Western Kenya faces high population pressure and this has increased demand for food. Smallholder farmers in the region have been forced to practice poor farming practices such as continuous cultivation and clearing of forests to put more land to crop production. This has resulted in severe land degradation, climate change and reduced farm productivity. Agroforestry trees have been reported to improve soil fertility through nitrogen fixation coupled with leaves and twig decomposition. However, this has not been ascertained in maize-banana agroforestry systems in Vihiga County. Understanding the effects of intercropping of maize and banana with Sesbania sesban, Calliandra calothyrsus and Leucaena diversifolia agroforestry trees on nutrient uptake may be a remedy to the challenges. Therefore there is need to fully understand the effects of intercropping selected agroforestry trees with maize and banana on nutrient uptake of maize and banana. The objective of the study was to determine the effect of intercropping agroforestry tree species on maize and banana tissue N, P, K, Mg, Ca uptake and partitioning. The study was conducted at Maseno university farm located in Vihiga County. The Williams varieties of banana of the same age were obtained from KALRO-Thika., Seeds of selected agroforestry trees were purchased from KEFRI – Muguga, planted in a seedbed and the seedlings raised in nurseries. Hybrid maize seed, H513 was purchased from an agrovet. Banana holes were dug 2x2 feet, 20 Kg of decomposed cow dung manure + 20 Kg of top soil + 200g of NPK fertilizer added in each banana hole and banana planted. Randomized complete block design (RCBD) with 3 replications were used with seven treatment levels of i.e. maize, banana, maize + banana + Calliandra, maize + banana + leucaena, maize + banana + sesbania, maize + banana, and fertilized maize. Maize were planted at 0.75 m inter row by 0.3 m spacing. Five maize plants per treatment and per replication were sampled randomly from the eight middle rows at harvest and partitioned in to leaves, shoots, roots, cobs and maize grains. Two banana plants were sampled and its leaves taken for mineral tissue analysis. The maize roots were washed in water to remove soil. The samples were oven dried to a constant weight at 72 ⁰C. The samples were then ground into powder for determination of nutrient analysis. Procedures by Motsara and Roy (2008) was used to determine the nitrogen, phosphorus, potassium, calcium and magnesium mineral nutrient in various plant tissues. Data was subjected to Analysis of Variance using Genstat statistical package Version 15.2. Maize and bananas that were intercropped with trees recorded highest nutrient uptake and partitioning. Sesbania sesban recorded higher nutrient uptake as compared treatments without tree intercrops. These findings can be used to advice smallholder farmers of Vihiga County on the best intercropping system to adopt for maximum maize and banana production.

Agroforestry is an alternative land management system that addresses many of the global challenges, including deforestation, unsustainable cropping practices, loss of biodiversity, increased risk of climate change as well as rising hunger, poverty and malnutrition. It can be an attractive choice for environmental, social and economic development because it does not pollute the environment and can generate additional income to the farmers. In the agroforestry systems, plant residues improve the soil fertility through enhanced nitrogen fixation and maintain microbial activity. Most soils in sub-Saharan Africa are often deficient in nutrients. In the tropics, resource-poor farmers rely on organic inputs to sustain soil fertility. Proper management of crop residues and multipurpose tree prunings can alleviate soil infertility and promote a positive impact on the nutrient dynamics of low-input, maize-banana based agroforestry system in Kisii County. Agroforestry trees are becoming an integral part of agriculture in agroforestry programmes and have been reported to improve soil quality and nutrient cycling. However, intercropping food crops with agroforestry trees may result to competition for resource nutrients. This has not been ascertained in maize-banana based agroforestry systems in Kisii County. Understanding the effect s of intercropping of maize and banana with Sesbania sesban, Calliandra calothyrsus and Leucaena diversifolia agroforestry trees on nutrient dynamics could be a remedy to the problem of nutrient deficiency. The objective of the study was to determine the effect of agroforestry tree species on soil carbon and nutrients (N, P, K, Mg and Ca) in Maize-Banana based agroforestry system. This study was conducted at Kenya Agricultural and Livestock Research Organization farm in Kisii County. The study was carried out on already on-going research which had commenced in March 2018. The experiment was laid out in a Randomized Complete Block Design (RCBD) with maize and banana intercropped with agroforestry trees. Soil samples were collected from the agroforestry fields in Kisii from September, 2018 according to the procedure of Mucheru-Muna [1]. A modified Walkley and Black procedure as described by Zhao et al. [2] was used in the determination of organic carbon. Nitrogen was determined by the Kjeldahl digestion and distillation procedure as described by Bayrakdar et al. [3]. Soil phosphorous, potassium, calcium, magnesium were determined by of Motsara and Roy [4]. Data was subjected to Analysis of Variance and means separated by least significant difference at (p<0.05) using Statistical Analysis Software (SAS). Soils from tree based treatments, Maize, banana and Calliandra calothyrsus, Maize, banana and Leucaena diversifolia and Maize, banana and Sesbania sesban had increased carbon, nitrogen, phosphorus, potassium, calcium and magnesium nutrient levels which increased with time of assessment. In conclusion agroforestry farming system can significantly contribute to provision of carbon and major soil nutrients in Kisii County and the surrounding areas.