HERMISTON - The trouble with center pivot irrigation systems is that they water a circular area, while most land is parceled out in squares. You don't have to remember much geometry to realize there are going to be some unirrigated corners.

But researchers at Oregon State University's Hermiston Agricultural Research and Extension Center are testing a variety of grasses and forages to cover problem areas such as these.

"These grasses are not just for farmers with irrigation pivots," said Jeffrey McMorran, an OSU Extension agent and agronomist. "They are applicable for anyone who has a 'back forty' that they don't want to blow away or become overrun with weeds."

Last fall, researchers planted trial patches of about 150 different species of grass and broadleaf forages. This spring it was found that Piute orchard grass, tall fescue, wild oats, tetraploid perennial ryegrass, covar sheep fescue and black mountain cereal rye are the best candidates for this job. Application rates should be about 15 pounds of pure live seed per acre, with plantings done no later than March 15.

"Typically, in this part of the Columbia Basin Russian thistle and puncturevine take over any disturbed land," McMorran said. "These weeds are generally not a problem on uncultivated lands such as native grasslands, but they are a big problem in places where the earth has been disturbed and no crops are growing, such as between pivots or in large backyards."

"Ideally you'd rather have something that will hold the soil, require little or no watering, out-compete the weeds and look nice," he said. "If it can provide food for birds and doesn't need to be mowed, all the better."