Even though Palouse growers have made a significant shift towards minimum tillage or direct seeding of winter wheat, surface residue cover from the legume crop alone is often inadequate for erosion control. Consequently, the wheat crop usually over-winters as small plants and provides little erosion protection. Surface runoff and soil erosion can both cause yield losses in grain legume and winter wheat crops. Water running off the fields is water not stored for grain production. The greatest impact would occur on upper slopes and ridgetops where yields are most limited by available water.
Erosion can reduce current crop yields by loss of plant stands and reduced plant vigor.
Soil loss will also reduce the yields of future crops due to loss of soil fertility, water holding capacity, rooting depth and other soil quality and productivity factors. Some innovative growers in the Palouse are beginning to plant spring legumes with direct spring seeding, with or without minimum fall tillage systems. An important development in direct spring seeding of grain legumes is the recent availability of herbicides that offer weed control without soil incorporation or that are applied post emergence. A 3-year research project by scientists from University of Idaho and Washington State University was initiated in 1996 to assist growers in developing integrated management systems for these production practices. It is an interdisciplinary team project coordinated by Stephen Guy, UI Crop Management Specialist.