Chapter 17

Soil Management for Field Crops

Crop Rotations

Rotating crops (i.e., growing different kinds of crops in recurrent succession on the same land) mimic natural systems by minimizing nutrient loss, providing ground cover, building organic matter, and adding organic matter for the benefit of the next crop. Thus, in the strictest sense, crop rotation is more than just changing crops from year to year based on current economic situations. Rather, it is a long-term plan for soil and farm management. At the farm management level, crop rotations are used to diversify income, spread labor requirements throughout the year, spread the crop loss risk associated with weather and pests across two or more crops, and increase crop productivity by enhancing soil quality. Yields of crops grown in rotations are typically 10 percent higher than those of crops grown in monoculture in normal growing seasons and as much as 25 percent higher in droughty growing seasons. One basic rule of crop rotation is that a crop should not follow itself. In terms of soil management, crop rotations are used to:

Crop Rotation Effect on Soil Properties

The extent that soil is affected by crop rotation depends on diversity of crop species grown in the rotation and the length of the rotation. A well-planned rotation will include crops that address the specific needs of the soil in the field or farm. Because there are so many possible rotations with many different crops and cropping practices, it is impossible to summarize all possible ways soil is affected. Rotations that include cash crops such high-residue crops, such as corn and small grains, then in low-residue continuous cotton are important in building and maintaining soil organic matter.

Crop Rotations and Water Use

Crop rotations can be used to manage water excesses and shortages. The relationship between water and rotations is especially important given the wide range of climate conditions observed over the past several years. Crop rotations provide protection from summer droughts by distributing the critical water use periods across the growing season. Typically, corn, wheat, and soybeans use different amounts of water and have different critical periods.

Crop Rotation Systems

A crop rotation system is the sum total of all crops and the practices used to grow crops on a field or farm over a 3-to-5-year cycle. Some of the more common crop rotations for field crops with well-proven track records are discussed below.

Corn-Soybean Rotation

The Midwestern United States is one of the world’s most fertile and productive farming regions, but it is a landscape dominated by just two crops. Across the 12 states of the Corn Belt, corn and soybeans account for 70 percent of the planted acreage.

Corn/Soybean/Wheat Rotation

Including wheat will break pest cycles and reduce weed problems that develop over time. Wheat following soybeans is an excellent sequence. Earlier maturing soybeans and no-tilling wheat into bean stubble provides a good disease-free seedling environment for wheat. Consider using a stacked rotation (corn, corn, soybeans, soybeans, wheat, wheat). The benefit of a stacked rotation is that the selection pressure is reduced by increasing the length of time between crops.

Corn/ Soybean/ Winter Wheat/Red Clover Rotation

Red clover can be an excellent green manure that fixes nitrogen, suppresses weeds, and increases corn yields. As a slow-growing cool-season legume, it is suitable to undersowing into winter small grains in early spring.

Corn-Hay Rotation

A corn/hay rotation is common on many dairy and beef farms. Corn usually follows an alfalfa-grass forage mix to maximize residual nitrogen and benefit from improved seedbed structure and reduced pest pressures. This rotation is most successful when hay rotations are relatively short (i.e., three to four years), because few corn fields on the farm will be more than one or two years away from a perennial forage crop.

Corn-Alfalfa Rotation

Corn often is planted as the first crop following alfalfa. Due to high water use by alfalfa relative to other crops, soil moisture following alfalfa can be limiting in areas of low precipitation or low soil water-holding capacity. This should be a consideration for deciding whether and when to plant corn.

General Principles for Crop Rotation

When implementing a crop rotation consider the following sustainable soil management principles:

Click on the following topics for more information on soil management for field crops.