Eucalyptus in Australia,Ag Drainage

Alberto C. Dela Paz albertoc at mozart.inet.co.th
Thu Aug 31 09:27:55 EST 1995


| In article <41kv7m$kan$1 at mhadf.production.compuserve.com>, Betty Yee <70262.2521 at CompuServe.COM> says:
| >
| >I'm looking for an article which came out either last year or early 
| >this year regarding the plight of Australian farmers due to high 
| >ground water.  The article blamed part of the problem on the lost of
| >Eucalyptus trees.  I don't recall what magazine that was in or what 
| >issue.  Can anyone help?
| >
| >Please reply to Betty2nd at aol.com
| >
| >Thanks

To:  Betty Yee,

I don't know if this will help.  I prepared a very short brief on some of 
the effects of eucalypts on soils and quote some passages from John 
Davidson's paper below.  Anyway, there goes...

Many annecdotal accounts of eucalyptus species causing ground water
depletion have been recorded.  In the past, such groundwater
depletion was ascribed to high water consumption of the fast
growing tree.  In a recent report entitled "Ecological Aspects of
Eucalyptus Plantations" by John Davidson, a different explanation
is put forward.  He mentions that soils under eucalyptus become
water repellent which means that soils do not get wet or absorb
water.  As the water has to drain, water which does not penetrate
the soil run-off causing soil erosion.  Water which should have
recharged groundwater is, therefore lost which could be one reason
for the observation that eucalypts "extract" much water from the
soil.

Water repellency of soils under eucalyptus plantations, however, is
said to be caused not by the tree itself but by a microorganism
(fungi) associated with it.  The condition is not isolated to
eucalypts.  Another tree in which repellent soils are observed are
citrus.

Fortunately, water repellency can be reversed by adding
surfactants.  Surfactants are chemicals which modify the surface
tension of water much like detergents.  As surfactants are rather
expensive, it may be possible to use detergents or better, soaps to
"cure" water repellent soils.

No recommendations for amount of surfactants per unit area,
however, were been given.

__________________________
In Proceedings of the Regional Expert Consultation on Eucalyptus. 
4-8 October 1993.  Vol.  1.,  Food and Agriculture Organization for
Asia and the Pacific.  Bangkok.  RAPA Publication  1995/6.


Alberto C. de la Paz
Population and Community Development Association
<PDA at mozart.inet.co.th> or <albertoc at mozart.inet.co.th>



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