摘要：The objective of this paper is to propose an alternative measure of irrigation water efficiency based on the concept of input- specific technical efficiency, which contracts with measures previously used in the literature. The proposed methodology is applied to a randomly selected sample of 144 citrus growing farms located in Nabeul (Tunisia). A stochastic production frontier approach, based on Battese and Coelli’s (1995) inefficiency effect model, is used to obtain farm-specific estimates of technical and irrigation water efficiency. In addition, a second-stage regression approach is used to identify the factors influencing irrigation water efficiency differentials across citrus growing farms. Results indicate that technical efficiency ranges from a minimum of 12.9% to a maximum of 90.7% with an average estimate of 67.7%. This suggests that citrus producers may increase their production by as much as 32.3% through more efficient use of production inputs. Further, mean irrigation water efficiency is found to be 53%, which is much lower than technical efficiency and also exhibits greater variability ranging from 1.6% to 98.87%. The estimated mean irrigation water efficiency implies that the observed quantity of marketable citrus could have been maintained by using the observed values of other inputs while using 47.0% less of irrigation water. Moreover, the estimated mean irrigation water technical cost efficiency is found to be 70.81% indicating a potential decrease of 29.19% in total cost by adjusting irrigation water to its efficient level. In addition, the vast majority of farms have achieved irrigation water technical cost efficiency greater than 90% (71% of farms). Finally, the analysis of the sources of efficiency differentials among farmers showed that farmer’s age, farm’s size, education level, agricultural training, the share of productive trees and the water disposable perception tend to affect positively the degree of both technical and irrigation water efficiency.
