Desempenho agronômico de diferentes cultivares de soja em função da época de semeadura e regime hídrico em Cachoeira do Sul - RS

Abstract

The present study aims to evaluate the agronomic performance of different soybean cultivars as a function of sowing time and water regime in Cachoeira do Sul - RS. The field experiment was carried out in a randomized block design with split plots, in a factorial scheme (2x3x4). The first factor comprises two water regimes: irrigated and rainfed. The second factor consists of three soybean cultivars with different GMR (relative maturation group): BMX GARRA (GMR 6.3), ND 5445 (GMR 5.4) and BMX RAIO (GMR 5.0). The third factor consists of four soybean sowing dates: October 23, 2019, November 19, 2019, December 19, 2019 and January 16, 2020. Irrigations were carried out using conventional sprinklers and the management of irrigation based on soil water balance. The morphophysiological variables were monitored throughout the development cycle and productivity and yield components were determined at the end of the cycle. The 2019-20 agricultural year was characterized by the low amount and irregular distribution of rainfall, requiring supplementary irrigation from 150 to 180 mm, which provided positive increases in soybean productivity by an average of 45%. Irrigated soybeans was less influenced by sowing season than rainfed soybeans, with a yield reduction of approximately 24 kg day-1 (irrigated) and 31 kg day-1 (rainfed) with the delay of sowing from October 23 to January 16. The yield values were very similar between the cultivars in the irrigated water regime for the first three sowing dates (>4000 kg ha-1 ) and in the fourth season the cultivar BMX RAIO stood out. However, for the rainfed water regime for sowing from November, the productive response of the cultivar should be evaluated, since the cultivar BMX GARRA showed better results for the last two seasons and the cultivar BMX RAIO for the second season.