A group of beef and sheep producers from the county, recently met on the farm of Desmond Knox, near Irvinestown, to discuss issues around soil compaction.

William Johnston, CAFRE Beef and Sheep Development Adviser who facilitated the event, explained that compaction occurs when a downward force reduces the capacity of the air and water spaces in the soil. Farmers listed poor drainage, poor root penetration and less grass production as its main effects.

William advocated digging inspection holes and examining the soil profile at several spots throughout a field to establish the condition of the soil and whether there was evidence of soil compaction. This should be the first step prior to any remedial action. Farmers intending to reseed this autumn should check for compaction before cultivation works begin.

The degree of compaction can be judged by removing a block of soil from the undisturbed side of the hole and breaking it up to see the size of the aggregates and how difficult they are to break up. Large, difficult to break aggregates are indicative of soil compaction.

Discussion among the group concluded that soils which are wet, have higher clay content and a poor soil structure are more prone to compaction. Heavy machinery emerged as the main culprit on local farms.

There are many different machines on the market to rectify soil compaction from soil aerators to grassland subsoilers. Subsoilers work by lifting and loosening the soil. Soil aerators work from the surface down rather than the sub-surface up. Essentially these devices push a blade into the ground increasing air and water entry into the soil. Desmond had treated one half of a field with a subsoiler and the other half with an aerator. William was keen to point out that whatever tool is used it is very important that the soil is dry enough, the implement is not worked below its critical depth and treated soils are given time to stabilise. Application of the wrong soil treatment could cause more harm than good by increasing the problem rather than alleviating it. For example subsoiling when the soil isn’t sufficiently dry is a waste of time and money, doesn’t effectively fissure and crack the soil layer and could cause long term damage to the soil structure.

After some discussion on the advantages and disadvantages of the two implements the evening ended after some thought was given to how soil compaction might be avoided or reduced. Reducing axle loadings, using larger, low ground pressure tyres and reducing the number of passes were highlighted as ways of reducing compaction from vehicular traffic.

More information can be obtained from your local CAFRE Beef and Sheep Development adviser by contacting 0300 200 7841.