Effect of Phosphorous and Rhizobia Inoculation on Growth and Yield of Desmodium and Lucerne in Kiambu County, Kenya
Miriko, Mutuerandu C.
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Integration of legumes into farming systems is one of the Integrated Soil Fertility Management options for improving soil fertility. Farmers can increase their production by using legumes (desmodium and Lucerne), which, in association with rhizobia, can fix atmospheric nitrogen. However, low P, a situation prevalent in the soils can limit its performance. Dairy production is mainly constrained by limited availability and access to high quality feeds especially during the dry season. It is documented that majority of soils in Africa have low levels of nitrogen and phosphorous and hence the capability to support plant, particularly fodder production is limited. The supply of these mineral nutrients is vital in enhancing legume growth and development. The aim of the study was therefore to examine quality and growth characteristics of Desmodium intortum and Lucerne trifecta supplied with different sources of Phosphorous and rhizobia inoculation in Kiambu County. The field experiments were conducted at Kenyatta University Field station. The field experiment was a split-split-plot arranged in a Randomized Complete Block Design (RCBD) with main plot being two plant species (desmodium intortum and Lucerne trifecata) while Sub-plot constituted of inoculation levels – (inoculation or no inoculation) and sub-sub plot was different phosphorus sources (rock phosphate, triple super phosphate and no Phosphorous application as a control). The treatments were replicated three times. The data collected from the field include: plant biomass, biomass of nodules, number of nodules per plant and nodulation effectivity of Desmodium and Lucerne. The Most Probable Number (MPN) experiment was conducted in the greenhouse, while the plant P and N analysis were carried out in the lab. All the growth data were subjected to analysis of variance (ANOVA) using the GenStat statistical software version 15.1. The means were separated using Fischer’s Protected Least Significance Difference test at 5% level of significance. Compared with the control, inoculation and P fertilization significantly improved nodulation by 10% and plant growth of the two species, with a more prominent improvement with TSP application which recorded 222.61 leaves, followed by RP (217.28 leaves) and control had 207.30 leaves. The highest number of branches (18) were observed on plants that received the TSP treatment, followed by RP which had (15) whereas the plants in the control produced the lowest number of branches (11). Similarly, the total plant nitrogen content and phosphorous plant content of the tissues for both Lucerne trifecta and Desmodium intortum increased compared to control due to inoculation and P treatments respectively, TSP treatment had 5% P tissue content while the control without P had 3.5%. On the other hand, the result of the MPN test showed that the soils of this area were inhabited by resident rhizobia (< 10 gram-1 of soil). This shows the indigenous population competed for nodule occupancy with the introduced Rhizobia. Rhizobial inoculation and phosphorus supplements are effective in improving growth and yield of Lucerne and Desmodium. From this experiment, it is strongly recommended to adopt these technologies in the cultivation of legumes in Kenya.