Water Depletion Pattern and Water Use Efficiency of Forage Sorghum, Pearl millet, and Corn Under Water Limiting Condition

In the semi-arid Texas High Plains, declining irrigation water supply hinders the profitable corn (Zea mays L.) silage production, the principle feed ingredient of the beef and dairy industries. Drought-tolerant and deep-rooting crops like forage sorghum (Sorghum bicolor L.) and pearl millet (Pennisetum glaucum L.) could be an alternative to corn silage under limiting irrigation. A field study was conducted during 2018 and 2019 at New Deal, TX to assess soil water depletion patterns, water use efficiency (WUE), and silage yield of forage sorghum, pearl millet, and corn under limited irrigation. The experiment was conducted in split-plot design with three irrigation levels [I₀ (55 and 29 mm), I₁ (172 and 147 mm), and I₂ (323 and 260 mm) in 2018 and 2019, respectively] as main-plots and five cultivars [P1498AM (corn), AF7401 and Silo700D (BMR sorghum), and Epic and Exceed (BMR pearl millet)] as sub-plots with three replications. The soil water depletion amount was greater in I₀ (105 and 57 mm) followed by I₁ (60 and 37 mm) and I₂ (44 and 13 mm) in 2018 and 2019, respectively. Fresh biomass yield was the greatest in I₂ followed by I₁ and I₀; however, the highest WUE was achieved in I₀ and I₂ in 2018 and 2019, respectively. Water depletion depth was greater for sorghum and pearl millet plots (0–1 m) than corn plots (0–0.6 m) which resulted in greater water depletion amount in sorghum (75 and 31 mm) and pearl millet (68 and 48 mm) plots than corn (67 and 28 mm) during 2018 and 2019, respectively. Average yield and WUE were the highest in sorghum cultivars, followed by pearl millet and corn. Results confirmed that the higher silage yield and WUE can be achieved by sorghum compared to pearl millet and corn under limited irrigation conditions.