A recent study published in Agronomy Journal provides information important to farmers growing oilseed crops. In the study, camelina and safflower were grown in three-year rotations with winter wheat and summer fallow. The study shows that using this rotation may require that no tillage should be done to the soil during the fallow year.

Oilseed crops produce relatively little residue-organic material such as roots that hold the soil together. Even light tillage can disintegrate the soil.

A cooperative study by the USDA-ARS and Washington State University researched the effects of growing oilseed crops-camelina and safflower-on blowing dust emissions. The Columbia Plateau of the Inland Pacific Northwest experiences significant windblown dust from excessively-tilled agricultural lands.

Brenton Sharratt and William Schillinger found that adding camelina or safflower crops into a rotation with winter wheat and summer fallow increased the amount of dust at the end of tillage-based fallow or when wheat is planted. "Farmers will need to protect the soil from wind erosion during the fallow phase after harvest of oilseed crops," says Sharratt.

Why grow oilseed crops, anyway? In an effort to help the United States be more energy-secure, legislation was passed in 2007 to create the "Energy Independence and Security Act." This mandates the use of biofuels by the transportation industry. In addition, the Act specifies a certain amount of the biofuel must come from "non-cornstarch feedstock."

Thus, the USDA created a roadmap to help meet this energy need. The roadmap requires various regions of the US to produce certain amounts of the biofuels. Additionally, the State of Washington has a law mandating that five percent of diesel fuel sold must be biodiesel.

In the USDA plan, the northwest United States is expected to produce 4.6% of the advanced biofuels to meet the goals by 2022. That means that the agriculture industry will need to change what it is planting. The Inland Pacific Northwest is the major production region of soft white wheat in the United States with wheat grown principally on semi-arid lands. However, the new mandate is making the northwest look at which crops will be best to grow to meet the biofuel demand.

The Pacific Northwest is a low-precipitation region. The typical crop rotation there is winter wheat-summer fallow. Thus, one crop is usually grown every other year. The fallow period allows the soil to store moisture from rains and snows over the winter. This stored moisture is critical for seed germination and emergence of winter wheat.

Winter wheat is currently the money crop for farmers in the region. Wheat has been produced with great success for 135 years in the northwest. Fallow still is practiced in the drier areas. Intensifying the rotation with a three-year rotation of wheat-oilseed-fallow is one strategy to produce more on the same land. The additional benefit of intensifying the rotation is to reduce dust emissions as a consequence of less time the land is in fallow.

Farmers in the Pacific Northwest are already taking measures to reduce the amount of dust created when tilling their lands. A style of tillage, called the "undercutter method" has been one of the best management practices in the area. The purpose of tilling the soil is to help preserve fallow moisture during the summer months.

The soil in the Columbia Plateau is particularly susceptible to wind erosion due to the small particle size of the soil. Undercutter tillage does not turn over the soil like other tillage methods. Thus, it leaves crop residue on the surface to help protect the soil from wind erosion.

The researchers measured dust particles, or wind erosion, using a portable wind tunnel. This tunnel was 24 feet long, 4 feet tall and 3 feet wide. A fan was used to generate conditions like those naturally occurring in the fields. Their findings show that adding camelina or safflower into the crop rotation increased the chances of wind erosion late in the fallow cycle. Thus, their caution to farmers is to use techniques to preserve the soil.

"Even the undercutter method is too much tillage for fallow after oilseeds in the dry region," say the researchers. "No-till fallow, or planting another crop without a fallow year, is the answer for controlling blowing dust. "