Development and Validation of Nutrient Expert for Maize in Bangladesh

Nutrient Expert® (NE), a fertilizer decision support tool for hybrid maize in Bangladesh, was developed for easy implementation of site-specific nutrient management (SSNM) strategies in farmer fields. The tool was evaluated in Rabi (winter) season in various districts of Bangladesh against existing farmer nutrient management practices to assess the robustness of the tool in different maize growing regions. On-farm NE validation trials in maize were conducted at 181 locations across Bhola, Barisal, Patuakhali, Satkhira, Khulna, Chuadanga, Rajbari, Rangpur, Dinajpur, Nilphamari, Kurigram, Mymensingh, Comilla, and Rajshahi districts of Bangladesh. Data across the fourteen districts showed that farmers on an average applied 161:66:68 kg/ha of N, P₂O₅ and K₂O, respectively in maize (ranging between 53 to 360, 0 to 258 and 0 to 149 kg/ha of N, P₂O₅ and K₂O, respectively). On the other hand, the average recommended rate from Nutrient Expert® was 168 kg N, 40 kg P₂O₅ and 120 kg K₂O (ranging between 82 to 322 kg N, 0 to 127 kg P₂O₅ and 0 to 210 kg K₂O/ha at different locations).

Average yield achieved by farmers was 7.9 t/ha (range 3.3 to 12.5 t/ha), while the NE treatment yielded 4.2 to 14.2 t/ha, with an average yield of 8.6 t/ha. This work clearly shows that the NE tool was able to capture the difference in growing environments across sites and increased the average yield by 0.7 t/ha, compared to the farmers’ current practice. The average N application rates by farmers did not differ significantly from the NE recommended rate. However, the P fertilizer application rate was significantly higher in farmers’ practice, while the K rates recommended by the NE tool were significantly higher than farmers’ current practice. The NE validation trials also included four treatments to assess the effect of nutrient omissions across sites. The treatments comprised of an ample NPK treatment and three treatments where each of the three nutrients were subsequently omitted. Ample application of NPK produced an average yield of 9 t/ha across 181 locations. Omissions of N, P and K from the ample NPK treatment reduced grain yields by 45, 12 and 13%, respectively (ranging between 2.4 to 11.4, 3.4 to 13.2, and 1.6 to 13 t/ha, respectively). Certain locations showed more pronounced K response than N response and highlighted the necessity of adequate and balanced K application to improve yields in such locations.