Efficient Strategy for Water and Nutrient Management to Economically Enhance Mombasa Grass Productivity

This study investigates the optimal water and nitrogen fertilization levels to enhance the productivity and quality of Mombasa grass (Panicum maximum cv. Mombasa) under drought-prone conditions. Four irrigation treatments were applied based on irrigation depth: high irrigation (I1 = 691.2 mm), control irrigation (I2 = 575.0 mm), moderate stress (I3 = 460.8 mm), and severe stress (I4 = 345.6 mm). Two nitrogen fertilization levels were tested: full fertilization (F1 = 300 kg N·ha−1) and half fertilization (F2 = 150 kg N·ha−1). Severe water stress (I4) significantly reduced growth parameters, with fresh weight (FW) decreasing by 21.9% and dry weight (DW) decreasing by 20.3% compared to the control. In contrast, higher irrigation levels (I1 and I2) notably improved FW and DW. Full nitrogen application (F1) enhanced FW, DW, and plant height, whereas the half dose (F2) resulted in lower growth performance. Water productivity (WP) was highest under moderate stress (I3) combined with F1, and under severe stress (I4) combined with F2, it was the worst. Protein percentage per irrigation water unit (PPW) increased with greater water deficits, while total protein production per irrigation water unit (TPW) peaked under higher irrigation levels. These findings indicate a trade-off between forage quality (PPW) and quantity (TPW), where PPW is more critical for marketing purposes and TPW is better suited for on-farm feeding. Economically, treatment I3F1 proved to be the most efficient option under moderate water availability. It combined reduced irrigation with a high fertilizer rate, resulting in a strong net return and the second-highest benefit-cost ratio among all treatments. This indicates its potential as a cost-effective and resource-efficient strategy in water-limited environments.