gh. r. khajoei-nejad

Reduction of the forage and grain yield of sorghum genotypes under different levels of deficit irrigation has been reported. The plants that have higher water use efficiency (WUE), have a better chance of survival in arid regions. On average, WUE of sorghum in clay, loamy soil has been reported equal to 1.46 kg m-3. Effects of drought stress and different levels of nitrogen on yield of two cultivars of sorghum were investigated and results showed significant effects on plant height, leaf area index, fresh and dry weight of leaf, dry weight of stem and forage yield. The purpose of this research is to investigate the effect of deficit irrigation on grain yield and WUE of sorghum cultivars in Kerman.

This study has been conducted in the research station of Shahid Bahonar University of Kerman with 56o 58' E longitude, 30o 15' N latitude and 1753.8 altitudes. According to the regional information from 1952 to 2005, the average temperature is 17.1 oC, the average rainfall is 154.1 mm, the average annual relative humidity is 32%. The climate of Kerman according to De Martonne method can be classified as semiarid. The experimental design was split-plot based on RCBD with three replications. Three levels of irrigation (after 50, 80 and 110 mm evaporation from class A pan) were assigned to the main plots and the five sub-plots of sorghum cultivars (Speedfeed, Pegah, Payam, Sepideh and Kimia). On the 20th of May all sorghum cultivars were planted at the distance of 10 cm from each other on ridges. On the 7th of October, with considering margins, four square meters of the two middle lines were selected to determine the grain and biological yield. The samples were weighed with a digital scale and heated for 48 hours in the degree of 75 oC-and then the dry weight of each samples were measured again. Finally, the data were analyzed by SAS software (v. 9.1). Comparision of the averages attributes was performed using, Duncan’s test at five percent level of significant.

The result of the analysis of variance (Table 3) has shown a non-significant effect of different irrigation regimes on the study attributes. Grain yields of different cultivars were shown to have a significant effect (P < 0.01) (Table 3). Among the cultivars, Sepideh with the production of 7806.7 kg ha-1 of grain had the highest and Payam with the production of 4721.9 kg ha-1 had the lowest yield (Table 4). The results of the analysis of variance (Table 3) showed that the biological yield of the cultivars were significantly different (P < 0.01). Pegah showed the maximum dry matter production with 30365 kg ha-1 and Payam showed the minimum dry matter production with 12865 kg.ha-1 (Table 4). Harvest index of different cultivars was significantly (P < 0.01) different too (Table 3). The highest harvest index belonged to Sepideh with 43% and the lowest belonged to Pegah with 18% (Table 4). The highest WUE was 1.12 kg m-3 in Sepideh and the lowest of WUE were equal to 0.85 and 0.86 kg m-3 for Speedfeed and Payam, respectively (Table 4). The water use efficiency (WUE) based on the biological yield, between the cultivars was statistically significant different (P < 0.01) (Table 1). The highest WUE belonged to Pegah with 4.34 kg m-3 and the lowest belonged to Payam with 2.33 kg m-3 (Table 2). The lowest crop water requirement was 0.91 m3 kg-1 for Sepideh and the highest was equal to 1.32 m3 kg-1 for Pegah (Table 2). Overall, the results showed that Sepideh is the most appropriate cultivar for the grain yield in arid regions.

The cultivar Sepideh with producing grain yield of 7806.7 kg ha-1 and the water use efficiency (WUE) of 1.12 kg.m-3 is the best choice for the region of Kerman. On the other hand, with the purpose of cultivating sorghum, biological yield, and achieving the minimum water requirement for biological yield of sorghum in this region, Pegah cultivar is the best suggestion.