Enhancing Nutrient Use Efficiency in Cowpea through Soil Test Crop Response and Decision-Support Tools in Karnataka

Nutrient imbalance and imprecise fertiliser use are significant constraints to crop productivity in India, often resulting from blanket recommendations that fail to consider the site-specific soil fertility status. Soil testing and modern nutrient management approaches, such as the Soil Test Crop Response (STCR) methodology and decision-support tools like Dhartimitra software, provide a scientific basis for balanced fertilisation and sustainable yield targets. To evaluate their effectiveness, a field experiment was conducted during the Kharif 2024 season at farmers’ fields in the Bangalore Rural, Tumakuru, and Chikkaballapura districts of Karnataka. The trial compared STCR-based recommendations (using Dhartimitra software and actual soil test values) with the soil test laboratory approach, the general recommended dose, farmers’ practices, and an absolute control in a randomised complete block design with three replications. Results showed that STCR-based nutrient management for a targeted yield of 15 q ha^-1 through Dhartimitra software achieved the highest mean grain yield (15.28 q ha^-1), followed by STCR through actual soil test values (14.97 q ha^-1), both significantly superior to conventional recommendations. These treatments also recorded the highest nutrient uptake of N, P₂O₅, and K₂O. Nutrient use efficiency indices revealed that nitrogen agronomic efficiency was maximum under STCR treatments (39.6 kg kg^-1), while phosphorus recovery efficiency remained low due to fixation; however, relative internal utilisation efficiency was stable. This study demonstrates that soil test–based STCR recommendations, particularly when supported by Dhartimitra software, enhance yield, nutrient uptake, and efficiency compared to blanket fertiliser use, ensuring sustainable crop production and improved nutrient stewardship.