To determine irrigation scheduling of pinto bean and evaluation of its planting date, a study was conducted with statistical split-plot design with four replications at Isfahan University of Technology Research Station in Shervedan, Falavarjan. The main plots were three irrigation treatments of T1 to T3 (irrigation after 50 + 3, 70 + 3 and 90 + 3 mm evaporation from class A pan evaporation, respectively) and the subplots were two planting dates of May 28 and June 28. A Piche atmometer' was also used to measure daily evaporation. Leaf water potential was measured using pressure bomb method, at sunrise and noon before each irrigation. Leaf water potential was also measured, hourly from sunrise to sunrise of the day before irrigation at each stage of development. At physiological maturity, the grain yield, grain yield components and biological yield were measured and harvest index was calculated. The results showed that class A pan evaporation and Piche atmometer were correlated (R 2 = 0.82) by the following equation:
Epan= 3.1 x(1 + Ea). Leaf water potential at sunrise and solar noon of the day before irrigation were about - 0.5 and - 1.75 Mpa, respectively. There was no significant difference between grain yield of T1 (3585.1 kg/ha) and T2 (3510.5 kg/ha) treatments. Treatment T3 had 1925.8 kgjha grain yield which was the lowest among the treatments. Thus, irrigation after 70 mm evaporation from class A pan was the best schedul. Also, delay in planting date caused grain yield reduction from 3530.3 kg/ha to 2484.1 kg/ha. The harvest index of T1 to T3 treatments were 45.5, 41 and 37%, respectively.
)