Modern agriculture relies heavily on synthetic nitrogen fertilizers to feed a growing global population, but traditional crop production often suffers from low nutrient recovery rates and high environmental pollution risks. While biochar has long been studied as a tool to retain soil nutrients and sequester carbon, its direct biochemical effects on plant metabolism and nitrogen assimilation have remained poorly understood. Understanding how organic soil amendments interact with internal plant pathways is essential for developing sustainable horticulture practices that maximize crop yields while minimizing chemical fertilizer inputs.

To investigate these physiological mechanisms, researchers conducted a controlled 31-day pot experiment using lettuce plants grown in different substrate mixtures containing varying proportions of vineyard-pruning-derived biochar, peat, and vermiculite. The team evaluated general plant growth, water status, and photosynthetic performance alongside the distribution of various nitrogen forms in the soil and plant tissues. Furthermore, they measured critical nitrogen use efficiency parameters and quantified the enzymatic activities of key proteins involved in the plant nitrogen assimilation pathway.

The results demonstrated that incorporating 30 percent biochar significantly elevated nitrogen uptake flux, partial nitrogen balance, and overall nitrogen productivity without causing any physiological stress symptoms or altering photosynthetic efficiency. Although total nitrogen concentrations in the roots and substrates decreased, the plants achieved a 34.8 percent higher nitrogen utilization efficiency. This occurred because biochar strongly upregulated essential enzymes like nitrate reductase, glutamine synthetase, glutamate synthase, and glutamate dehydrogenase. These biochemical changes enabled the lettuce plants to rapidly convert absorbed inorganic nitrogen into valuable organic compounds and soluble proteins.

Source: Garcia-Rodriguez, A. F., Moreno-Racero, F. J., Álvarez, R., Colmenero-Flores, J. M., Knicker, H., & Rosales, M. A. (2026). Biochar enhances nitrogen use efficiency in lettuce by promoting its metabolic assimilation. Plant and Soil, 518, 299–317.