Effects of Organic Amendments at Phosphorus Rate on Sulphur Fractions and Maize (Zea mays L.) Performance in Soils of Southwest Nigeria

Abstract

Sulphur (S) deficiency in agricultural soils is an increasing concern, particularly in Southwest Nigeria where continuous cropping and nutrient depletion have become prevalent. This study investigated the effects of organic amendments (poultry manure and cow dung) applied at varying phosphorus (P) rates on sulphur fractions and maize performance in soils of Southwest Nigeria. The experiment was conducted as a 2×4 factorial in a Randomized Complete Block Design (RCBD) with three replicates. Treatments comprised two organic amendments (poultry manure at 5 t/ha and cow dung at 5 t/ha) and four phosphorus rates (0, 30, 60 and 90 kg P₂O₅/ha). Results showed that organic amendment application significantly (p ≤ 0.05) influenced soil sulphur fractions, with poultry manure consistently outperforming cow dung in terms of total S, available S and organic S contents. Phosphorus application at 60 kg P₂O₅/ha combined with poultry manure recorded the highest values for most soil S fractions and maize performance indicators including plant height, leaf area index, cob weight and grain yield. The study concluded that the combined application of poultry manure at 5 t/ha and phosphorus at 60 kg P₂O₅/ha optimizes sulphur availability and enhances maize performance in the studied soils.