University of Tehran Press Iranian Journal of Soil and Water Research 2008-479X 50 9 2020 01 21 Irrigation scheduling of Black Gram based on Crop Water Stress Index (CWSI) under drip irrigation Irrigation scheduling of Black Gram based on Crop Water Stress Index (CWSI) under drip irrigation 2125 2138 71191 10.22059/ijswr.2019.280132.668179 FA Afshin Khorsand Ph. D Candidate of Irrigation and Drainage, Department of Water Engineering, Urmia University, Urmia, Iran Vahid Rezaverdinejad Associate Professor, Department of Water Engineering, Urmia University, Urmia, Iran Hossein Asgarzadeh Assistant Professor, Department of Soil Science, Urmia University, Urmia, Iran Abolfazl Majnooni Heris Associate Professor, Department of Water Engineering, University of Tabriz, Tabriz, Iran Amir Rahimi Assistant Professor, Department of Agriculture, Urmia University, Urmia, Iran Sina Besharat Assistant Professor, Department of Water Engineering, Urmia University, Urmia, Iran Journal Article 2019 05 01 Empirical and theoretical methods (energy balance) are widely used to calculate the Crop Water Stress Index (CWSI) and irrigation scheduling to describe crop water status. In this study, irrigation scheduling was performed at the research farm of College of Agriculture, Urmia University, using a manual infrared thermometer and the empirical method of Idso et al. (1981) for the black gram under different irrigation regimes using drip irrigation in 2017. The experimental design was carried out in a randomized complete block design with three levels of irrigation I1, I2 and I3 which were 50, 75 and 100 percent water requirement in three replications, respectively. Using the baselines obtained for each treatment, the average CWSI values during the growth season of black gram for I1, I2 and I3 treatments were calculated to be 0.37, 0.23 and 0.15 respectively. The relationship between CWSI and total irrigation depth (mm) was determined as CWSI = -0.0008 (I) + 0.58, and the relationship between black gram grain yield (ton/hec) and CWSI was determined as Yield = -1.8237 (CWSI) + 2.1435 which their correlation coefficients (R2) were 0.98 and 0.99 respectively, which shows the high accuracy of regression models. In general, if the amount of water decreases with stress during the plant growth, the CWSI value increases, and as a result of increasing CWSI, the crop grain yield decreases. Finally, the no stress treatment (I3) with CWSI=0.15 was the basis for irrigation scheduling and then some relationships were established for determining the irrigation time using CWSI in Urmia climate for four stages of black gram growth; flowral induction-flowering, pod formation, seed and pod filling, and physiological maturity as (Tc ̶ Ta)C = 1.9498 ̶ 0.1579(AVPD), (Tc ̶ Ta)C = 4.4395 ̶ 0.1585(AVPD), (Tc ̶ Ta)C = 2.4676 ̶ 0.0578(AVPD) and (Tc ̶ Ta)C = 5.7532 ̶ 0.1462(AVPD), respectively. Empirical and theoretical methods (energy balance) are widely used to calculate the Crop Water Stress Index (CWSI) and irrigation scheduling to describe crop water status. In this study, irrigation scheduling was performed at the research farm of College of Agriculture, Urmia University, using a manual infrared thermometer and the empirical method of Idso et al. (1981) for the black gram under different irrigation regimes using drip irrigation in 2017. The experimental design was carried out in a randomized complete block design with three levels of irrigation I1, I2 and I3 which were 50, 75 and 100 percent water requirement in three replications, respectively. Using the baselines obtained for each treatment, the average CWSI values during the growth season of black gram for I1, I2 and I3 treatments were calculated to be 0.37, 0.23 and 0.15 respectively. The relationship between CWSI and total irrigation depth (mm) was determined as CWSI = -0.0008 (I) + 0.58, and the relationship between black gram grain yield (ton/hec) and CWSI was determined as Yield = -1.8237 (CWSI) + 2.1435 which their correlation coefficients (R2) were 0.98 and 0.99 respectively, which shows the high accuracy of regression models. In general, if the amount of water decreases with stress during the plant growth, the CWSI value increases, and as a result of increasing CWSI, the crop grain yield decreases. Finally, the no stress treatment (I3) with CWSI=0.15 was the basis for irrigation scheduling and then some relationships were established for determining the irrigation time using CWSI in Urmia climate for four stages of black gram growth; flowral induction-flowering, pod formation, seed and pod filling, and physiological maturity as (Tc ̶ Ta)C = 1.9498 ̶ 0.1579(AVPD), (Tc ̶ Ta)C = 4.4395 ̶ 0.1585(AVPD), (Tc ̶ Ta)C = 2.4676 ̶ 0.0578(AVPD) and (Tc ̶ Ta)C = 5.7532 ̶ 0.1462(AVPD), respectively.

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