Biochar: Its Uses And Method Of Application

What actually biochar is?

Biochar is a carbon-enriched, fine-grained and porous by-product of slow pyrolysis when organic matter like wood material, tree bark, dairy manure, crop residues, chicken litter is thermally decomposed at moderate temperature under limited supply of oxygen. Biochar is being investigated as a means of carbon sequestration (capturing and storing atmospheric CO2) and it may be a means to mitigate global warming and climate change.

How is biochar produced?

Biochar is a high-carbon, fined-grained residue that is currently produced through modern pyrolysis process. It is the direct thermal decomposition of biomass in the absence of oxygen (preventing combustion), which produce a mixture of solids, liquid and gas products. The specific yield from pyrolysis is depends on process condition such as temperature residence time and heating rate. These parameters can be optimized to produce either energy or biochar. Temperature of 400-500°C produces more char, whereas temperature above 700°C favor of the yield of liquid and gas fuel components.

Figure: Method of production of biochar

What are its uses?

1. Carbon sink: Biochar presents a stable means of storing carbon in the ground for centuries, potentially reducing or stalling the growth in atmospheric greenhouse levels.
2. Soil amendment: The extremely porous nature of biochar is found to be effective at retaining water and water-soluble nutrients. It is a habitat for many beneficial micro- organisms. Biochar has been shown to leaching of E-coli. It was also found under certain circumstances to induce plant systemic response to induce plant systemic response to foliar fungal disease.
3. Biochar increases the soil fertility of acidic soils, increase agricultural productivity and provide protection against soil borne diseases.
4. Biochar improves pore size distribution, bulk density and consequently leading to an increase in soil available water needed for crop growth.
5. Biochar has the potential capacity to restore a degraded soil when added to the soil. Biochar mineralizes gradually over a long period of time when applied to soil.
6. Biochar enhances soil surface area, bulk density, porosity, resistance and moisture content. Also helps to enhance soil pH, organic carbon and Cation Exchange Capacity.
7. Modification of soil physical, chemical and biological properties by biochar application resulted to improve plant nutrient retention and availability, leading to improved biomass growth, dry matter content and crop yield.

Figure: Application of biochar in fields to improve soil and productivity

How to apply biochar in soil?

There are many ways for application of biochar. Some of them are mentioned below:

• By the process of broadcasting and incorporate: A mixture of manure and biochar is the best combination for broadcasting as well as incorporation. In case of incorporation animal draft plough, disc harrows, chisel etc are used.
• Traditional banding method: By this the biochar can be applied without making any disturbance to soil by making bands in the soil.
• Mixing biochar with manures, compost or lime can be a method of biochar application.
• Subsurface banding is a new concept in field of biochar application which prevents soil from runoff during rainy season.
• Biochar can be applied in the horticultural crops either by top dressing or can be applied to the drip line from which the roots obtain the nutrients in case of normal as well as transplanted trees.

Findings of biochar application by National Agricultural Research Council (NARC)

Biochar has been a matter of research for the scientist of Soil Science Division, NARC. Findings has shown that biochar application can help the soil against erosion, increases water availability in soil as well as purify the underground water. An application of half kg of biochar in cucumber and pumpkin along with manures has shown to increase the productivity by 200%. Use of biochar in cabbage, chili, bitter gourd has resulted in 80% increase in productivity, tea which is suitable in acidic soil when applied biochar found to have increase in leaf number by 50%. Beside that application of biochar in tomato, potato, maize, onion, garlic found to increase productivity by 20-30% and 25% of increase in productivity of coffee, banana, ginger, sugarcane, cardamom.

NARC has reported no any increment in productivity in case of rice and crops grown in submerged condition when biochar is applied  as biochar has lesser weight and it easily leach out from soils.