According to a study published in the journal Biochar by authors Yuanyuan Feng and Yuanhao Liu, nitrogen is a fundamental nutrient that limits the productivity of plants and microbes in land-based ecosystems. In the soil, nitrogen exists mostly as organic matter, with a specific portion known as acid-hydrolyzable nitrogen serving as the primary indicator of how well the soil can supply nutrients to plants. This specific nitrogen pool is highly sensitive to changes in the environment, particularly the effects of acid rain. Even as the frequency of acid rain decreases in some parts of the world, its legacy effects like soil acidification and the loss of essential minerals continue to threaten the stability of these vital nitrogen supplies. To combat this, researchers looked toward alkaline biochar as a potential solution to mitigate soil damage and restore nutrient cycles.

The team established a field experiment in a plantation to observe how biochar made from tree leaf litter would interact with simulated acid rain over a two-year period. Their findings revealed that the application of biochar was highly effective at raising the soil pH and significantly increasing the accumulation of available nitrogen. Under the stress of acid rain, the biochar treatment boosted the total acid-hydrolyzable nitrogen content by 64.8 percent. Within this nitrogen pool, different fractions showed varying levels of improvement. For instance, acid-ammonia nitrogen increased by 45 percent, while acid-amino sugar nitrogen and acid-amino acid nitrogen rose by 61.3 percent and 80.6 percent, respectively. These results suggest that biochar does more than just neutralize acid; it fundamentally changes how nitrogen is stored and transformed in the ground.

The researchers discovered that these positive changes were driven largely by biological shifts rather than just chemical ones. Biochar application under acid rain conditions led to the highest complexity in the network of soil bacteria, which helps in the efficient recycling of nutrients. Interestingly, while the bacterial networks became more robust, the connectivity of fungal networks actually decreased. The study identified that the amount of nitrogen stored within the bodies of soil microbes was a key factor in how much beneficial nitrogen accumulated in the soil. Furthermore, the efficiency with which these tiny organisms used nitrogen improved by over 21 percent when biochar was present, even when the soil was being sprayed with acidic solutions.

This biological regulation proved to be the dominant force in protecting the soil. The researchers used advanced modeling to show that the regulatory effects of biochar on soil nitrogen were actually stronger than the negative impacts caused by the acid rain itself. By increasing the activity of specific enzymes and supporting a larger biomassBiomass is a complex biological organic or non-organic solid product derived from living or recently living organism and available naturally. Various types of wastes such as animal manure, waste paper, sludge and many industrial wastes are also treated as biomass because like natural biomass these More of microbes, the biochar created a buffer that kept nitrogen from leachingLeaching is the process where nutrients are dissolved and carried away from the soil by water. This can lead to nutrient depletion and environmental pollution. Biochar can help reduce leaching by improving nutrient retention in the soil.   More away or becoming unavailable to plants. This suggests that for forest managers and environmental scientists, biochar is not just a waste product but a sophisticated tool for sustainable nutrient management. It helps ecosystems remain productive and resilient even when faced with the long-term challenges of environmental pollution and changing climates.

The implications of this research extend to broader strategies for ecological restoration. By understanding that biochar-driven biological regulation dominates the way nitrogen is handled in stressed soils, experts can develop better ways to manage plantations and natural forests. The study highlights that the interaction between biochar and soil life creates a slow-release nitrogen pool that is essential for long-term health. Because biochar is produced through the controlled burning of organic waste, this approach also supports a circular economy where forest litter is turned back into a valuable resource that protects the very trees it came from. This research provides a clear scientific basis for using biochar to restore the nitrogen cycle in areas hit hard by industrial pollution.

Source: Feng, Y., Liu, Y., Liu, J., Hu, H., Zhou, M., Feng, Y., & Xue, L. (2026). Biochar-driven biological regulation dominates acid-hydrolyzable nitrogen accumulation in plantation soils under acid rain stress. Biochar, 8(55).