Two soybean experíments were performed at lhe Agronomic Experimental Farm of the Federal University of Rio Grande do Sul, in the county of Eldorado do Sul - RS. In the 1994/95 growing season the cultivars FT-Saray and OCEPAR 14 (both early maturity and determinate type) were used, in row spacings of 20 and 40cm, and the soils with very low and sufficient phosphorus leveis, and population of 40 plants m-2. In the 1996/97 growing season the cultivar FT-Saray was used, row spacings of 20 and 40cm, soils with three fertility leveis (actual fertility, recommended fertiliwtion and twice the recommendation), and populations of 30 and 40 plants m-2. When the soil fertility reached the crop requirements, according to the technical recommendations, the row spacing reduction from 40 to 20cm increased grain yield from 3554 to 4104kg ha-1 (+15%), in the first year, and from 4322 to 5420kg ha-1 (+ 25%) in the second. When the soil fertility was below the critical level, the same decrease in row spacing lowered yield from 1843 to 1520kg ha-1 (-17%).
Glycine max; plant arrangement; intraspecific competition; fertilization
