Abstract :
Abstract:The field experimental carried out during spring season 2005 at Gorgan city (Asrieh field) in Iran, to study the effect of different irrigation water regimes (i.e. W1:70, W2:80, W3:90 and W4:100) per cent of field capacity on grain yield, and water use efficiency. Randomize block design with three replications was used in this study. The results showed that there was significant difference between the yield and (WUE) under different levels of irrigation, excepting of soil moisture content at field capacity (W4) and 90% of field capacity (W3) on yield and water use efficiency (WUE). The seasonal irrigation water applied were (i.e. 375, 338, 300 and 263 mm ha-1) under different irrigation water treatments (100, 90, 80, 80 and 70%) of FC, respectively. Grain yield productions under treatments were 4180, 3955, 3640, and 3355 (kg ha-1) respectively. Furthermore, the results showed that water use efficiency (WUE) at different treatments were 7.67, 7.79, 7.74 and 7.75 Kg mm ha-1 for (100, 90, 80 and 70) per cent of field capacity, therefore the 90 % of FC treatment (W3) is recommended for Soybean irrigation for water saving. The comparison of actual crop coefficient that obtained by lysimeter, and others methods (viz.pan class A and two empirical methods Hardgrave’s and Blany-Cridle). The results showed that Hardgrave’s method is better than other methods for estimation of crop coefficient (Kc) for soybean in this region. Furthermore, the result showed that the treatment of 90 % of filed capacity (W3) seemed to be better adapted to product a high crop yield with acceptable yield coupling with water use efficiency in Golestan province.
