Seasonal Analysis of Yield and Loss Factors in Bt Soybean Crops in North Brazil

Tropical crops face significant challenges from abiotic and biotic stressors, resulting in substantial losses. This study aimed to assess the yield and losses in Bt soybean crops in Tocantins state, northern Brazil, during the 2017/2018 and 2018/2019 growing seasons. We monitored and estimated yield losses and their contributing factors in commercial fields, spanning dry and rainy seasons, from planting to harvest. Our findings revealed that crop yields remained consistent between the dry season (4349.85 kg/ha) and the rainy season (4206.51 kg/ha). Similarly, the overall yield loss showed no significant variation between seasons, with values of 902.86 kg/ha (dry) and 1007.92 kg/ha (rainy). Nevertheless, the factors contributing to these losses exhibited season-dependent variations. We observed higher plant mortality rates during the dry season, whereas insects (particularly stink bugs) and fungi were the primary contributors to grain yield losses during the rainy season. Conversely, losses due to flower abortion and pod malformation remained relatively consistent between the two seasons. Our study underscores the increase in soybean yield in one of Brazil's agricultural frontiers. While overall yield and losses remained stable between dry and rainy seasons, the distinct seasonal patterns influencing yield losses call for nuanced and season-specific strategies in sustainable crop management.