IPI International Potash Institute
IPI International Potash Institute

Research Findings: e-ifc No. 39, December 2014

SoilCares mobile lab in action. Photo by SoilCares.

Soil Fertility Status and NPK Blends at Planting for Maize Growing in the Western Kenyan Counties Uasin Gishu and Busia

van Erp, P.J.(1)(1a), T. Terhoeven-Urselmans(1), and R. van der Meer(2)
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(1)SoilCares Research BV, Binnenhaven 5, 6709 PD Wageningen, The Netherlands
(2)SoilCares Holding BV, Binnenhaven 5, 6709 PD Wageningen, The Netherlands
(1a)Corresponding author: Peter van Erp


Crop production on smallholder agricultural land must increase considerably if the growing world population is to be fed. To achieve this, affordable soil testing methods, fertilizer recommendations and the accessibility of optimal fertilizers containing the required nutrients are required. The SoilCares mobile laboratory offers affordable soil testing using infrared spectroscopy and slightly modified Quantitative Evaluation of the Fertility of Tropical Soils (QUEFTS) for fertilizer recommendations (through the use of blends) to smallholders. SoilCares soil testing results from 2,107 samples from Uasin Gishu and Busia counties in Kenya were analyzed using archetype analysis and QUEFTS to derive: i) more accurate soil fertility classification; and ii) to optimize the formulation of NPK planting blends for maize. The study showed that eight soil archetypes could be distinguished of which four were dominant. Additionally, four fertilizer-blend archetypes were distinguishable for all counties which comply reasonably well with the NPK fertilization at planting necessary for 5 t ha-1 maize production. These blends are 12:25:0, 6:22:14, 0:40:0, and 13:33:0 (N-P2O5-K2O). Median relative difference between the advised and optimally needed N, P2O5 and K2O application rates at planting were 36, -10 and 0 %, respectively. The method described, including mapping, may be useful in assisting decisionmaking by the fertilizer industry, traders and policymakers on the production and availability of crop or region specific NPK blends.

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