Studies on genotypic variation in biological nitrogen fixation in pigeonpea (cajanus Cajan L. millsp) inoculated by various rhizobia strains and phosphate fertilizer application in kenya
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Pigeonpea (Cajanus cajan L. Millsp) is an important pulse crop in the semi-arid areas in Kenya because of its drought tolerance, wide adaptability and as a source of protein. Low grain yields have been partly attributed to low soil fertility, non-availability and the high cost of chemical fertilizers. A study was initiated to determine if there was genotypic differences in nitrogen fixation ability by local and exotic pigeonpea genotypes, and to determine the response of the genotypes to inoculation with various Rhizobia strains. Fifteen pigeonpea genotypes from three maturity groups were inoculated with five Rhizobia strains, and grown in soils with and without phosphate fertilizer application at four locations in 1984and 1985in Kenya. The experimental design for all experiments was a split plot with three replications. The results indicated that inoculation increased the number of primary branches, reduced duration to flowering and maturity, increased nodulation and grain yield. Inoculation increased xxi plant height in late maturing genotypes but reduced it in the medium and early maturing genotypes. Significant genotype x inoculation interactions was detected for the number of primary branches, nodules per plant and IOO-seed weight at Thika. The results also indicated that response to Rhizobium strain is genotype specific and that Rhizobia strains differ in effectiveness in fixing atmospheric nitrogen. Native Rhizobia proved to be more effective on particular pigeonpea genotypes.