|Boletim de Pesquisa Online Nº 2, dez./99|
Aiming to indicate wheat sowing dates for the state of Rio Grande do Sul, southern Brazil, a study was carried out considering frost ocurrence at flowering time and excess of rainfall at harvest as majors climatic risk for the wheat crop. This study of zoning of climatic risk integrated techniques of crop modeling and simulation with geoprocessing tools in order to indicate the areas with lower risk for wheat crop in Rio Grande do Sul, for each sowing period. The analysis of the risk maps shows that there is variability of climatic risks to growing wheat in the state, according to the region and sowing period. A combination of risk of frost ocurrence at anthesis with the risk of excess rainfall at harvesting time was used to define, for each county, the wheat sowing period of minimum risk, in wich the risk of losses due to the climatic factors studied would be kept bellow the high risk range in 80% of the years.