Yield gap of the double-crop system of main-season soybean with off-season maize in Brazil

The succession of main-season soybean (Glycine max (L.) Merr.) with off-season maize (Zea mays L.) is an important Brazilian agricultural system contributing to increased grain production without the need for crop land expansion. Yield-gap studies that identify the main factors threatening these crops are pivotal to increasing food security in Brazil and globally. Therefore, the aim of the present study was to determine, for the soybean-off-season-maize succession, the magnitude of the grain and revenue yield gap (YG) caused by water deficit (YG(W)) and suboptimal crop management (YG(M)), and to propose strategies for closing these gaps in different Brazilian regions. The ensemble of three previously calibrated and validated models (FAO-AZM, DSSAT and APSIM) was used to estimate yields of soybean and off-season maize for 28 locations in 12 states for a period of 34 years (1980-2013). Water deficit is the biggest problem for soybean and off-season maize crops in the regions of Cocos (state of Bahia), Buritis (Minas Gerais) and Formosa (Goias), where the YG(W) accounted for similar to 70% of total YG. The YG(M) revealed that locations in the central region of Brazil, mainly in the state of Mato Grosso, presented an opportunity to increase yields of soybean and off-season maize, on average, by 927.5 and 909.6 5 kg ha(-1), respectively. For soybean, YG(M) was the main cause of total YG in Brazil, accounting for 51.8%, whereas for maize, YG(W) corresponded to 53.8% of the total YG. Our results also showed that the choice of the best sowing date can contribute to reducing soybean YG(W) by 34-54% and off-season maize YG(W) by 66-89%.