Winter wheat evapotranspiration and irrigation requirements across tropical and sub-tropical producing regions in Brazil

Agricultural intensification is often seen as an appropriate approach to meet the growing demand for agricultural products. In regions affected by seasonal or chronic water scarcity, closing the yield gap depends on irrigation. Brazil is the second-largest wheat importer of the world and irrigated wheat has high yield potential in Brazil, especially in tropical and sub-tropical regions of the country. The crop coefficient (Kc) is still a practical and simple way of quantifying crop irrigation requirements. In this paper, we provided Kc values based on a robust experimental dataset across different wheat-producing regions in Brazil. Four experiments were conducted in three sites [season 2017 in Piracicaba, State of Sao Paulo (Southeast region); season 2012 Maringa, State of Parana (Southern region); and seasons 2016 and 2017 Rondonopolis, State of Mato Grosso) (Midwest region)] using lysimeters and the Bowen ratio energy balance method for crop evapotranspiration measurements. Our data showed that Kc values varied among the regions analyzed. For the Midwest region, Kc values ranged from 0.88 to 1.36; the Southeastern region from 0.81 to 1.15, and the Southern region from 0.67 to 1.01. Considering values suggested by FAO, those for arid climates should be used in the Midwest region, sub-humid values for the Southeast, and humid values in the Southern. Differently, that was observed for other crops, our database showed wheat Kc values being stable disregarding the ETo range, which might be related to relatively lower ETo during the winter.