Effects of mycorrhizal and Rhizobium inoculation on soybean growth in acidic soils of Gatanga, Kenya

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NAOMI NJERI KAMAU
JAMES B. KUNGU
DANIEL MUGENDI

Abstract

Abstract. Kamau NN, Kungu JB, Mugendi D. 2018. Effects of mycorrhizal and Rhizobium inoculation on soybean growth in acidic soils of Gatanga, Kenya. Cell Biol Dev 2: 1-16. Farmers in Central Kenya have found it challenging to appropriately conserve and replace soil nutrients due to small landholdings and poverty. The inevitable result has been soil erosion and nutrient leaching, resulting in soil acidity. The purpose of this study was to see how inoculating soybeans (Glycine max Merr.) with both mycorrhiza and Rhizobium as a biological approach of enhancing soil fertility in acidic soils in Gatanga, Thika District, affected soil fertility. Field studies on sterilized and non-sterilized soils taken from Gatanga were conducted at Gatanga and Kenyatta University (on-station). The field studies used a complete randomized block design, whereas the on-station experiments used a complete randomized design. Genestat for Windows Version 8.11 was used to analyze variance (ANOVA) on the data, with means separated using LSD at a 5% significance difference. As a result of the dual inoculation with mycorrhiza and Rhizobium, the growth parameters of height, root collar diameter, shoots, and root dry weight all increased. Higher nitrogen fixation by soybeans, as demonstrated by increased nodulation and grain yields, was also a result of dual inoculation. On the germination of soybeans, dual inoculation with mycorrhiza and Rhizobium had no significant effect (p<0.05). In the long rains, the height of soybeans increased greatly over the control by 88 %, but in the short rains, the growth was not significant. In the on-station experiments, there was no significant difference in height between sterilized and non-sterilized soil. In the long and short rains, dual inoculation improved root collar diameter by 80% and 8.6%, respectively. Dual inoculation raised the dry weight of the shoots by 140 % in the on-farm long rains 2005 season, whereas the changes were not significant in the short rains season and on-station experiments. In the on-farm long rains 2005 season, dual inoculation improved grain yields by 356 %, while on-station experiments saw grain yields increase by 76 % and 107 % in sterilized and non-sterilized soils, respectively. Despite the fact that nodulation was poor in all of the experiments, the number of nodules increased by 676 % over the control during the long rains of 2005. The control (S) had no nodules in the on-station experiments. Insufficient precipitation caused the short rains crop to perform worse than the long rains crop. Finally, mycorrhiza and Rhizobium biological organisms could boost the productivity of the legume soybean in acidic soils. However, technologies to make microorganisms available to farmers must be developed, as the obligatory nature of mycorrhizal fungi makes cultivation and commercialization difficult, and the short shelf life of Rhizobium at room temperature precludes its usage by resource-limited farmers.

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