Beyond Soil Carbon Sequestration

The world’s soils and their potential to sequester carbon have been driven into global dialogues on climate change mitigation. This is highlighted in the new discussions on Climate Smart Agriculture (CSA), which promotes agricultural practices that increase productivity, increase resilience, and reduce and/or remove greenhouse gases.

Depending on how the soil is managed, soil organic carbon can increase or decrease in magnitude over time. However, there is still debate on the feasibility of soil carbon sequestration in aiding in the mitigation of climate change, as it will require international commitment reflected in national level policies. Further challenges also arise in land tenure issues of smallholder farmers in developing counties, as increasing soil organic carbon takes investment and time.

The sequestration of carbon in the soil has many co-benefits that also deserve attention in these dialogues beyond climate change mitigation. Soil carbon is the building block of Soil Organic Matter (SOM), which increases soil quality and better provides essential ecosystem services. Increased SOM simultaneously increases water infiltration into a soil, water storage potential within a soil, and the ability of the soil to hold and supply plant nutrients over time.

The SOM increase of water infiltration in the soil decreases runoff over land which is a large contributor to soil erosion.  Increases in SOM can result in higher plant yields, more resilient agroecosystems, and can decrease greenhouse gas emissions or even capture greenhouse gases from the atmosphere.

Just as these soil properties and processes can be enhanced with increased levels of SOM, the properties and processes can be disrupted with the loss of SOM. A great way to conceptualize this is in areas of the world experiencing desertification. Desertification is the transformation of once fertile land into desert through a combination of drought and unsustainable land management practices.

Among other side effects, these land management practices deplete the soil carbon pool, thus disturbing the vital ecosystem functions listed above. However, many projects are showing that implementing certain sustainable land management practices can combat desertification. These practices typically include practices that increase SOM and its beneficial effects.

With the benefits of SOM established, how can this be increased in soils? To simplify this, it can be broken into two steps; input of organic matter and minimal disturbance of the soil.

Many people already have some notion of this as each spring they will purchase manure, compost, or peat moss to put in their flowerbeds and gardens. Most have an understanding that this will benefit plants, but do not realize the specific functions it plays.

This same idea can be taken and applied to larger pieces of agricultural land. Inputs of organic material typically involve plant residue left from previous crops or manure and compost applied directly to the field. However, to ensure that the SOM stays in the soil, it is essential that the soil is only minimally disturbed, as any disturbance to the soil can increase soil microbial respiration and the breakdown and loss of SOM.

Effectively increasing SOM is not accomplished overnight. It typically takes multiple years to see significant increases in SOM and the associated benefits. In developing countries, smallholder farmers typically have difficulty in establishing land tenure rights. Due to this issue, smallholder farmers are often hesitant to invest the resources necessary to increase SOM as they are unsure they will still have access to the land when the returns would be realized.

Sustainable development in all parts of the world requires careful management of soil organic carbon. While there is potential for some climate change mitigation through soil carbon sequestration, policy makers need to be aware of the implications of soil organic carbon in providing other essential ecosystem services through increased SOM.

Taking this view on soil carbon can surpass political boundaries, as increasing soil quality has desired outcomes that most political parties can agree on: increased agricultural productivity and resilience as well as environmental protection and improved ecosystem functioning. Furthermore, as the CSA concept is taking center stage in agricultural development discussions, recognizing the co-benefits in promoting practices that protect and increase SOM is essential to ensure that CSA moves towards more sustainable food systems in a more dynamic future climate.

Image courtesy of Wikimedia Commons. Originally published by S&S on July 29, 2015.


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