FARMERS have been advised to take care when dealing with soil compaction.

Dr Liz Genever, Eblex senior livestock scientist, said aerators or sward-lifters should only be used when there are clear signs of compaction, and at the appropriate time.

She said: “Before taking any action, producers need to carry out a soil assessment by digging holes.

“This may reveal that the situation isn’t as bad as initially thought and will help prioritise fields needing attention.

“If soil compaction is identified, producers may decide that using aerators to deal with compaction in the top 5-10cm of soil, or sward lifters, which deal with compaction 10-25cm down, is appropriate.”

Dr Genever said guidelines from Adas work in the 1980s provided some clear messages for producers when using topsoil looseners.

“The most timely one is to aim to remedy compaction in the autumn, as dealing with compaction in the spring may cause more problems,” she said.

The Adas guidelines are:

  • Do not use topsoil looseners unless there are clear signs of soil compaction and the moisture content is suitable;
  • Examine the soil by digging holes to find out the nature and depth of any compacted layers, as well as the moisture content and friability of the soil;
  • Topsoil loosening in conditions which are too wet will potentially lead to increased soil damage through smearing and wheel slip;
  • Topsoil loosening in dry conditions is likely to lead to the formation of large clods, sward-tearing and excessive surface heave giving an uneven surface finish;
  • Topsoil loosening is not recommended in poorlydrained soils if no drainage system is present, as this is likely to cause excessive wetness in low-lying areas which will potentially be at further risk of poaching and recompaction.

In these situations, and on heavy-textured soils, a mole plough may be more effective in improving the soil drainage status than topsoil loosening; 

  • Topsoil loosening should be carried out in the autumn when grass growth is declining. If carried out in the spring or summer when grass is growing rapidly, disturbance to the root system can lead to severe sward death.
  • Use the appropriate equipment and set it up correctly.

The depth of compaction will dictate the depth of working required – make sure the compacted layer is about 2.5cm above the critical working depth of the implement used and examine the extent of shatter on a trial run, adjusting the equipment if necessary;

  • Recently-loosened soil is very sensitive to recompaction and it is important to allow the newlyloosened structure to be stabilised by root activity and natural soil processes;
  • Cut or graze the site immediately before treatment to ensure sward height is low.