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CROP ROTATION
by Vyapaka dasa

In our last article entitled Orchestrating Fertility and Waste Management , we spoke about the various benefits crops can provide besides nutrition. They can fulfill varied functions such as a green manure (to replace lost organic matter and/or nitrogen), cover crop, catch crop, break crop or smother crop. How we place them into a planting schedule comprises crop rotation. If one is to have any chance at developing self-sufficiently, crop rotation will play an important role.

In 1990, I helped research a book on the transition to organic agriculture by the Canadian Organic Growers. The name of the book is the Organic Field Crop Handbook. My main contribution was in providing information on crop rotation and the design of a crop rotation work sheet. As a result of this work, I will be borrowing heavily on the Handbook as a source of information for this article. Please note that the information in the handbook was compiled with a Canadian growing season (i.e. Ontario and Quebec) in mind, so many of the following points may need to be adjusted to your own time and circumstance.

Srila Prabhupada was always insistent that our devotional farms concentrate on producing food crops rather than cash cropping. Some of his instructions are listed in the sidebar emphasizing this along with another instruction prohibiting agricultural chemicals. So our first priority must be to grow crops destined to nourish the Deity, the devotees and the cows and animals living on our properties.

However, I could also see the time where, if capable individuals were available, that some cash cropping could be entertained if a mortgage, equipment or community infrastructure (roads, wells, etc.) could be paid for from selling produce produced on the property. This would make even greater sense if further processing of the grains could be undertaken to create employment, add increased value to the raw resource and to gradually eliminate spouses traveling away from their families in an attempt to supply the family's needs. One of the realities of community development is that while the mortgage, housing and infrastructure is left unpaid, then by necessity, we are still linked into the outside cash economy. So these are some considerations that may come to bear during the design of the rotation.

While developing the rotation, there are several other agronomic goals and factors that should be considered for each crop. These include:
1. Value as a food, cash crop or livestock feed.
2. Soil building potential (green manure, nitrogen fixing, etc.).
3. Nutrient conservation, fertility needs (catch crop) and erosion control (cover crop).
4. Weed, disease and pest control ability (break, smother, allelopathic crop, etc.)
5. Demand on labor, equipment and knowledge of the crop.

Each crop should be evaluated as to which role(s) it is required to play and then placed into the correct place(s) in the rotation.

Two things that this article will not be able to cover is tillage practice and calculating the fertility of plowdowns (green manures) and compost/manure applications. I have noticed that some farmers, when plowing with animal draft, have the tendency to work the headlands too often. So our devotional farmers must be aware that over-working the soil, be it on either the headlands or elsewhere, that the soil's structure can be damaged reducing the soil's structure to a powder. This is something that must be avoided. As well, it will be useful to know how much fertility that a plowdown or compost application is replacing. Knowing this in addition to the nutrients in the soil as described by a soil test and then subtracting the crop's nutrient requirements will give one a ball park understanding if fertility is being maintained.

These subjects will have to be left to future articles but please do not minimize their importance. The less the soil can be turned over and worked generally results in healthier soils. During a conference on community development at Prabhupada Village in Sandy Ridge, NC. this spring, Gokula Prabhu from the Australian New Goverdhana project informed us of a plow which does not invert the soil but rather leaves the sod intact and allows one to plant a cereal crop directly into the grass. This is revolutionary in the sense that it provides soil conservation without the heavy use of herbicides that is popular with the conventional no-till method.
moisture users (corn); others require lesser amounts (barley).

Soil Building
Green manures play an important role due to their capability to conserve moisture, control erosion and reduce the leaching of nutrients off the farm. Some techniques that should be considered that will help maintain the soil’s fertility are as follows:

• Ensure a balance of food and cash crops and soil conserving cover crops.
• Deep-rooted crops (sweet clover, alfalfa) should alternate with shallow- rooting crops (cereals) to help keep the soils structure open and assist in drainage.
• Alternate between crops with high­root biomass (rye) and low-root biomes (oats). Pasture grasses with their high-root biomass provide soil organisms, particularly earthworms, with food.
• Diversify the rotation in terms of moisture use  some crops are high moisture users (corn); others require lesser amounts (barley) Allelopathic crops (rye and sunflowers) should be alternated to prevent a build up of their own chemical toxins (allelopathy is the suppression of growth of one plant species by another due to the release of toxic substances, generally root exudates).

Conserving nutrients
The key to successful farming is fertility management. The following are some tips that will help you conserve nutrients, especially nitrogen.

• Avoid leaving the soil bare by planting cover crops and undersowing.
• Plant green manure crops
• To meet all the farms requirements from within the system, nitrogen- fixing crops should alternate with high nitrogen demanding crops.
• Legumes should occur often in the crop rotation. They are an essential part of the crop rotation because of their ability to fix nitrogen.
• Heavy-feeding crops should be followed by medium- or light-feeders (please refer to table below).
• Also include pasture in the crop rotation for its valuable role in recycling nutrients and in soil conservation. To be nutritious and palatable to the cows, a pasture should contain a wide variety of grasses and legumes.
• Do not sell straw off the farm; incorporate residues or use for livestock bedding.

Weed and pest control During the course of researching the Handbook, I spoke with Roger Samson, the Director of Resource Efficient Agriculture Project (REAP) at McGill University. They do on-farm research regarding reduced input and in many instances organic farming practice. He told me that the main concern with farmers, especially organic farmers, was weed control. In this regard crop rotation coupled with a properly designed tillage program, weed populations can be held in check. The following are some suggested techniques:

• Slow-growing crops, which are more susceptible to weed invasions, should follow weed-suppressing crops.
• Alternate between warm-season and cool-season crops so that you alternate your seeding and tillage dates. This means that one year you can eradicate early germinating weeds, and the next year late germinating weeds.
• Include plants that have natural weed germination inhibitors (like rye and sunflowers) in the rotation.
• Include forage legumes in the rotation. They compete well with weeds and choke them out.
• Include row crops that give the opportunity for mechanical weed control
• Avoid too many years of perennial forage in the rotation as this may encourage the growth of perennial weeds.
• If you have a particular problem, like Canada Thistle, adjust the rotation to include a control measure
• Grow mixed hay stands, rye or buckwheat to choke out persistent annual weeds.

In regards to pest and disease control:

• Where risks of disease or soil-born pest problems exist, potential host crops should only occur in the rotation once every four years; break crops should be grown in the intervening years.
• Avoid excessive use of cruciferous green manures, (e.g. oil radish), that encourage certain disease and insect pests.
• Similar crops (e.g. small grains) should be separated by a crop of a different type - a legume or broadleaf crop such as oil radish or buckwheat.

Demands on labor, equipment and knowledge
Srila Prabhupada’s instruction that we develop towards self-sufficiency naturally directs us to planting a wide variety of crops. Often a conventional agriculture focuses on a two or three year rotation of corn, soybeans and wheat. However, if we are to provide our communities with a diverse diet then a wider variety of crops need to be grown.

By growing a wider variety the demands on labor and machinery usually diminish. However, if one is growing field and row crops, then a wide inventory of machinery may be required. In any case, as we move away from a monoculture the variety of crop staggers the planting and harvesting dates allowing better use of equipment and devotees engaged on the farm.

Specific types of crops have various attributes which should be considered when planning the rotation.

Winter cereals:

• In Ontario, the seeding of winter cereals is usually done in September when the soil is frequently drier that in the spring, so there is less chance of soil compaction that with spring cereals.
• Harvest of winter cereals is in July and August or September.
• Winter cereals produce more straw  than spring varieties.
• Winter cereals protect the soil from  erosion over winter.
• Having both winter and spring cereals in the rotation spreads the  workload.
• They are able to compete more  strongly with weeds that are spring varieties.
• When dormancy breaks in early spring, winter cereals can use snow melt for growth.
• An earlier harvest means better  grain quality and better drying conditions to remove kernel moisture.
• Winter cereal yields can be up to 50 per percent higher than spring-sown cereals.
• They demand good drainage and snow cover in cold climates but snow mold can be a problem in snow belts when heavy snow cover lasts more than 90 days.
• In some areas, it may not be possible to grow winter cereals because of winter kill.
• Winter wheat and winter barely are heavy feeders in comparison to spring cereals. Rye and triticale are less demanding.

Spring Cereals

• They can frequently be grown where winter cereals are not grown.
• They grow best when planted early in the spring on fertile, well drained soils.
• They are lighter feeders than winter cereals.
• Oats grow almost as fast as buckwheat and are an excellent smother crops.
• Yields are generally lower than winter cereals.

Row crops (includes corn, soybeans)

• Organic corn can be grown if given a heavy application of compost, or if planted after a legume hay or a one-year red clover stand which will suppress weeds as well as fix nitrogen.
• Row crops are not generally susceptible to the same range of disease problems as cereals and therefore form useful breaks in the rotation between cereals. Note, however, that wheat following corn can be infected by the fusarium fungus.
• Inter-row cultivation provides weed control for the following crop and breaks the weed cycle in grain crops.
• Soybeans can fix up to 150 kg. of N per hectare and leave up to 30 kg! ha available for the following crop
• Corn is difficult to manage during the transition years because if its high nitrogen requirements and the problems it poses for control of weed. However, it is successfully grown by many organic farmers once a stable soil system has been achieved.

Forage Crops (Includes alfalfa, clovers, vetch, grasses)

• Forage crops are effective in restoring soil structure, encouraging earthworm populations and replenishing organic matter.
• The deep tap root of the legumes can penetrate hardpan and the fibrous root systems of the grasses aid in soil aeration.
• Leguminous green manures are essential in providing sufficient nitrogen and organic matter to maintain organic systems.
• Forages act as a main break in the rotation to assist weed, pest and disease control. A two- to three-year stand of alfalfa will control persistent weeds like milkweed and thistle.
• Clovers are prone to certain diseases and insects so it may be necessary to limit their frequency in the rotation.
• Forage crops can be grown for livestock feed, green manure or for seed harvest. It is not advisable to sell hay because large amounts of nutrient will leave the farm system.

Oil seeds and other broadleaf crops (Includes oil radish, canola, flax and buckwheat)

• Oil radish possesses a central tap root which extends well into the subsoil with a large amount of lateral roots which loosen and aerate the soil.
• Oil radish is an extremely fast-growing, green manure crop (10 tons of green matter per acre after only 45 days of growth has been reported).
• It has an ability to absorb nutrient and tie them up for the winter making the nutrient available for the following crop.
• Canola, oil radish and buckwheat are able to make good use of rock phosphate.
• Buckwheat will tolerate poor soils better than other crops.
• Buckwheat is a fast growing, smother crop and is often used specifically to help control weeds.
• Buckwheat is prone to few diseases.
• Volunteers can be a problem if buckwheat is allowed to go to seed before incorporating as a green manure or if ripe seed falls to the ground before harvesting.
• Flax is a good companion crop for underseeded legumes.

Where to Start in the Rotation:
When making the change from conventional to organic farming, the best crops to start the crop rotation are usually pasture, a hay crop or annual legume. Some of the options and other useful guidelines are given below.
 

• It is not a good idea to begin your first crop rotation with corn because it is too nutrient-demanding and delays soil improvement.
• When beginning the transition, apply compost to as many acres as possible, even if it is only a light application. Its value is in its capacity to stimulate biological activity, rather than in the nutrients it supplies.
• A good way to start a crop rotation is to plow down a bay field to a depth of about 10 cm/4 in (summer or fall) and follow with a thorough seedbed preparation. Seeding the field with a green manure crop (rye or buckwheat is recommended.
• If all the fields have been seeded with food and cash crops, underseed with red clover to improve the soil without taking land out of production. Over-winter the clover, incorporate it into the soil in the spring and begin the rotation.
• For a food and cash crop rotation, start with buckwheat; it provides good weed control.
• Seed down a hay crop which will help control weds and build up the soil.
• Choose crops with which you are familiar.

The following is a copy of the Crop Rotation Worksheet.

 
 
 
 

 

Review check-list

Use this short questionnaire as a double-check after you have completed the detailed worksheet.

•  Do deep-rooted crops follow shallow rooted crops?
• Do crops with small root systems alternate between those with large root systems?
• Do nitrogen-fixers alternate with high-N feeders
• Do slow-growing crops follow weed-suppressing crops?
• Have adequate green manure and/or cover crops been included in the rotations to sustain fertility and minimize erosion?
• Have you alternated warm- and cool-season crops to disrupt the weed cycles?
• Have you put breaks between crops that may suffer the same diseases or pests?
• Do the crops allow for effective use of the existing farm machinery and labor?
• Does your rotation meet livestock feed requirements (i.e., protein and energy self-sufficiency)?

NOTE: It may be difficult to arrange a rotation that would answer affirmatively to all the above questions. However, questions that have been answered negatively should be given careful reconsideration as to their importance in the success of the cropping system.

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