To quantify defoliation effects resulting from several grazing periods with cattle on white oat (Avena sativa L.) an experiment was run at Experimental Station of Fundação Agrária de Pesquisa Agropecuária in Guarapuava, Paraná State, Brazil, from April to November of 1999. The specific objectives were to evaluate potential forage and grain yield of white oat cv. FAPA 2 after different grazing periods as well as to identify the maximum weeks of grazing so as to yield good forage animal grazing without reducing grain yield. In a split plot experimental design 9 treatments with 3 replications were used. The treatments were: no grazing and grazing periods of 1, 2, 3, 4, 5, 6, 7 and 8 weeks. The white oat showed good leaf area recovery after grazing resulting in high dry matter yield provided that grazing period did not last more than 4 weeks. Grazing periods from 1 to 4 weeks allowed grain yield increase as a result of lower apical meristem height and lower number of lodged plants. From 5 to 8 weeks of grazing defoliations the grain yield reduction was the result of reduced spike number per area, reduced spikelets number per spike and reduced grain number per spike. Controlled grazing up to 4 weeks duration for white oat resulted in a good dry matter production which allowed animal and grain production, demonstrating that this cultivar have high potential for double purpose use.
Avena sativa L.; defoliation; double purpose system
