Temporal Change of Plant Coefficients Calculated According to Different Evapotranspiration Methods in Pistachio

Abstract

Irrigation is the most important cultural practice affecting vegetative yield and productivity. It is an obligation to determine the correct water consumption of the plant in order to make suitable irrigation practices and to develop appropriate irrigation programs. Many empirical models used in determining plant water consumption have been developed. The comparative plant water consumption values determined through empirical models are obtained by multiplying by a coefficient (Kc) for that plant in order to determine the actual plant water consumption. In this study, the plant water consumption values determined by different empirical models and the Kc values determined by using the actual plant water consumption values calculated by the water budget technique in pistachio irrigated by drip irrigation method were compared. The Kc values obtained by using the reference ETo values estimated by the methods of Hargreaveas (H), Penman-1948, Priestley & Taylor (PT) with FAO-PM as the standard method were compared under semi-arid climatic conditions. According to the results, during the 4 years (1999-2002) when the calculations were made, the Kc values calculated with the standard PM method gave higher values compared to other methods, the highest Kc value was determined in July with 1.49 and the lowest Kc value was determined in November with 0.40. The highest Kc values compared to other compared methods were obtained from the standard method. The lowest Kc values were obtained from the values calculated through Penman-1948. The highest and lowest Kc values were determined in July and November with values of 0.63 and 0.01, respectively.