Aptidão edafoclimática do milho de sequeiro em diferentes cenários de pluviometria no estado do Ceará

Abstract

The corn is one of the most produced and used cereals in the world, being an important crop of economic and social interest for several countries due to its nutritional value, the versatility of the production system and the high productive potential. In semiarid conditions, the maize production is directly associated with rainfall and soil characteristics, since these environmental factors are very limiting in these regions. But by following a few best management practices referenced in information and analysis about the geolocation and the spatiotemporal variability of climatic series and soil conditions, dryland growers can decrease their risk and get the highest potential return of corn. Thus, the present study had as general objectives: (1) to analyze the spatiotemporal variability of the dry spell occurrence in a semiarid region and to define how these dry spell and the phenomena of El Niño and La Niña of long duration impacted the historical productivity of maize and (2) to study the edaphoclimatic suitability of dryland corn, in a semiarid region with different rainfall regime (dry, neutral and wet years). For the definition of the frequency of the different classes of dry spell (with 5-10, 11-15, 16-20, 21-25, 25-30 and> 30 days without rain) an analysis of rainfall behavior was made within eight different pluviometrically homogeneous regions (RPH) of the state of Ceará, using 245 meteorological stations with a historical series of at least 20 years. From these data together with the historical information of temperature the decade climatologic water balance for each station was elaborated, in the 3 scenarios of rainfall regime. This information was used in the definition of the agricultural calendar of corn planting and in the elaboration of climate risk maps, which were later used in map algebra together with thematic maps of soil classification, use and occupation, slope and hypsometry, thus producing maps of Agroecological Zoning for corn. As results obtained, the highest number of dry spells was found in the most inland regions of the semiarid, outback concentrated in the first and last months of the rainy season, and the corn yield reached significant values with dry spells of up to 15 days without rain. In the case of maize cultivation on dry farming is recommended for the end of the first month of the rainy season, this in years of neutral or wet rainfall regime of precipitation, since in conditions of dry years and/or El Niños long duration increase the number of dry spells with more than 20 days and the conduction of dryland corn is impracticable.