Water use efficiency in the sugarcane cropping in different planting dates in Brazil

In global terms, irrigation is a human activity with greater demand for fresh water and strategies are needed to minimize this consumption. Therefore, the objective of this study was to establish the sugarcane planting date, which results in a greater water use efficiency, considering the summer planting of the Northeast region of Brazil. The sugarcane cultivar was RB92579, drip irrigated, and the stage of the plant was first ratoon. The experimental design was a randomized complete block design, with four replications and five treatments referring to the planting date (PD) equivalent to the months of October (PD1), November (PD2), December (PD3), 2013, January (PD4) and February (PD5), 2014. Water use efficiency was defined as the ratio of the tonnes of sugar per hectare to the volume of water entering the system, either through irrigation, total rainfall plus irrigation or effective rainfall plus irrigation. The planting dates in October and January showed the highest water use efficiency, as well as higher agro-industry productivity and higher net revenue. Planting in October maximized the use of rainfall and, in November, minimized the use of irrigation water. Key words: phenology, effective precipitation, evapotranspiration, soluble solids content, irrigation.