Nitrogen response and water use efficiency of sweet sorghum cultivars

Sweet sorghum [Sorghum bicolor (L.) Moench] is a biofuel crop, which can be grown under tropical rainfed conditions without sacrificing food and fodder security. Three sweet sorghum cultivars (CSH 22 SS, NTJ 2 and ICSV 93046) with two row spacings (60 and 45 cm) and six nitrogen levels (0, 30, 60, 90, 120, and 150 kg ha−1) were grown on Vertisols during three post rainy (November to April) seasons at the ICRISAT center farm in Patancheru, India. The results showed that the row spacings (60 or 45 cm) had no influence on performance of the cultivars. Sweet sorghum hybrid CSH 22 SS produced the highest green stalk yield (45.4 Mg ha−1) and grain yield (2.33 Mg ha−1) compared to NTJ 2 (32.66 Mg ha−1 and 1.70 Mg ha−1) and ICSV 93046 (38.44 Mg ha−1 and 2.03 Mg ha−1). Net economic return from CSH 22 SS (US$ 681 ha−1) was also significantly higher than that from NTJ 2 (US$ 415 ha−1) and ICSV 93046 (US$ 539 ha−1). All cultivars responded to applied N up to 150 kg ha−1; however beyond 90 kg ha−1 N rate, the increase in yield was insignificant. Estimated N use efficiency (NUE) values indicated that 90 kg N ha−1 was an optimum N level for sweet sorghum crop. Simulated soil water balance components revealed that reduction in total transpiration due to water stress was 20 to 45% compared to the no-stress. In case of water use efficiency, CSH 22 SS showed the highest economic returns per unit volume of water input. Based on these results, it is concluded that sweet sorghum hybrid CSH 22 SS at 90 kg N ha−1 is the best remunerative combination for maximizing yield, economic returns and resource use efficiency.