CLIMATIC INFORMATION FOR PLANNING SOYBEAN IRRIGATION IN RIO-GRANDE-DO-SUL, BRAZIL

Soybean crop yield variability from year to year in Rio Grande do Sul is mainly associated with the occurrence of drought. Irrigation is a possible solution for the drought problem. In planning irrigation systems some knowledge of the most probable water demands is required. A daily hydric meteorological budgeting technique was used for estimating irrigation water requirements over a long-term period of time for ten locations representing most climatic situation and for most soil types across the state. The total water irrigation requirements over the whole crop life cycle are statistically expressed in terms of risks, interpreted as two years out of ten that the irrigation requirements exceeds the calculated value. The irrigation requirements are given in a map representing the climate-soil regions.