Good rotations are the key to creating and managing a viable zero till program. Rotations influence every aspect of a zero till system.

Zero till catches and stores more soil moisture. This enables, and may actually require, farmers to diversify into more profitable rotations. These rotations can be optimized by discovering which crop sequence best suits individual environments, labour force, size of farm, attitudes to risk and other economic, social and agronomic factors.

Understanding the intensity and diversity of different rotations is a solid platform for determining which rotations might best suit which environment and farmer.

THE SYSTEMS APPROACH

Designing a proper crop rotation for no-till is both an art and a science. A systems approach to crop sequences is needed because agronomic, economic and engineering factors will overlap.

Many factors must be considered in the process of planning a proper crop rotation. Among them are crop water use patterns, historic rainfall patterns, snow catch ability, disease organisms, insect cycles, phytotoxic effects of residue, weed control problems, herbicide rotation, profit potential, equipment needs, optimum row widths, seeding and harvesting dates, workload spread, individual attitudes and access to markets.

Using successful crop rotations requires good management skills. In any environment there is a range of rotations that give an appropriate balance of risk and profitability. This range varies according to the amount of tillage used. In any environment, good crop rotations effectively catch and use water by converting it into the most economic gain.

The best no-till rotations differ greatly from those used in tillage-based systems.1 In most of the northern plains, zero tillage saves enough moisture to allow rotations not possible with conventional tillage. However, in some very dry regions, a combination of herbicides and reduced tillage might be more cost effective than zero till alone in a wheat: fallow rotation.2

There are a few concepts to consider in designing a proper crop rotation for your farm, particularly cropping intensity and crop diversity. (Editor's note: these concepts are still quite new and are yet to be tested extensively but we believe they help explain what many zero tillers have experienced.)

USE APPROPRIATE INTENSITY

Rotation intensity is the level of demand for water created by the rotation. Growing high water using crops will increase intensity. The level of intensity should match the water supply. Therefore, zero till rotations should be more intense than conventional till rotations.

Producers in dry areas should strive for a mix of high and low water use crops. In less arid areas more high water use crops should be adopted. Soils with high water holding capacity support greater intensity than coarse soils. If fields are consistently too wet, then the current rotation lacks intensity. If fields are too dry, intensity is too high.

Failure to use the extra water in a no-till soil increases weeds and diseases and lowers profits.

Several generations of experience in an area have probably found the appropriate level of intensity for tillage-based systems. This is not so with the newer zero tillage systems. By using common conventional till rotations as a starting point, rotation intensity can be calculated by using Table 1.3

Rotation intensity can be increased by growing crops that use more water or adding crops where fallow currently exists. For example, a wheat-fallow rotation could become wheat-corn-fallow or wheat-wheat-lentil.

High water use crops like corn, alfalfa and sunflower increase cropping intensity. The practice of cover cropping also increases intensity. This involves broadcast seeding a forage legume such as sweet clover into a ripening wheat crop. The legume uses water and competes with weeds until it is sprayed out the following spring.

Adopting zero tillage typically increases crop intensity capacity by 20-50%. However, increasing intensity by moving from fallow to continuous zero tilled wheat will increase weeds, diseases and insects. This could also require more labour at peak times and require larger equipment. As shown in Table 3 of the Economics section, this approach reduces profits.

In developing rotation intensity, risk must be considered. In a dry year, wheat in a wheat-corn-fallow rotation would yield better than in a continuous wheat rotation. Yet according to Table 1 both rotations have an intensity of 1.

Adding intensity without increasing crop diversity can lead to management problems. So, to complete the job of rotation planning, crop diversity should also be assessed.

USE ADEQUATE DIVERSITY

Crop rotation diversity depends on how many types of crops are used. More crop types means more diversity! Diversity can spread risk, allow varied herbicide rotations to manage weed populations, reduce plant diseases, manage workloads and create good seedbeds for subsequent crops. As managing no-till rotations advances, more acres can be farmed with smaller equipment.

Crop characteristics, listed in Table 2, are helpful when planning balanced rotations.3 A potential limitation to some rotations could be a lack of approved herbicides. State and provincial weed control guides are available to determine this.

There are four types of plants available as crops that can be grown in rotation:

• cool season grasses
• warm season grasses
• cool season broadleafs
• warm season broadleafs

Different plant types will have different growth and maturity habits. These traits will affect seeding and harvest periods, pest susceptibilities, and water use capacities. These help determine the intensity and diversity of the rotation.

Crops of the same type have similar pests and similar water and heat needs. However, both cool and warm broadleaf crops have common diseases.

Cool season crops, like wheat and canola, prefer short growing seasons and cool temperatures. In northern areas, more warm season grass options are required to improve diversity. Warm season crops, like corn and soybean, need more heat. In southern parts, the option of a cool season broadleaf crop is needed.

GETTING THE RIGHT MIX

Planning rotations is made easier when using crop types as a guide. However, even using different species within a crop type, like wheat, oats or barley, can add useful diversity to a rotation.

Specific crops can be selected to fit particular conditions. For example, lentils and peas are both cool season broadleafs but lentils are better in drier areas. Winter and spring wheat are both cool season grasses but differ in their seeding and harvest dates.

It could be useful to compare the diversity of different crop rotations by creating a diversity index (See reference #4). Briefly, rotation diversity increases according to:

• the years separating the same crop type
• the presence of both grasses and broadleaf crops
• the presence of both spring and fall sown crops
• the presence of warm and cool season crops

Diversity decreases if crops must be seeded and/or harvested during the same time period.

ECONOMICS

Crop rotations can be viewed at two levels - across the whole farm and on individual fields. This is important because substituting crops changes the level of economic risk of the rotation while the risk of growing each crop depends on its place in the rotation.

Above all, diversity should improve profitability. Diverse rotations will be most profitable only if they have proper water use intensity and include adapted crop types.

Estimations of total returns expected for a given rotation should be compared for wet and dry years; government programs; and low, medium and high market prices.

Crops can be selected which best fit current economic conditions. Changes in economic, agronomic, engineering or political factors may force more changes in the future.

To make the most economic use of farm machinery and labour resources which were formerly used in doing tillage, they must be redirected, not left idle. Cutting the number of tractor hours by 50% doubles the fixed costs associated with each of those hours. Growing more types of crops will allow the machine to be used more efficiently in a zero tillage system.

TWO CROP-TYPE ROTATIONS

In the northern plains these rotations combine a cool season grass with a cool season broadleaf crop. In warmer areas a warm season grass is followed by a warm season broadleaf. Here are some examples of two crop-type rotations in order of increasing diversity.

• Wheat-canola
• Corn-soybean
• Winter wheat-canola
• Barley-winter wheat-sunflower

As shown in Table 3 of the Economics section, two crop-type rotations have improved yields and lowered machinery costs for early no-till farmers.

Simple two crop-type rotations work for a while, but over time, problems with weeds, insects and diseases can develop. These rotations can be intense enough with proper crop choices but they lack diversity.

A crop pest is rarely eliminated in a single year. With only a one year break between the same crop type, and no control applied in alternate years, surviving pests may gradually build up. At the same time, other pests invade because they are adapted to the window of opportunity offered in narrow rotations. Two crop-type rotations may also mean poor workload spreading. This can result in increased machinery and labour costs per acre and limit the number of acres a family can farm.

Many no-tillers face the challenge of managing two crop-type rotations more effectively. Strategies for avoiding the introduction and buildup of pests are developed in this manual in the following components on weeds, diseases and forage crops.

Diversity can play a role in managing two crop-type rotations. For example, substituting a fall sown cereal such as winter wheat for a spring crop is an easy way to improve diversity.

For good crop establishment and overwintering, winter wheat should be seeded by recommended seeding dates. Potential conflicts with harvesting other crops should be considered when planning rotations with winter wheat.

A winter wheat-canola rotation will have better workload spread than spring wheat-canola. Winter wheat competes better with wild oats but used too frequently, it will invite foxtail barley problems. Canola is usually harvested in time to get the winter wheat seeded. In some areas, barley-winter wheat-canola improves the chances of timely winter wheat seeding while keeping the profit potential of canola. This rotation is slightly more diverse but has the same intensity as winter wheat-canola.

Barley-winter wheat-sunflower increases intensity and spreads harvesting. Spring wheat before winter wheat has greater potential in dry areas where disease carryover to the winter wheat is less. Two cereal crops between either sunflower or canola improves the control of sclerotinia and breaks broadleaf weed cycles.

The value of flax in no-till rotations is often underestimated. Flax can substitute for a cool season grass or broadleaf. It breaks disease, insect and grassy weed cycles in rotations dominated by grass-type crops. Flax-canola-winter wheat or flax-sunflower-spring wheat are good options when cereal prices are low. Although flax catches snow well, in short season areas, it is often harvested too late for seeding winter wheat. Flax must be planted shallow (1-2 cm;-1/2 in).

Cool season legumes like peas and lentils are well established as no-till crops. Diversity is increased by substituting field beans in the legume year. Field beans are seeded in late May. The later burndown adds diversity to weed management. Field beans are a row crop which have been adapted to seeding on narrow rows with conventional no-till seeders. However, no-till row planters offer more precise seed placement. Field beans should follow a cereal or flax. Crop quality is very important in the marketplace. Harvesting must avoid cracking or soiling the beans. New varieties of beans are more upright and are therefore better suited to swathing.

Crops such as alfalfa or perennial grass provide an excellent opportunity to increase diversity and intensity particularly in short growing seasons. Further diversity is gained by including annual crops for use as forage, flexible forage/grain or green fallow. Producers with livestock find it less difficult to diversify rotations.

THREE CROP-TYPE ROTATIONS

These rotations combine a cool season grass, a warm season grass and a cool or warm season broadleaf. Because they contain a warm season grass, three crop-type rotations have been limited to southern areas of the northern plains.

Three crop-type rotations could help solve many of the problems now appearing in mature no-till operations. As crop-types increase, so do management options. This option requires more attention from researchers.

Here are some examples of 3 crop-type rotations in order of increasing diversity.

• Wheat-canola-fallow
• Wheat-corn-canola
• Winter wheat-sunflower-millet
• Wheat -winter wheat-canola-millet
• Barley -w. wheat-corn-sunflower

Three crop-type rotations can vary in intensity from 1.0 (winter wheat-corn-fallow) to 1.67 (spring wheat-corn-sunflower). They can be made up of 75% cool season and 25% warm season species - reflecting the mix of plant types in natural vegetation in the northern plains.

Using a warm season grass crop like corn or millet breaks weed and disease cycles of both cool season grass and broadleaf crops. Unfortunately, few varieties of corn are available for areas with less than 2500 corn heat units. Research should emphasize the development of corn genetics and herbicide options for the northern plains.

Both winter and spring wheat can be included to spread the workload and provide a two season break between the other crop types. For example, in spring wheat - winter wheat - corn - pea, the risk of disease in the spring wheat, pea and corn is low. Disease pressure in the winter wheat may be high, but it can escape yield loss if it matures early enough.

The pea segment benefits from the three years between broadleafs. Peas could be substituted with sunflower, canola, or field bean. Sunflower following corn is risky in dry areas but this greater intensity may fit in more humid zones. Peas, canola and beans limit the use of atrazine in the corn, causing yield losses. Millet would be a good alternative since it is tolerant to atrazine. New corn herbicides belong to the sulfonylurea family which may also carry over to the next year.

Another alternative for northern areas is to substitute sunflower for corn. Then to avoid back-to-back broadleafs, substitute millet for peas. Thus, the rotation becomes spring wheat-winter wheat-sunflower-millet. The late seeded millet helps control weeds in the cool season grasses. Likewise, the spring wheat-winter wheat years provide sanitation for the sunflower and millet.

Crops and sanitation can be managed effectively with three crop-type rotations. Most seeds from weeds which cannot be controlled in a given crop will germinate within 2 years. During this time, crop types are grown which will allow chemical control of these weeds. When the original crop is grown again with no chemical control, the problem weed population is greatly reduced. This principle is not applicable in non-diverse rotations using tillage. Even some high disturbance 'zero till' systems will move dormant seeds to the surface where they can germinate.

Clearly, many different crop sequences are possible. Personal attitudes toward risk will dictate which one to choose but it is also clear that rotations require the development of warm season grass and cool season broadleaf crops for the northern plains.

ECONOMICS AGAIN!

Crop rotation is the best way to manage risk and improve efficiency. On each farm, diversity and intensity need to be balanced to achieve the desired level of risk and return. High intensity with low diversity (wheat-field bean) offers high risk and potentially high returns until major problems develop. Moderately intense, highly diverse rotations such as spring wheat-corn-canola-winter wheat-sunflower or spring wheat-corn-sunflower are less risky and return less gross per acre. They can spread workload and fixed costs, reduce price and weather risk and reduce weed, disease and insect problems. As a result, these rotations can be profitable. Low intensity with high diversity (winter wheat-millet-canola, winter wheat-corn-oat greenfeed) have lower risk in dry years but less gross returns in good years.

Low intensity with low diversity rotations like wheat-canola, wheat-fallow or continuous wheat have little future in no-till. They have high fixed costs per acre, higher risk and lower gross return.

Crop rotation will depend on a producer's personality and that of the banker, landlord and spouse. Ultimately, though, the future of no-till requires increased emphasis on crop rotation.

An example of the systems approach

The systems approach is complex, but is an important and necessary part of "advancing the art" of no-till. The process is demonstrated in the following example from the northern mixed grass prairie area.

• In this area, drought is more common than excess water
• Spreading the workload is useful for economic, labour and family reasons.
• The rotation is: Winter wheat-millet-sunflower-wheat-corn-canola. Workload is spread over four seeding and harvesting windows.
• A two year interval between crop types gives control of wheat root diseases and four crop types allow a good herbicide rotation.
• A short season corn hybrid is used and millet is grown for birdseed.

The spring wheat can be seeded very early since sunflower stubble is the first to be ready in the spring. However, following sunflower with wheat may be risky in a dry cycle so a cool season oilseed like canola or flax could be substituted for sunflowers. In this case, winter wheat should be substituted for spring wheat since using spring wheat would compromise workload spreading by requiring seeding three spring crops prior to corn planting. Depending on markets, pests, forecasts, and input prices, peas, lentils, or edible beans can substitute for canola. This would force a change from winter to spring wheat because of potentially poor winter hardiness when sown into the low residues from annual legumes. Again, workload spread is reduced but can be partially regained by substituting canola-winter wheat for sunflower-spring wheat. The recovery in workload spread is only partial because sunflowers would normally be harvested well after the other crops.

Growing corn and sunflowers would require modifying a drill or obtaining a row crop planter. A corn head or all-crop head would be needed for harvest. These higher fixed costs may be offset by savings in other areas and by the increased profit potential from a diverse array of crops. Where the risk is too great to justify the equipment expense, millet and safflower can substitute for corn and sunflower respectively. Similarly, in warmer broadleaf areas, sorghum can replace corn. The risk is greatest in short season areas where rotations may shift to alfalfa, sweet clover cover crops or grass to maintain appropriate intensity.

Prepared from information provided by:

Dwayne Beck, Dakota Lakes Research Centre

P.O. Box 2, Pierre, South Dakota 57501

Telephone (605) 224-6357 Fax (605) 224-0845

References:

1. Dhuyvetter KC et al (1996). J Prod. Agric. 9:216
2. Rourke D and Hargrave (1995). Rpt Cons. Till Prod. Centre, Minto, MB
3. Beck DL and Doerr (1992). No-till Guidelines. South Dakota State U

Beck DL (1993) Proc. MB-ND Zero Till Farmers Workshp