PLANTING SIMULATION TO ESTIMATE THE CROP COEFFICIENT OF IRRIGATED TOMATO ACCORDING TO THE FAO-56 METHODOLOGY

Abstract

Studies on evapotranspiration (ET) as well as accurate crop coefficient (cc) values are important for irrigation water management, agricultural planning and water resources. The objective of this study was to estimate the local crop coefficient (dual cc) of tomato (Solanum lycopersicum L.), using the methodology of the Food and Agriculture Organization – FAO (Bulletin-56) in irrigated cultivation with the drip system. A planting simulation was carried out to estimate tomato cc and meteorological data (average air temperature, relative air humidity, wind speed and solar radiation) were obtained from the automatic agrometeorological station, installed in the experimental field of the Federal Institute of Education, Science and Technology of Maranhão, located in the municipality of Codó, MA. The evapotranspiration estimate was performed based on the standard Penman-Monteith (PM) methodology with the aid of the Ref-ET^® software. As for the cc estimate, the Microsoft Excel 2010^® spreadsheet was used according to the instructions contained in Annex 8 of the FAO Bulletin – 56. The evapotranspiration of irrigated tomato was 506.53 mm for the entire crop cycle, which corresponds to an average value of 3.75 mm day^-1. The cc values found for irrigated tomato under edaphoclimatic conditions in Codó, MA were: 0.15 (initial); 0.15 – 1.01 (development); 1.01 (production) and 1.01-0.66 (final).