Synergistic effects of vermicompost and NPSZnB fertilizers on potato development and production

Abstract

In Ethiopia, potato productivity is constrained by declining soil health and inconsistent fertilizer use. This study evaluated the effects of vermicompost (VC) and blended NPSZnB fertilizer on potato growth, yield, and economic returns in East Wollega during the 2022 main cropping season. A 4 × 4 factorial experiment was conducted using a randomized complete block design with three replications, testing four VC rates (0, 2.5, 5, and 7.5 t ha⁻¹) and four NPSZnB rates (0, 150, 195, and 240 kg ha⁻¹) with the Gudane variety. Soil analysis indicated that VC generally improved cation exchange capacity, organic carbon, and available phosphorus. Significant interactions between VC and NPSZnB affected maturity, plant height, tuber numbers, unmarketable yield, and tuber size distribution. The combination of 7.5 t ha⁻¹ VC and 240 kg ha⁻¹ NPSZnB produced the highest marketable tuber yield (19.4 t ha⁻¹), approximately 57% higher than the control, while reducing unmarketable tubers. PCA explained 85.7% of the total variation, revealing contributions to PCA and positive associations among major yield traits. Economically, this treatment generated a net benefit of 266,091 ETB ha⁻¹ and a marginal rate of return of 799%. Further studies across multiple locations and seasons are recommended to more validate these findings.