[permaculture] arid soil building

Robyn Francis erda at nor.com.au
Fri Dec 4 21:49:04 EST 2009

I came up with a technique for a similar climate in southern NSW, where they
also dealt with incredible winds that would simply blow mulch away. We put
down a mulch layer and covered the mulch with a thin layer of soil - this
stopped the mulch from being blown away and improved moisture retention in
the topsoil. I would have preferred to use rocks on the mulch, as rock mulch
condenses moisture escaping from the soil back into the soil, but there were
no rocks in this particular landscape so we used soil.

The straw/soil mulch insulated the topsoil which increased biological
activity, the soil-straw mulch accepted water well when dry. Also, there's
less crusting when the humus and organic matter levels are restored to the
topsoil and it has some form of protective mulch or litter layer.

In Cuba where many have a reticence to use mulch, I recommended laying palm
leaves down between the rows to provide share and help reduce soil
temperature and evaporation. Others warmed to the suggestion of a deep mulch
on their paths as an initial experiment. The soil life really gets hammered
by the heat from direct sun on bare earth, so any form of shade is critical.

There's also occasions where different types of mulch may be appropriate. In
the dry tropics (& humid tropics dry season) rice hulls, coffee hulls, nut
shells and other such crop residues are spread on the soil as an open or
scattered litter. At least providing some shade and protection.

Leaving the stubble from winter grain crops (e.g. Between fruit trees,
vinyard rows etc) is another beneficial strategy to build organic matter and
protect the soil more effectively than bare earth.

Its good to experiment, adapt and explore alternative strategies to counter
the issues. Understanding the rationale behind the local dirt mulch
technique (thanks for your explanation Dieter), exploring the why's, is
essential for developing other ways of resolving the problems that
regenerate soil health and productivity.


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