Sorghum grain yield and nutrient dynamics under varying rates of fertilizer application in the Sub-Sudanian Zone of Burkina Faso

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Soil fertility depletion is known as the most important limitation to food security in Burkina Faso. Low yield of sorghum is constrained by inadequate supply of fertilizers and there is the need to establish optimum rates for sustainable use by farmers. This study is a short-term experiment conducted during the 2014 cropping season on a Luvisol in the sub-sudanian zone of Burkina Faso and was laid in a split-plot, arranged in a randomized complete block design with three replications. Cattle manure (CM) at two rates (0 t ha-1 and 5 t ha-1) constituted the main plot whilst mineral fertilizer (kg ha-1) at eleven rates (0N-0P-0K, 40N-0P-0K, 60N-0P-0K, 40N-15P-0K, 60N-15P-0K, 60N-7.5P-0K, 60N-22.5P-0K, 60N-15P-10K, 60N-15P-20K, 60N-15P-30K and 90N-15P-20K-15S-2.5Zn-10Mg-0.5B) constituted the sub-plots. Analysis of variance showed that sorghum grain N, P and K uptake were significantly (P < 0.05) influenced by the application of mineral fertilizer and cattle manure while their interaction did not significantly affect (P > 0.05) these parameters. Sorghum straw N, P and K uptake were significantly influenced (P < 0.05) by cattle manure and mineral fertilizer rates applied as well as their interaction except the effect of manure on straw K uptake. Soil nutrient contents during plant growth decreased due to the larger quantities of nutrients exported by plant uptake. The highest grain yield response was observed under sole application of 60 kg N ha-1 and 22.5 kg P ha-1. However, the yield obtained under these treatments was not significantly different from the grain yield observed under the applications of 40 kg N ha-1 and 15 kg P ha-1. Since lower N and P rates gave similar grain yield as the reference plot (90N-15P-20K-15S-2.5Zn-10Mg-0.5B), sole application of 60 kg N ha-1 and 22.5 kg P ha-1 can be considered as appropriate rate for optimum grain yield production. The interaction effect of cattle manure and mineral fertilizer did not xiii significantly (P > 0.05) increase sorghum grain yield. The highest grain yield obtained in this case, was with the interaction between 5 t of cattle manure ha-1, 60 kg N ha-1 and 7.5 kg P ha-1 mineral fertilizer rates applied. No significant difference (P > 0.05) in sorghum grain yield was obtained above this fertilizer rate which can undoubtedly be suggested as the optimum rate. The Value Cost Ratio (VCR) of 2.01 and 2.23 obtained respectively under 60N-22.5P-0K and the interaction of cattle manure with 60N-7.5P-0K at the beginning of the wet season slightly exceeded the critical value of 2 required to motivate farmers to apply mineral fertilizer. Thus, fertilizer requirement for sustainable sorghum grain production at the study area in Burkina Faso is 5 t ha-1 of cattle manure combined with 60 kg N ha-1 and 7.5 kg P ha- 1.
A thesis presented to the Department of Crop and Soil Sciences, Faculty of Agriculture, College of Agriculture and Natural Resources, Kwame Nkrumah University of Science and Technology, Kumasi, Ghana, in partial fulfillment of the requirements for the award of the Degree of Master of Philosophy in Soil Science, 2015