Intercropping

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From Wikipedia (http://en.wikipedia.org/wiki/Intercropping), the free encyclopedia
Intercropping is the agricultural practice of cultivating two or more crops in the same space at the same time (Andrews & Kassam 1976). A practice often associated with sustainable agriculture and organic farming, intercropping is one form of polyculture, using companion planting principles. It is commonly used in tropical parts of the world and by various indigenous peoples (Altieri 1991), but in the mechanized agriculture of Europe, North America, and parts of Asia it is far less widespread. Intercropping may benefit crop yield or the control of some kind of pest, or may have other agronomic benefits.


Design

In intercropping, there is often one main crop and one or more added crops, with the main crop being the one of primary importance because of economic or food production reasons. The two or more crops used in an intercrop may be from different species and different plant families, or they may simply be different varieties or cultivars of the same crop species, such as mixing two kinds of wheat seed in the same field.

The most common goal of intercropping is to produce a greater yield on a given piece of land by making use of resources that would otherwise not be utilized by a single crop. Careful planning is required, taking into account the soil, climate, crops, and varieties. It is particularly important not have crops competing with each other for physical space, nutrients, water, or sunlight. Examples of intercropping strategies are planting a deep-rooted crop with a shallow-rooted crop, or planting a tall crop with a shorter crop that requires partial shade.

When crops are carefully selected, other agronomic benefits are also achieved. Lodging-prone plants (those that are prone to tip over in wind or heavy rain) may be given structural support by their companion crop (Trenbath 1976). Delicate or light sensitive plants may be given shade or protection, or otherwise wasted space can be utilized. An example is the tropical multi-tier system where coconut occupies the upper tier, banana the middle tier, and pineapple, ginger, or leguminous fodder, medicinal or aromatic plants occupy the lowest tier.

Intercropping of compatible plants also encourages biodiversity, by providing a habitat for a variety of insects and soil organisms that would not be present in a single crop environment. This biodiversity can in turn help to limit outbreaks of crop pests (Altieri 1994) by increasing the diversity or abundance of natural enemies, such as spiders or parasitic wasps. Increasing the complexity of the crop environment through intercropping also limits the places where pests can find optimal foraging or reproductive conditions.


Types of Intercropping

The degree of spatial and temporal overlap in the two crops can vary somewhat, but both requirements must be met for a cropping system to be an intercrop. Numerous types of intercropping, all of which vary the temporal and spatial mixture to some degree, have been identified (Andrews & Kassam 1976). These are some of the more significant types:

Mixed intercropping, as the name implies, is the most basic form in which the component crops are totally mixed in the available space.

Row cropping involves the component crops arranged in alternate rows. This may also be called alley cropping. A variation of row cropping is strip cropping, where multiple rows (or a strip) of one crop are alternated with multiple rows of another crop.

Multi Harvest Intercropping also uses the practice of sowing a fast growing crop with a slow growing crop, so that the fast growing crop is harvested before the slow growing crop starts to mature. This obviously involves some temporal separation of the two crops.

Further temporal separation is found in relay cropping, where the second crop is sown during the growth (often near the onset of reproductive development or fruiting) of the first crop, so that the first crop is harvested to make room for the full development of the second.

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from http://www.organicagcentre.ca/NewspaperArticles/na_snider_jd.asp
Alberta Organic Grower Earns Outstanding Title

By John Dietz

President of his district Ag Society, Olds College graduate 1990, Alberta's Outstanding Young Farmer of the Year (2003), all apply to Steve Snider of Edberg, Alta.

Add one more characteristic - committed organic grains farmer.

Steve, along with members of his family, operates Little Red Hen Mills (LHRM) near Camrose. Steve has been practicing organic cropping methods since 1986. An active speaker, he enjoys teaching the techniques he's learned. He has actively promoted crop rotation and organic cropping methods in Alberta and in other provinces for many years. He also holds regular tours of Little Red Hen Mills, demonstrating the benefits of organic growing and explaining the crop rotation methods he uses.

Organic crops and seed cleaning are a perfect fit for the Snider family. "We are able to clean grain right up to milling grade, so we've marketed directly to processors. This was critical in the early stages of the organic industry," Steve says. "We sold primarily to California-Washington-Idaho. Most of it still goes there."

Steve's father Robert produced organic wheat flour in the 1970s and has been a pedigreed seed grower since 1967. He'd become ill from a chemical exposure; after that, he avoided using farm chemicals. His experiments with "intercropping" in the 1980s became Steve's key to sustainable organic production.

Intercropping is the technique of growing two crops together on the same field. After harvest, the LRHM uses a screening machine and gravity table to separate the legumes and cereals. Spiral separators, rotary drum separators or scalpers also could do the work.

Initially, the Sniders planned to improve the quality of their seed peas. Intercropped peas supported by cereal straw stayed standing and free of mildew. Stored together, the two seed types buffered the moisture when one was tough. Today, the family has 2,080 acres certified by the OCIA. They cultivate 1,600 acres. The rotation varies, but has roughly 675 acres of organic crops, 500 acres of green manure and 425 acres of hay. Organic wheat and rye stand alone. Other fields are always intercropped, always a legume (lentils, peas or fababeans) with a cereal (oats, barley, buckwheat or triticale). The intercropped legume and cereal need a close match in days to maturity. They also need the strength to survive disease and insect attacks that most growers control with crop protection chemicals.

All this narrows the seeding choices. "Older varieties seem to stand pretty good against disease and insects, but we do need research on which varieties are better suited to our system," he says. His best seed mix is triticale and fabeans. They mature about the same time and are shatter-resistant. Finding the right mix of barley or oats with peas is tricky. Some peas are prone to shattering. The cereal needs to mature before the pods dry and pop open. The Sniders use Radley green peas in a mix with either Derby oats or Bonanza or Klages barley. They also have a shorter-season yellow pea, First-And-Best, they can mix with Klages barley.

Steve uses green manure and organic fertilizer treatments or micronutrients blended with seed to fertilize his crops. Soft rock phosphate, mined and granulated in Idaho, is a key component. Sometimes he coats the seed with an emulsifiable ocean-based product from fish or seaweed. Steve's prepared seeding mixture ends up as a combination of two kinds of seed, an inoculant for the legume, plus micronutrients or an organic fertilizer. He puts it all in the ground with his 30-foot hoe drill in a single pass. "It's not too complicated," he says.

Plowdown issues
Early plowdown of "green manure" crops provides both fertility, and a measure of weed control. Steve's "green manure" is a blend of oats, barley, peas and fababeans. It puts fiber and energy back into the soil. "We put the four crops together to get as much competitive biomass as possible. We get a lot of tonnage per acre to turn under," he explains. He lets the legumes grow long enough to fix nitrogen for the next crop. Cereals add tonnage and boost competitiveness against weeds. They do the plowdown in late July with a 32-foot discer. They work the green manure 4 inches into the soil and disc it once more if required. Formerly 'conventional' land, added to the organic farm a few years ago, is more mellow soil and has more moisture retention. Steve says, "You don't pull up big lumps, and sandier stuff has less tendency to blow. When you do a plowdown every two or three years, you put back a lot of fiber."

Increased fiber counterbalances the moisture loss potential from tillage. Steve says, "Our soil has more fiber, so it holds more moisture."

Plowdown has its best results if there's a weed flush in early May. When that happens, Steve uses a cultivator and rodweeder in late May to kill the weeds. A day or two later, he's seeding down through a couple inches of dry soil. "The cereal will come shooting through and get ahead of the weeds. If the crop is ahead of the weeds by 4 to 5 days in June, it makes a world of difference in your dockage." He admits, "We do rely on having a weed flush before we seed. If it's dry or cold, the weeds aren't flushing. Then we wait and wait. That's hard for anybody."

Weed issues
Extremely dry conditions in 2001 and 2002 challenged all farming techniques in the region. The Sniders had some "extra" weeds, but it wasn't a major concern. Steve said, "They can be knocked back with a plowdown crop. Then, we'll be back to lower dockage." Weeds and neighbors, for the organic grower, can be a flash point. He tells visitors, "You never control weeds as an organic producer. You manage weeds. We strive to raise a crop that will out-compete the weeds. You want a dominant crop population, so the weeds are suppressed." He adds, "There's no excuse for a messy field."

Neighbors and rural officials sometimes see red when they see thistles drifting across the road from an organic field. "You've got to be very diligent," he says. "If you have a weed that's mobile, contain it as best as possible." He believes organic growers should go the extra mile to maintain weeds in the ditches. Regularly mow and tidy the ditches, Steve suggests. That kind of attitude will go miles in good relations, and will eliminate the need for roadside spraying that could be a problem for the organic grower.

Rotation issues
Crop rotations in an organic system can be complex. Steve has experimented once, over the years, with most of the options. The basic system that worked really well through the 1990s was a six-year rotation:


Plowdown
Fall rye
Peas & oats
Plowdown
Wheat
Peas & barley


"This rotation is very stable and seems to work very well for us," he says. Having five or six crops in the bins improves the supply of market opportunities and a measure of financial stability. Recent dry conditions pushed them to move into a 50/50 rotation between crops and plowdown. He says, "It's obviously good for the soil, but the farm's got to pay for itself. At this point, it seems to be holding its own."

Milling grade organic grains provide the highest returns per acre and per bushel. To date, by increasing the plowdown ratio, they're improving both quality and yield. Long term sustainability for the soil base seems well assured by the organic practices.

Sustainability for the family, on the farm, could be another issue. Steve says, "There's a lot of ways of looking at the economics and viability of family farms. I don't think there's one answer." Little Red Hen Mills doesn't produce the crop volume that a conventional family farm does in Alberta. However, it also doesn't have the same expenses. He says, "My risk is lower. My inputs are lower. We use our own seed. Our fertilizer cost is minimal. Our equipment cost is fairly low. Fuel is probably one of our higher inputs per acre." He accepts living with less yield per acre, but also gains substantial premiums for basic organic products, then cleans the products to milling grade for additional value. "None of us work off the farm," Steve adds. "This keeps us all here, and we're making a living."

Source:
Steven Snider
Little Red Hen Mills
New Norway AB
E-mail lrhm@telusplanet.net
Ph 780 855-2164
Cell 780 608-0905
Robert 780 855-2286

John Deitz is a consultant for the Organic Agriculture Centre of Canada. Please send comments or questions by phone to 902-893-7256 or by email to oacc@nsac.ca.