ARCHIVE: Soil indicators: Organic matter

The Sustainable Food and Farming Strategy (SFFS) has published a list of indicators to monitor sustainability in farming and food. The SFFS considers soil organic matter as a headline indicator for Outcome 5 on the better use of natural resources. The data sheet for this indicator can be found via this link.

Trends in Soil Organic Matter Content

Recent evidence has suggested that average SOM content has declined across all land uses in England and Wales1. The precise extent and the causes of the losses are the subject of significant ongoing research. Under the SFFS headline indicator, Defra has committed to achieving the following target:

“To halt the decline of soil organic matter caused by agricultural practices in vulnerable soils by 2025, whilst maintaining, as a minimum, the soil organic matter of other agricultural soils, taking into account the impacts of climate change.”

The setting of this target was informed by project SP0546.

Measures beneficial to soil carbon levels are already being delivered under the cross-compliance component of the Single Payment Scheme and Environmental Stewardship. A programme of research will address what further policy measures are required to achieve this target.

Soil organic matter

Organic matter enters soils from plant, animal or microbial remains/products and is made up of carbon, nitrogen, phosphorus and potassium, as well as trace elements.

As an important ingredient of mineral-based soils, organic matter has an influence on its chemical, physical and biological characteristics. It also impacts plant growth through, for example:

  • Altering soil pH
  • Assisting with a good structure for root growth
  • Easing trafficking and tillage
  • Making soils more resistant to erosion
  • Supplying nutrients.

SOM also increases the ability of the soil to bind chemicals and can buffer the release of pollutants into air or water.

Changes in SOM content can affect the potential of soils to perform the functions we require of them, for example:

  • Acting as a growing medium for food and fibre
  • Water storage
  • Buffering and transforming chemicals
  • Providing a reservoir of biodiversity
  • Ecosystem support.

Research

Further details of the following SOM research projects are available:

  • SP0501 - Effects of farm manure additions on soil quality and fertility

  • SP0504 - Effects of fertiliser nitrogen additions on soil quality and fertility

  • SP0519 - Critical levels of soil organic carbon in surface soils in relation to soil stability, function and infiltration

  • SP0521 - Changes in organic carbon content of non-agricultural soils

  • SP0523 - Development of economically & environmentally sustainable methods of C sequestration in agricultural soils

  • SP0530 - Organic manure and crop organic carbon returns - effects on soil quality

  • SP0533 - Initial assessment of projected trends of SOC in English arable soils

  • SP0545 - Spatial analysis of change in organic carbon and ph using re-sampled National Soil Inventory data across the whole of England and Wales

  • SP0546 - Soil organic matter as a headline indicator of soil health

 

1. Bellamy P.H., Loveland P.J., Bradley R.I., Lark R.M. & Kirk G.J.D. (2005) Carbon losses from all soils across England and Wales 1978–2003. Nature, 437, 245-248

Page last modified: 7 August 2009
Page published: 9 March 2005