Evaluating the Effect of Regulated Deficit Irrigation and Partial Root-Zone Irrigation on Water Use Efficiency Based on Forage Production and Quality of Pearl Millet

Water scarcity in arid and semi-arid regions is a serious challenge for fodder production. Therefore, optimizing irrigation techniques and selecting drought-resistant cultivars, such as millet, is essential. This study investigated the effects of two irrigation methods, namely, regulated deficit irrigation and partial root-zone irrigation, at four irrigation levels (100%, 80%, 60%, and 40% of the plant's water requirement, WR) on forage yield, irrigation water use efficiency, forage protein percentage, and yield of hybrid pearl millet (Nutrifeed variety). The research was conducted using a split-block (strip-split-plot) design based on a randomized complete block design (RCBD) with three replications, utilizing the drip irrigation method with tape strips at the research farm of Shahid Bahonar University of Kerman, during the 2017 and 2018 growing seasons. The results demonstrated that the partial root-zone irrigation treatment, by supplying 100% WR resulted in the highest fresh and dry forage yields, with 80.20 and 16.27 t/ha, respectively. The 80% WR in the same method, in addition to being ranked second, with fresh and dry forage yields of 71.71 and 15.47 t ha-1, respectively, yielded the highest dry forage protein yield (1418.7 kg/ha) and water use efficiency based on fresh and dry forage yields (13.74 and 2.97 t/m3, respectively). Additionally, the highest protein percentage (11.41%) was observed in the partial root-zone irrigation treatment by supplying 60% WR. Overall, partial root-zone irrigation, by providing 80% WR, is recommended as a suitable strategy to improve irrigation water use efficiency and maintain the quality and quantity of forage under water-limited conditions.