Revitalizing degraded Alfisols: the promising impact of timely organic manure application on soil health and productivity

Farmland degradation in south Ethiopia presents critical challenges to sustainable agriculture, underscoring the urgent need for effective soil restoration strategies. This study investigated the effects of varying rates of organic manure application on the physico-chemical properties of a degraded Alfisol, and identified optimal management practices that enhance soil health and crop productivity. Poultry manure (PM) was applied at rates of 0, 10, 15 and 20 t ha−1 to five vegetable crops: Amaranths (Amaranthus cruentus), Okra (Abelmoschus esculentus), Celosia (Celosia argentea), Eggplant (Solanum melongena) and African Eggplant (Solanum macrocarpon). The experiment employed a randomized complete block design with three replicates to ensure robust statistical analysis. Results demonstrated that PM application significantly reduced soil Bulk Density (BD) from 1.45 g cm⁻³ (control) to 1.30 g cm⁻³ (20 t ha⁻¹), while soil pH decreased from 6.5 to 5.8. In contrast, Electrical Conductivity (EC) increased from 0.15 dS m⁻¹ (control) to 0.35 dS m⁻¹ (20 t ha⁻¹), and Water-Stable Aggregates (WSA) improved from 32 to 55%. Additionally, Total Nitrogen (TN) rose from 0.12 to 0.25%, Available Phosphorus (Av. P) increased from 10 mg kg⁻¹ to 25 mg kg⁻¹, and Soil Organic Carbon (SOC) enhanced from 1.5 to 3.2%. Strong positive correlations were observed between SOC and EC, Av. P, and TN, while an inverse relationship with BD was noted. Multivariate analysis confirmed significant effects of PM on Av. P, TN, and BD (p < 0.05). Even with a short evaluation period, application of organic manure is beneficial for restoring physically degraded soils and enhancing crop production potential.