Water Deficit Irrigation and Nitrogen Response of Sudan Grass under Arid Land Drip Irrigation Conditions

The present study evaluated the interactive effect of water deficit irrigation (WDI) and nitrogen application on Sorghum sudanense growth, biomass accumulation, nitrogen content and water productivity for two consecutive seasons and three cuts. The WDI of 50, 30 and 10% depletion ratios (different application rate and frequency) along with four levels (0, 100, 200 and 300 kg ha−1) of nitrogen fertilizer were applied in three splits. The WDI of 10% depletion ratio recorded significantly higher (15–17%) fresh and dry biomass accumulation of both leaf and stem as compared with WDI of 50%. Nitrogen application improved all growth traits irrespective of the applied levels of WDI, season and cut number. The interaction of WDI of 30% depletion ratio and N200 outcompeted all other treatments for plant nitrogen and protein contents, as the resulting increment was 10–22% higher as compared to control. Of the different cut numbers, the first cutting ascribed the maximum value for plant protein contents and stated up to 32% improvement over second and third cuttings. By increasing the rate of nitrogen application, a significant increment in crop water productivity was also measured that attributed at least a threefold higher value for stem over leaf. In essence, WDI of 10% depletion ratio and nitrogen rate of 200 kg ha−1 were the optimum levels that improved Sudan grass growth, biomass and water use efficiency; moreover, the 30% depletion ratio favoured plant nitrogen content. By using a WDI approach, we can improve our forage yield with a limited amount of water by increasing irrigation frequency. Copyright © 2017 John Wiley & Sons, Ltd. Résumé La présente étude a évalué l'effet interactif de l'irrigation déficitaire (WDI) et de la fertilisation azotée sur la croissance du sorgho du Soudan, sur l'accumulation de biomasse, la teneur en azote et la productivité de l'eau pendant deux saisons consécutives et trois coupes. On a appliqué des déficits hydriques de 50, 30 et 10% (taux d'application et fréquence différents) ainsi que quatre doses (0, 100, 200 et 300 kg ha−1) d'engrais azotés. Le WDI de 10% a permis l'accumulation de biomasse fraiche et de tiges de 15 à 17% par rapport à l'IDM 50. L'application d'azote a permis d'améliorer tous les caractères de la croissance, indépendamment des niveaux appliqués de WDI, de la saison et du nombre de coupes. L'interaction du WDI de 30% et du traitement N200 a dépassé tous les autres traitements pour les teneurs en protéines et