Climatic aptitude zoning for cotton in Piauí State, Brazil

Abstract

Climatic zoning of cotton crop (Gossypium hirsutum L. race Latifolium Hutch) in Piauí State have been made to establish regions of high climatic potential and to order sowing dates with small climatic risk. Climatic factors were considered at distinct rainfall scenarios (drought, regular and rainy years). Daily rainfall data series of 20 years at least, at 136 rainfall stations were analyzed. The capacity zoning was established by the use of criteria suggested by Varejão-Silva e Barros (2001). Reference evapotranspiration (ETo) was calculated by Thornthwaite method. Climatic maps of the rainfall annual, air temperature, relative humidity of air, nebulosity and P/ETo indexes were plotted by the use of GIS Software (Spring 4). The effects of climatic elements were decisive to define cotton crop climatic aptitude zoning to the Piauí State, especially rainfall spatial variability occurrence at the adopted study rainfall scenarios. Climatic capacity zoning of cotton crop at Piauí State changed substantially due to evaluated rainfall scenario. Independently of the used criteria and the rainfall scenario, the counties in the south and southwest regions of Piaui State, the savanna region, show complete aptitude to cotton crop cultivation.