Evaluation of water-energy productivity and nutritional traits in silage sorghum in arid regions

Deficit irrigation is known as an effective method for alleviation of drought impacts on crop yield. It also saves a large amount of irrigation water without having a negative impact on yield. Considering the relationship between water consumption and the amount of energy consumed, the evaluation of water productivity (WP) and energy productivity (EP) seems essential to develop a suitable method for efficient use of water for agriculture in the arid regions with limited water resources. Therefore, in this study, it was attempted to investigate WP and EP, some nutritional traits and stress indices for silage maize and silage sorghum in a loamy sandy soil using a drip tape irrigation system. For this purpose, a field experiment was performed using a randomized complete block split-plot design with three replications under three irrigation levels of I1: 100% (conventional), I2: 80%, and I3: 60% of the crop evapotranspiration (ETc), and four cultivars of sorghum and maize were planted as the main and split plots. The irrigation scheduling was done using a reference crop evapotranspiration (ETo) calculator (Penman–Monteith equation) and AquaCrop simulation model. The results showed that the amount of irrigation water had a significant effect on fodder and dry yield, WP and EP (p < 0.01). The values of fresh and dry yields and WP for silage maize were 61.23 tons/ha, 18.91 tons/ha and 10.73 kg/m³, respectively. However, for silage sorghum, with relatively lower water requirements, these values were much higher (103.84 tons/ha, 30.00 tons/ha and 19.82 kg/m³, respectively). The maximum WP and EP for sorghum and maize were obtained in I3 and I1 treatments, respectively. It was also found that the nutritional traits, including dry matter (DM) and crude protein (CP), were affected by crop type (sorghum and maize) and deficit irrigation levels. Hence, the maximum DM (31.72%) and CP (9.607%) were observed for Speedfeed sorghum cultivar under I1 irrigation level, the maximum ash (9.86) was reported for Speedfeed sorghum cultivar under I3 irrigation level, the maximum neutral detergent fiber (NDF) (74.47%) was obtained for Maxima maize cultivar under I1 irrigation level, and the maximum acid detergent fiber (ADF) (39.183%) was achieved for Pegah sorghum cultivar under I1 irrigation level. According to the results, it was concluded that it would be wise to replace sorghum with maize in order to achieve higher WP in arid regions.