Assessment of Alternative Warm-Season Annual Grasses for Forage Production in Water-Limited Environments

Abstract

As traditional forage crops demand substantial water, exploring alternatives with lower water demands can mitigate the strain on water supplies. This pot study evaluated five annual warm-season forages (forage sorghum (FS) [Sorghum bicolor (L.) Moench], prussic acid-free forage sorghum (PF) [Sorghum bicolor subsp. Drummondii], sorghum x sudangrass hybrid (SS) [Sorghum bicolor x drummondii], sudangrass (SU) [Sorghum sudanense (Piper) Stapf], and pearl millet (PM) [Pennisetum glaucum (L.) R. Br.]) under two different irrigation treatments (40% and 80% ETo). Morphological (leaf area, leaf count, plant height), biomass yield, nutritional content (nitrogen (N), acid detergent fiber, and in vitro true digestibility (IVTD)), and water use efficiency (WUE) parameters were assessed at 35 and 49 days after planting (DAP). Irrigation effects varied with time, more strongly influencing nutritive value at 35 DAP and morphological traits at 49 DAP. WUE was significantly affected by irrigation at both timepoints. No single forage consistently outperformed across all metrics. PF and SU had the most biomass (p < 0.01), while PM had the greatest N content (p < 0.01). However, PF and SU had the highest WUE for biomass and digestible dry matter (p < 0.01). These findings suggest PF and SU may improve forage system sustainability under limited water availability.