Key Points
- Soil compaction is often an unrecognised constraint to achieving maximum crop production.
- This occurs by limiting the soil volume from which roots can extract water and nutrients.
- Penetration resistance (PR, a common measure of soil compaction) is strongly affected by soil water content and to a lesser extent by soil texture.
- Overseas research has shown that root growth can be restricted at PR values >2.5 MPa, but the critical limit may be much lower for some crops and needs to be established for different soils and crops in NZ.
- PR under sheep pasture is soil type dependent. Compared to sheep pasture, on some soil types cropping increases the risk of soil compaction whereas on other soils cropping reduces PR.
- This Update describes some of these findings as well as options to avoid and mitigate soil compaction.