Knowledge for better food systems

Climate-smart soils

Recent assessments have strongly suggested that meeting the widely agreed target of limiting global warming to less than 2°C will require the deployment of substantial carbon sinks in addition to measures to curb greenhouse gas (GHG) emissions. This perspective article examines the latest research and thinking on the ability of agricultural soil management to reduce GHG emissions and promote soils as carbon sinks, and the practical feasibility of implementing available soil management practices

Recent assessments have strongly suggested that meeting the widely agreed target of limiting global warming to less than 2°C will require the deployment of substantial carbon sinks in addition to measures to curb greenhouse gas (GHG) emissions. This perspective article examines the latest research and thinking on the ability of agricultural soil management to reduce GHG emissions and promote soils as carbon sinks, and the practical feasibility of implementing available soil management practices.

The authors begin by discussing the major agricultural practices that could be undertaken to reach these goals. Briefly, these are:

  • Promoting soil C sequestration by improved management of land (e.g. reducing disturbance and increasing below ground biomass) and applying exogenous sources of carbon (such as compost or biochar) to fields
  • Reducing N2O emissions by, for example, applying inhibitors of N2O production pathways to soils and increasing the precision and specificity of fertiliser application
  • Reducing CH (methane) emissions by, for example, making changes to drainage systems in flooded rice agriculture.

Specific and ordered practices that can, in theory, lead to crop-based GHG mitigation are also presented in the following diagram from the paper:

 

 

It is noted that there exist synergistic effects between these practises, such that, for example, increasing net soil C storage by planting cover crops has the additional benefit of reducing nutrient losses and subsequent N2O emissions. However, the authors also note that there are also trade-offs and uncertainties about the extent to which the proposed crop and soil management practices can lead to significant long-term emissions reductions.

Based on the estimates of multiple analyses of the global mitigation potentials of several different approaches the authors estimate that soil management practices may have a net GHG mitigation potential of as high as ~8 billion tonnes CO2(eq) yr-1, although the likelihood of this potential to be met (determined by multiple socioeconomic and political factors) is much harder to estimate.

The article goes on to discuss how the above (and other) practices may be financially incentivised to increase the global implementation of soil GHG reductions, and also the available options for quantifying and monitoring impacts.

The authors conclude that multiple soil management strategies offer real potential to mitigate agricultural GHG emissions while also contributing to wider environmental benefits. They identify the management of existing uncertainties in measuring and modeling agricultural GHG emissions as key priorities for facilitating soil GHG emission mitigation policies, and strongly recommend meaningful engagement with land users themselves, in order to vastly increase the probability of successful implementation.  

While this article provides an excellent overview and critique of the GHG mitigation potential of available arable soil management practices, it does not specifically address the role of ruminant livestock in, on the one hand, contributing to soil carbon sequestration and, on the other hand causing emissions of carbon dioxide (through deforestation and other forms of land use change), methane and nitrous oxide.  If this further aspect of soil carbon sequestration is of interest to you however, please do take at look at this FCRN publication and also Chapter 8 of the FCRN’s Foodsource resource (section 8.3.2).

Abstract

Soils are integral to the function of all terrestrial ecosystems and to food and fibre production. An overlooked aspect of soils is their potential to mitigate greenhouse gas emissions. Although proven practices exist, the implementation of soil-based greenhouse gas mitigation activities are at an early stage and accurately quantifying emissions and reductions remains a substantial challenge. Emerging research and information technology developments provide the potential for a broader inclusion of soils in greenhouse gas policies. Here we highlight ‘state of the art’ soil greenhouse gas research, summarize mitigation practices and potentials, identify gaps in data and understanding and suggest ways to close such gaps through new research, technology, and collaboration.

Reference

Paustian, K., Lehmann, J., Ogle, S., Reay, D., Robertson, G.P., and Smith, P. (2016) Climate-Smart Soils. Nature 532 (7597), 49–57

Read the full article here (paywall)

 

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