Determination of Production Function and Water Productivity for Bean under Condition of Nitrogen Use in Astaneh Ashrafiyeh Region

This research was conducted to determine the production function of common bean and cowpea and evaluation of water use efficiency in Astaneh Ashrafiyeh, in 2016 and 2017.  The present study was conducted as split plot in a randomized complete block design with 3 replications. Main treatments consisted of irrigation of 40%, 60%, 80%, and 100% of water requirement of the plant, and nitrogen treatments in sub plots consisting of no fertilizer, 30, 60, and 90 kg N ha-1 and two bean varieties (ordinary beans and cowpea). The results showed that the effects of irrigation and nitrogen fertilizer on seed yield and other agronomic traits were significant (P< 5%), in 2016 and 2017. Two-year average seed yield in 100% water requirement and 60 kg N ha-1 treatments in common bean and cowpea cultivars were 3446 and 3646 kg ha-1, respectively. The highest water productivity in 2016 and 2017 was obtained for the interaction of cultivar and irrigation on seed yield, and was 0.48 and 0.47 kg m-3, respectively. Water use productivity of the interaction between nitrogen fertilizer and bean cultivars in 2016 and 2017 in 100% water requirement treatment and 30 and 60 kg N/ha was between 0.42 and 0.46 kg m-3. The results of the estimation of production function indicated that the seed yield increased with nitrogen fertilizer application up to 30 kg ha-1, but with gradual increase in nitrogen fertilizer, the yield decreased. Based on the present study, 100% water requirement for seed yield can be recommended for both bean cultivars, however, the amount of fertilizer should be 60 kg N/ha for common bean and 30 kg N/ha for Cowpea.