Field Kit Soil Tests to Assess Acidity, N, P, S and K Fertility in Kenyan Soils.

Currently, the practical application of soil science in sub-Saharan Africa is marginal because of poor infrastructure and inefficient systems. Although most countries operate a national soil laboratory, limited functionality, irrelevant analyses, expense and extremely slow response times limit use by farmers. SoilDoc is a new kit that allows in-situ measurements of a suite of critical soil properties essential for assessment of the soil fertility and making on the spot management recommendations. SoilDoc uses mainly commercially available, battery-powered, miniaturized instruments, suitable for use in farmersÕ fields. The results are feed into website using Android software and a smart phone allowing calculations, interpretations and recommendations to be instantly returned to the user. SoilDoc is being developed for use by extension agents and agro-dealers working with smallholder farmers in developing countries, but will also be useful for agricultural consultants in any setting. Challenges being addressed include building calibration dataset for CaCl2 extractable nutrients, embedding automatic quality control measures, developing simplified training materials and building supply chain systems. The parameters include soil pH, electrical conductivity (indicative of general fertility levels), labile organic carbon, and 0.01 M calcium chloride extractable macronutrients, nitrate-N, sulfate-N, phosphate-P and potassium-K. A diverse set of soils from different regions in Kenya was analyzed using this field kit and compared to conventional wet chemistry analysis. In addition, soils from 16 on-farm nutrient response trials were analyzed to assess the ability of the kit to predict maize crop responses to applied N, P, S and K.