Soil Organic Carbon– Smart strategy to mitigate climate change and increasing farmer’s income

Nilesh Heda

SAMVARDHAN SAMAJ VIKAS SANSTHA, KARANJA LAD, DIST. WASHIM 444105

nilheda@gmail.com

9765270666

In the presence of climate change, land degradation and biodiversity loss, soils have become one of the most vulnerable resources in the world. Soils are a major carbon reservoir containing more carbon than the atmosphere and terrestrial vegetation combined. When people think ‘carbon’ they usually think ‘trees’, but in reality 82% of carbon in the terrestrial biosphere is in the soil 80% (2500 GT) (Lal 2008). Healthy grasslands may contain over 100 times more carbon in the soil than on it, making a well managed perennial ‘grass ley’ the quickest and most effective way to restore degraded land. Soil organic carbon (SOC) is dynamic, however, and anthropogenic impacts on soil can turn it into either a net sink or a net source of GHGs. Enormous scientific progress has been achieved in understanding and explaining SOC dynamics. Yet, protection and monitoring of SOC stocks at national and global levels still face complicated challenges impeding effective on-the-ground policy design and regionally adapted implementation.

After carbon enters the soil in the form of organic material from soil fauna and flora, it can persist in the soil for decades, centuries or even millennia. Eventually, SOC can be lost as CO2 or CH4 emitted back into the atmosphere, eroded soil material, or dissolved organic carbon washed into rivers and oceans. The dynamics of these processes highlight the importance of quantifying global carbon fluxes to ensure maximum benefits of SOC to human well-being, food production, and water and climate regulation. Every tonne of carbon lost from soil adds 3.67 tonnes of carbon dioxide (CO2) to the atmosphere. Conversely, every one tonne increase in soil carbon represents 3.67 tonnes of carbon dioxide sequestered from the atmosphere and removed from the greenhouse equation.

SOC is the main component of soil organic matter (SOM). As an indicator for soil health, SOC is important for its contributions to food production, mitigation and adaptation to climate change, and the achievement of the Sustainable Development Goals (SDGs). A high SOM content provides nutrients to plants and improves water availability, both of which enhances soil fertility and ultimately improves food productivity. Moreover, SOC improves soil structural stability by promoting aggregate formation which, together with porosity, ensures sufficient aeration and water infiltration to support plant growth.

With an optimal amount of SOC, the water filtration capacity of soils further supports the supply of clean water. Through accelerated SOC mineralization, soils can be a substantial source of greenhouse gas (GHG) emissions into the atmosphere. Although the overall impact of climate change on SOC stocks is very variable according to the region and soil type, rising temperatures and increased frequency of extreme events are likely to lead to increased SOC losses.

Globally, SOC stocks are estimated at an average of 1500 Pg Carbon in the first meter of soil, although their distribution is spatially and temporally variable. SOC hot-spots and bright spots, which are respectively areas of high SOC content (e.g. peat lands or black soils) and large surface areas of low SOC content (e.g. dry lands) constitute major zones of concern. With climate change and unsustainable management, these areas are likely to become net sources of GHG emissions. However, if managed wisely, they have the potential to sequester large amounts of carbon in their soils, thus contributing to climate change mitigation and adaptation.

Climate change poses a major threat to food security through its strong impact on agriculture. It is thought to negatively affect crop, livestock and fishery production through yield reductions, biological migration and loss of ecosystem services, which ultimately lead to a reduction in agricultural incomes and an increase in food prices. SOC sequestration can support the mitigation of these issues while offering part of the solution to a warming climate. Therefore, a number of suggested SOC conserving practices need to be implemented in order to reach the maximum potential of climate change mitigation and adaptation and food productivity.

Food production in developing countries, estimated at 1223 million metric tons (Mg), must be increased by 778 million Mg or 2•5 percent per year between 2000 and 2025 to meet the needs of an increased population and projected change in diet. Among numerous options, the one based on enhancing soil quality and agronomic productivity per unit area through improvement in soil organic carbon pool has numerous ancillary benefits. The available data show that crop yields can be increased by 20–70 kg per hectare for wheat, 10–50 kg per hectare for rice, and 30–300 kg per hectare for maize with every 1 Mg per hectare increase in soil organic carbon pool in the root zone. Adoption of recommended management practices on agricultural lands and degraded soils would enhance soil quality including the available water holding capacity, cation exchange capacity, soil aggregation, and susceptibility to crusting and erosion. Increase in soil organic carbon pool by 1 Mg per hectare per year can increase food grain production by 32 million Mg per year in developing countries. While advancing food security, this strategy would also offset fossil fuel emissions at the rate of 0•5 Pg of Carbon per year through carbons sequestration in agricultural soils of developing countries (R. Lal 2005).

1. Indian scenario: 

Indian agriculture soil is experiencing decrease in the Soil Organic Carbon (SOC). SOC content has come down to 0.3 - 0.4 per cent in the country. It is well below the acceptable limit and is a cause for concern. The SOC should be between 1 to 1.5 per cent. But it had been coming down rapidly because of increasing atmospheric temperature, over exploitation, extensive mining of soil fertility, soil degradation, inappropriate soil tillage, poor crop management, indiscriminate use of fertilizer, and accelerated soil erosion. 

2. Agronomic Management practices and SOC: 

Our association with farmers doing sustainable agriculture practices and percentage of SOC in their soil provided encouraging results. The key practices rely on the principles of: (1) decreasing Carbon output by minimizing disturbance to soils from tillage, and eliminating fallowing, stubble burning, and heavy grazing; and (2) Increasing Carbon inputs by retaining stubble, adding Carbon rich amendments, practicing integrated nutrient management, incorporating clay in sandy soils, changing cropland to mixed crop-pastures and agro-forestry, and increasing crop diversity. A farmer from Yavatmal district, Mr. Subhash Sharma, doing sustainable agriculture practices since a decade shown steady increase in SOC from 0.5 % to 1.5 %. The highlights of the model are as follows:

1. Contour farming:  Plowing and planting across slope contours create man-made water breaks that not only allows enough time for the water to enter the soil, but also settles the topsoil without washing it down the slope. Carefully and accurate contour mapping is key to water and soil conservation. 

2. Trees: Plantation of variety of trees ensures lot of leaves and such other biodegradable waste that enriches Organic Carbon in the soil. Besides it also helps generates farmer friendly pests and birds. 

3. Seeds:  Seeds are not purchased from the market. 

4. Production of bio-fertilizer in the farm itself from cow dung and other material. 

5. Dynamic cropping pattern that ensures marketing and reduces the threat of pest attacks 

6. Laborers friendly but efficient human resource management to ensure that they live in the farm with cattle, dogs and other pets. This reduces the risk of wild animals straying in the farm.  

7. Almost zero input cost coupled with marketing intelligence makes the farm products competitive.

In summary we are suggesting 5 point agenda of Soil carbon restoration schematically represented in flowing figure.

 

Figure 1 Five Principles for Soil Restoration (After JONES 2018).

 

3. The way forward

 For a long term policy level intervention in the SOC increment, in near future following three primary things needed.

1. Creation of the database of the farmers doing sustainable agriculture practices and SOC augmentation in their soil.

2. Standardization of the agronomic practices to increase SOC in the soil. 

3. Incentivize farmers - Formulations of methodology to provide the incentives to farmers who are involved in the SOC increase process is important step to be taken. Such an attempt has been made by the Australian government under the Australian Soil Carbon Accreditation Scheme (ASCAS), carbon sequestration is measured within Defined Sequestration Areas (DSAs) located on regeneratively managed broad acre cropping and grazing lands. Soil Carbon Incentive Payments (SCIPs) are paid annually and retrospectively for validated soil carbon increases above initial baseline levels determined within each DSA. Receipt of Soil Carbon Incentive Payments is similar to being paid 'on delivery’ for livestock or grain, with the bonus being that sequestered carbon remains in the soil, conferring production and NRM benefits. Soil Carbon Incentive Payments are calculated at one-hundredth the 100-year rate ($25/ton CO2-e). The ASCAS model is based on financial reward from the private sector, creating a collaborative and progressive market based instrument to help address a wide range of environmental issues. Increased levels of soil carbon have multiple landscape health and productivity advantages. The Australian Soil Carbon Accreditation Scheme is a first in the Southern Hemisphere, placing Australia among world leaders in the recognition of soils as a verifiable carbon sink.

 

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