Sustainable Yield and Economic Efficiency of Para Grass (Brachiaria mutica) Using Composted Cow Manure

Abstract

This study evaluated a sustainable strategy for Para grass (Brachiaria mutica) forage using composted cow manure in the Mekong Delta, Vietnam. At Nam Can Tho Experimental Farm (January–September 2023), a completely randomized design with three replications and three harvest cycles tested five topdressing rates: 0, 2.5, 5.0, 7.5, and 10 t/ha/year (TDM0–TDM10). Tiller emergence, plant height, forage quality, biomass yield, and cost–benefit were measured. Tiller counts were unaffected (p > 0.05), but plant height rose significantly with manure rate. Forage quality remained optimal (CP 7.10–7.85%, NDF 60.5–63.8%). Average fresh biomass yield (FBM, t/ha) increased linearly: y = 0.788x + 14.9 (R2 = 0.937), where x is manure rate (t/ha/year). TDM10 yielded 50% more fresh forage (22.6 t/ha) and 48% more dry matter (4.43 t/ha) than the control (15.0 and 2.98 t/ha; p = 0.001), with crude protein up 56% (0.347 t/ha) and neutral detergent fiber up 41% (2.68 t/ha). Total cost increased slightly (from 521 to 552 USD/ha), but per-ton cost dropped 30% (from 34.7 to 24.4 USD). At 10 t/ha/year, manure optimized yield, profitability, circular nutrient use, and reduced fertilizer dependence, providing a scalable model for tropical smallholder livestock feed.