Soil Nutrient Status and Nutrient Interactions as Influenced by Agro Wastes and Mineral Fertilizer in an Incubation Study in the South West Nigeria
The objective of this study was to compare the effects of NPK 20:10:10 fertilizer, cocoa pod ash and poultry manure on soil nutrient status as well as their interactions. The study was conducted in South Western Nigeria. Two levels of cocoa pod ash at 5 and 10 t ha-1; poultry manure at 5 and 10 t ha-l and NPK 20:10:10 fertilizer at 100 and 200 kg ha-l were separately mixed with soil constituents. There was a control without any treatment. The treatments were replicated nine times on completely randomized design and were sampled at 30, 60 and 90 days for analysis. Three samples per treatment were analysed and discarded each month. Cocoa pod ash and poultry manure rates significantly increased (p<0.05) soil pH, organic matter, N, Ca, Mg, CEC and percent base saturation. Cocoa pod ash at 10 t ha-1 recorded the highest pH and Ca at 30, 60 and 90 days. NPK fertilizer at 200 kg ha-1 had the highest N, P and exchangeable acidity at 30, 60 and 90 days. Cocoa pod ash applied at 10 t ha-1 had highest CEC at 60 days of incubation. Cocoa pod ash and poultry manure decreased exchangeable acidity, while NPK rates increased it. Cocoa pod ash at 10 t ha-1 had the widest Ca: Mg ratio among the treatments and thus may be prone to nutrient antagonism. Cocoa pod ash and poultry manure rates reduced K: Ca ratio compared with control. Among the treatments, OC: N, Ca: Mg and K: Ca ratios fall within the acceptable range for arable crop production in Southwestern Nigeria.
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