Evaluation of nitrogen fixation potential of cowpea varieties and effect of residue nitrogen for maize production

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Field experiments were conducted in the major and minor seasons in 2014 to study the nitrogen fixing potentials of ten cowpea varieties and to determine the effect of residual fertility on maize growth and yield. The experimental design was Randomized Complete Block with four replications. Each replication had 10 cowpea plots and a reference plot of maize. Data collected were plant height, number of leaves, number of branches, stem girth, emergence, plant stand, days to 50% flowering, plants harvested, shoot dry weight, nodule number, nodule dry weight, percentage nodule effectiveness, number of pods per plant, number of seeds per pod, 100 seed weight, harvest index and grain yield per hectare. After the cowpea was harvested, the residues were incorporated back in to the soil and maize was sown on all plots. A control plot received the normal fertilizer recommended rates. Data collected on maize were plant height, number of leaves, stem girth, shoot dry weight, number of cob per plant, number of seeds per cob, 100 seed weight, harvest index and grain yield per hectare. The results showed that all the varieties nodulated freely with the native rhizobia in the soil. „Asetenapa‟ variety fixed the greatest amount of nitrogen and the maize grain yield was greater in the „Asetenapa‟ residue incorporated plots. The grain yield from the fertilizer applied treatments was not significantly higher than any of the residue incorporated treatments. The results indicated that if cowpeas are cultivated on plots and their residues are effectively recycled, the field would be fertile enough to support maize yields similar to the application of recommended
A thesis submitted to the Department of Crop and Soil Sciences, Faculty of Agriculture of the College of Agriculture And Natural Resources, Kwame Nkrumah University of Science and Technology, Kumasi, Ghana. This is in partial fulfillment of the requirement for the award of M.Phil. in Agronomy (Crop Physiology).