Restoration Potential of Organic Manure on Abandoned Farmlands for Solanum Crops in Awka, Nigeria
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Abstract
This study assessed the ecological characteristics of two abandoned farmlands within Nnamdi Azikiwe University, Awka, Nigeria, and evaluated the effectiveness of cow dung manure in restoring soil fertility and enhancing the early growth of Solanum melongena (eggplant) and Solanum lycopersicum (tomato). The study was conducted at two sites within the Nnamdi Azikiwe University campus. An ecological survey was carried out using standard quadrat sampling techniques (20 quadrats of 25 m² per site) to assess floristic composition, species diversity, and phytosociological attributes. Soil samples were collected and analysed for physico-chemical properties, including nitrogen, phosphorus, potassium, organic matter, organic carbon, pH, and particle size distribution. A pot experiment employing a Randomised Complete Block Design (RCBD) was conducted to evaluate the effects of cow dung manure on germination percentage and early seedling growth parameters. A total of 535 and 587 individual plants were recorded in Site 1 and Site 2, comprising 21 species in 10 families and 18 species in 9 families, respectively. Vegetation in both sites was dominated by herbaceous species, particularly members of Poaceae and Asteraceae, indicating disturbed ecosystems undergoing secondary succession. The Shannon–Wiener diversity index values of 2.56 (Site 1) and 2.47 (Site 2) indicated moderate species diversity with low evenness. The Sørensen similarity index of 31.03% revealed low floristic similarity between sites, suggesting pronounced spatial heterogeneity. Soil analysis showed that Site 1 had higher nitrogen (5.41 ± 0.72%) and organic matter (2.67 ± 0.67%), while Site 2 exhibited higher phosphorus (7.85 ± 1.10 mg/g) and organic carbon (9.44 ± 0.73 µg/g). Both sites were classified as sandy loam with slightly alkaline pH conditions. Organic manure application significantly (p < 0.05) improved germination percentage, seedling height, leaf number, and root length of both test crops across both sites. Germination rates increased from 65.4% to 89.6% in S. melongena and from 68.2% to 91.3% in S. lycopersicum under organic manure treatment at Site A. The findings show that although abandoned farmlands in this landscape support moderately diverse vegetation, they are dominated by opportunistic species, reflecting nutrient limitations and disturbance pressures. The findings also demonstrate that cow dung manure is an effective, low-cost soil amendment for restoring soil fertility and supporting the establishment of vegetable crops on such lands.
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