Influência da densidade de semeadura e da irrigação suplementar no desempenho agronômico de cultivares de soja

Abstract

Management strategies that contribute to increasing soybean productivity are relevant in view of the current scenario of Brazilian agribusiness in which this crop stands out as the main annual spring-summer crop. The objective of this study was to evaluate the productivity of three soybean cultivars, cultivated at two sowing densities, in irrigated and dryland water regimes, for the 2021/22 agricultural year in Cachoeira do Sul - RS. The experiment was carried out in the field, at the Agronomic Station of the State University of Rio Grande do Sul (29º53' S and 53º 00' W, altitude of 125 m), in welldrained soil. The experimental design used was randomized blocks in a factorial scheme (3x2x2), with four replications. Factor A is formed by the cultivars used, namely: i) BMX Raio IPRO, ii) BMX Zeus IPRO and iii) BMX Garra IPRO; the B factor of sowing density: i) 14 plants m⁻¹ linear (311,100 plants ha⁻¹) ii) 20 plants m⁻¹ linear (444,400 plants ha⁻¹) and the factor C by water regimes: i) with irrigation supplement ii) no irrigation. The row spacing was 45 cm. Supplementary irrigation was performed based on the water balance of the crop to maintain the soil with a depletion fraction of up to 40% of the total available water. The interaction between the factors showed that in the irrigated water regime, the Zeus and Raio cultivars were the most productive (average of 5344.7 kg ha-1 ) with a sowing density of 20 plants m⁻¹ and in the rainfed water regime, the cultivars Zeus and Garra were the most productive (average of 2927.3 kg ha-1 ) without influence of sowing density. Supplementary irrigation provided an average yield increase for the two sowing densities of 198 % (Raio cultivar), 72 % (Garra cultivar) and 51 % (Zeus cultivar).