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.
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RUFORUM Working document series
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