Fertility Evaluation Of Soils After Ten Years Of Intensive Rural Vegetable Production In Nsukka, Southeastern Nigeria

Abstract

A medium-term assessment of soil fertility of continuously cultivated fields for vegetable production is an important factor for long-term soil sustainability. This study investigates the potentials and limitations of ten-year nutrient management on the fertility of soils under semi-commercial cultivation of four different vegetables [fluted pumpkin (Telfairia occidentalis), tomato (Solanum lycopersicum), red, and green pepper (Capsicum annuum)] in Nsukka, Southeastern Nigeria. Topsoil samples (0-30 cm) were collected in triplicate from the different vegetable fields and characterized. The results showed that the soils were sandy loam, loamy sand and sandy clay loam (SCL) with similar bulk density, total porosity and saturated hydraulic conductivity. However, the soils under red and green peppers had the lowest percentage of the 0.50-1.00 mm water-stable aggregate (WSA), but the highest percentage of aggregate stability (AS) than the other soils. The soils differed significantly in pH, organic matter (OM), available phosphorus (Av.P), exchangeable magnesium (Mg²⁺), sodium (Na⁺), potassium (K⁺), hydrogen (H⁺) and effective cation exchange capacity (ECEC). The moderately acid pH soils under red pepper and tomato cultivation had the highest values for OM, Na⁺, K⁺ and H⁺, as well as ECEC, while the slightly acid pH soil under fluted pumpkin cultivation had the highest Mg²⁺ content. The soils had low N but high Av.P reserves, indicating low P use efficiency. While the favourable pH, organic matter, and Av.P represent the potential of the soils for vegetable cultivation, N and K are the main potentially limiting nutrients in the studied soils. Overall, the soils under red pepper and tomato cultivation had a better fertility status due to their SCL texture and the application of organic and inorganic fertilizers, which contributed to better soil structure and greater nutrient retention compared to the soils under fluted pumpkin and green pepper.