The research published on the platform Preprints.org by lead author Zhengrong Bao and a team of researchers from Liaodong University and Shenyang Agricultural University highlights a sustainable solution for enhancing soil fertility and crop productivity. The study focuses on the rhizosphere, which is the critical soil zone directly influenced by plant roots where the most complex nutrient exchanges occur. By conducting a long-term field trial, the scientists investigated how maize straw-derived biochar affects various forms of potassium in this vital zone. Potassium is an essential nutrient for crops, acting as a regulator for vital processes like protein synthesis and photosynthesis. However, most potassium in soil is not readily available to plants, making the discovery of biochar’s ability to unlock these nutrient pools particularly significant for global agriculture.

The findings demonstrate that biochar serves as both a direct source of nutrients and a powerful soil conditioner. Because biochar is produced through the high-heat processing of organic materials like maize straw, it naturally contains high levels of potassium that can be directly released into the soil. Beyond this direct supplement, the study found that biochar fundamentally changes the environment around plant roots. It significantly increased microbial 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 carbon, meaning it stimulated the abundance and activity of soil microorganisms. These microbes play a silent but crucial role in breaking down minerals to release even more potassium for the plants to use. Furthermore, biochar increased the soil’s cation exchange capacity, which effectively expands the soil’s ability to hold onto nutrients and prevents them from washing away during heavy rains.

Quantitatively, the impact on soil chemistry was substantial over the two-year observation period. Biochar application increased water-soluble potassium in the rhizosphere soil by over 18% in the first year and 11% in the second. It also boosted exchangeable and non-exchangeable potassium forms, which act as important reserves that plants can draw upon as they grow. The researchers observed that when biochar and standard potassium fertilizer were used together, the results were even more impressive. This combination yielded the highest potassium content across all measured forms, suggesting a positive synergy where biochar helps the plant make better use of applied fertilizers.

The physical growth of the maize plants mirrored these chemical improvements in the soil. Plants treated with biochar were taller, had thicker stems, and possessed a larger leaf area index for more efficient energy production. Perhaps most importantly, the root systems were much more developed. Biochar treatment led to significant increases in root length, root surface area, and the number of root tips. A more extensive root network allows the plant to explore more soil volume and absorb more water and nutrients. This intensified root growth, combined with the enriched soil environment, resulted in an above-ground dry weight increase of nearly 14% and a massive spike in potassium uptake of up to 43.87%.

In addition to nutrient management, biochar improved other foundational soil properties. It raised the soil pHpH is a measure of how acidic or alkaline a substance is. A pH of 7 is neutral, while lower pH values indicate acidity and higher values indicate alkalinity. Biochars are normally alkaline and can influence soil pH, often increasing it, which can be beneficial More, making the environment less acidic and more favorable for maize growth. It also increased electrical conductivity, which is a sign that more soluble salts and nutrients were available in the root zone. These collective changes create a more resilient and fertile soil structure that supports long-term agricultural sustainability. This research confirms that returning biochar to the fields is not just a method for sequestering carbon to fight climate change, but a practical and highly effective strategy for meeting the nutrient demands of modern crops while building healthier, more productive soils for the future.

Source: Bao, Z., Ji, C., Dai, W., Liang, X., Wang, C., Liu, Z., & Meng, J. (2026). Effects of long-term biochar application on potassium in maize rhizosphere soil. Preprints.org.