POTASSIUM NUTRITION OF PERENNIAL RYEGRASS

J.M. Hart, D.A. Horneck, M.E. Mellbye, G.A. Gingrich,
W.C. Young and T.B. Silberstein
Oregon State University, Department of Crop & Soil Science
Corvallis, OR 97331, USA

Perennial ryegrass is grown for turf or forage seed on broad range of soil and landscape positions in western Oregon. Between two-thirds and three-quarters of the perennial ryegrass acreage has straw baled and removed. Baling and removing straw removes five to ten times more potassium than removing only seed. Unlike seed, the potassium concentration of perennial ryegrass straw increases as soil test potassium increases. The straw potassium concentration increase is not linear, it increases rapidly as soil test increases, and then becomes constant, about 1.5%, even though soil test potassium increases. To compensate for potassium removed in baled straw, recommendations for potassium fertilizer application vary with straw management.