Soil aggregation, the process where soil particles bind together, is fundamental to soil health, influencing water infiltration, aeration, and nutrient cycling. While 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, a carbon-rich material 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, is known to improve these properties, its specific impact, particularly from pig manure, on clay soils has been less understood. A recent short-term field experiment (120 days) in Bangladesh, conducted by Rahman et al. and published in Plant Science Today , investigated how pig manure biochar affects soil organic carbon (SOC), aggregate stability (Mean Weight Diameter, MWD), and microbial biomass carbon (MBC) in clay soil under pumpkin cultivation.

The study evaluated five treatments: a control with no biochar (T0), inorganic fertilization (T1) at 2 t/ha, and biochar at 4 t/ha (T2), 8 t/ha (T3), and 16 t/ha (T4). The results demonstrated that biochar significantly enhanced soil aggregation. Large macroaggregates (2-4 mm) increased by 1.9, 2.2, and 2.7 times in the T2, T3, and T4 treatments, respectively, compared to the control (T0). Correspondingly, the Mean Weight Diameter (MWD), a key indicator of aggregate stability, increased by 53%, 75%, and 103% in the T2, T3, and T4 treatments, respectively, compared to the control (P<0.01). This dose-dependent improvement highlights biochar’s capacity to bind soil particles, creating a more stable soil structure.

Beyond structural improvements, biochar significantly boosted soil organic carbon (SOC) content. All biochar treatments, as well as the inorganic fertilizer treatment, increased SOC compared to the control (P<0.001). Specifically, the highest biochar application rate (T4) led to a 38% increase in SOC content compared to the control. The study also found a strong linear relationship between MWD and SOC (R²=0.62, P<0.001), underscoring the critical role of organic carbon in fostering stable soil aggregates. Macro-aggregates, particularly those larger than 2 mm, showed a notable 47% increase in SOC levels with the T3 and T4 biochar treatments.

The positive effects of biochar extended to the soil’s microbial community. Microbial biomass carbon (MBC) was enhanced by 4.5 times, and glomalin-related soil protein (GRSP) increased by 1.23 times with the 16 t/ha biochar addition (T4) (P<0.001). GRSP, a substance produced by arbuscular mycorrhizal fungiThese are friendly fungi that form a partnership with plant roots. They act like an extension of the root system, helping plants access water and nutrients more effectively. Biochar can create a cozy habitat for these helpful fungi, boosting their growth and improving plant health.   More, plays a vital role in gluing soil particles together, thereby enhancing aggregation. The increased MBC and GRSP observed in the study indicate that biochar provides a favorable environment and nutrient source for microbial activity, stimulating fungal growth and GRSP production. A positive relationship was observed between MWD and GRSP (R²=0.29, P<0.05) and between MWD and MBC (R²=0.41, P<0.05), reinforcing the link between microbial activity and aggregate stability.

Interestingly, while biochar improved several soil properties, its application did not significantly impact different iron oxides or their ratio (P>0.05). Similarly, no significant relationship was found between amorphous iron oxide and MWD (P>0.05) , which contrasts with some previous research, possibly due to the specific clay mineralogy of the study soil.

This research highlights that pig manure biochar, especially at higher application rates, offers a sustainable solution for enhancing soil structure and carbon storage in clay soils. By significantly increasing macroaggregate formation, SOC content, and microbial biomass, biochar contributes to improved soil health and productivity, offering a valuable approach for sustainable soil management in regions like Bangladesh.

Source: Rahman, T., Ahmad, S. J., Joardar, J. C., Nasrin, S., Islam, M. U., & Halder, M. (2025). Pig manure biochar enhances soil organic carbon, aggregate stability and microbial biomass in the clay soil of Bangladesh. Plant Science Today (Early Access).