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Title Farm typology, nutrient balances and soil fertility management in agricultural systems of Kakamega

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Author(s) Mussgnug, F.; Diwani, T., Ngome, F.; Becker, M.

Presenting author Mussgnug, F.

Institution(s) Institute of Crop Science and Resource Conservation, Department of Plant Nutrition, University of Bonn, Germany

Keywords BNF; Discriminant and Hierarchy Cluster Analysis; NUTMON; Phaseolus vulgaris L. ; Zea mays L.

Abstract The agricultural matrix in Kakamega is dominated by a heterogeneous mix of small-scale farming systems. Intensified land-use with little external inputs has led to soil fertility and yield declines. Classifying the systems is a precondition to successfully target intervention strategies. Data from a structured questionnaire and soil analysis of 182 farms were subjected to a Cluster and Discriminant Analyses. Based primarily on land availability and production orientation, eight clusters were identified. The most common cluster groups comprise farms with subsistence orientation, small landholdings and low external labour use. A small cluster was characterised by market-oriented production, industrial crops, and large farm sizes. Based on this typology, 24 farms were selected for resource and nutrient flow mapping. Chemical analyses were complemented by model estimates. Nutrient balances at the farm gate differed by soil type and farm cluster. Within farms, nutrient balances tended to be negative for maize, and positive for vegetables and industrial crops, leading to nutrient-depleted areas and fertility hotspots. Fertility management strategies accounting for these differences were evaluated. The N accumulation by common bean ranged from 6 to 83 kg ha-1 depending on soil type and farm cluster. Options contributing P increased N accumulation most on Ultisols and on strongly degraded fields. The proposed tools can improve the targeting of site- and system-specific fertility management.

Congress Topic Land use, impact and value

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