Organic carbon and nutrient enrichment in clay-rich calcareous soils in self-regenerating fallows in humid tropical agroecology

Abstract

Self-regenerating fallows are areas left to regenerate naturally after agricultural use and are typically characterized by diverse plant species and minimal human intervention. To measure the efficiency of this natural fallow system, we evaluated soil organic carbon (SOC) and nutrient concentrations vis-à-vis the fallow duration. The study site was located in the Onigbedu community, Ogun State, Nigeria, with large commercial limestone deposits. Mining and agriculture are the main land use types. The study was oriented on 100 hectares of land previously cultivated at different times and left to fallow. The fallow duration ranged between less than 3 years and more than 20 years. At the end of this study, it was observed that the soils are within a large group of calcareous soils. SOC ranged from 15 to 26 mg/g, available phosphorus from 3.0 to 6.0 mg/kg, total nitrogen from 0.5–2.0 mg/g, effective cation exchange capacity (ECEC) from 2.0–24.0 cmol₍₊₎/kg, calcium from 2.0–20 cmol₍₊₎/kg, Mg from 1.0–2.0 cmol₍₊₎/kg, 0.1–0.4 cmol₍₊₎/kg, manganese from 19 to 80 mg/kg, and zinc from 1.5–2.0 mg/kg in increasing order of fallow duration. Soil nutrients and SOC improved consistently with increasing fallow periods. While fallow duration influenced soil nutrient build-up, other management practices and environmental factors also play significant roles. Farmers can enhance soil fertility and nutrient levels by optimizing fallow durations and using efficient soil management practices, leading to sustainable agriculture and improved crop yields.