What is the aging of biochar and effect of biochar aging in agricultural soil on its wetting properties and surface structure?
Biochar Aging and its Impact on Agricultural Soil
Biochar is a charcoal-like material produced by heating organic matter in an oxygen-limited environment. It's increasingly used as a soil amendment due to its beneficial properties. One key aspect to consider is how biochar behaves over time in soil, which is referred to as biochar aging.
Here's how aging affects biochar's interaction with agricultural soil, particularly its wetting properties and surface structure:
Improved Wetting Properties:
- Studies have shown that biochar aging in natural soil conditions leads to increased wettability. This means aged biochar attracts and absorbs water more readily compared to fresh biochar.
- This improvement is attributed to various factors like:Surface oxidation: Over time, biochar's surface gets exposed to air and moisture, leading to the formation of oxygen-containing functional groups. These groups make the surface more "water-loving" (hydrophilic). Interactions with soil components: As biochar resides in soil, it interacts with clay particles and organic matter. These interactions can create a porous network that facilitates water retention.
Changes in Surface Structure:
- Biochar's surface undergoes physical changes during aging.
- The lateral surfaces (sides) can develop a loose and porous layer, filled with mineral particles and clay. This enhances water absorption.
- However, the effect of mineral fertilizers on biochar's surface can be negative. Fertilizer application might lead to the formation of a crust on the biochar surface, blocking pores and hindering water absorption.
Overall Impact:
- Enhanced wetting properties due to aging can significantly improve the soil's ability to retain water and nutrients. This is beneficial for plant growth and reduces the need for irrigation.
Additional Points:
- Research suggests that aging under controlled conditions (like in a lab) can also improve biochar's water holding capacity compared to fresh biochar.
- The specific effects of aging can vary depending on factors like the type of biochar, soil properties, and climatic conditions.
If you'd like to delve deeper, you can explore research papers on "biochar aging in agricultural soil" or "effect of biochar aging on wettability."
Mechanical strength of biochar particles was improved after the field aging. The aged biochar could significantly inhibit CO2 and N2O emissions from the soil. The wetting properties and the water absorbing capacity of the lateral surface of the biochar aged in the agricultural soil for 6 years have improved dramatically the sample exhibits hydrophilic properties, not only due to the formation of organo-mineral complexes on the surface. An application of biochar to soil improves soil structure, increases porosity, decreases bulk density, and enhances aggregation and water retention in acidic, degraded and sandy soils. The decrease of ash in aged biochar can inhibit the adsorption of heavy metals. The loss of aromatic components and the formation of three-dimensional water clusters during the ageing process have a negative impact on high-temperature biochar (>500° C) for organic pollutants adsorption. Biochar aging can reduce its ash content and increase its acidity level. Aging by chemical oxidation results in biochar acidification and the release of ash minerals whereas physical aging is much milder, resulting in only slight variations in biochar pH. Aging of biochar changes its physiochemical properties, while a range of biochar-derived organic materials (BDOMs) can be formed. These changes have significant consequences for the bioavailability and transport of nutrients and contaminants. Increased in cation exchange capacity and soil pH have been noticed by the application of biochar. Application of biochar improved the overall sorption capacity of soils and consequently it may persuade the transport, and fate of dissimilar heavy metals and toxicity in the soil.
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