Yield and benefit optimization of soybean production through integrated use of vermicompost and phosphorus fertilizer

Abstract

Soybean (Glycine max L.) is a versatile leguminous crop that is widely grown in many parts of the world. However, its productivity is challenged by several limitations of which declining soil fertility is one of the major factors. The problem is aggravated by lack of integration in use of organic and inorganic fertilizer. A study was conducted in 2023 and 2024 at two potential soybean growing locations in southern Ethiopia to investigate effects of combined applications of vermicompost and phosphorus fertilizer on soybean yield and economic benefits. Experimental treatments consisted of factorial combinations of four levels of vermicompost (0, 2.5, 5, and 7.5 t ha⁻¹) and four levels of phosphorus (0, 10, 20, and 30 kg ha⁻¹) and were tested in a randomized complete block design with three replications. Results had shown significant differences in yield and yield-related components due to both main and interaction effects. Application of 10 kg ha⁻¹ phosphorus combined with 7.5 t ha⁻¹, vermicompost resulted in the highest number of pods per plant with 44 in 2023 and 42 in 2024. This combination increased the number of pods per plant by 240% compared to the control, averaged over the 2 years. The highest biomass was obtained from the combined use of 10 kg ha⁻¹ phosphorus with 7.5 t ha⁻¹vermicompost, resulting in 10.3 t ha⁻¹ average biomass yield. The combination 10 kg ha⁻¹of phosphorus with 7.5 t ha⁻¹of vermicompost resulted in the highest average grain yield of 3.67 t ha⁻¹. Similarly, this combination provided the highest net benefit of $995 and a benefit–cost ratio of 3. In conclusion, the study recommends the combined application of 10 kg ha⁻¹ phosphorus and 7.5 t ha⁻¹vermicompost for the two test sites and similar agro-ecological environments based on best crop yield and economic benefit.