Estimativa do Balanço Hídrico Climatológico para determinação do cultivo de milho no Rio Grande do Sul: período atual e projeções futuras

Abstract

In national territory, Rio Grande do Sul is a former maize producer, having a significant role in the country's economy. Commonly the grain yield is limited by the amount of water available in the soil and, therefore, affected during periods of drought that can affect the State. The main goal of this research was to verify the water availability for maize culture in Rio Grande do Sul, also having as specific objectives: to ascertain the average yield and the production of the corn crop in the State and municipalities that were selected in the period 1981-2018; identify the potential water availability and maize crop for these municipalities by calculating the climatological water balance (CWB) proposed by Thornthwaite and Mather (1955); evaluate the performance of the Coupled Model Intercomparison Project (CMIP5) models through statistical analysis between observed and estimated monthly data of average air temperature and total precipitation in the period from 1981 to 2010; determine future projections of potential CWB and culture based on data from the best performing model, allowing to identify if the regions under study will present deficit or excess water in the soil in the future, thus helping in the planning of maize cultivation in RS. Cruz Alta, Iraí, Campo Bom, Cambará do Sul and Pelotas were selected as outstanding regions in the production of corn in the State. The crop failures identified in 2005, 2009 and 2012 may be associated with the intense performance of ENOS. In the current period, only Pelotas and Campo Bom had a water deficit. The HadGEM-2-ES model presented the best performance, being used to provide necessary temperature and precipitation forecasts for the calculation of the future CWB in two periods (2041-2070 and 2071-2100). In the optimistic scenario (RCP 4.5), Campo Bom had a water deficit in both periods, and Pelotas only in the last. Within the pessimistic scenario (RCP 8.5), only Campo Bom and Pelotas showed a water deficit in the first period and, with the exception of Cambará do Sul, until the end of the century, other locations continued to present this problem.