Economic indexes of maize under levels of water, nitrogen and planting seasons

The objective of this work was to evaluate economic indexes of maize under water and nitrogen (N) levels. The experiment was conducted in two seeding seasons (spring/summer and autumn/winter) in Rio Largo, Alagoas, Brazil, with 20 treatments and four repetitions. Maize was submitted to five irrigation levels (40, 80, 120, 160 and 200% of crop evapotranspiration - ETc) and four nitrogen fertilization rates (0, 75, 150, 225 kg ha-1 of N). The crop was drip irrigated, where the costs of irrigation and nitrogen fertilizer more the sale price of the corn sack were used to determine the economic level of water and N. The maximum yield of maize grains grown in the rainy and dry seasons can be obtained with nitrogen rates equal to 156 kg ha-1 and above 225 kg ha-1, respectively. In the dry season, maximum yield can be obtained with irrigation level equivalent to 164% of ETc. Depending on input prices and grain sales, the most economically efficient nitrogen dose for the rainy season is around 93 kg ha-1, while for the dry season it averages 200 kg ha-1; for spring-summer cultivation, the maximum economical irrigation depth corresponds to 96% of ETc.