Economic use of water in the cultivation of irrigated caupi beans in the semi-arid region of Brazil

Irrigation in agriculture allows to give conditions for plants to express their full production potential in the field, but scientific studies are needed to optimize the use of water in regions that are difficult to access, such as semi-arid regions. In view of this, the present work aimed to determine the economic irrigation depth for the cultivation of cowpea beans in the region of Sertão Alagoano. A creole bean variety commonly cultivated by farmers was used, which was subjected to five irrigation depths (30, 60, 90, 120 and 150% of the evapotranspiration of the culture, ETc). The experiment was developed at the Federal Institute of Alagoas/Campus Piranhas, during the months of February to May 2018. The crop was irrigated by drip, in which the costs of irrigation plus the costs of planting and cultural treatments were used to determine the economic level of water, through the analysis of grain yield. Agricultural yield differed statistically between the depths applied, according to F test (p<0.05). The caupi bean has a low response to irrigation, in which the economic irrigation depth is independent of the sale price of the grain and is close to the irrigation depth that provides maximum physical yield.