Preparation and evaluation of two enriched biochar-based fertilizers for nutrient release kinetics and agronomic effectiveness in direct-seeded rice

Biochar is a pyrolyzed product of organic matter having enormous potential for nutrient loading and enhancing nutrient use efficiency. In the present study, two enriched biochar (EB)-based fertilizers were prepared, having a fertilizer grade of 6-6-4 N-P2O5-K2O by intercalation of NPK fertilizers mixture solution as EB-1 and additional humic acid and seaweed extract with EB-1 as a formulation of EB-2. The batch experiments were conducted to compare nutrients (NH4+, NO3-, P, and K+) release patterns of developed fertilizers with conventional fertilizers. Enriched biochar fertilizers (EB) demonstrated a much slower release pattern of NH4+, P, and K+, but NO3- release was similar to conventional fertilizers. The total release of N from EB fertilizers was like conventional fertilizer; however, significantly less P and K were released during the period of 36 h. The field response study in direct-seeded rice revealed that the application of EB fertilizers 11.7-29.5, 32.9-64.0, and 31.4-38.0% higher apparent use efficiency of N, P, and K, respectively than conventional fertilizer at 100% application rate. This implies the possible utilization of EB fertilizers in sustainable rice production with reduced losses and enhanced nutrient use efficiency (NUE).