Crop scientists work to improve organic yields.

Crop scientists work to improve organic yields: Researchers at the University of Nebraska, Lincoln last week began to brainstorm ideas to help organic farmers improve yields on crops like corn, soybeans and wheat. Rotating crops is key, but the best patterns for rotation on an organic farm without use of chemical fertilizers and insecticides aren't known, said Liz Sarno. Other challenges include keeping enough nitrogen in fields to naturally fertilize crops. Researchers are experimenting with field covers of such nitrogen-rich plants as Berseem clover, said Jim Brandle, a university professor in shelterbelt ecology. Another hurdle is finding the right kind of equipment to cultivate ground for mechanical weed control. Demand is growing for organic foods as people become more concerned about the use of pesticides, herbicides and fertilizers in conventional farming.