Some production practices influence soil health in a way that impacts both long-run productivity and environmental outcomes such as nutrient run-off and carbon sequestration. Tillage and crop rotations are two such practices.
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 have choices for how they prepare the soil; reduce weed growth; incorporate fertilizer, manure and organic matter into the soil; and seed their crops, including the number of tillage operations and tillage depth. In general, the less the soil is disturbed the more organic matter it retains and the less it erodes. No-till is generally the least intensive form of tillage; no-till operations accounted for an estimated 35 percent of U.S. cropland planted to eight major crops in 2009. The crops--barley, corn, cotton, oats, rice, sorghum, soybeans, and wheat--constituted 94 percent of total U.S. planted acreage in 2009. Furthermore, the use of no-till increased over time for corn, cotton, soybeans, and rice, the crops for which the Agricultural Resource Management Survey (ARMS) data were sufficient to calculate a trend.
No-till adoption varied substantially across crops, however, even for those that have generally similar production practices. For example, land planted to barley had roughly twice the percentage of no-till (28 percent in 2003) as land planted to oats (14 percent in 2005).
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. One indication of how prevalent crop rotations are in U.S. production is how relatively rare it is for farms to continuously produce the same crop from year to year on the same field. For corn, soybean, and wheat, between 84 and 92 percent of acreage involves some sort of rotation.