Plant arrangement that decrease interplant competition can improve soybean growth and yield by better use of resources. The experiment was performed at the Agronomic Experimental Station of the Universidade Federal do Rio Grande do Sul, in Eldorado do Sul, Rio Grande do Sul, Brazil, in the 2000/01 growing season. The objectives were to evaluate how soybean plant arrangement modify the interplant competition and the effect in grain yield and yield components. The cultivar tested was 'BRS 137'(early, determinate), in no-till planting. The treatments were arranged in a split-plot randomized complete-block design,whith four replications. The treatments tested were two water availability (with and without irrigation) , two row spacing (20 and 40cm) and three population levels (20, 30 and 40 plants.m-2). The grain yield was affected by irrigation and by the interaction of row spacing and population. The irigated treatment (5015kg.ha-1) had grain yield 18% higher than the non irigated (4253kg.ha-1). The larger grain filling rate (GFR), resulted in larger seed weight, and explain, the greater yield in the irrigated treatment. The plant arrangemnt of 20 cm row spacing with the population of 20 plantas.m-2 provided the better results (5014kg.ha-1 compared to 4322 kg.ha-1 in 40 cm row spacing). There is a linear decrease in grain yield with the increase in plant population with reduced row spacing (20cm). These results can be explained by more branche number, fertil nodes and fertil pods.m-2 obtained. The arrangement of 20cm row spacing and 20 plants.m-2, attenuated the interplant competition resulting in larger grain yield.
Glycine max; row spacing; plant population; plant arrangement
