Integrated application of nitrogen, phosphorus, and lime for boosting faba bean (Vicia faba L.) yield on acidic nitisols of Ethiopia

Abstract

Combining nitrogen (N) and phosphorus (P) fertilizers with lime (CaCO₃) significantly enhances faba bean yields in central Ethiopia by mitigating soil acidity and bridging existing productivity gaps. During the 2023 cropping season, a field trial was conducted at Welmera and Ejere districts to evaluate the effects of N, P, and lime on grain yield and economic returns. The treatments comprised three levels of N (0, 18, 36 kg ha⁻1), P₂O₅ (0, 46, 92 kg ha⁻1), and lime (0, 4.5, 9 t ha⁻1),with three replications arranged in a randomized complete block design in a factorial arrangement. Results showed that the soil pH at the two sites is strongly acidic; however, after harvest, the pH dramatically increased from 5.08 and 5.11 to 5.8 and 5.6 at Welmera and Ejere, respectively. Application of 36 kg N ha⁻1, 92 kg P₂O₅ ha⁻1, and 9 t lime ha⁻1 significantly improved plant height, nodule number, number of pods per plant, and harvest index. Notably, N and P interactions alone (p ≤0.001) also increased the number of effective nodules and nodule dry weight. Maximum number of seeds per pod (3.63) increased by 44.9% and pod number (36.3,), hundred-seed weight (123 g), Above-ground dry biomass (13.88 t ha⁻1) and straw yield (7.4 t ha⁻1 at Ejere) was recorded with 92 kg P₂O₅ ha⁻1 and 4.5 t lime ha⁻1. Grain yield (7.10 t ha⁻1, an 84.65% increase over the control), was achieved at Welmera, yielding a net economic return of ETB 251,335.3 and a marginal rate of return (MRR) of 165%. under the highest N-P-lime combination. In conclusion, the integrated application of N, P, and lime increased grain yield by 77.6% compared to the control, and effectively addressed soil fertility and acidity issues that hinder faba bean productivity, promoting sustainable food security in an economically and environmentally safe manner.