Land degradation is one of the major problems affecting the world. The term “Land degradation” refers to the decrease in soil productivity and deterioration of soil quality. When we talk about soil quality; it means the capacity of a specific kind of soil to function within natural and managed ecosystems.
The soil quality also refers to sustain animal and plant productivity; to maintain or enhance water / air quality, and support human health and habitation. Soils getting deplete of all essential nutrients due to high temperature and as a result vegetation gets disturbed.
These soils can be made alive again by many ways as application of organic matter, manures and other artificial sources of nutrients as fertilizers. But the best and safe way to make soil alive is application of Biochar.
Biochar the soil conditioner
The concept of “Biochar” came from terra preta soils. It’s use as a soil amendment was introduced in 2006. In recent years, it has received tremendous attention as one of the most useful technique for soil restoration.
Biochar is the carbon-rich product, obtained by heating of wood, manures etc in close container with little or no available air. The main components of Biochar are Carbon (C), Hydrogen (H), Nitrogen (N) and other trace elements. Almost 70-80% by weight is carbon and <3% is nitrogen.
Biochar may be a source of many nutrients but their amount depends on pyrolysis temp as total amount of Phosphorus appears to be increasing with high pyrolysis temperature.
Biochar is slow to decompose because carbon atoms in it are so strongly bound that it is resistant to microbial attack. Soils with Biochar treatment can retain these properties for many years. So it’s an effective sequestration and bioremediation tool. Biochar may be of different types, depending upon the type of feedstock and heating conditions of feedstock. But by properly processing, following multiple benefits are achievable:
Biochar and soil health
Biochar improves soil physical properties (bulk density, pore spaces, total number of pores) and chemical properties (pH, EC, CEC) as well. It can bring a change in bulk density of soil because it contains macro and micro pores which have air and water, resulting in decrease of bulk density.
Biochar can have pH values below 4 and above 12 depending upon its type. It has high cation exchange capacity (CEC) values which result in more nutrient retention and increase in fertility of soil.
Biochar is most appropriate for heavy metal removal by adsorption. The adsorption mechanisms mainly include electrostatic interaction, ionic exchange, chemical precipitation and complexion with functional groups on Biochar surface.
As far as Biochar effects on soil microbes: it’s application increases not only fungi to bacteria ratio but also their activity by following ways:
- Periodic drying of soil leads to stress conditions and dormancy or mortality of microbes. Biochar has more pore space which result in continuous hydration of microbes. Even survival capacity and reactivation of Oxygen sensitive bacteria during freezing and drying will also increase in presence of it.
- Biochar may also increase microbial activity by adsorbing some compounds which may be toxic for microbes such as catechol.
In short, biochar provides safe refuge for microbes, experiencing harsh environmental conditions and provides a suitable habitat for their numbers to proliferate.
Drought and salt stress conditions
In drought and salt stress conditions of soil, biochar is also quite beneficial. As it has more pore spaces, it retains sufficient amount of water. In Drought conditions, it results in increase in growth and biomass of plants. Loss of nitrogen by volatilization or leaching is one of the biggest problems in our soils. Biochar has potential to control the rates of nitrogen-cycling in different ways:
- Enhancing soil content of ammonium (NH4+) and Nitrate (NO3– ) through direct adsorption by Biochar and reducing the losses of nitrogen.
- Increase in activity and population of soil nitrifying bacteria
Biochar application results in control of some weeds which are parasitic; may affect agricultural productivity. The major mechanism responsible for Biochar interference with parasitic weed seed germination, is adsorption of stimulant molecule because weeds require stimulant molecule for seed germination. It plays an important role in activating plants innate defenses against disease causing microbial pathogens.
Environmental interactions of Biochar
Biochar is suitable to manage wastes. All wastes that may contaminate our environment are useful for pyrolysis bioenergy. Ultimately volume of waste materials will also greatly reduce. It mitigates climate changes by reducing methane emissions, recovering energy from waste material and increasing carbon sequestration in soil.
Biochar reduces release of greenhouse gases. It binds all nitrogenous compounds. As a result, release of N2O will minimize. By using waste in biochar production process, we can reduce methane, which is also a greenhouse gas. Otherwise natural decomposition of waste results in release of methane gas.
Biochar amendments to soil are likely to reduce the bioavailability and efficacy of pesticides. The incorporation of even very small amount of biochar inhibits microbial degradation of pesticides / herbicides as well as reduce their plant availability.
Quality of desert soils can also be improved by biochar application. Active Biochar comprises of nutrients and (Plant Growth Regulators) PGR’s. It’s amendment improves desert soil hydraulic properties as water holding and water retention capacity.
Nowadays, biochar modification is also in use. They have advance surface properties and significantly increase plant yield. Nanoparticles of Biochar are also used to characterize their effects on soil properties. But before the use of these nanoparticles, assessment of their environmental impact is necessary.
Moreover, Biochar activation amendment doesn’t result in production of Persistent Organic Pollutants, so it’s also known as the wonderful soil conditioner or enricher.