Optimizing Soybean Yield in the Sub-humid Savanna of Nigeria: A Study on Poultry Manure and Phosphorus Fertilizer Effects

Abstract

Field experiments were conducted during the rainy seasons of 2003 and 2005 in Samaru in the Northern Guinea 
Savanna zone of Nigeria to test the response of two soybean varieties to application of poultry manure and 
phosphorus fertilizer levels. Soybean varieties TGx 1448-2E and TGx 1019-2EB were grown without and with 1t/ha 
of poultry manure and four levels of P (0, 13.2, 26.4 and 39.6 kgP/ha) in all possible factorial combinations using 
randomized complete block design with four replicates. TGx 1448-2EB was shorter, had more pods and heavier 
seeds than TGx 1019- 2EB. Grain yield and total dry matter per hectare were higher in TGx 1448- 2EB. Application 
of manure consistently influenced most parameters in both years. Manure application increased leaf area index, 
plant height, nodule dry weight, total dry matter per plant and per hectare, number of pods per plant and grain 
yield per hectare. Phosphorus application increased leaf area index, plant height, nodule dry weight, total dry 
matter per hectare and grain yield per hectare. Highest grain yield was obtained with 26.4 kgP/ha which was not 
significantly different from yield obtained with 39.6 kgP/ha. Regression model showed a quadratic response and 
the agronomic optimum was 23.3 kgP/ha for a grain yield of 1.7 t/ha when averaged over both years. Application 
of 1 t/ha of poultry manure significantly (P<0.05) increased grain yield. Averaged over both years, application of 1 
t/ha of manure increased grain yield by 33.7% compared with plots without poultry manure. There were no 
interactions between poultry manure and phosphorus fertilizers in any of the years or when weighed over the 
years.