Belowground Influence Of Farmer-Produced Composts On Soil Biota, Foliar Pests And Yields Of Common Bean (Phaseolus Vulgaris) In Western Kenya

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.

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