Efficacy of Organic and Inorganic Soil Amendments on the Growth of Indigenous Vegetables: Implications for Watershed Restoration in Southeastern Nigeria

Abstract

Restoring degraded watersheds requires strategies that rebuild soil fertility and promote vegetative cover. This study evaluated the effectiveness of organic (poultry manure) and inorganic (NPK 15:15:15) soil amendments in enhancing the growth of two indigenous, nutrient-responsive vegetables; Amaranthus hybridus L. (African spinach) and Telfairia occidentalis Hook f. (fluted pumpkin), as a potential restoration tool for degraded tropical watershed soils. A randomized block six-week pot experiment was conducted with three treatments: poultry manure, NPK fertilizer, and an unamended control. Growth parameters (plant height, stem girth, number of leaves, leaf area) were monitored over six weeks. Results showed that both amendments significantly (p < 0.05) improved all growth parameters compared to the control. NPK fertilizer produced the tallest plants for both A. hybridus (104.06 cm) and T. occidentalis (61.52 cm) and the largest leaf area. Poultry manure resulted in the highest number of leaves for T. occidentalis (30.08). While NPK promoted rapid initial growth, poultry manure demonstrated robust performance in overall biomass development. The study concludes that integrating both amendments using NPK for quick initial establishment and organic manure for sustained soil health, offers a promising, sustainable strategy for enhancing vegetative cover and initiating ecological recovery in degraded watersheds of southeastern Nigeria.