Soil structure issues

Published 10 August 12

Soil structure issues

Grazing paddocks in poor, wet conditions is unlikely to cause any serious long term damage to soil structure unless it is a prolonged event, or if subsequent grazing also takes place in poor conditions, says DairyCo extension Officer Chris Duller.

In most situations, soils will recover from light poaching without intervention. However key to recovery is a decent earthworm population and several months without further damage.

Monitor conditions closely this autumn in fields that have been poached. If growth rates are low and soil remains wet on the surface then you may need to step in and improve. This is likely to happen where earthworm numbers are low or damage is more severe.

Slitting soils with an aerator may help speed up recovery and help water to move through surface compacted layers, but will only be effective if the soil compaction is in the top 12cm. If there is deeper compaction then water will continue to hold in the soil surface. If aerating,make sure soils are dry enough to avoid smearing the slits.

If compaction is deeper than 12cm then a grassland 'sward lifter' type machine may be beneficial. Working depth and soil conditions are crucial to its success but beware of going too deep and missing the problem area of the soil. Avoid using this machine if soils are too wet.

Where you have slight poaching damage, manage your soils to aid recovery. A slightly damaged soil is very vulnerable to further, more severe damage.

  • Avoid further grazing in wet conditions if possible.
  • If you do have to graze in the wet, don't graze too tightly (come out at around 1800kgDM/ha) and back fence to protect soil after initial grazing.
  • Consider on-off grazing for a few hours at a time to limit the time cows spend walking around the field.
  • Rather than risk damage during the final grazing round, maybe even consider sheep grazing to clean out wetter fields.
  • Avoid slurry applications to give worm populations a better chance to develop.