determination of economic threshold of deficit irrigation on cotton in darab district

drought is common across the south of iran, especially in darab district. accordingly, studying the economic aspects of deficit irrigation technique – that is one of the basic strategies in water saving for reducing water use of cotton as one of the main agricultural products in darab district is essential. in order to investigate the deficit irrigation technique and to determine its economic threshold in darab district, in the bakhtajerd research station a split plot experiment was conducted on cotton in a completely randomized block design with four replications in two years. the partial budgeting and english technique were used to analyze the collected data. the main study treatments were: 1) irrigation in all furrows, 2) irrigation in odd furrows, 3) periodic irrigation (one time irrigation in odd furrow and another time in pair furrows), 4) two irrigations in odd furrows and another full irrigation, 5) two full irrigations and another irrigation in odd furrows. sub-treatments were plant growth regulators including peaksofauxinsat the two levels of 0 and 1 liter per hectare .the results showed that the economic threshold of deficit irrigation of cottonis 8869 (cm3/ha) of irrigation waterthat saves 30.96 percent (3977 cm3/ha)of full irrigation.