Assessment of enriched biochar-based fertilisers for nutrientrelease kinetics and agronomic efficacy under direct-seeded rice in the Tarai Region of North India

Biochar is a pyrolyzed organic matter product with significant potential for nutrient loading and nutrient-use efficiency. In this study, two enriched biochar (EB)-based fertilizers with a fertilizer grade of 6-6-4 N-P2 O 5 -K2 O were created by intercalation of NPK fertilizer combination solution as EB-1 and added humic acid and seaweed extract as EB-2 formulation. The batch experiments were carried out to compare the nutrient release patterns (NH4 + , NO 3 -, P, and K+ ) of created fertilizers with conventional fertilizers. Enriched biochar fertilizers (EB) released NH4 + , P, and K+ at a significantly slower pace, while NO 3 release was comparable to standard fertilizers. The cumulative release of N from EB fertilizers was comparable to that of traditional fertilizers; however, much less P and K were released during the period of 36 hours. The field response study laid-out at Norman E. Borlaug Crop Research Centre, G. B. Pant University of Agriculture and Technology, Pantnagar, Uttarakhand in direct seeded rice with randomized block design having eight treatments, i.e., 100% recommended dose of fertilizer (RDF) through conventional fertilizers, 75, 100, and 125% RDF through enriched biochar-based fertilizers EB-1+UEB-1, and EB-2+UEB-2 and no fertilizer application as controls were replicated three times. Highest growth, yield parameters, and yield of DSR were recorded under the application of EB-2+UEB-2 at a 125% fertility level. The EB fertilizers resulted in 6.5-11.8% higher additional grain yield and 11.7-29.5, 32.9-64.0, and 31.4-38.0% greater apparent use efficiency of N, P, and K, respectively, than using conventional fertilizer at 100% application rate. Application of both EB fertilizers at 75% fertility level resulted in a par yield with the application of 100% fertility level through conventional fertilizers. This means that EB fertilizers could be used in sustainable rice production with lower losses and higher NUE.