Biochar-Based Boron Fertilization Effects on Growth and Nutrient Use Efficiency in Rice-Wheat System in Mollisols

Biochar enriched with boron acts as a sustainable nutrient management approach offers a promising solution to address the micronutrient limitations and declining soil fertility. A field experiment was conducted during Kharif and Rabi 2024-25 in Mollisols at Pantnagar to study the influence of levels of boron (0.50, 0.75, and 1.00 kg B/ha), applied alone or in combination with biochar, on crop growth, photosynthate translocation, and nutrient use efficiency (NUE) indices. The experiment was laid out in a randomized block design with eight treatments, including sole boron, biochar enriched boron and control treatments to know the effect of boron enrichment in biochar. Results showed that boron-enriched biochar treatments achieved a superior result in comparison to sole boron application across all parameters. The treatment BC-B 1.00 observed the highest photosynthate translocation in both rice (74.06%) and wheat (74.78%), while BC-B 0.75 showed superior growth performance in wheat, which shows a diminishing response at higher B enrichment. Nutrient use efficiencies were maximized under moderate biochar-enriched treatments, particularly BC-B 0.50 and 0.75, which augmented PFP and AE by improving nutrient availability and uptake. In contrast, higher B doses (1.00 kg/ha) resulted in reduced efficiency, which explains lower marginal returns at higher concentrations. The improved performance under biochar-based treatments is mainly attributed to its high surface area, CEC, and functional groups, which facilitate slow and sustained B release, reduced leaching losses, and enhance soil physicochemical properties. Taken together, enriching biochar with B provides an efficient and sustainable approach for improving B use efficiency (BUE) and maintaining productivity in the rice-wheat system.