Determination of partial nutrient balances for improved soil fertility management in small holder farms of Kirege Location, Central highlands of kenya
Muthamia, Joses Muthomi
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Soil fertility decline is an acute problem facing smallholder farmers in central highlands of Kenya. Availability of organic and inorganic nutrient resources, their management under spatially variable soil fertility conditions has consequences on the soil resource base, cropping patterns and crop yields. Smallholder farms in the central highlands of Kenya exhibits a high degree of heterogeneity, which are influenced by a complex set of socio-economic and biophysical factors. The farms consist of multiple plots managed differently in terms of allocation of crops, nutrient inputs and labour resources; making within-farm soil fertility gradients caused by management strategies a common feature. A monitoring study involving nutrient stocks, flows and balances was conducted in Kirege Location, central highlands of Kenya to explore soil heterogeneity with the aim of improving soil fertility management. Focus group discussions were conducted where criteria for wealth ranking and grouping farmers into different wealth status was developed. A rapid survey was conducted on a sample of 50 households randomly selected from the list of households in Kirege obtained from the local chief's office to characterize and classify the farms into three different types (rich, medium and poor). Nine case-study farms were randomly selected for detailed resource flow mapping (3 from each of the 3 farm types). The farms were visited to record movement of nutrients stock materials using a monitoring protocol covering household, crops, livestock, soil and socio-economic aspects of the farm. Soil in the plots identified in resource flow mapping at different distances from the homesteads were sampled at the end of 2006/2007 short rains cropping season (March 2007). The sampling depth was 0 - 20 cm to capture the level of nutrient stock in the topsoil. The soil samples were analyzed for pH, C, N, P, K, Mg and Ca at ICRAF laboratory using Infrared spectroscopy method. Resource flow mapping data was analyzed using IMPACT program version 2.0. Results revealed use of Results revealed use of nutrient resources varied for different field types and was strongly influenced by distance from the homestead. Home fields received more nutrient inputs compared to outfields. In wealthy farms, home fields received 109.1 kg N ha 1, 72.9 kg P ha 1, and 379 kg K ha 1, compared to 42 kg N ha-, 32.1 kg P ha-1 and 55 kg K ha -1 in the outfields. In poor farms, home fields received 56.8 kg N ha 1, 32.8 kg P ha-1 and 106 kg K ha -1 compared to 8.1 kg N ha 1, 4.6 kg P ha 1 and 16 kg K ha 1 for the outfields. Variations in resource allocation were also observed with regard to farmers' level of resource endowment. Wealthy farmers used a mean of 74.5 N kg ha 1, 50.9 kg P ha -1 and 244 kg K ha 1, compared to 27.3 kg N hat, 16.2 kg P hat and 50.7 kg K ha -1 for poor farms. Partial nutrient balances and stocks were higher in home fields and in wealthy farmers' farms as compared to outfields and poor farmers' farms. Due to nutrient heterogeneity in smallholder farms, there is a need for a more targeted approach to soil fertility intervention that differentiates between farm fields, agro-ecological zone and resource endowment status.