SWARM Hub

Soil carbon

Improving soil carbon levels in farm soils is one of the most important projects that farmers and society can engage in.

There are two important aspects to increasing soil carbon levels, reducing losses and maximising gains. It is important to consider both when designing management strategies that work on-farm. For more information on how to build soil health by improving carbon levels in farm soils, click here to see the information on the Farm Carbon Cutting Toolkit pages.

The 4per1000 initiative

This initiative, launched by France, sets out to bring together all willing contributors in the public and private sector under the framework of the Lima-Paris Action Agenda.

The aim is to demonstrate that agriculture, and agricultural soils in particular can play a crucial role where food security and climate change are concerned.

The goal of the Initiative is to engage stakeholders in a transition towards a productive resilient agriculture, based on a sustainable soil management and generating jobs and incomes, hense ensuring sustainable development. For more information on the initiative, click here.

The initiative has designed an animation which explains the issues in more detail. Why not watch it below?

 

 

Soil Identification

Identification of soil group
Identification of soil texture

What is compaction?

  • Soil scientists describe good soil structure as having 50% of the soil volume occupied by particles of soil and organic matter, 25% by water, and 25% by air
  • Compaction describes when soil has been squashed into a solid impermeable layer, either at the surface or within the topsoil. This band of squashed soil restricts the movement of air, water, and nutrients down through the soil profile
  • For more information please click here

What causes compaction?

  • Soil composition and moisture content affect compaction, with wet and clay type soils being more prone to compaction
  • Ground pressure on soils imposed by tracks or wheels
  • Approximately 80% of soil compaction occurs during a machine’s first pass over loose soils
  • Poaching from livestock causes compaction, due to overstocking, or grazing animals in susceptible fields in wet conditions
  • Read more

How can I identify compaction?

  • Dig a hole to a depth of 30cm when the soil is not excessively wet or dry
  • Notice how far roots and moisture extend down the soil profile, and any obvious changes in soil structure
  • Pay particular attention of any areas where the spade meets resistance. The depth of resistance will help indicate the cause of compaction
  • For more information and to register for a free advice visit from the Soils for Profit scheme, in which compaction can be targeted, please visit the Soils for Profit page.
  • Watch the video at http://www.environment-agency.gov.uk/business/sectors/123420.aspx

Costs of compaction

  • It impacts on a wide range of processes that occur in soil leading to a reduction in yield from the affected field, increased nutrient loss and soil degradation
  • It reduces the ability of grass to utilise fertiliser as the roots cannot fully exploit the soil and reach the nutrients
  • It reduces the uptake of artificial fertiliser - if the soil becomes waterlogged this causes the fertiliser Nitrogen to convert into gases which are lost to the air
  • It reduces the availability of mineralised Nitrogen from soil organic matter and the Nitrogen fixing potential of legumes (including clover)
  • It reduces the crop germination rates, plant seedling establishment and crop emergence
  • Read more

How can I get rid of compaction?

Download document here.

What are the benefits of removing compaction?

  • Introduction of oxygen to the soil which improves biological and worm activity
  • The physical opening up of the soil structure improves surface drainage and absorption of slurry which helps reduce run off
  • Increased rooting activity which improves the plant’s ability to use nutrients and trace elements
  • More persistent leys with more grazing days per season, and less need for reseeding
  • A more effective microbial population fixes Nitrogen for free, and improves utilisation of applied fertiliser. Grass on uncompacted soil can recover 60% of applied fertiliser , whereas only 26% of applied fertiliser is recovered by the crop in compacted soil (Defra, 2000)
  • Well aerated soils warm up faster in the spring and recover faster after grazing and cutting
  • Increased yields – a potential grassland yield increase of up to 900kg DM/Ha in the following year after addressing compaction issues. A crop of grass silage (£30/t) would result in an extra £108/ha (2006)
  • IGER trials have shown that aeration and the removal of compaction can increase productivity in grazing swards by 26kgDM/Ha/day and also due to the physical opening up of the soil, reducing ammonia losses and boosting the nutrients available to the plant (2006)
  • Read more

Step 1: Extract the soil block

If it is loose soil, remove a block of soil about 15 cm thick or to the full depth of the spade and place the spade and soil on to the ground or a surface where it can be easily examined.

If it is firm soil, dig a hole slightly wider and deeper than the spade leaving one side of the hole disturbed. On the undisturbed side, cut down each side of the block with the spade and remove the block placing the spade and soil on to the ground/surface

Step 2: Examine the soil block

If the soil block is a uniform structure, remove any compacted soil or debris from around it. If there are two or more horizontal layers of differing structure, estimate the depth of each layer and make sure that you assign scores to each separately (see step 7).

Step 3: Break up the block

Gently manipulate the block using both hands to reveal any cohesive layers or clumps of aggregates. If possible separate the soil in to natural aggregates and man-made clods. Clods are large, hard, cohesive and rounded aggregates.

Step 4: Break up the aggregates

Break large pieces apart and look at the internal structure of the cross-section. A crumb-like appearance with rounded aggregates easily broken apart and embedded in a finer matrix indicates a well-developed natural structure and lower score.

If clods can be broken in to non-porous aggregates with angular corners it would indicate poor structure and therefore a higher score.

Identification of Soil Group

Source: Think Soils, Environment Agency

Identification of Soil Texture

Source: Think Soils, Environment Agency