Influence of Mavuno and farm yard manure fertilization on soil carbon fractions in soils of western Kenya

Soil management practices alter organic carbon fraction distribution and hence the ability of the soil to sequester carbon and/or resist erosion. The current study’s main objective was to investigate the influence of organic (FYM) and inorganic (Mavuno) fertilizer on C fractions and C and N concentration in the fractions for soils obtained from Siaya and Vihiga Counties of Western Kenya. The IR maize variety was initially planted on the soils. A randomized complete block design with a split plot arrangement replicated four times (with each farmer acting as a replicate) was used to test the effect of fertilizer application on soil carbon fractions. The main plots were the fertility gradients (high and low) and the subplots were the fertilizer treatments; control, IR + manure and IR + manure+ mavuno. The IR maize was used as the test crop and mavuno was applied at a rate of 20 kg P per ha whilst FYM was applied at a projection of two tons per ha. Soil were wet sieved to separate into carbon fractions and C and N thereof determined. Results indicated that there were significant differences in the carbon fraction distributions in different soils but no significant differences in the large macro-aggregates (LM), small-macro-aggregates (sM), microaggregates (m) and silt and clay (S+C) fraction proportions in different sites, treatments and fertility gradients. Elemental combustion was carried out and significant differences in %C and %N organic C fractions were observed with the highest % C (2.05) and % N in (0.18) in the silt and clay fraction. A combination of both manure and mavuno increased % N and % C in carbon fractions. The treatments, fertility gradients and sites had no effect on the carbon fraction distribution.