No-Till and Nitrogen Optimize Grain Yields and Environmental Protection

With proper nitrogen fertilization and a no-till production system, Great Plains dryland farmers can grow crops continuously, reduce erosion and improve the soil's ability to store carbon, ARSsoil scientist Ardell Halvorson reported today at the American Chemical Society's national meeting in Washington, D.C.

Typically, farmers in the Great Plains grow rain-fed grain crops like wheat, corn or barley one year and leave the land fallow the next. Or they may have a three-year cycle that includes two crops before fallow. With conventional tillage--which means mechanically tilling the leftover plant material, or crop residue, back into the soil--a fallow period is needed to allow enough water to accumulate in the soil to support the next crop.

But this practice leaves the soil susceptible to wind erosion. Tillage also speeds decomposition of plant material, a process that releases carbon dioxide to the atmosphere.

Researchers have long promoted "no-till," or planting directly into the previous year's residue without tilling the soil, as a method to reduce erosion and make more efficient use of water. More recently, they've also found that no-till enhances the soil's ability to store carbon, which helps mitigate global change by reducing the amount of carbon dioxide that reaches the atmosphere.

Halvorson's work shows that nitrogen may mean the difference between economic success and failure using no-till in the Great Plains. He works at the ARS Soil-Plant-Nutrient Research Unit in Ft. Collins, Colo.

No-till benefits the crop by increasing water held in the soil, allowing farmers to grow crops every year without the fallow period. But nitrogen availability limits grain yields. In several no-till studies lasting from nine to 12 years, Halvorson found that adding sufficient nitrogen fertilizer increased grain yields and improved water use enough to make continuous cropping feasible. The added nitrogen also increased the amount of plant material left as crop residue. Over time, the nitrogen/no-till combination led to increased soil organic carbon and improved soil quality.

ARS is the chief research agency of the U.S. Department of Agriculture.

Scientific contact: Ardell Halvorson, ARS Soil-Plant-Nutrient Research Unit, Ft. Collins, Colo., phone (970) 490-8230, fax (970) 490-8213, [email protected].