Evaluating Soil Quality and Productivity of Different Clusters in Kabanon-Kapkamak Irrigation Scheme, Kenya
This study investigated soil conditions with an objective of differentiating the area into different clusters on the basis of topographical characteristics, hydrological processes, and degree of erosion, soil surface characteristics, soil colour, depth, texture, structure and consistence across the rolling uplands into the valley bottom. Within each cluster, five composite (replicate) samples were collected at the depth of 0-20 cm and subjected to laboratory determination of soil quality attributes such as pH, soil organic carbon, macro- and micro-nutrients. The adequacy of soils for plant growth was assessed, using semi-quantitative land evaluation methods, where ranges of numerical values of the selected soil quality indicators were rated and assigned fractional values (in percentage). The functional relationships between the measured soil quality attributes and relative crop yields were applied to determine the soil quality and productivity index for describing the biophysical production potential of each of the clusters. All the soil data and land evaluation processes were subjected to analysis of variance (ANOVA) at 95% confidence level, using Genstat Computer Software. Six clusters were identified and the major differences between them were found to be the degree of erosion, stratification and compactness, with an important bearing on the planning and designing of the irrigation layout. The soil pH for all the clusters fell between 6.0 and 7.6, an appropriate pH for most crops. The variations of soil pH between different clusters were found to be insignificant (P>0.05). The most limiting factors were found to be nitrogen and soil organic carbon, with percentage deficiency levels ranging from 51 to 76 in all the six clusters. These deficiencies called for blanket fertilizer recommendation across the six clusters with respect to all soil quality indicators with exception of phosphorous and potassium. Since phosphorous and potassium levels varied widely between the six clusters, the fertilizer types and levels required to enhance the availability of these nutrients to plants should be cluster-specific.
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