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This chapter describes the agricultural systems of Kenya, including the agroecological zones (AEZ), and soil fertility management. The chapter then provides a diagnosis of nutrient deficiencies in the region. Further, the chapter presents information on optimizing fertilizer use and fertilizer use optimization tools for Kenya. Finally, the chapter enumerates targeted crops and cropping systems by AEZ.

Soil phosphorous and nitrogen are the major constraints to maize production in Nyanza Province of Kenya. The yields are typical of low input systems ranging below 1.0 t ha-1 against a potential of 5.0 t ha-1 per season. This study was conducted at Bototo, Kisii County in Nyanza Province, Kenya, during the long and short rains seasons in 2007. The aim was to determine the effects of phosphatic fertilizers and manure on nutrient uptake, nutrient use efficiency, maize yields and soil nutrients content at harvest. A Randomized Complete Block Design (RCBD) was used with the farms as blocks. Maize H614 hybrid was sown at a spacing of 0.75 × 0.60 m. The plot sizes were 3.75 m by 4.8 m. All plots were top dressed with Calcium ammonium nitrate (CAN) fertilizer at a uniform rate of 30 kg N ha-1. Diammonium Phosphate (DAP), Minjingu Rock Phosphate (MRP) and Triple Super Phosphate (TSP) fertilizers were applied at a rate of 60 kg ha-1 P 2 O 5 (P) and farmyard manure (FYM) at 10 t ha-1. One rate of P at 60 kg ha-1 was applied on all the phosphorus fertilizers and a no P treatment (check) plus lime only treatment was included in determining the effects due to the applied P in the acidic soils. Complete soil chemical analysis was done in all the plots at the planting time. There was significant (p≤ 0.01) crop growth vigour, grain yield, total dry matter, harvest index, nutrient uptake and removal by the crop, available soil P, agronomic phosphorus use efficiency (APUE), physiological P use efficiency (PPUE) due to fertilizers and manure application, with a corresponding reduction in the total soil N, P, K, Ca and Mg. Phosphate fertilizers and manure applications are essential to improve maize yields and nutrient P use efficiency.

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