Current status of soil organic carbon in Indian soils

The soil organic carbon (SOC) content in Indian soils has declined from 1% to 0.3% in the past 70 years. This is a cause of concern for the agriculture sector, as SOC plays a vital role in soil health, fertility, and productivity.

There are a number of factors that have contributed to the decline in SOC in Indian soils, including:

• Intensive agriculture: Intensive agricultural practices, such as monocropping, excessive use of chemical fertilizers and pesticides, and burning of crop residues, have depleted SOC levels.
• Deforestation: Deforestation leads to the loss of trees and other vegetation, which are a major source of organic matter for soils.
• Erosion: Soil erosion removes the top layer of soil, which is typically the richest in SOC.
• Climate change: Climate change is also having an impact on SOC levels in Indian soils. For example, increasing temperatures and more frequent droughts can accelerate the decomposition of organic matter.

How rapidly does soil organic carbon change?

The rate at which SOC changes depends on a number of factors, including climate, soil type, and land use. In general, SOC levels change more slowly in colder climates and on soils with a high clay content. Land use practices that add organic matter to the soil, such as cover cropping and composting, can help to increase SOC levels over time.

Difference between organic matter and humus in soil

Soil organic matter (SOM) is any organic material that is present in the soil, including living and dead organisms, plant residues, and animal manure. Humus is a stable form of SOM that has been decomposed by microorganisms. Humus is dark in color and has a high water-holding capacity. It is also rich in nutrients, which makes it essential for plant growth.

SOM is important for soil health and fertility because it:

• Improves soil structure and aeration
• Increases water-holding capacity
• Releases nutrients for plant growth
• Supports microbial activity

Humus is especially important for soil health because it is more resistant to decomposition than other forms of SOM. This means that it can remain in the soil for longer periods of time, providing a steady source of nutrients for plants.

What can be done to improve soil organic carbon levels in India?

There are a number of things that can be done to improve SOC levels in Indian soils, including:

• Adopting sustainable agricultural practices: Sustainable agricultural practices, such as cover cropping, composting, and crop rotation, can help to add organic matter to the soil and build SOC levels over time.
• Reducing deforestation: Reducing deforestation and planting trees can help to increase the amount of organic matter that is available to soils.
• Controlling soil erosion: Soil erosion can be controlled through a variety of practices, such as contour farming, terracing, and strip cropping.
• Improving irrigation practices: Efficient irrigation practices can help to reduce water evaporation and leaching, which can preserve SOC levels.

By taking these steps, we can help to improve soil health and fertility in India, and ensure that our soils are productive for future generations.

Dr Murtadha Shukur thank you for your contribution to the discussion

Generally, soil organic carbon can be increased by increasing organic carbon inputs and/or reducing losses. Increase SOC inputs, increase crop yield. Optimize rotations to increase carbon inputs per unit land area.Typically, the organic carbon content of WA dryland agricultural soils is between 0.7% and 4% although SOC can be as low as 0.3% for desert soils and as high as 14% for intensive dairy soils. Most organic matter is located near the soil surface. The mean carbon footprint of every Indian was estimated at 0.56 tonne per year--0.19 tonne per capita among the poor and 1.32 tonne among the rich. Emissions from India rank third in the global list, accounting for 2.46 billion metric tonnes of carbon or 6.8% of the total global emissions. The Earth's soils store 2,500 billion tons of carbon more carbon than the atmosphere (780 billion tons) and plants (560 billion tons) combined. In 2016, India had a net carbon sink of 308 MtCO2e. India's target for its land and forestry sector remains unchanged in its updated NDC as it plans an additional 2.5–3 GtCO2e of carbon sink by 2030 through additional forest cover. Indian soils traditionally have low nitrogen and phosphorus content, but high potassium. As per the 2019-20 Soil Health Survey conducted by the Indian government, 55 percent of the country's soil is deficient in nitrogen, 42 percent in phosphorus and 44 percent in organic carbon. Overall, models predicted 1.9–2.2% SOC as the critical concentration range for high yields. The critical range of SOC concentrations corresponded to 3.5–5.0 g kg −1 sand-sized C and 9–11 g kg −1 for clay-sized C. Organic matter starts as anything that was alive bacteria, fungi, insects, plants, animals and their waste products, in or on the soil, in the process of decomposition. Humus is the end product of dead organic matter that has fully decomposed and been converted by microorganisms to a resistant state of decomposition. The uppermost horizon is called the topsoil layer. The topsoil layer is a mixture of sand, silt, clay and broken down organic matter, called humus. Humus is rich, highly decomposed organic matter mostly made from dead plants, crunched-up leaves, dead insects and twigs. Humus is well-decomposed organic matter. Organic matter includes things like bark, twigs, and ground up tree trimmings, vegetable peelings or leftovers from meals, eggshells, dead plants, thinning from garden that can all go into a compost pile.