Abstract
Inoculating groundnut and cowpea with highly effective and competitive rhizobial strain improves nodulation. A field experiment was carried out at the experimental field of the Faculty of Agriculture, University for Development Studies, Nyankpala, to evaluate the growth and yield responses of cowpea and groundnut to five rhizobial inoculant strains in the Guinea Savanna zone. The experiment was laid out in a randomized complete block design (RCBD) with eight (8) treatments replicated four (4) times. The treatments included five rhizobial inoculant strains (NC 92, KNUST 1002, KNUST 1003, KNUST 1006, and BR 3267), two N fertilizer levels (20 kg·N/ha and 40 kg·N/ha), and a control. The results showed that rhizobial inoculation and N fertilizer application increased nodulation, biomass yield, pod number, pod weight, hundred seed weight, nodule dry weight, and pod yield of groundnut compared with the control. Rhizobial inoculation averagely increased the nodulation and yield by 63 and 67%, respectively, compared with the control. Mineral N fertilizer (20 kg N/ha) on average increased the nodulation and yield by 24 and 25%, respectively, compared with the control plots. It can be recommended from this study that, in the absence of highly competitive rhizobial strains such as KNUST 1006 and NC 92 as biofertilizers for increasing the nodulation and yield of cowpea and groundnut, 20 kg·N/ha can be used for the purpose. Further research is recommended using these rhizobial strains in combination with lower rates of N fertilizers (<20 kg·ha−1).
Highlights
Groundnut (Arachis hypogaea L.) and cowpea (Vigna unguiculata (L.) Walp) are among the most important leguminous crops cultivated worldwide, especially in tropical and subtropical regions as food crops [1] due to their drought resistance [2]
Rhizobial inoculation and N fertilizer application averagely increased nodule dry weight of groundnut by 71% and 23%, respectively compared with the control
Rhizobial Inoculant Strains Improved Biomass in Cowpea and Groundnut. e greater biomass/dry shoot recorded by 20 N and 40 N in cowpea and groundnut, respectively, compared with other treatments in this study shows that mineral fertilizers do increase soil fertility, which in turn increases plant growth and development. is result is in conformity with [16], who observed that nitrogen-fertilized plots produced significantly greater biomass
Summary
Groundnut (Arachis hypogaea L.) and cowpea (Vigna unguiculata (L.) Walp) are among the most important leguminous crops cultivated worldwide, especially in tropical and subtropical regions as food crops [1] due to their drought resistance [2]. Groundnut and cowpea are grain legume crops cultivated in the Guinea Savanna zone of Ghana and are ranked as the number one grain legumes [3]. Is eventually makes it difficult for farmers to get the required amount of fertilizer necessary to increase crop yield. Biological nitrogen fixation is a less expensive alternative for overcoming these challenges and results in soil nitrogen replenishment and crop productivity improvement [7]. Groundnut and cowpea can obtain much of their N requirements through symbiotic nitrogen fixation if the root nodules are infected by effective strains of rhizobia [8]. Rhizobial inoculation has the capability of increasing the growth and yield components of nodulating legumes, and this will eventually increase the number of nodules and the amount of nitrogen fixed into the soil [9]. Reference [10] reported that groundnut and cowpea plants with symbiotic nitrogen fixing bacteria are able to fix about 15 to 210 kg/ha of nitrogen per season in Africa. e use of rhizobia as biofertilizer (inoculants) has been reported to increase
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