Soybean-maize succession in Brazil: Impacts of sowing dates on climate variability, yields and economic profitability

The soybean-maize succession is an important production system used in Brazil. The greatest challenge related to this kind of system is to define the best sowing dates for the producing regions with different climatic characteristics, improving farmer's economic profitability. Thus, the aim of this study was to determine the best sowing dates for the above-mentioned crop system considering simulations with three crop simulation models (FAO-AZM, DSSAT and APSIM) in a multi-model approach, and to determine the economic profitability of this system at national scale. Previously calibrated and validated models were used to simulate soybean yields for 29 locations in 12 states, with sowing dates ranging from end of September to beginning of January for a period of 34 years (1980-2013). The maize off-season sowing was done just after the soybean harvest, ranging from end of January to beginning of May. The yield data was converted to gross revenue according to the prices commonly practiced in Brazil and then to net revenue by subtracting the production costs for each assessed region. The optimal sowing date varied according to the Brazilian region. For Central Brazil, the highest net revenue was obtained when soybean was sown between the end of September and beginning of October. This period is also recommended in Southern Brazil, because sowing delay can reduce maize yield due to risks of frosts and low solar radiation availability. In the Northern Brazil, mainly in Para state, the soybean sowing should start in November, when net revenue is maximized.