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How to manage a soil makeover

Now is the best time to plan for a good grass growing season. Chloe Palmer finds out how farmers can give their soil a spring makeover.


Many farmers will be itching to take to the tractor seat to start field operations at the first sign of good weather but carefully assessing soils and swards beforehand is time well spent.

This is according to independent grassland consultant Dr George Fisher who points to the importance of understanding the issues associated with soil health and structure before deciding on a remedial strategy for each field.


He says: “Measure everything you can because if you do not measure it, you cannot manage it. Time spent looking at soils to identify compaction or drainage issues will save time and money.”


Dr Fisher suggests now is the best time to start planning for the grass growing season so farmers can take best advantage of a good summer and a glut of grass.


“It is simpler to ease back than react to excess grass. In the event of a shortfall, farmers can always return silage land to the grazing platform.”


Ensuring soil is in the best possible shape is the best way to maximise grass growth and tackling soil compaction is a top priority, according to Dr Fisher.


“Research from SRUC demonstrated 10-15 per cent losses in grass yields due to poaching on grazing land and 15-25 per cent losses on silage ground because of wheeling damage. Farmers should assess areas where they know there are problems first to get an idea of what compaction looks like in their fields.


“To do this, dig out one spade-sized block of soil to a depth of about 30cm. Cut down on three sides and lever the block out to leave one side undisturbed so it is possible to gently open up the soil block.”

When you assess soil, you are looking for:

  • Rooting patterns Roots should extend 30cm or more in healthy, well-structured soil
  • Soil aggregates There should be plenty of small aggregates – granules and crumbs – with rounded edges. Larger aggregates with sharp edges are a sign of compaction
  • Cracks and pores Look for vertical channels between soil aggregates which allow free movement of water, air and nutrients
  • Earthworms There should be evidence of earthworms and their activity, such as burrows and casts, in the section removed
  • Colour Topsoil rich in organic matter will be dark. Rusty, grey mottled soils indicate poor drainage and previous waterlogging
  • Smell If water lies trapped in soil for any length of time, the air-less condition prevents breakdown of organic matter and manures. A foul-smelling dead layer of debris may form

Identifying the depth and cause of compaction will enable farmers to take the appropriate action to remedy it. Dr Fisher says measuring the depth at which compaction occurs can provide clues.


“Sheep will create compaction in the top 5cm of the soil profile whereas for cattle this will be at a depth between 5-10cm. It is not uncommon to find a wet compacted layer at the top of the soil profile with dry and crumbly earth underneath as the water cannot penetrate through.”


Maintaining the right physical soil condition is as important as ensuring the soil contains adequate nutrients, Dr Fisher says.


“Soil must be in good physical and biological health to facilitate good aerobic functioning. The microorganisms turning over organic matter in soil need air and if this soil biology is working it can reduce the need for fertiliser inputs.”

What is the cause of compaction?

Compaction type Typical causes

Surface capping

(0–10cm deep)

Grazing in wet conditions

High stocking densities


(10–15cm deep)

Rainfall on new cultivations

Silage and muckspreading operations

Plough pans

(10–15cm deep)

Repeated re-seeding at one depth



Dr Fisher points out it may not be necessary to take any action to relieve compaction if there have been prolonged periods of hard frost. Following recent milder winters, some remedial works will be necessary.


“For surface compaction caused by poaching, as soon as ground conditions are travelable, farmers should consider spiking their fields with an aerator. This should ideally be done before applying slurries or fertilisers.


“It is vital to achieve the right depth of spiking to ensure spikes pass right through the compacted layer. Otherwise the problems could be made worse by water travelling down spike holes but then being trapped above the compacted layer, unable to drain away.”


Where farmers have identified a compaction problem lower down the soil profile, indicating it is caused by machinery trafficking, they may consider using a sward lifter, however, Dr Fisher urges caution with this.


“I would not advocate any farmer to sward lift in spring as it is an invasive technique. A 10 per cent reduction in grass growth is often seen in the three to four weeks following use of a sward lifter, which farmers do not want just at the time when there is the greatest opportunity to make the most of spring grass growth.


“If sward lifting is necessary, it should be done in autumn, when growth losses are less significant. For all these operations, the heavier the soil the more careful we need to be when carrying them out.”



Top Tips – Soil remediation operations:

  • Always examine the soil profile in each field carefully to identify the extent and depth of the compaction problem
  • Ensure ground conditions are appropriate. Form a ball of soil in the hand taken from the compacted depth. If it is wet, the conditions are too damp
  • Drive slowly when carrying out any remedial operations such as spiking or sward lifting – no more than 3mph (5kph)


Do not forget soil nutrition

Winter is the best time to identify any nutrient deficiencies or to measure pH in soil samples so the amount of lime needed can be calculated.


  • Do not soil sample within eight weeks of applying fertiliser or 12 weeks of manure or slurry application for P, K and Mg analysis, or sooner than a year after liming for pH analysis
  • Aim to sample each field on the farm every three years
  • Walk the field in a ‘W’ taking regular samples - for a regular shaped field, sample four cores per leg of the W
  • Mix the cores from each sample into a single composite sample in a bucket and then take a sub-sample of this to send to the laboratory
  • Grassland should be sampled to a depth of 7-10cm (3-4in) and temporary grassland (less than three-year leys) should be sampled to the plough depth – about 20cm (8in)
  • Ensure field parcel names or numbers are written clearly on the sample bag or box
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