ABSTRACT The production of common bean Phaseolus vulgaris in Kenya has been reducing due to declining soil fertility. The use of synthetic fertilizers has been linked to soil acidification, which constrains plant growth and interferes with beneficial rhizosphere biota. The application of composts is being encouraged, and farmers in Western Kenya are being trained on composting of locally available organic materials. However, there is need to establish the performance of such farmerproduced composts in terms of improving soil fertility and biota, for instance Rhizobium, rhizobacteria, fungi, micro- invertebrate, as well as mitigating infestations by foliar pests such as Aphis fabae, Frankliniella occidentalis, Colletotrichum lindemuthianum. A field experiment was conducted on Masinde MuliroUniversity of Science and Technology farm, to assess belowground influence of farmer-produced composts on the soil biota, the foliar pests and yields of common bean. The experiment comprised 2 × 7 factorial treatments, with common bean cultivar having two levels i.e. Mwezi Moja (GLP 1004) and KALRO Kakamega 8 (KK8); with seven levels of soil fertility amendments, comprising five farmerproduced composts(FC 1-5), with varying plant and animal waste ingredients , DAP fertilizer and untreated controls. Each of the resulting 14 treatment combinations comprised of twin plots (3 m × 2 m) for the two bean varieties, each having n = 40 plants per variety, spaced at 50 cm × 15 cm, replicated in 3 blocks (24 m × 14 m) in a randomized block design, over a period of 2 seasons i.e. long rains (1st April to 30th June 2014) and short (17th July to 5th October 2014). Data collected includes, root endophytic (Rhizobium) and rhizosphere microbes (bacteria and fungi), soil microinvertebrates (nematodes and arthropods), the foliar pests A. fabae, F. occidentalis and C. lindemuthianum; and plant growth and yields. Statistical analysis was conducted using SAS 9.1 at p≤0.05. Apart from N and P, farmer-produced composts contained a variety of additional nutrients including, K, Ca, Mg, Fe, Cu, Mn and Zn that DAP lacks. Germination % was lowest in bean seeds grown with DAP (72.0 % b) and highest in those receiving FPC1 (85 % a), FPC3 (86.9 % a) and the controls (84.8 % a). Germination percentage was higher in KK8 bean variety (96 % a) than in Mwezi Moja bean variety (67 % b) (P0.05). At harvest, compost-treated plots had pH 5.3 and improved nutrient concentrations than DAP and control plots. The results of this study shows that, trained farmers produced composts contained important nutrients that were utilized by common bean to promote growth and yields, while enhancing endophytic colonization by beneficial Rhizobium species, and promoting rhizosphere colonization by bacteria and fungi, but suppressing soil nematode populations. Farmer-produced compost CF3 was relatively better in performance. However, there was no evidence that farmer-produced composts influenced bean infestation by the foliar pests.
