Soil Tillage and Crop Rotation
Tillage and crop rotations are production practices that influence soil health in ways that impact both long run productivity and environmental outcomes, such as nutrient run-off and carbon sequestration. These practices can also be adjusted in response to evolving weather and climate patterns in farmers' production environments.
Tillage—turning the soil to control for weeds and pests and to prepare for seeding—has long been part of crop farming. However, intensive soil tillage can increase the likelihood of soil erosion, nutrient runoff into nearby waterways, and the release of greenhouse gases into the atmosphere. A reduction in how often or how intensively cropland is tilled enables the soil to retain more organic matter, which leaves the soil less susceptible to wind and water erosion and helps store, or "sequester," carbon. Farmers' choices about soil preparation, including tillage depth and the number of tillage operations, can reduce weed growth, improve nutrient management, and influence crop seeding. In general, less disturbance of soil can lead to more organic matter and lower potential for soil erosion and compaction. No-till is generally the least intensive form of tillage, while conventional tillage is the most intensive form of tillage. Conservation tillage, in which at least 30 percent of plant residue remains on the field following harvest, is less intensive than conventional tillage.
Crop rotations are planned sequences of crops over time on the same field. Rotating crops provides productivity benefits by improving soil nutrient levels and breaking crop pest cycles. Farmers may also choose to rotate crops in order to reduce their production risk through diversification or to manage scarce resources, such as labor, during planting and harvesting timing.
- Conservation practices vary by crop and region. The ERS report, Conservation-Practice Adoption Rates Vary Widely by Crop and Region (EIB-147, December 2015), analyzed national and regional adoption of no-till and strip-till planting systems, cover-crop use, and nitrogen-fertilizer application rates/timing/methods. U.S. farmers' adoption of these practices varies widely by crop and region. Many farmers are "partial" adopters, adopting these conservation practices on some but not all acres of their farm. Roughly 40 percent of combined acreage of corn, soybean, wheat, and cotton were in no-till/ strip-till in 2010-11, with adoption rates higher for some crops (e.g., soybeans) and some regions. Cover crops were in use on less than 2 percent of total cropland (for all crops) during 2010-11 (6.8 million acres), with adoption rates higher in some regions.
- Recent trends in multi-cropping. Over the last decade, growing demand for agricultural commodities—for both food and fuel—has increased the incentives for farm operators to increase production. Double-cropping has drawn interest as a method to intensify production without expanding acreage. The ERS report, Multi-Cropping Practices: Recent Trends in Double-Cropping (EIB-125, May 2014), developed a baseline analysis of U.S. double-cropping patterns from 1999 to 2012 and briefly explored factors that may influence farmers' double-cropping decisions. Viewed as shares of each region's total cropland, double cropping was most common in the Northeast, Southeast, and Southwest regions. Changing commodity prices are likely one factor in the decision to double crop.
- Conservation programs and drought risk adapting. The ERS report, The Role of Conservation Programs in Drought Risk Adaptation (ERR-148, April 2013), evaluated the extent to which farms facing higher levels of drought risk are more likely to participate in conservation programs, and found a strong link between drought risk and program participation. Crop farms facing higher drought risk were more likely to be enrolled in EQIP contracts with conservation tillage practices. And crop producers who utilize conservation tillage were often able to improve the capture and storage of soil moisture, which provides their crops an important buffer against drought impacts.