mycorrhizal fungi inoculum
Mycorrhizae are soil fungi associated with plant roots and increase nutrient and water absorption by the roots. The fungal hyphae extend beyond the root zone, expanding the area from which nutrients and water may be absorbed. Certain mycorrhizae also produce growth regulators that stimulate feeder root development. Some mycorrhizal fungi produce antibiotics that are lethal to certain root pathogens. Barriers formed through root association with mycorrhizal fungi may also aid in defending against pathogens. Mycorrhizal association decreases drought stress, yet increases salt tolerance and root regeneration. Mycorrhizal fungi can be introduced into the media during mixing to shorten the length of time for reinoculation to occur. Consult the following references for additional information and possible inoculum sources: Landis et al., 1990 and Digat, 1988.
Pasteurization and sterilization
Sterilizing media eradicates all living organisms from the components while pasteurizing eliminates only some microorganisms from media. The presence of some fungi, bacteria, and actinomycetes may be desirable in container media; in such cases pasteurizing the media is recommended to eliminate injurious organisms while retaining beneficial organisms. Steam may be used to sterilize or pasteurize media, depending on the treatment temperature. During pasteurization, media is heated to temperatures of 140°F to 177°F (60°C - 82°C) for at least half an hour.
Some inorganic media constituents, such as perlite and vermiculite, are sterile as a result of their processing method. Organic components, including peat, may not be sterile after processing. Commercially prepared media is usually free of insects, pathogens, and weed seeds if contamination has not occurred during storage. However, custom-mixed container media may require pasteurizing before using. Avoid incorporating fertilizers before pasteurizing or sterilizing media; if fertilizers are present, the high temperatures used during these processes could lead to soluble salt accumulation and associated problems.
(18.) Conclusion (http://web.archive.org/web/20060916183939/www.hort.cornell.edu/department/faculty/good/growon/media/conclu.html)
Rooted in success
Carefully consider the many factors that define suitable container media before making a selection. In addition to chemical and physical properties of media components, review other important characteristics during media evaluation:
media uniformity,
reproducibility,
wettability,
bulk density,
stability,
availability, and
ease of storage.
Trial media on a small scale to resolve any potential problems before adopting the mix for widespread use. Selecting container media that is appropriate for a particular nursery crop operation lays the foundation for producing woody plants rooted in success.
(19.) Literature Cited (http://web.archive.org/web/20061013195148/www.hort.cornell.edu/department/faculty/good/growon/media/litcit.html)
Bartok, J. W., Jr. 1985. Media mixing systems offer efficiency, variety. Greenhouse Manager 4(8):108-110, 112-113.
Barnett, J. P. 1977. Effects of soil wetting agent concentration on southern pine seed germi- nation. Southern Journal of Applied Forestry 1(3):14-15.
Barnett, J. P. and J. C. Brissette. 1986. Producing southern pine seedlings in containers. Gen. Tech. Rep. SO-59. New Orleans, LA: USDA Forest Service, Southern Forest Experiment Station.
Bilderback, T. E. 1982. Container soils and soilless media. In: Nursery Crops Production Manual. Raleigh, NC: North Carolina State University, Agricultural Extension Service.
Bunt, A. C. 1988. Media and mixes for container-grown plants. Boston: Unwin Hyman.
Digat, B. 1988. The bacterization of horticultural substrates and its effects on plant growth. Acta Horticulturae 221:279-288.
Handreck, K. A. and N. D. Black. 1984. Growing media for ornamental plants and turf. Kensington, NSW, Australia: New South Wales University Press.
Hoitink, H. A. 1980. Composted bark, a lightweight growth medium with fungicidal prop- erties. Plant Disease 64(2):142 - 147.
Hoitink, H. A. and H. A. Poole. 1976. Composted bark media for control of soil-borne plant pathogens. International Plant Propagators' Society Combined Proceedings 26: 261- 263.
Judd, R. W. Jr. 1984. Making soilless mixes not without its problems. Greenhouse Manager 3(2):135, 137.
Kusy, W. 1989.Beware of hidden costs in mixing your own media. Greenhouse Manager 8(5):134, 136, 138, 141.
Landis, T. D. 1990. Containers and growing media, Vol. 2, The container tree nursery manual. Agric. Handbk. 674. Washington, DC: U.S. Department of Agriculture, Forest Service 41 - 85.
Landis, T. D., R. W. Tinus, S. McDonald, and J. Barnett. 1990. The biological component: Nursery pests and mycorrhizae, Vol. 5, The container tree nursery manual. Agriculture Handbk. 674. Washington, DC: U.S. Department of Agriculture, Forest Service.
Mastalerz, J. W. 1977. The greenhouse environment. New York: John Wiley & Sons, Inc..
Moore, G. 1987. Perlite: Start to finish. International Plant Propagators' Society Combined Proceedings 37: 48-52.
Pawuk, W. H. 1981. Potting media affect growth and disease development of container- grown southern pines. Res. Note SO-268. New Orleans, LA: USDA Forest Service, South- ern Forest Experiment Station.
Peck, K. 1984. Peat moss and peats. Hummert's Quarterly 8(3):1, 4-5.
Perlite Institute. 1983. Typical chemical and physical properties of perlite. Tech. Data Sheet 1- 1. New York.
Pokorny, F. A. 1987. Available water and root development within the micropores of pine bark particles. J. of Environmental Horticulture 5(2):89-92.
Pokorny, F. A. 1979. Pine bark container media: an overview. International Plant Propagators' Society Combined Proceedings 29:484-495.
Stewart, N. 1986. Production of bark for composts. International Plant Propagators' Society Combined Proceedings 35: 454-458.
Swanson, B. T. 1989. Critical physical properties of container media. American Nurseryman 169(11): 59-63.
Ward, J., N. C. Bragg, and B. J. Chambers. 1987. Peat-based composts: their properties defined and modified to your needs. International Plant Propagators' Society Combined Proceedings 36:288-292.
Whitcomb, C. E. 1988. Plant production in containers. Stillwater, OK: Lacebark Publications.
Wilson, G. 1985. Effects of additives to peat on the air and water capacity. Acta Horticulturae 172: 207-209.
Wolffhechel, H. 1988. The suppressiveness of sphagnum peat to Pythium spp. Acta Horticulturae, 221:217-222.
OK, I'm done for now...Time to take my last hit of b.hash :( and take a nap :)
Anyone have thoughts, ideas, etc, etc???
...
More very useful info to make your brains hurts ;) :farm: :up:
This post is by "Al" (aka "tapla") who is on gardenweb. This is a very nice and informative post on building media. I believe Al may have read the info from Cornell U. (I just posted) and other sources I've seen when he developed his methods...needless to say I agree with a lot of his post.
A very imporant point I want to stress is Al's explainatin and resoning for NOT adding a 'so-called' "drainage layer" to your containers. While the Cornell U. page say to add a course materia (broken ceramic, etc) to help drainage I disagree. I think Al is spot on in his reasoning...I don't add a drainge layer, my whole container is filled with exactly the same media (70% peat and 30% axis for OD grows).
I'd be interested to hear ppl's opinion about drainage layer vs. no drainage layer. IMVHO the days of "put an inch or two of perlite in the bottom to help drainage" are dead and gone so I hope we'll never have to beat that dead horse again :horse: ...lol
Note:
Al doesn't like organics and doesn't agree that it needed.
Al is trying to make media with around >40% air porosity
Keep that in mind while reading the following excellent information...
Container Soils - Water Movement and Retention (http://forums2.gardenweb.com/forums/load/contain/msg0420085231701.html?102)
A Discussion About Soils
As container gardeners, our first priority should be to insure the soils we use are adequately aerated for the life of the planting, or in the case of perennial material (trees, shrubs, garden perennials), from repot to repot. Soil aeration/drainage is the most important consideration in any container planting. Soil is the foundation that all container plantings are built on, and aeration is the cornerstone of that foundation. Since aeration and drainage are inversely linked to soil particle size, it makes good sense to try to find and use soils or primary components with particles larger than peat. That components retain their structure for extended periods is also extremely important. Pine and some other types of conifer bark fit the bill nicely and I’ll talk more about them later.
The following also hits pretty hard against the futility of using a drainage layer in an attempt to improve drainage. It just doesn't work. All it does is reduce the amount soil available for root colonization. A wick will remove water from the saturated layer of soil at the container bottom. It works in reverse of the self-watering pots widely being discussed on this forum now.
Since there are many questions about soils appropriate for use in containers, I'll post basic mix recipes later, in case any would like to try the soil. It will follow the Water Movement info.
Consider this if you will:
Soil need fill only a few needs in plant culture. Anchorage - A place for roots to extend, securing the plant and preventing it from toppling. Nutrient Sink - It must retain sufficient nutrients in available form to sustain plant systems. Gas Exchange - It must be sufficiently porous to allow air to the root system and by-product gasses to escape. And finally, Water - It must retain water enough in liquid and/or vapor form to sustain plants between waterings. Most plants could be grown without soil as long as we can provide air, nutrients, and water, (witness hydroponics). Here, I will concentrate primarily on the movement of water in soil(s).
There are two forces that cause water to move through soil - one is gravity, the other capillary action. Gravity needs little explanation, but for this writing I would like to note: Gravitational flow potential (GFP) is greater for water at the top of the container than it is for water at the bottom. I'll return to that later. Capillarity is a function of the natural forces of adhesion and cohesion. Adhesion is water's tendency to stick to solid objects like soil particles and the sides of the pot. Cohesion is the tendency for water to stick to itself. Cohesion is why we often find water in droplet form - because cohesion is at times stronger than adhesion, water’s bond to itself can be stronger than the bond to the object it might be in contact with; in this condition it forms a drop. Capillary action is in evidence when we dip a paper towel in water. The water will soak into the towel and rise several inches above the surface of the water. It will not drain back into the source. It will stop rising when the GFP equals the capillary attraction of the fibers in the paper.
There will be a naturally occurring "perched water table" (PWT) in containers when soil particulate size is under about .125 (1/8) inch.. This is water that occupies a layer of soil that is always saturated & will not drain from the portion of the pot it occupies. It can evaporate or be used by the plant, but physical forces will not allow it to drain. It is there because the capillary pull of the soil at some point will surpass the GFP; therefore, the water does not drain, it is "perched". The smaller the size of the particles in a soil, the greater the height of the PWT.
If we fill five cylinders of varying heights and diameters with the same soil mix and provide each cylinder with a drainage hole, the PWT will be exactly the same height in each container. This saturated area of the pot is where roots seldom penetrate & where root problems frequently begin due to a lack of aeration. Water and nutrient uptake are also compromised by lack of air in the root zone. Keeping in mind the fact that the PWT height is soil dependent and has nothing to do with height or shape of the container, we can draw the conclusion that: Tall growing containers will always have a higher percentage of unsaturated soil than squat containers when using the same soil mix. The reason: The level of the PWT will be the same in each container, with the taller container providing more usable, air holding soil above the PWT. Physiology dictates that plants must have oxygen at the root zone in order to maintain normal root function.
A given volume of large soil particles has less overall surface area when compared to the same volume of small particles and therefore less overall adhesive attraction to water. So, in soils with large particles, GFP more readily overcomes capillary attraction. They drain better. We all know this, but the reason, often unclear, is that the height of the PWT is lower in coarse soils than in fine soils. The key to good drainage is size and uniformity of soil particles. Mixing large particles with small is often very ineffective because the smaller particles fit between the large, increasing surface area which increases the capillary attraction and thus the water holding potential.
When we add a coarse drainage layer under our soil, it does not improve drainage. It does though, conserve on the volume of soil required to fill a pot and it makes the pot lighter. When we employ this exercise in an attempt to improve drainage, what we are actually doing is moving the level of the PWT higher in the pot. This simply reduces the volume of soil available for roots to colonize. Containers with uniform soil particle size from top of container to bottom will yield better and more uniform drainage and have a lower PWT than containers with drainage layers. The coarser the drainage layer, the more detrimental to drainage it is because water is more (for lack of a better scientific word) reluctant to make the downward transition because the capillary pull of the soil above the drainage layer is stronger than the GFP. The reason for this is there is far more surface area for water to be attracted to in the soil above the drainage layer than there is in the drainage layer, so the water "perches".
I know this goes against what most have thought to be true, but the principle is scientifically sound, and experiments have shown it as so. Many nurserymen are now employing the pot-in-pot or the pot-in-trench method of growing to capitalize on the science.
If you discover you need to increase drainage, you can simply insert an absorbent wick into a drainage hole & allow it to extend from the saturated soil to a few inches below the bottom of the pot, or allow it to contact soil below the container where it can be absorbed. This will successfully eliminate the PWT & give your plants much more soil to grow in as well as allow more, much needed air to the roots.
Uniform size particles of fir, hemlock or pine bark are excellent as the primary component of your soils. The lignin contained in bark keeps it rigid and the rigidity provides air-holding pockets in the root zone far longer than peat or compost mixes that too quickly break down to a soup-like consistency. Conifer bark also contains suberin, a lipid sometimes referred to as nature’s preservative. Suberin is what slows the decomposition of bark-based soils. It contains highly varied hydrocarbon chains and the microorganisms that turn peat to soup have great difficulty cleaving these chains.
In simple terms: Plants that expire because of drainage problems either die of thirst because the roots have rotted and can no longer take up water, or they starve/"suffocate" because there is insufficient air at the root zone to insure normal water/nutrient uptake and root function.
To confirm the existence of the PWT and the effectiveness of using a wick to remove it, try this experiment: Fill a soft drink cup nearly full of garden soil. Add enough water to fill to the top, being sure all soil is saturated. Punch a drain hole in the bottom of the cup & allow to drain. When the drainage stops, insert a wick into the drain hole . Take note of how much additional water drains. Even touching the soil with a toothpick through the drain hole will cause substantial additional water to drain. This is water that occupied the PWT before being drained by the wick. A greatly simplified explanation of what occurs is: The wick "fools" the water into thinking the pot is deeper, so water begins to move downward seeking the "new" bottom of the pot, pulling the rest of the water in the PWT along with it. If there is interest, there are other simple and interesting experiments you can perform to confirm the existence of a PWT in container soils. I can expand later.
I remain cognizant of these physical principles whenever I build a soil. I haven’t used a commercially prepared soil in many years, preferring to build a soil or amend one of my 2 basic mixes to suits individual plantings. I use many amendments when building my soils, but the basic building process starts with conifer bark and perlite. Sphagnum peat usually plays a minor, or at least a secondary role in my container soils because it breaks down too quickly and when it does, it impedes drainage and reduces aeration.
Note that there is no sand or compost in the soils I use. Sand, though it can improve drainage in some cases, reduces aeration by filling valuable macro-pores in soils. Unless sand particle size is fairly uniform and/or larger than about ½ BB size I leave it out of soils. Compost is too unstable for me to consider using in soils. The small amount of micronutrients it supplies can easily be delivered by one or more of a number of chemical or organic sources.
My Basic Soil
I'll give two recipes. I usually make big batches. I also frequently add agricultural sulfur to some soils for acid-lovers or to soils I use dolomitic lime in.
5 parts pine bark fines
1 part sphagnum peat (not reed or sedge peat please)
1-2 parts perlite
garden lime (or gypsum in some cases)
controlled release fertilizer (if preferred)
micronutrient powder, other continued source of micronutrients, or fertilizer with all minors
Big batch:
2-3 cu ft pine bark fines
5 gallons peat
5 gallons perlite
2 cups dolomitic (garden) lime (or gypsum in some cases)
2 cups CRF (if preferred)
1/2 cup micronutrient powder (or other source of the minors)
Small batch:
3 gallons pine bark
1/2 gallon peat
1/2 gallon perlite
4 tbsp lime (or gypsum in some cases)
1/4 cup CRF
micro-nutrient powder (or other source of the minors)
I have seen advice that some highly organic (practically speaking - almost all are highly organic) container soils are productive for up to 5 years or more. I disagree and will explain why if there is interest. Even if you were to substitute fir bark for pine bark in this recipe (and this recipe will long outlast any peat based soil) you should only expect a maximum of two to three years life before a repot is in order. Usually perennials, including trees (they're perennials too, you know) ;o) should be repotted more frequently to insure vigor closer to their genetic potential. If a soil is desired that will retain structure for long periods, we need to look more to inorganic components. Some examples are crushed granite, pea stone, coarse sand (see above - usually no smaller than ½ BB size in containers, please), Haydite, lava rock (pumice), Turface or Schultz soil conditioner, and others.
Thank you for your interest.
Al Fassezke
If there is interest, please find the previous postings here:
Posting I (http://forums2.gardenweb.com/forums/load/contain/msg031557203792.html?150)
Posting II (http://forums2.gardenweb.com/forums/load/contain/msg0321395926870.html?150)
Posting III (http://forums2.gardenweb.com/forums/load/contain/msg0201290112896.html?148)
Posting IV (http://forums2.gardenweb.com/forums/load/contain/msg0918361520140.html?149)
Hey all,
Here's some info I've collected on the three main amendments I am currently working with and testing
Pore size:
This effects CEC and water tension within the pores and on surface of media particles. A high level of water tension makes it harder for roots to extract the water held in the pores of the media particles. Even if some media has the best CEC in the world, if it also has high water tension the CEC doesn't mean sqat.
There is a relationship between pore size and water tension. The smaller the pores the higher the water tension. Ideally, a pore size of 1 micron is what you want for low water tension.
The "water release rate" refers to the % of total water retained by the particle which is available for the plant. If a media particle has a water release rate of 50% that means only 50% of that water held by the particle is available to the roots...the rest of the water (the other 50%) is held so tightly (internally) that the roots can not extract it.
Peat:
Med to large pores
Med water tension
High water release rate (93%)
High internal porosity (eg. roots also penetrate individual peat particles to access the water stored within, then they can extract it)
Axis "regular":
Large pores (average pore size for is +/-0.9 micron...sweet!)
Very low water tension
High water release rate (90%)
Aged Pine Bark:
Small pores
High water tension
Low water release rate (?%)
CEC
This refers to the retention and release of cations which is a way to judge the potential ability of a media particle to act as a storage place for nutrients. Basically, a low CEC means the media won't hold the proper nutrients, a high CEC means the media will hold proper nutrients.
See the following links for more info:
THIS (https://www.cannabis-world.org/cw/showpost.php?p=74305&postcount=26) post for info on CEC
See THIS (https://www.cannabis-world.org/cw/showpost.php?p=74306&postcount=27) post for info on specific media's CEC level
Peat:
High CEC
Axis "regular":
Med CEC (which is fine)
Aged Pine Bark:
Med CEC (but a high water tension, low water porosity and low water release rate; so the CEC isn't helpful in the media)
Particle Size:
Thus far I have not really talked about particle size except in passing. Ideally you want a majority of you particles to be near the same size so they will form a nice structure. Particles of similar size won't clog, they will randomly lock against each other keeping air space in the medium, etc.
A good particle size for our purposes (non-fleshy root, 20-35% air porosity, 15-30% water porosity) would be particles from 1/16-1/8". While screening to achieve this partice size this may be practical for axis, vermiculite, turface, pumace, etc, IMVHO, it's not overly practical for perlite as perlite tends to breaks apart when griding against itself while screening.
Many of the amendments used to build a substrate (perlite, vermiclute, peat, coir, etc) beaks down over time so even if you take the time to screen them the particle size isn't gonna stay that size.
This is why I don't screen my outdoor mix because it's 70% peat and 30% axis. Peat has particles from <1/2 to >3/4" and peat particles will break down kinda fast...so it's a waste of time and resources to screen the axis before I mix it with the peat. Even if the partials where similar in size they aren't going to stay that way with a majority of peat in my mix...
Peat:
<1/2 to >3/4"
Axis 'regular':
<1/16 to 1/4" (70% of axis "regular" is 1/8" :up:)
Aged Pine Bark Fines:
<1 to 1"
Pine bark: Make sure it's AGED and you want "fines", but they are sometimes called "soil conditioner"
Main Uses:
These is my personal list, it makes sense to me...I hope makes sense to you too...let me know otherwise :loco:
Peat:
CEC
Water
Air
Stability
Microbes
Axis "regular":
CEC
Water
Air
Stability
Structure
Aged Pine bark:
Air
Stability
Structure
Microbes
Known to fight root rot (eg. pathogenic fungi), yet AM will thrive in it, as far as I know.
***NOTE:
When you buy peat make sure it's Canadian peat, I like Premiere because I know they use as environmentally sound practices as they are able...see HERE (https://www.cannabis-world.org/cw/showpost.php?p=72729&postcount=22)
HTH
YOu want axis...you got axis :cool2:
Western US:
EnviroTech Soil Solutions, Inc. (based in PNW)
http://www.axisplayball.com/AXIS.htm
Call 866-546-3722
Tell him what state you live in...
Eastern/Southen/Northern US:
EaglePicher Filtration & Minerals, Inc. (they are the ones who make Axis)
http://www.epcorp.com/EaglePicherInternet/Filtration_Minerals/
Call 775-824-7600
Press #3
Tell them what state you live in and they'll tell you the nearest distributor
Western Canada [maybe Eastern too]: (for all my friends up there)
Turf Canada
Call 604-850-7857
ask for Pat Differ
tell Pat what Province you live in...
NOTE:
Make sure you get Axis "regular", it is about $15.00 per cu ft(25lbs)...not too expensive when it's only 30% of the mix and it's so beneficial and it means you don't have to by perlite and/or vermiculite...hell, you could reuse the mix indefinitely if you choose :up:
purplehaze2
06-27-2008, 02:22 AM
holly shit gojo you went off.dont hold back,you own this page.
Particle size...
Thus far I have not really talked about particle size except in passing. Ideally you want a majority of you particles to be near the same size so they will form a nice structure. Particles of similar size won't clog, they will randomly lock against each other keeping air space i