ESTIMATION OF CROP EVAPOTRANSPIRATION IN BULGARIAN CLIMATE CONDITIONS

Precisely managed irrigation scheduling provides for on-time meeting of crop water needs, for high yields and high economic effect. Most important in crop water needs estimation is the right choice of an evapotranspiration calculation method. Comparative analyses of some calculation methods which are suitable for Bulgarian climatic conditions give advantage to the temperature-based ones. Since last decades, FAO Penman-Monteith method has been globally recognized as most accurate in various climatic conditions as it is based on great number of meteorological and plant factors. In this paper, decadal values of Kc factor in the course of vegetation of 25 crops, grown in Bulgaria ? cereals, forage, industrial, vegetables, and berries are presented. Their accuracy is statistically evaluated. The standard error of the mean is mainly around 10%. A narrow correlation between the crop factors of FAO method and the temperaturebase method, which is currently used in Bulgaria, has been established. Simulation of the irrigation scheduling of three crops by both methods is performed. The results show that FAO Penman-Monteith method is suitable for Bulgarian climatic conditions. The temperature-based method is simpler and easily maintained with meteorological information, hence it is recommended for practical purposes.