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Browsing by Author "Woomer, P. L."

Now showing 1 - 2 of 2
  • Diagnostic indicators of soil quality in productive and non-productive smallholders' field of Kenya's Central Highlands
    Murage, E. W.; Karanja, N. K.; Smithson, P. C.; Woomer, P. L. (Elsevier, 2000)
    Food security in the East African Highlands is dependent upon the productivity of lands managed by smallholders who face difficult challenges in maintaining the fertility of their soils. A study was conducted to identify indicators of soil fertility status that are consistent with farmers' perceptions of soil fertility. Physical, chemical and biological properties of soils were measured from paired fields identified as either productive or non-productive by 12 farmers and compared to findings of a household survey on soil fertility management. Special attention was given to the potential of different soil organic matter fractions to serve as diagnostic indicators of soil fertility. Farmers' criteria for distinguishing soil productivity included crop performance, soil tilth, moisture and colour and presence of weeds and soil invertebrates. All farmers attributed low fertility to inadequate use of organic and inorganic fertilisers (100%) and removal of crop residues (100%). Other causes included continuous cropping (83%), lack of crop rotation (66%) and soil erosion (42%). Productive soils had significantly higher soil pH, effective cation exchange capacity, exchangeable cations, extractable P and total N and P than non-productive soils. Total organic C and several estimates of soil labile C including particulate organic C (POC), three Ludox density separates of POC, KMnO4-oxidizable C and microbial biomass C were significantly greater in productive soils. Soil microbial biomass N, net N mineralisation and soil respiration were also significantly higher in productive soils. Farmers' perceptions of soil quality were substantiated through soil chemical analyses and soil organic matter fractions provided precise information on these differences. The similarity of soil physical properties in productive and non-productive fields suggests that differences in chemical and biological indicators may have resulted, in part, from smallholders' management and are not inherent properties of the soils.
  • Soil organic matter and nutrient dynamics in a Kenyan nitisol under long-term fertilizer and organic input management
    Kapkiyaia, J. J.; Karanja, N. K.; Qureshib, J. N.; Smithson, P. C.; Woomer, P. L. (Pergamon, 1999)
    This paper examines three different soil fertility management practices and their effect on the soil quality in smallholder farming systems in the Kenyan Highlands. Soil organic matter (SOM) is greatly affected by how the soil is managed and treated. When testing humic nitisol (Kikuyu Red Clay) under a maize-bean rotation, it was found that the management practice of retaining the maize stover and adding manure produced the best results. Fertilization and crop residue removal resulted in the greatest decline in SOM. This research shows that effective soil management practices are important to soil quality and crop production in this area of Kenya.