Greenhouse Evaluation of Biochar-Based Controlled-Release Nitrogen Fertilizer in Corn Production

Low nitrogen use efficiency (NUE) in corn production leads to reduced harvest and substantial nitrogen (N) losses, adversely impacting environment and agricultural sustainability goals. Controlled release of N fertilizers can improve NUE by controlling the release of N from fertilizer granules, extending N availability to crops, and reducing N loss to the environment. Biochar-based controlled-release N fertilizers (BCRNFs) are a new concept to address the N loss problem and increase yield. In this research, different BCRNFs were developed by impregnating ammonium sulphate (AS) into biochar (BC) and mixing with bentonite (Be), biosolid (BS), rice starch (RS), and bioasphalt (BA) in a different ratio to formulate three new BCRNFs— S1: 40% AS + 55% BC + 5% RS; S2: 50% AS + 15% BC + 15% BS + 20% RS; and S3: 15% AS + 30% BC + 10% Be + 45% BA. Dry pellets of S1 and S2 were coated with 5 wt% poly-lactic acid solution, while pellets of S3 were not coated. The release pattern of N from the BCRNFs was studied in water. The cumulative release of NH₄⁺–N from S1, S2, and S3 was significantly slower than that from AS. The release time of 80% N from S3 was extended up to 30 h. The greenhouse evaluation of BCRNFs consisted of six treatments: control (no N), non-BC commercial controlled-release fertilizer (CCRF), AS, S1, S2, and S3. S1, S2, and S3 corn yields were 196.4%, 209.6%, and 135.7%, respectively, greater than the control treatment (p ≤ 0.05, Tukey’s test). S2 yielded 13.5% and 28.8% more than the non-BC controlled-release fertilizer and AS, respectively. The study demonstrated that BCRNFs coated with poly-lactic acids extend N release duration, boost yield, and reduce N loss in leachate collected in the greenhouse trial of the BCRNFs. Biochar-based BCRNFs have a good prospect for corn production.