Evaluation of morpho-physiological traits and yield of two forage sorghum cultivars under water stress and nitrogen levels

In order to evaluate the effect of water stress and nitrogen levels on yield and morpho-physiological traits of two forage sorghum cultivars, a field experiment was conducted at the College of Agriculture, Shiraz University, during spring and summer 2011. The experiment was carried out as a split-split plot design based on RCBD with 3 replications. 100, 75 and 50% FC were considered as main plots, whereas nitrogen levels (150, 300 and 450 kg urea.ha-1) and forage cultivars (Pegah and KFS2) were considered as sub- and sub-sub plots. Results showed that water stress significantly reduced crop growth rate (CGR) and leaf area index (LAI) over the growing season, while decreased forage dry weight and yield at harvest time. Nitrogen fertilizer application significantly enhanced the above traits. Two sorghum cultivars showed significant differences in terms of morphological characters and some measured traits. So that Pegah cultivar was found superior as far as CGR, forage dry weight and forage yield were concerned, while, KFS2 cultivar showed higher LAI. Results also indicated that increasing soil moisture and nitrogen levels can have considerable effect on forage yield improvement. In general, Pegah cultivar and the interaction of 300 kg urea per ha. and 100% FC, achieved the greatest forage yield and could be recommended as the best treatment for similar agro-climatic conditions.