Effect of weed competition on grain sorghum yield

Abstract

A field experiment was conducted in a "Terra Roxa Estruturada" (Ultisol, clay), during three years (1978/79, 1979/80 and 1980/81) to study the effects of weeding time and number on yield and yield components of grain sorghum cv. Contiouro. The experimental design was a randomized blocks with the following treatments: 1) free weed competition; 2) weeding at 15 days after seedling emergence (DASE); 3) weeding at 15 and 30 DASE; 4) weedingat 15, 30 and 45 DASE; 5) weeding at 15, 30, 45 and 60 DASE; 6) weeding at 30 and 45 DASE; 7) weeding at 30 and 45 DASE; 8) weeding at 45 DASE. The grain yields of the treatments with weeding did not differ significantly among then, but differed from those treatments in plots free of weeds. When grain sorghum was allowed to grow without weed competition there was an increase in head weight and number of panicles per hectare, resulting in higher yields. One weeding 15 DASE was sufficient to get a grain yield as high as that of the treatment with the greatest number of weedings.