Diagnosing hostile clay loam to clay subsoil
Many Western Australian soils have cemented, dense or poorly structured clay subsoils or hardpans that restrict root growth.
What to look for
- Soils compacted by machinery have a distinct compaction layer in the loam to clay subsoil with a blocky fractured structure featuring a distinct upper and lower layer.
- Dense fine textured subsoils.
- Cemented layers such as silcretes or red-brown hardpans.
- Moist subsoils after a reasonable season with a dry finish.
- Clay subsoils are more often waterlogged.
- These soils frequently have other constraints such as boron toxicity, high alkalinity and salinity.
- Plants are more susceptible to waterlogging, spring water stress and damage by root pruning herbicides.
- Restricted subsoil root growth, with thickened roots often restricted to cracks or old root channels.
What else could it be
|Diagnosing spring drought in wheat and barley||Also causes head and grain shrivelling and early senescence. This may be more common on heavy soils||Hostile subsoil areas will drought before other heavy soils when there is still subsoil moisture.|
|Diagnosing boron toxicity in wheat||Also causes water stress, head and grain shrivelling and early senescence||Boron toxicity occurs mostly on very alkaline morrel loams and north Esperance clay and shallow duplex soils.|
|Diagnosing soil acidity in crops||Subsoil acidity also causes water stress, head and grain shrivelling and early senescence||Can be distinguished by soil pH|
|Diagnosing waterlogging in cereals||Seedling root damage from early waterlogging also causes water stress, head and grain shrivelling and early senescence when there is still moisture at depth||History of early waterlogging at the site|
Where did it come from?
- Compaction by repeated action of cultivation equipment forms plough pans just below the cultivated depth.
- Relatively few fine-textured soils have subsoils that permit deep root growth.
- Red-brown hardpan loams that have variable depth to natural hardpan are common in the north eastern and northern wheatbelt.
- Mallee soils with silcrete layers or silica cemented subsoils occur sporadically but tend to be more widespread in low rainfall areas, often below breakaways.
- Dense non-cracking grey clays such as moort soils that are common in the Great Southern and South-Eastern wheatbelt.
- Amelioration is expensive and must be done in moist soil. Responses to ripping plough pans and poorly structured clays are variable. Large responses occur but are often short lived.
- Incorporated organic matter or gypsum and minimising recompaction with tramline farming may maintain the benefits of deep ripping. Raised beds are an option where waterlogging is common.
Page last updated: Wednesday, 28 February 2018 - 9:55am