LP92

Location: Gooroc

Australian Soil Classification: Epicalcareous-Epihypersodic, Crusty, Brown VERTOSOL
Northcote Factual Key: Ug 5.3
Great Soil Group: brown clay

General Landscape Description: Level plain with gilgai ('crabholey') microrelief.

Site LP92 Landscape

A1	0-10 cm	Dark reddish brown (5YR3/4); light medium clay; moderate coarse blocky structure; strong consistence dry; pH 7.0; clear change to:	Site LP92 Profile
Subsoil
B21	10-20 cm	Reddish brown (5YR4/4); medium clay; moderate coarse prismatic, parting to strong coarse blocky structure; weak consistence moist; pH 8.2; clear change to:
B22	20-30 cm	Dark reddish brown (5YR3/4); medium heavy clay; moderate coarse prismatic, parting to strong coarse blocky structure; very firm consistence dry; pH 8.6; clear change to:
B31k	30-70 cm	Brown (10YR4/3); medium heavy clay; moderate coarse blocky, parting to moderate medium polyhedral structure; firm consistence moist; contains angular quartz (20 mm size) and a few (2-10%) carbonates; pH 9.2; gradual change to:
B32	70-100 cm	Brown (10YR4/3); medium heavy clay; moderate medium polyhedral, parting to strong fine polyhedral structure; slickensides evident; firm consistence moderately moist; contains gypsum crystals (< 2 mm size), ironstone nodules and quartz fragments; pH 9.3; gradual change to:
B33	100-150 cm	Brown (10YR5/3); light clay; moderate structure; firm consistence moderately moist; pH 8.7.

• High clay content throughout soil profile.
  
  
• Vertic properties (i.e. significant shrink-swell characteristic).

	pH	Salinity Rating	Sodicity	Dispersion
Surface (A1 horizon)	neutral	very low	non-sodic	none1
Subsoil (B21 horizon)	moderately alkaline	very low	sodic	strong
Deeper subsoil (at 1 m)	strongly alkaline	high	strongly sodic	-

• Plant available water capacity (PAWC) is considered to be low-medium (estimated at 100 mm). This is based on available laboratory data and assumes an effective rooting depth of 60 cm. Rooting depth will be restricted by the strongly sodic subsoil.

• The surface soil disperses completely after remoulding. This indicates that excessive cultivation of the soil when in a moist to wet condition may promote dispersion and result in soil structural degradation (e.g. surface sealing). Raindrop impact on bare soil is also likely to result in structural degradation.
  
  
• Tillage of cracking clay soils should be avoided if the soil is wet (i.e. wetter than the plastic limit). At such moisture conditions, excessive tillage, trafficking or overstocking can result in structural degradation (e.g. compaction, smearing) occurring. Ideally, tillage and trafficking should take place when the soil is drier than the plastic limit, down to at least the depth of tillage.

• The coarsely structured upper subsoil is sodic and disperses strongly. This indicates that root and water movement will be restricted in the subsoil.
  
  
• The deeper subsoil (from 20 cm depth) is strongly alkaline, which indicates that some nutrients (e.g. iron, manganese, copper, zinc) may be poorly available to plants at depth.
  
  
• The level of soluble salts becomes high in the deeper subsoil at a depth of about 1 metre and is only likely to restrict the growth of deeper rooted salt sensitive species.

• Gypsum response trial established in this paddock and gypsum applied.
  
  
• Originally this soil had to be worked separately from the rest of the paddock as it was extremely hardsetting. Since reduction in cultivation and stubble retention it can now be worked with the rest of the paddock and has darkened in colour.
  
  
• Will probably apply more gypsum next year.