As we mark World Soil Day, and with COP21 well into its first week, Dr Katrin Glatzel of Agriculture for Impact takes a look at how good soil and land management practices can help us achieve important climate and development goals.
Soil matters. The decision made at the Rio+20 conference to develop a set of Sustainable Development Goals (SDGs) and the agreement ‘to strive to achieve a land degradation neutral world in the context of sustainable development’ gave momentum to discussions on the role of soils in the global sustainable development agenda. This is now, at least partially, reflected and anchored in SDG goal #15, ‘Sustainably manage forests, combat desertification, halt and reverse land degradation, halt biodiversity loss.’
In addition to this, earlier this year the French Government launched its “4 per 1000” initiative, aimed at making agriculture a solution in addressing climate change while also advancing food and nutrition security. Agronomic techniques, including for example Sustainable Intensification practices, can sequester carbon from the atmosphere – at an average rate of four-thousandths of the existing carbon stock in the soil.
The quality and amount of soils’ humus (decayed organic matter) and its soil organic carbon (SOC) are a key determinant of soil quality and crop productivity. When the concentration of SOC falls below a certain threshold, key soil properties are adversely affected inhibiting plant growth. Increasing the amount of humus and SOC in the soil requires adding nitrogen (N) and other plant nutrients, such as phosphate (P) and sulphur (S) in order for the transformation of biomass carbon into SOC to occur.
Conventional means of soil management often cause more harm than good, while organic approaches are sometimes too demanding of labour, reliant on scarce or unavailable inputs and insufficient to produce the yields required to move people out of poverty and achieve food security. Part of the solution is to combine the best of organic and conventional approaches in a way that is environmentally appropriate and sustainable. This includes bringing nutrients to the soil in from the outside to improve the SOC, either through livestock manure, the prudent use of inputs, such as the microdosing of fertilisers, or cultivation of legumes.
Engaging with smallholders
Smallholder farmers can contribute through their willingness to adopt new agricultural practices that bring multiple benefits in the short and longer term. This willingness must be nurtured with strong political leadership, substantial investment in infrastructure, education and training and the provision of new technologies.
Improved land management practices will not only make farmers more resilient in the face of weather shocks and climatic stresses, but will also significantly contribute to climate change mitigation efforts. Globally, the soil contains about 1,500Gt of organic carbon: more than double the amount of carbon in the atmosphere and three times that in plants, animals and micro-organisms. The cumulative historic loss from ploughing and mining the soil’s humus is between 50Gt and 78Gt.
The process of carbon sequestration – adding more organic matter to the soil than decays – however, can help to minimise atmospheric greenhouse gas (GHG) levels. For example, agroforestry systems can capture carbon in the range of two to four tonnes per hectare per year – an order of magnitude higher than conservation farming.
In practice, effective sequestration depends on the available technologies, the soil texture and structure, climatic conditions, the farming system and associated practices of soil management. Whilst there are many successful small-scale projects, taking sequestration to scale can be rather challenging. There are difficulties in measuring both the pre-existing carbon in the soil and ongoing levels. As a consequence technical skills are essential but often limited. There are also likely to be significant institutional barriers linked to issues such as determining land rights, monitoring and ensuring compliance and finally paying farmers for sequestering carbon in their soil – payment for ecosystem services (PES).
Setting the right incentives
Farmers can and will undertake actions that have co-benefits for mitigation, but they need to be provided with the right incentives such as PES, land rights, improved knowledge and training. Paying farmers or landowners to better manage their land or watersheds, to conserve biodiversity or to sequester carbon have been shown to help conserve and restore forest areas and aquifers.
For example, in order to improve soil quality and to support local livelihoods, Niger has embraced a set of wide-ranging approaches which has helped restore arable land and increase farmers’ capacity to withstand droughts.
As global leaders work to agree on a new international climate agreement, let us hope they will remember that soil holds the key not only to improving agricultural productivity, but also to increasing the resilience of millions of vulnerable smallholder farmers, whilst making significant contributions to climate mitigation.
Find out more
Find out how intensive agriculture can be more sustainable in the Grantham Centre (Sheffield University) briefing note: A sustainable model for intensive agriculture