Soil Capping

Soil capping is a hard crust on the soil surface that severely limits permeability.  

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There are several degrees of capping, known as broken capping, recent capping, immature capping and mature capping.  

It is important to look down on your land rather than across it.  When you do look down you may be surprised at the extent of capping that your see!

Recent and broken capping
The photograph below shows recent capping in a very brittle tending environment in western Queensland.  The capping is the ‘crusty’ surface that tends to have ‘craze’ patterns throughout itself.  This capping causes some impediment to the ingress of water, but is normally not more than a millimetre or so thick (0.04”).  Over time, if recent capping is left undisturbed it will advance and become immature, and then mature capping, causing significant problems.

The photograph also show that a passing animal has disturbed some of the capping, and it has become broken capping.  If left undisturbed the broken capping would, over time, begin to cap again.

Immature capping
Immature capping is is bare, capped soil, often 3 to 5 mm thick (1/8 to 3/16 of an inch).  When the soil surface is ‘tapped’ with the points of fingers it will reverberate like a drum.  Typically, immature capping looks much like the photograph below, clearly showing a serious impediment to the inflow or water into the soil.

Mature capping
Mature capping is an advanced form of immature capping.  Nature abhors a vacuum, and always tries to cover herself, with the highest successional species possible.  Unfortunately, the highest successional species that can establish in bare soil environments are single celled mosses and algaes, what are known as cryptogams (Note: Be careful not to confuse the spelling with a type of puzzle known as cryptograms!).

At the tip of each arrow in the photo below is the slightly greenish colouration that is mosses and algae’s.   You can find these almost anywhere.  A favourite place to look is around garden edges, particulary if there is a history of knockdown herbicide use, where succession has been constantly reduced to zero.  

Move out the front fence and into any paddock, and be pleasantly surprised if you proceed more than 20 metres (22 yards) without observing mature capping.  In terms of efficiency in creating ineffective water cycles, both mature and immature capping are equal in performance.

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