CORN AGRO CLIMATIC ZONING BY SOWING DATES IN THE STATE OF RIO GRANDE DO SUL, BRAZIL

Abstract

Aiming to delimit areas showing climate aptitude for growing com, an agroclimatic zoning based on growing degrce-days and water deficit as agroclimatic indexes, at different sowing dates, was generated for the State of Rio Grande do Sul, Brazil. The zoning was established for sowing dates 8/1, 9/1, 10/1, 11/1,12/1, and 1/1, and six maps (1:750,000), which are presented in a reduced forre in this papei, were obtained. The zoning areas were classified as Preferential I and II. Tolerable. Marginal, and Not Recomended for com. Planalto, Serra do Nordeste, Serra do Sudeste, and Alto Vale do Uruguai are the regions showing higher potential for com in the state. Additionally, Médio and Baixo Vale do Uruguai, Missões, Depressão Central, Litoral Sul, and Campanha regions, though also showing potential for com, have the highest values of water deficit and, by using irrigation, are clssified through the temperature index. The main limitation to high com yields in the state is linked to water deficit that normaly occurs in southwestern and southeastern state arcas and in part of Depressão Central region in 9/1 to 1/1 sowing dates. Low temperaturas and frost occurrence are the most limiting factors in the sowings centered in 8/ 1. The results obtained show that climate aptitude for com in Rio grande do Sul varies according to the sowing date and region, evidencing the importante of carrying out the zoning by sowing dates.