Climatological risk zoning for beans cultivation in the state of Rio Grande do Sul, Brazil: favorable seeding periods per municipality, agricultural year 2002 – 2003

The present study is carried out to identify areas showing lower agroclimatological risk for common beans associated to water deficit, in the State of Rio Grande do Sul, Brazil. The investigation was based on Common Beans Crop Agroclimate Zoning, in the State of Rio Grande do Sul. A Complementary Risk Index (CRI) was applied to areas suitable for common beans determined in the agroclimate zoning. The purpose of such index is to detect those periods showing lower risk of occurring water deficit. CRI is based upon the interaction between water availability and critical development period of beans, as the main factor determining economic yield of common beans in the state. The module Sarrazon was used in calculating daily water balance. Water balance simulations were carried out for common beans, early and normal varieties, considering the seeding dates on 5, 15, and 25 of each month. Main variable for the zoning was ISNA (Crop Water Requirement Index) of the third development period (flowering-grain filling). CRI is based upon the interaction between water availability and critical development period of common beans, as the main factor determining economic yield of common beans in the state. The module Sarrazon was used in calculating daily water balance. Water balance simulations were carried out for common beans, early and normal varieties, centering the seeding dates on 5, 15, and 25 of each month. The values of ISNA were calculated for a minimun frequency of 80% and then plotted on Spring v.3.4. Three categories were used: desirable (ISNA > 0.55), intermidate (ISNA between 0.45 and 0.55) and undesirable (ISNA < 0.45). The recomended sowing periods were stablished based on areas delimited by desirable ISNA values.