The agricultural sector faces a pressing challenge: balancing increased crop yields with environmental sustainability. Traditional reliance on chemical phosphorus (P) fertilizers, while effective in boosting production, contributes to ecological damage and water pollution through eutrophication. The need for environmentally friendly, controlled-release fertilizers is urgent. A recent study published in Water Air Soil Pollution by Yanjiao Qi, Jiazhi Gao, Shen Yang, Qian Li, Linshan Wang, Bo Zhang, Yidan Duan, Huining Lu, Lan Wu, Hong Zhang, and Yamin Zhao, explores a promising solution: a composite material called B@PM. This innovative fertilizer combines biocharBiochar is a carbon-rich material created from biomass decomposition in low-oxygen conditions. It has important applications in environmental remediation, soil improvement, agriculture, carbon sequestration, energy storage, and sustainable materials, promoting efficiency and reducing waste in various contexts while addressing climate change challenges. More enriched with insoluble calcium and phosphorus minerals (BCEKH) with Paenibacillus mucilaginosus, a silicate bacterium known for its ability to dissolve soil minerals.
The core idea behind B@PM is to transform phosphorus-containing waste into a slow-release fertilizer that can effectively deliver nutrients to plants while minimizing environmental impact. Biochar, a carbon-rich material produced from 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 pyrolysisPyrolysis is a thermochemical process that converts waste biomass into bio-char, bio-oil, and pyro-gas. It offers significant advantages in waste valorization, turning low-value materials into economically valuable resources. Its versatility allows for tailored products based on operational conditions, presenting itself as a cost-effective and efficient More, has shown potential in adsorbing phosphorus from wastewater, making it a valuable component for sustainable agriculture. The researchers specifically designed BCEKH by co-pyrolyzing corn straw, eggshells, potassium dihydrogen phosphate, and phosphoric acid, creating a porous biochar rich in P, K, and Ca nutrients. This process forms insoluble compounds like Ca2P2O7 and K2CaP2O7 within the biochar.
The crucial element of B@PM is the inclusion of Paenibacillus mucilaginosus. This bacterium is well-regarded for its capacity to dissolve various soil minerals, including phosphorus, potassium, and silicates, thereby releasing these essential elements for plant uptake. The study confirmed that Paenibacillus mucilaginosus effectively dissolved pyrophosphate crystals, like Ca2P2O7 and K2CaP2O7, which are often locked within the biochar structure. The biochar itself, with its porous structure, provides an ideal habitat for the bacteria, protecting them from other microbes and ensuring their continued activity.
The researchers conducted a potting experiment using Chinese cabbage to assess the effectiveness of B@PM. The results were compelling. The application of B@PM significantly increased the growth of Chinese cabbage: root length increased by 30.77%, leaf width by 71.67%, and plant height by 81.08%. The optimal growth was observed with a low dose of the B@PM composite, suggesting an efficient use of the material.
Beyond plant growth, B@PM also had a profound impact on soil health. The concentrations of organic matter (OM), available phosphorus (AP), available potassium (AK), and total calcium (TCa) in the soil all increased significantly. Compared to the control, the AP, AK, and TCa in the B@PM treatment (20 TJ) increased by 22.25% to 54.69%, 34.12% to 93.58%, and 56.81% to 73.86%, respectively. This indicates that the bacteria’s metabolic byproducts, such as phytohormones and organic acids, play a vital role in mobilizing these nutrients.
Furthermore, the activities of key soil enzymes, which are indicators of soil health and nutrient cycling, were enhanced. Catalase activity increased by 82.84%, and alkaline phosphatase activity increased by 39.64%. These enzymes are crucial for degrading hydrogen peroxide and converting organic phosphorus into plant-available inorganic phosphorus, respectively. The study also observed an increase in urease activity, suggesting that Paenibacillus mucilaginosus helps mineralize organic nitrogen into ammonium nitrogen, which is then fixed in the soil in combination with biochar.
The microbial community in the rhizosphere soil also underwent positive changes. The abundance of beneficial bacteria such as Proteobacteria, Actinobacteria, Bacteroidetes, and Firmicutes increased after B@PM application. These bacterial groups are known to play crucial roles in carbon and nitrogen cycling, soil ecological stability, and even nitrogen fixationNitrogen is a crucial nutrient for plant growth, but plants can’t directly absorb it from the air. Nitrogen fixation is a process where certain bacteria convert atmospheric nitrogen into a form that plants can use. Biochar can provide a home for these nitrogen-fixing bacteria, enhancing More. The study found strong correlations between these dominant bacterial species and various environmental factors like OM, URE, EC, TCa, AK, CAT, AP, and ALP.
The findings of this study provide a strong basis for the application of B@PM as an effective slow-release fertilizer in alkaline soils. The combination of nutrient-enriched biochar and beneficial bacteria offers a dual benefit: directly supplying nutrients and enhancing the soil’s natural capacity to make nutrients available through microbial activity. This approach represents a significant step towards more sustainable agricultural practices, addressing both crop productivity and environmental concerns related to chemical fertilizer use.
Source: Qi, Y., Gao, J., Yang, S., Li, Q., Wang, L., Zhang, B., Duan, Y., Lu, H., Wu, L., Zhang, H., & Zhao, Y. (2025). Enhanced Nutrient Release and Microbial Activity: Assessment of Ca-P mineral enriched biochar loaded with Paenibacillus mucilaginosus. Water Air Soil Pollut, 236(511).
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