Abstract
Field experiments were carried out during the 2008 and 2009 cropping seasons to evaluate the effects of enriched organic manure on both nodule count and N-fixing ability of two varieties of cowpea (ITAS EARLY and IAR 1060). The treatments were: poultry manure (0 , 3 ,and 6 t ha-1); NPK 20-10-10 fertilizer (0 , 30, and 60 kg N ha-1). Treatments were combined factorially to give nine treatment combinations. The experiments were laid-out in a randomized complete block design (RCBD) with three replications. Each experiment plot measured 3 m x 4 m with an alley of 1 m between blocks and 0.5 m between plots. Four seeds were planted per hole at 25 cm plant-to-plant distance in a maize mixture and later thinned to two plants per stand at two weeks after planting (2 WAP).,This gave a total population of about 80, 000 plants per hectare. The nodule count and N-fixed were determined at 3, 6, and 12 weeks after planting (WAP). The results showed that the combined NPK 20-10-10 with poultry manure contributed to the differences (P<0.05) in number of count obtained per plant of cowpea as well as the amount of N-fixed in the experiment. The higher rates of NPK 20-10-10 fertilizer, number tend to reduce the number of nodules as well as the amount of N-fixed. The highest nodules (86.6 and 102.2) and N-fixed (42.05 and 59.50 kg ha-1) for 2008 and 2009, respectively were from the combination of 6 t ha-1 of poultry manure and no NPK 20-10-10 fertilizer application on cowpea variety, ITAS EARLY. This suggested that cowpea variety (ITAS EARLY) tolerated high nutrient in N-fixation and as such a better choice as a leguminous component than IAR 1060 in a cropping system.Keywords: Enriched organic manure, N-fixation, nodules count, cowpea varieties
Highlights
The use of food and non-grain legume species in cropping systems has been demonstrated to have positive attributes especially as soil ameliorants
In 2008 at 6 weeks after planting (WAP) the highest average count was obtained from 6 t ha-1 poultry manure (85.6), this was followed by 3 t ha-1 poultry manure (68.8) and the third highest was obtained from 3 t ha-1 poultry manure + 60 kg N ha-1 NPK 20-10-10 (52.5), while in 2009 at WAP the highest average count was obtained from 6 t ha-1 poultry manure (102.2), the second highest count from 3 t ha-1 poultry manure
Effect of the enriched poultry manure on cowpea varieties shows that negative effect was more pronounced on variety IAR 1060 than ITAS EARLY, and seems to suggest that varietal difference is an important factor in legumes nodulation
Summary
The use of food and non-grain legume species in cropping systems has been demonstrated to have positive attributes especially as soil ameliorants. To ensure productivity and increase in crop yield, Ande et al (2008) suggested that appropriate systems and inputs such as organic, inorganic and biological fertilizers be adequately understood. Legumes commonly form a symbiosis with species of the bacterial family Rhizobiaceae, which can result in an efficient biological nitrogen fixation system. Available research results have consistently demonstrated the ability of the legume species when integrated into cropping systems to enhance N-fixation and N-transfer and most often with exertion of N-sparring effects. The overall cumulative advantages were increase in yield, improved resource use, efficiency of high economic values, crop diversification and reduced environmental pollution. The use of food legumes as components in the system significantly improved the yield of the cereal components
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