The scale of the effects and their persistence will depend on the amounts added. The effects cannot be permanent: consider the millions of years of fires

It is believed that biochar has a long average dwelling time in soil, ranging from 1000 to 10,000 years, with an average of 5000 years. When biochar is present in the soil mixture, its contribution to the physical nature of the system is significant, affecting the depth, texture, structure, porosity, and consistency by changing the surface area, pore and particle-size distribution, density, and packing. Biochar amendment can significantly improve soil physical, chemical, and biological fertility on the long-term even under intensive viticulture management, with no detectable detrimental effects on microbial diversity and soil functions, and potential of soil organic carbon storage. Biochar enhanced the physical properties of soil by improving its water holding capacity, moisture levels, and oxygen content. Biochar chemical properties, such as contaminant fixation and carbon sequestration, are also improved. Abiotic factors such as acid rain, flooded environment, changes in soil condition (pH, redox and dissolved organic matter) and changes in biochar (Cl− and alkali leaching).

Biochar's long-term effectiveness in soils is influenced by its original material and how it was made, along with the type of soil, climate, and how it's used in land management. Different combinations of these factors can affect how well biochar improves soil health, stores carbon, and supports plant growth over time.

Biochar, a carbon-rich product derived from the pyrolysis of organic materials, is used as a soil amendment for its potential benefits in improving soil fertility, enhancing crop productivity, and sequestering carbon. However, its long-term effectiveness varies depending on several factors. Here's a comprehensive overview of the key factors influencing biochar's long-term stability and effectiveness across different soils and environmental conditions:

1. Biochar Properties

a. Feedstock Type

• Source Material: The type of organic material used (e.g., wood, crop residues, manure) affects the chemical composition and physical properties of the biochar. Woody biochars tend to have higher stability and lower nutrient content, while biochars from manure or crop residues may contain more nutrients but degrade faster.

b. Pyrolysis Conditions

• Temperature: Higher pyrolysis temperatures typically produce biochars with higher carbon content, greater stability, and lower volatile matter. Low-temperature biochars may contain more labile carbon fractions that are more easily decomposed by soil microorganisms.
• Duration: Longer pyrolysis times can also increase biochar stability by promoting more complete carbonization.

c. Chemical Properties

• pH: Biochar pH can range from acidic to alkaline depending on the feedstock and pyrolysis conditions. Alkaline biochars can help neutralize acidic soils, while acidic biochars may be more suitable for alkaline soils.
• Nutrient Content: Biochar can provide essential nutrients (e.g., phosphorus, potassium) to the soil, but this depends on the feedstock and pyrolysis process.

2. Soil Properties

a. Soil Type

• Texture: Sandy soils benefit from biochar’s ability to improve water retention and nutrient-holding capacity. In clay soils, biochar can enhance aeration and reduce compaction.
• Organic Matter: Soils with low organic matter may see more pronounced benefits from biochar addition, as biochar can increase soil carbon content and microbial activity.

b. Soil pH

• Acidic Soils: Alkaline biochar can raise soil pH, improving nutrient availability and microbial activity.
• Alkaline Soils: Acidic biochar may help lower pH and improve nutrient availability.

c. Nutrient Availability

• Initial Nutrient Levels: The effectiveness of biochar in enhancing nutrient availability is influenced by the initial nutrient levels in the soil. In nutrient-poor soils, biochar can significantly improve nutrient retention and availability.

3. Environmental Conditions

a. Climate

• Temperature and Precipitation: Biochar stability can be affected by climatic conditions. In warmer, wetter climates, biochar may degrade faster due to increased microbial activity. In cooler, drier climates, biochar tends to be more stable.
• Seasonal Variations: Seasonal changes in temperature and moisture can influence the interactions between biochar and soil, affecting its long-term stability and effectiveness.

b. Land Use and Management Practices

• Tillage: Frequent tillage can expose biochar to oxygen and microbial activity, potentially accelerating its decomposition. No-till or reduced-till practices can help maintain biochar stability.
• Cropping Systems: The type of crops grown and their root structures can influence biochar interactions with soil. Deep-rooted crops may enhance the incorporation of biochar into deeper soil layers.

4. Biochar-Soil Interactions

a. Microbial Activity

• Microbial Decomposition: Soil microorganisms can break down biochar, influencing its long-term stability. The presence of labile carbon in biochar can stimulate microbial activity and decomposition rates.
• Microbial Community Composition: The type of microorganisms present in the soil can affect how biochar is decomposed and the nutrients it releases.

b. Soil-Water Interactions

• Water Retention: Biochar can improve soil water retention, which is beneficial in drought-prone areas. However, in waterlogged conditions, biochar may contribute to anaerobic environments, affecting plant growth and microbial activity.
• Hydraulic Conductivity: The addition of biochar can alter soil hydraulic properties, potentially improving water infiltration and drainage in heavy soils.

5. Long-Term Stability

a. Carbon Sequestration Potential

• Recalcitrant Carbon: The proportion of stable, recalcitrant carbon in biochar determines its long-term carbon sequestration potential. High-temperature biochars generally have higher recalcitrant carbon content.
• Degradation Rate: Environmental factors, such as temperature and microbial activity, influence the degradation rate of biochar in the soil.