DEFOLIATION EFFECTS ON BIOMASS YIELD COMPONENTS OF WINTER WHEAT

Abstract

Short duration, high intensity grazing is often used to maximize production of grazed forage crops. Relatively little information is currently available for this practice on dual purpose cereal crops such as wheat. Components of soft white winter wheat biomass yield were studied during the 1979 and 1980 crop years near Corvallis, Oregon. Treatments were a factorial arrangement of two defoliation times (mid-April and mid-May) and three defoliation intensities (undefoliated and clipped to either an 8-cm or 4-cm stubble). All defoliation regimes reduced grain yields compared to undefoliated controls. However, biomass yields of 8-cm vs. 4-cm treatments were similar within defoliation dates. Grain yields primarily reflected the most recent defoliation event, suggesting that plant phenological stage and/or the length of the regrowth period following defoliation was more important than the intensity of the defoliation event in determining plant yield.Key words: Short duration grazing, grazing wheat