On-farm evaluation of fertilizer recommendation methods: Impacts on rice yield and economic benefits in subtropical soils

Bangladesh publishes fertilizer recommendations but most farmers do not use these recommendations. In this study, we tested the performance of the Fertilizer Recommendation Guide (FRG), Rice Crop Manager (RCM) and Soil Testing Kit (STK) for determining fertilizer requirements of monsoon rice (Oryza sativa L) against Farmers’ Fertilizer Practice (FFP). Rates of nitrogen, phosphorus, potassium, sulfur and zinc were determined by four methods and used on 72 farmer’s fields in five agro-ecological zones (AEZ) over two years. All methods produced significantly higher grain yield than FFP (4.12 t ha-1): they were 13.8%, 9.6% and 8.3% higher for STK, RCM and FRG, respectively. RCM didn’t perform consistently across the locations. Overall, the STK performed the best followed by FRG. The superiority of STK is attributed to its assessment of current soil status while the FRG recommendation is grounded on an older data set of soil analysis for each AEZ. The N dose was comparable among the methods while P dose was much higher for FFP, and RCM underestimated the K requirement of rice. Farmers declined to adopt the STK. By contrast, the supply of FRG information to the farmers by providing a simplified card with training is a simple and accessible technology.