Biochar‐based fertilizers improve nutrient use efficiency in sunflower grown on a subtropical tidal soil

Abstract

Improving fertilizer use efficiency is essential for reducing environmental pollution, sustaining agricultural production, and maximizing the economic profitability of crop production systems. This study tested the hypothesis that the formulation strategy of biochar‐based fertilizers, rather than nutrient addition alone, is associated with systematic differences in crop performance and nitrogen‐use efficiency under field conditions. Using sunflower as a test crop, biochar‐based fertilizers developed using different decision frameworks (soil test, crop nutrient harvest, agroecological zones (AEZs), and industry recommendation) were evaluated against conventional chemical fertilization. Biochar was added at two different rates: 20% or 10% of the total fertilizer quantity. The results showed a consistent pattern: soil test‐based formulation approaches provided higher nutrient use efficiency than other formulations and standard fertilizer treatment. Soil test‐based formulations achieved seed yields up to 1.75 t ha ⁻¹ , representing a 23.87% increase in seed yield compared with conventional fertilization. Other formulations resulted in intermediate yield performance between soil test‐based formulations and the standard recommendation. However, there was no statistical difference in seed yield and aboveground biomass production between the 20% and 10% biochar treatments. Correlation analysis, principal component, and redundancy analyses indicated that improvement in crop yield under selected biochar‐based fertilizer formulations occurred as a result of enhanced bioavailability and plant uptake of key soil nutrients. This study identified fertilizer formulation strategy as a critical, yet often overlooked, aspect of biochar‐based fertilizer formulation. From an applied perspective, the results offer opportunities to develop decision‐guided biochar‐based fertilizers that could improve input efficiency and may lower dependence on synthetic fertilizers, with relevance for farmers, fertilizer manufacturers, and policymakers. Future research should address multiseason validation, cost–benefit assessment, underlying mechanisms, economic robustness, and broader applicability across agroecological contexts.