ESTIMATION OF CROP YIELD LOSS DUE TO INTERFERENCE BY MULTIPLE WEED SPECIES

Previous efforts to model crop yield loss from multiple weed species c onstructed competitive indices based on yield loss from individual wee d species. Our model uses a multispecies-modification of Cousens' rect angular hyperbolic yield function to estimate a nonlinear competitive index for weed-crop interference. Results from 13 Minnesota and Wiscon sin data sets provide measures of the relative competitiveness of mixe d green and yellow foxtails, common lambsquarters, redroot pigweed, ve lvetleaf, and several other weed species. Competition coefficient esti mates are stable over years, but not locations.