WIA22

Cereal cropping on cracking clay soils		Site Code	WIA22	Endocalcareous-Endohypersodic, Massive, Grey Vertosol
		Location	Riverside, western Victoria
		Landform	Terrace
		Geology	Quaternary Coonambidgal Formation: fluvial to lacustrine clays and sands
		Element	Terrace flat
		Slope	0–1%
		Aspect	–
Horizon	Depth (cm)	Description
A1	0–5	Dark grey (10YR4/1); medium clay; cracking massive (structureless) surface condition when undisturbed; weak subangular blocky structure; very strong consistence dry; moderately sticky consistence wet; pH 6.3; sharp and smooth boundary to:
B21	5–25	Dark grey (10YR4/1); light medium clay; subplastic; moderate coarse prismatic structure; strong consistence dry; moderately sticky consistence wet pH 7.1:
B22	25–60	Dark grey (10YR4/1); heavy clay; moderate coarse prismatic structure; weak consistence dry; moderately sticky consistence wet; very few (<2%) hard carbonate segregations; pH 7.2; gradual and smooth boundary to:
B31	60–95	Grey (10YR5/1); heavy clay; plastic; moderate coarse subangular structure; very few (<2%) hard carbonate segregations; pH 6.4; gradual boundary to:
B32	95–115	Light greyish brown (10YR6/2); heavy clay; plastic; moderate coarse subangular structure; very strong consistence dry; moderately sticky consistence wet; very few (<2%) hard carbonate segregations; pH 6.3; gradual boundary to:
B33	115–150	Greyish brown (10YR5/2); heavy clay; plastic; strong coarse angular blocky structure; strong consistence dry; moderately sticky consistence wet; very few (<2%) hard carbonate segregations pH 5.9.
Management considerations
Cracking clay soils with self-mulching properties Plant available water capacity (PAWC) is considered to be low (estimated at 55 mm). This is based on available laboratory data and assumes an effective rooting depth of 30 cm. The high level of soluble salts in the subsoil will restrict effective rooting depth. When the soil is dry, heavy rains will move down soil cracks. This rapid recharge can be valuable for the survival of plants near wilting. When wet, the soil will swell and further infiltration of water will be relatively slow. Tillage of cracking clay soils should be avoided if the soil is wet (ie. wetter than the plastic limit). At such a moisture condition, excessive tillage, trafficking or overstocking can result in structural degradation (eg. compaction, smearing) occurring. Ideally, tillage should take place on clay soils such as these when the soil is drier than the plastic limit, down to at least the tillage depth The level of soluble salts is high in the upper subsoil and becomes very high from 55cm depth.

Site WIA22	Sample depth cm	pH		EC dS/m	NaCl %	Ex Ca cmol-/kg	Ex Mg cmol-/kg	Ex K cmol-/kg	Ex Na cmol-/kg	Ex Al mg/kg	Ex acidity cmol-/kg	FC -30^okPa	PWP -1500^okPa	KS %	FS %	Z %	C %
Horizon	Sample depth cm	H₂O	CaCl₂	EC dS/m	NaCl %	Ex Ca cmol-/kg	Ex Mg cmol-/kg	Ex K cmol-/kg	Ex Na cmol-/kg	Ex Al mg/kg	Ex acidity cmol-/kg	FC -30^okPa	PWP -1500^okPa	KS %	FS %	Z %	C %
A1	0–5	6.3	5.4	0.12	0.02	7.2	10	0.7	0.8	NA	8	NA	22.7	1	27	27	44
B21	5–25	7.1	NA	0.14	0.03	10.1	16.2	0.8	2.7	NA	8.6	NA	21.1	0	14	20	65
B22	25–60	7.2	NA	0.53	0.11	9.8	16.2	0.7	4.2	NA	6.4	NA	23.8	0	13	23	61
B23	60–95	6.4	NA	0.14	0.14	9.2	15.9	0.6	5.2	NA	6.3	NA	21.9	0	12	24	63
B31k	95–115	6.3	NA	0.74	0.12	7.5	13	0.6	5.2	NA	7.5	NA	21.4	1	13	24	61
B32	115–150	5.9	NA	0.86	0.17	6.9	12.4	0.6	4.5	NA	7.5	NA	20.7	0	14	23	62

Note: NA=not assessed

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