Precision agriculture, using high-tech equipment and in-formation science software, is not appropriate for the farmers of small parcels of land in the tropics. Our hypothes is, however,is that the concepts of precision agriculture and participatory action research have a similar philosophical basis and complement each other. We have adopted an approach of both empowering farmers and simplifying nutrient management technology to enable farmers to use the concepts. The simplified technology includes a visual tool to identify soil series, a soil test kit that brings the laboratory to the field, and a decision-aid that enables farmer leaders to interpret the soil test kit data in light of the soil series. The results have demonstrated increased yields with reduced fertilizer inputs over a three-year period in Central Thailand.