WATER DEFICIT IN MAIZE CONSIDERING PHENOLOGY, EFFECT ON YIELD AND WATER USE EFFICIENCY

The occurrence of low water availability periods and low irrigation efficiencies force irrigation districts (DR) to take actions such as reducing the crop area and the number of applied irrigations. This, in many cases, causes negative yield impacts when not applied in a scientific way. The objective of this research was to experimentally evaluate the water stress effects on yield components and water use efficiency of maize (Zea mays L.) based on phenology. The experiment was conducted in the DR-075 irrigation district, during the autumn-winter (OI) 2012-2013 season, and four treatments (T) of water deficit and a control (TES) were evaluated, designed under the FAO function that relates water deficit to yield. T1 received two auxiliary irrigations (RA) distributed in growth stages V12 and R2; T2 received three RA distributed in V9, R1 and R3; T3 received four in V7, V12, R1 and R3-R4. T4 received five RA in V5, V12, R1, R3 and R4. TES received four RA distributed in the same way as T3 but applied in a conventional manner. The evaluated variables were application efficiency (EA), fresh matter (MF), dry matter (MS), grain yield (Ya), harvest index (IC) and water productivity (PA). Irrigation and phenology monitoring was carried out with the IRRIMODEL computer platform complemented with field observations; soil moisture monitoring was performed with a portable TDR type sensor. Results provided scientific information to manage corn crop irrigation considering phenology, under normal and restricted water availability conditions. In the first scenario, the fifth auxiliary irrigation should be avoided, and in the second, the three auxiliary schedule (T2) should be used to obtain application efficiencies equal to or greater than 64%.