Passo Fundo, RS
Mapping of water deficiency risks for soybean in Rio Grande do Sul state, Brazil
Abstract The mapping of water deficiency risks for soybean in Rio Grande do Sul state, Brazil was based on daily water balance calculations using data from 251 meteorological stations from ANEEL network. Typical development cycles of Early, Normal and Late soybean varieties, sown from October to December were used. It also used three fixed Available Water Capacity (AWC) in the soil: 35mm, 50mm and 75mm. After running the water balance simulations, the indexes of relative evapotranspiration (ETr/ETm) for the period bloom-grain filling were plotted in maps, for three classes with frequencies above 80%: ETr/ETm > 0.65 (desirable), ETr/ETm between 0.65 and 0.55 (intermediate), and ETr/ETm < 0.55 (undesirable). The results showed regional differences in Rio Grande do Sul state, Brazil, associated with rainfall distribution, soil type (mainly AWC), and varieties cycle. It should be noted that this conclusion is based solely in availability of water for the crop. By no means it suggests that every municipality included in a same water deficiency risk area has the same yield potential, because there are many other variables of soil and climate which are not accounted by this study.
Keywords: Glycine max (L.) Merril, climatic risk, crop zoning.
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