Effect of Soil Amendment With Manure on Nodulation, Biomass and Yield of Soybeans and Climbing Beans in Meru County, Kenya
Kithira, I. J.
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The consequence of intense permanent cultivation of land has been severe loss of soil nutrients through removal of harvested produce, removal of crop residue, leaching and gaseous losses. Experiments were designed to investigate the effect of soil amendment with cow manure, chicken manure and fertilizer on nodulation and nitrogen fixation in climbing beans (MAC 64) and soybeans (Gazelle). Isolation and characterization of isolates together with greenhouse experiments were carried out at Kenyatta University laboratory and greenhouse respectively. Field experiments were carried out at Kaguru Farmers Training Centre and Munithu Girls Secondary School farm. The experimental design was a randomized complete block design with four replications. Each of the legume was planted in soils amended with cow manure, chicken manure, fertilizer and other soils left unamended for control. Data was obtained at 75 % podding and full physiological maturity. Laboratory experiments were carried to isolate and characterize the rhizobia nodulating and fixing nitrogen with climbing beans and soybeans. This was carried out using congo red, litmus milk, Bromothymol blue and peptone agar. Greenhouse experiments were carried out to authenticate the rhizobia obtained from the field. Inocula was prepared from the root nodules of each of the legumes. Isolates from climbing beans inoculated radicles of soybeans and those of soybean inoculated climbing beans. Uninoculated climbing beans and soybeans were used as controls. Cross inoculation was also established in the greenhouse. Rhizobia nodulating and fixing nitrogen with soybeans nodulated and fixed nitrogen with climbing beans. Data obtained from the field experiments was analyzed and significance difference determined in nodule number, root dry weight, stover dry weight, pod number and dry weight of 100 seeds. Results were subjected to standard statistical analysis and presented using both descriptive and quantitative statistical procedures. The effect between amendments was determined using Genstat software for the analysis of variance (ANOVA) and mean separated using least significance tests at 5% level. Indigenous bradyrhizobia do not nodulate effectively in soybean and climbing beans in soils with low levels of nitrogen. Nodules did not form in beans planted in the soils amended with nitrogen fertilizer. Cross inoculation of rhizobia was observed between soybean and climbing beans in the greenhouse. Chicken manure, cow manure and nitrogen fertilizer application had effect on nodulation, root dry weight, stover dry weight, pod number and dry weight of 100 seeds on both soybeans and climbing beans. Climbing beans at Munithu Girls secondary School farm showed better performance in soils amended with chicken manure in the parameters assessed. BNF should be exploited with the view of decreasing overdependence on nitrogen fertilizer for sustainable agriculture. There is need for continuous screening of large numbers of native bradyrhizobia to understand their specificity in nodulation and nitrogen fixation