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Abstract

In the changing climate of semi-arid regions, optimizing mineral fertilizer regimes is essential to minimize environmental degradation, support ecological recovery, and sustain biomass crop production. Significant research gaps remain regarding the macronutrient (nitrogen (N), phosphorus (P), and potassium (K) requirements of untraditional and underutilized leguminous forage crops like rice bean (Vigna umbellata), especially in the low-fertility soils of semi-arid regions. To bridge this research gap, a two-year field experiment was conducted to study the growth, forage yield and nutritional quality of rice bean as affected by different fertilization regimes, including a single fertilization regimen (N 150 kg ha-1), double fertilization regime (N 150 kg ha-1 and P 100 kg ha-1), and triple fertilization (N 150 kg ha-1, P 100 kg ha-1, and K 100 kg ha-1), along with a control (no fertilization) treatment. The results showed that the triple fertilization remained superior by producing the highest plant density, plant height, and leaf area index, along with fresh and dry weight of rice bean during both seasons. Additionally, this fertilization treatment recorded its supremacy by producing the highest green forage yield (179% greater than control) and dry matter biomass. Concerning the nutritional quality of forage rice bean, the triple fertilization regime gave the greatest contents of crude protein, ether extractable fats, and total ash, whereas fiber content was significantly decreased. Double fertilization followed it, which in turn was followed by a single fertilization, underscoring the need for integrated and balanced supplementation of macronutrients for forage rice bean production in semi-arid regions. Moreover, correlation analysis revealed a highly significant association of plant height (R2= 0.987***), leaf area index (R2= 0.977***), and fresh weight per plant (R2= 0.977***) with green forage yield of rice bean. However, further research is needed to examine the impact of these fertilizer regimes on nitrogen fixation rate in rice bean root nodules, along with the estimation of nutrient losses in the form of leaching and volatilization.

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