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.

Plough pan is blocky and fractured with a distinct upper and lower layer.
Roots are thickened and confined to cracks.
Moort soils have naturally compact subsoil.
Red brown hardpans may affect yield when shallow.

What to look for

    Paddock

  • 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.

    Plant

  • 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

Condition Similarities Differences
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.

Management strategies

Cultivation
Cultivation
Spreading gypsum
Spreading gypsum
  • 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.

Where to go for expert help

Page last updated: Wednesday, 28 February 2018 - 9:55am