Comparison of Portable Soil Test Kits for Smallholder Farmers.

Fertilizer use in combination with improved crop varieties and irrigation has been instrumental in the dramatic gains in food grain production in the past decades. Despite these gains, global agricultural production systems face enormous challenges with rising population, food requirements, land degradation, land use pressure, and climate change. Imbalanced application of fertilizers and blanket fertilizer applications have also resulted in low fertilizer use efficiency, stagnation of yield, and environmental pollution. Fertilizer recommendations therefore must be more specific to crops’ complete nutrient needs and soil and climatic conditions. Investment in fertilizer inputs by farmers should be preceded by proper analysis of soil chemical and physical properties in order to ascertain which nutrients are suboptimal. Farmers in developing countries, however; have limited access to standard soil testing.  Soil test kits with their mobile features and low costs are an attractive options in remote regions and in areas without functional laboratories.

Based on the recognition that portable soil test kit would facilitate smallholder farmers to have an onsite capability for soil analyses the following soil test kits were evaluated against standard laboratory tests: Hach, SoilDoc, and Kasetsart University (KU) soil test kits. Other innovative techniques being evaluated include chromatographic and spectral analyses. The results showed the different capabilities from each test kits. For instance, Kasetsart was the cheapest with very limited capability but with the ability to analyze for ammonia-N besides nitrate-N, P, K, and pH. Hach and SoilDoc were a lot more expensive with more capabilities. Hach has the ability to analyze for N, P, K, Ca, Mg, Na, acidity, salinity, gypsum and lime requirement. SoilDoc’s major quality is the feedback and recommendations done through a digital media (tablet). It can analyze nitrate-N, Ca, Mg, P, K, acidity, sulfate, EC, and active carbon. The comparison of results from these soil test kits and wet-chemistry method is presented for a wide range of soils. Modifications to improve the kits are also discussed.