By Muhammad OsamaReviewed by Lexie CornerMar 27 2025A recent study published in Scientific Reports explores the development and performance of biochar-based slow-release fertilizers (SRFs) enhanced with semi-interpenetrating polymer networks (Semi-IPNs).
This approach addresses common issues with conventional chemical fertilizers (CFs), such as nutrient loss, environmental pollution, and declining soil health. The goal was to improve nutrient availability and water retention in soil, supporting more sustainable agricultural practices.
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Advancements in Sustainable Fertilization Technology
While chemical fertilizers have played a key role in increasing crop yields, their overuse has led to problems like soil degradation, nutrient leaching, and groundwater contamination.
Most CFs have low nutrient use efficiency, so significant amounts of nitrogen (N), phosphorus (P), and potassium (K) are lost to the environment, contributing to imbalanced soils and water pollution.
Slow-release fertilizers (SRFs) offer a solution by gradually delivering nutrients, improving plant uptake and reducing waste. Biochar, a carbon-rich material made from biomass through pyrolysis, has become a promising SRF component.
Its porous structure helps retain both nutrients and water. When combined with biodegradable polymers like chitosan in a semi-IPN structure, biochar-based SRFs can further improve nutrient release kinetics and moisture retention.
Exploring Biochar-Based SRFs
In this study, the team created SRFs by combining biochar, mica (MI), and a chitosan-based semi-IPN. The biochar was made from Conocarpus erectus biomass, processed at 400 °C. This biochar was then enriched with N, P, and K nutrients.
The researchers mixed the enriched biochar with finely ground mica and chitosan in water, followed by a controlled polymerization process to form the semi-IPN structure. The final products included different SRF formulations: biochar-only (BC-SRF), mica-only (MI-SRF), and composite (BCMI-SRF) versions.
They characterized the materials using several techniques, including scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), Fourier-transform infrared spectroscopy (FTIR), and Brunauer–Emmett–Teller (BET) analysis. To test nutrient release, the SRFs were placed in soil and monitored over 30 days.
Key Findings and Insights
The inclusion of biochar and semi-IPN polymers improved both water retention (WR) and water-holding (WH) capacity in the soil. After 30 days:
- BC-SRF increased WH capacity by 40.61 % and WR by 32.55 %
- BCMI-SRF increased WH by 47.80 % and WR by 35.52 %
These improvements were mainly due to the porous nature of biochar, which helps retain moisture and slows evaporation.
Nutrient release studies also showed strong results. While conventional fertilizers released nearly 100 % of nutrients within 30 days, the SRFs released them more slowly:
- BC-SRF released 69.76 % of NH4+ -N, 70.36 % of P, and 75.47 % of K over 30 days
Adding mica not only strengthened the material mechanically but also contributed to potassium availability. BCMI-SRF showed the highest water-holding capacity, with a 91.58 % increase compared to untreated soil and 35.52 % of water retained after 30 days.
The nutrient release kinetics followed parabolic diffusion and first-order models, indicating that nutrient release was predominantly governed by mass transport and diffusion through the polymer matrix of the SRFs.
These results suggest that biochar-based SRFs present a viable approach to sustainable agriculture by enhancing soil moisture retention, controlling nutrient release, and reducing nutrient losses.
Practical Applications in Sustainable Agriculture
This research has significant potential for sustainable agriculture, particularly in arid and semi-arid regions where water scarcity challenges crop production. The BC-SRFs enhance soil moisture retention and provide controlled nutrient release, reducing reliance on traditional CFS while improving crop yield and soil health.
Biochar's porous structure also supports microbial activity, promoting efficient nutrient cycling. Integrating agricultural waste, such as Conocarpus biomass, contributes to waste management and fosters a circular economy.
By minimizing nutrient leaching and utilizing biodegradable polymers like chitosan, these fertilizers align with global sustainability goals, offering an eco-friendly alternative to conventional fertilizers. Their adoption could revolutionize farming practices by improving productivity, conserving resources, and reducing agriculture's environmental footprint.
What’s Next
The researchers suggest further work to refine production, assess long-term impacts on soil and crop health, and test scalability in different agricultural systems. Optimizing slow-release technologies like these will be key to building more resilient and resource-efficient farming practices.
Journal Reference
Rafique, M.I., et al. (2025). Incorporation of biochar and semi-interpenetrating biopolymer to synthesize new slow release fertilizers and their impact on soil moisture and nutrients availability. Sci Rep. DOI: 10.1038/s41598-025-90367-8, https://www.nature.com/articles/s41598-025-90367-8
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