Water deficit risk for maize in the State of Parana, Brazil

The goal of this work was to determine soil water deficit risk and the best sowing periods for maize (Zea mays L.) in the State of Parana, Southern Br azil. A climatological soil water balance model adapted for maize was simul ated, using historical series of daily values of maximum evapotranspiration and precipitation from 32 weather stations. Soil water holding capacity wa s calculated using an initial soil depth of 20 cm at plant emergence, which increased exponencially up to 80 cm depth at the beginning of plant flower ing, and remained constant until harvest. Ten sowing dates spaced at 10 day s interval were simulated between August 20 and November 20, and the freque ncy of soil water deficit during the flowering period (800 degree-days afte r emergence) was estimated. Using cluster analysis, Parana State was classi fied in five homogeneous zones for soil water deficit risk. Results have sh own that the North and Northwest regions have very high risk. Appropriate s owing periods with lower risks were identified for all zones.