Effect of Organic and Inorganic Fertilizer and Tillage Practice on Soil Properties in a Coastal Plain Sand Soil, Etinan, Nigeria

Abstract

A field study was conducted to evaluate the effects of organic and inorganic fertilizers, conventional and tillage practices on soil physical and chemical properties in a Coastal Plain Sand soil of Etinan, Akwa Ibom State, Nigeria. The experiment employed a split-plot design in a randomized complete block layout with three replications. Tillage formed the main plot treatments while fertilizer types control (no fertilizer), poultry manure (PM), NPK 15:15:15, microbial fertilizer (MF), and their combinations (PM+NPK, PM+MF, NPK+MF, PM+NPK+MF) served as subplots. Composite soil samples were collected before and after treatment application to determine changes in soil properties including bulk density, porosity, pH, organic carbon, total nitrogen, available phosphorus, and exchangeable bases. Initial soil analysis revealed poor fertility status typical of Coastal Plain Sand soils, with low pH (4.8), organic carbon (0.92%), total nitrogen (0.09%), and available phosphorus (7.0 mg/kg). Results showed that poultry manure and its combinations significantly reduced bulk density and improved porosity compared to sole NPK and the control. Organic and integrated fertilizer treatments under reduced tillage notably increased soil pH, organic matter, total nitrogen, available phosphorus, calcium, magnesium, and base saturation. The highest improvements were observed in the PM+NPK+MF treatment under reduced tillage, which significantly outperformed other treatments in enhancing soil fertility indices. The findings suggest that combining organic and inorganic fertilizers under reduced tillage can ameliorate the fertility constraints of sandy soils in humid tropical regions. This integrated nutrient and soil management approach holds promise for sustainable agricultural productivity in fragile agro-ecological zones.