Crop rotation is the process of planting a different crop after each previous crop, which allows the different plants to take advantage of nutrients the previous plants didn’t use, and to put different nutrients into the soil to avoid depletion of overall nutrients. For example, corn uses nitrogen; soybeans replace it. Following corn with soybeans avoids nitrogen depletion.
Crop rotation dates back to Roman times. Farmers in those days began rotations to replenish the land instead of using up its fertility and abandoning the field.
A rotation should be planned so that you have the greatest possible value of salable or usable crop material during a period of years. When planning a rotation, also consider labor needs and soil fertility. Ideally, a rotation will help spread out your labor needs, because you have a diversity of crops ready to harvest at different times of the year.
Crops are divided into three classes: grain crops, like wheat and barley; grass crops, including sods and legumes used for pasture/hay; and cultivated crops, like corn and soybeans. You can substitute crops within types, depending on weather conditions and year. For instance, you can plant barley instead of wheat; both are small grains. Ideally, farm fields would be square, but this often does not happen in real life, so just try to keep plots all the same size — that is, if you plant 10 acres of corn, follow it with a full 10 acres of soybeans, then 10 acres of hay, and so on.
Advantages of Rotation
There are many advantages to crop rotation. The biggest one is building and maintaining organic matter and putting nitrogen back in your soil by plowing under immature forage crops, primarily legumes. (Legumes are plants that fix nitrogen in the soil.) Crop rotation lets you grow a soil crop or legume crop on all the fields of your farm.
Here are some other advantages:
• Rotations of different crops provide varying root systems, some deep, some shallow, which bring different crop nutrients to the plow layer for use by the next planting.
• Rotations improve drainage tilth and water-holding capacity of the soil, which also reduces erosion.
• By alternating crops on the same fields, you use a natural method of breaking up insect pest and disease cycles, and this also helps in eliminating weed species.
• Rotation hosts beneficial microbiological life, which discourages disease; improves microbiological activity, which helps plants absorb nutrients better; and creates an inhospitable soil environment for many soil-borne diseases.
• By rotating crops, a farmer’s labor load is spread throughout the season, making for more timely operations.
• Rotation or diversification of your crops provides protection against total crop and economic failure, and provides year-round distribution of labor.
• Rotations cut costs and time by reducing purchased fertilizer and allowing easier tillage because of improved tilth.
• On the average, rotating your crops will give you a 10 per- cent increase in yields; continual planting of the same crop results in mineral depletion. Crop rotation allows you to make money while you build your soil.
Seven Advantages of Crop Rotation
- Keeps soil in suitable physical condition
- Helps maintain the supply of organic matter and nitrogen in the soil
- Is a practical means of using farm manure
- Keeps soil occupied with crops
- Changes location of feeding range roots
- Counteracts possible development of toxic substances
- Improves crop quality
From Clyde E. Leighty, “Soils and Men,” USDA Yearbook of Agriculture, 1938
(Washington, DC: U.S. Department of Agriculture, 1938), 410.
Rotation can be either short term or long term. A short-term rotation will take place in 1 year or less. An example is fall-planted wheat overseeded in spring with red clover. To protect the wheat, the clover should be overseeded on a snow cover or on frozen ground, preferably both. This can be done by hand, by powered seeders mounted on tractors, pickup trucks, or all-terrain vehicles, and even by plane! After the grain is harvested in July, the clover grows through the wheat stubble and can be grazed in the fall or incorporated by plowing or disking before another fall grain crop is planted
Another short-term rotation might be rye and hairy vetch seeded in standing corn. After the corn is picked, the rye and vetch grow through the winter and are then plowed under in the spring for a green-manure crop, after which corn, beans, or milo may be planted. A short rotation for vegetables might be broccoli followed by buckwheat, then perhaps rye or turnips.
Minor rotations are another type of short-term rotation. (Both major and minor rotations can be used on the same farm.) A minor rotation is when a small area is set aside for a short-term use — a truck garden, a hog pasture, a lambing area, for example. The minor rotation can be part of the major rotation, or it can be temporarily or permanently set aside and fenced. A more permanent setup of a minor rotation allows you to add feeding and watering systems.
An example of a minor rotation might be hog pasture, potatoes, then truck garden or alfalfa. The hogs turn up the soil for potato planting and contribute manure to the soil fertility, as does a legume like alfalfa. A late summer/fall garden of crops such as beets, cabbage, collards, lettuce, and spinach will allow you some late sales, along with extra greens at the table.
Factors in the Maintenance of Soil Fertility
- Cover crop
- Crop residues
- Crop rotation
- Farm manures
- Organic matter
From Clyde E. Leighty, “Soils and Men,” USDA Yearbook of Agriculture, 1938
(Washington, DC: U.S. Department of Agriculture, 1938), 409.
Long-Term Crop Rotations
Long-term rotations are usually 2 to 5 years. They are more complicated than short-term rotations, but usually not more difficult. They often include hay and sod crops, which are utilized by livestock. A popular eighteenth- and nineteenth-century rotation was the Norfolk rotation: root crop/barley/legume/wheat. The legume allowed introduction of livestock such as sheep or cattle into the rotation, by using the legume for grazing or hay.
Some common 3-year rotations are corn/rye/clover or corn/barley/clover. An example of a 5-year rotation is:
A common 5-year rotation in the southern United States is given above (left), with a variation at right.
Planning a Rotation
Every farm has its own set of management and climatic constraints to deal with, but there are some basic rules of thumb to rotations, as mentioned by Nicolas Lampkin in Organic Farming. The following ideas are adapted from his rotation designs for England, but are applied to circumstances in the United States:
• Alternate deep-rooted plants (e.g., corn) with shallow-rooted plants (e.g., cabbage) to improve soil structure and thus drainage.
• Alternate between plants having a high biomass of roots (legumes such as red clover and orchard grass) with crops with a low biomass root system, like corn and soy- beans.
• Nitrogen-fixing crops like soybeans should be followed by nitrogen-using crops like corn.
• Keep the soil covered with crops as much of the time as possible to prevent erosion and reduce weeds (see box).
• Some crops grow extremely fast, like sun hemp, buck-wheat, radishes, and corn. They should be alternated with crops that grow slowly, such as winter wheat and red clover. Slow-growing crops are more susceptible to weed pressure and should follow weed-suppressing crops like winter rye, which has an alleopathic effect, that is, an ability to suppress weed germination and growth.
• Alternate from leaf to straw crops to help with weed suppression. Mechanical cultivation reduces weeds in row crops, while straw crops shade out and steal nutrients and water from weeds, thereby stunting the weeds’ growth.
• Alternate between fall and spring plantings of crops. This spreads out your workload, reduces weather risk, and helps suppress weeds that germinate at different times of the year.
• Balance your rotation between the cash and non-immediate cash crops, because, as I’ve said before, it has to be profitable to be sustainable. This system makes it more profitable because it spreads risk and allows for cash crops (corn, wheat) and crops that build the soil (legumes, grasses, cover crops).
Keep it Covered
I sow rye and hairy vetch in the standing corn in August. When the corn is harvested, there is a ground cover until spring plowing. The soil is uncovered only about 30 days in the spring after the corn is planted and between then and when it is about knee-high in mid-June. The corn planted in mid-May will be shading out weeds, slowing rainfall with its leaves, and holding the soil with its roots. The rye that was plowed under just before planting the corn sops up any leftover nitrogen from the previous year’s crop and makes it available to the next crop. The hairy vetch, a legume, puts up to 100 pounds of nitrogen back into the soil. The rye and vetch together make a huge amount of biomass to turn under, improving the soil tilth and increasing microbiological activity of the soils.
More from Making Your Small Farm Profitable:
Excerpted from Making Your Small Farm Profitable (c) Ron Macher, line drawings by Chuck Galey, used with permission from Storey Publishing.