deficit irrigation in surface irrigation: challenges, approaches and prospect

deficit- irrigation is one of the measures for water saving and optimum application of water in surface irrigation. however, lack of enough evidences, doubts on the proper application of deficit- irrigation, dissemination of research results and its application by the farmers are of practical challenging issues. this paper summarizes and analyzes some research results on deficit- irrigation in iran. it also brings up the results of a working workshop on the issues and challenges involved in deficit-irrigation for surface irrigation. as an achievement, the paper provides the concept of differentiation between deficit-irrigation techniques, which is actually an optimization technique, and the common ways of using less water. moreover, these research projects had been conducted in small plots, having high irrigation efficiency (100%), and might not be adopted under field conditions with commonly low water application efficiencies. based on the results' analyses, there are gaps on the number of comprehensive deficit-irrigation projects. it was concluded that currently the common farmers showed not much knowledge or experiences on deficit-irrigation. most of the conducted projects were technically oriented and did not consider socio-economic aspects of the farmers. based on analysis of the results of different research studies and also considering low farm irrigation efficiencies, it was recommended that deficit irrigation about 20 to 25 percent, except at the sensitive stages of crop growth, could be practiced for the common crops. as a future perspective, the paper concludes that most of the conducted research projects have been carried out on small plots, focusing on crop responses to water stress (sometimes with crop water-yield functions results), and optimization issues have not been addressed well. however, even with present knowledge on deficit-irrigation and water-yield optimization, there are doubts on use of these results for the small-land holder farmers and more comprehensive research activities should be carried out in this regard.