Detailed Explanation:

Answer: Option 4 — 1, 2 and 3

Biochar is a carbon-rich, porous material produced through pyrolysis of biomass. It serves multiple functions in agriculture by improving soil structure, supporting beneficial microorganisms, and enhancing water retention. All three statements correctly describe the agricultural uses of biochar.

✅ Statement 1 – Correct: Biochar can be used as a component of growing media in vertical farming systems, where it improves substrate structure and nutrient retention.
✅ Statement 2 – Correct: The porous structure and chemical properties of biochar create favorable conditions for nitrogen-fixing microorganisms, enhancing biological nitrogen fixation in the soil.
✅ Statement 3 – Correct: Due to its high porosity and large surface area, biochar can absorb and retain significant amounts of water, making it available to plants over extended periods.

📝 Short Notes: Biochar in Agriculture

• Definition: Biochar is a stable, carbon-rich solid obtained from the pyrolysis (thermal decomposition in absence of oxygen) of biomass.
• Soil Amendment: Improves soil structure, porosity, and cation exchange capacity (CEC), leading to better nutrient retention.
• Water Retention: Its porous nature can hold 2-5 times its weight in water, reducing irrigation requirements.
• Microbial Habitat: Provides surface area and micro-habitats for beneficial soil microorganisms, including nitrogen-fixing bacteria.
• Carbon Sequestration: Stores carbon in soil for hundreds to thousands of years, contributing to climate change mitigation.
• Nutrient Management: Reduces nutrient leaching, improves fertilizer efficiency, and can adsorb contaminants.
• Applications: Used in conventional farming, vertical farming, container gardening, and soil remediation projects.