Assessment of economic returns by using a central pivot system to irrigate common beans during the rainfed season in Central Brazil

Irrigation improves yield, but can create conflicts with other water uses during dry periods. Based on this, the aim of this study is to assess the economic returns provided by irrigation of common beans during the rainfed season in Central Brazil. Common bean yield was simulated for 30 growing seasons using the crop model DSSAT-CROPGRO-Drybean, with parameters calibrated for the cultivar Pérola. The yield simulations considered sowing dates from Nov. 01 to Jan. 01 at each 15 days, and four water managements: rainfed and irrigation starting at 70, 50 and 30% of the total soil water available (TSWA). Yield and irrigation costs were obtained from official institutes that assess net revenue considering sales prices from R$ 1.33 to R$ 5.00 per kg. The rainfed system yield ranged from 500 to 3000 kg ha−1. The irrigation at 70, 50 and 30% of TWSA increased yield, respectively, from 26.7 to 41.4%, from 5.5 to 14.5%, and from 0.4 to 2.4% in relation to the rainfed system with ranges depending on sowing dates. The average demand of 53 mm cycle−1 (range between 0 to 100 mm cycle−1) was required by the water management 70% of TSWA. However, the 50% of TSWA required an average demand of 19 mm cycle−1, and the 30% of TSWA in most growing seasons did not require irrigation. The net revenue was affected by sales prices and sowing dates (preferentially early sowing). A minimum sales price ranging from R$ 1.85 to R$ 2.83 per kg is required, according to the water management and the sowing date, for an internal return rate higher than 12%. Irrigation at 70% of TSWA provided a similar or better economic index and a higher yield than the rainfed system. It is an interesting water management option because water is used when the river water level is higher, ensuring yield stability and food production.