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algae control with barley straw

Francois Benadie faben at isat.co.za
Mon Oct 14 15:41:07 EST 2002

This post has probably been seen before, but I wan to know if there has
been new light shed on this subject.

This is a piece from a leaflet from an agricultural agency in England
(ACR-Centre for Aquatic Plant Management):
"Although the exact mechanism by which straw controls algae has not been
fully proven we believe that the process may occur as follows. When
straw rots, chemicals in the cell walls decompose at different rates.
Lignins are very persistent and are likely to remain and be released
into the water as the other components decay. If there is plenty of
oxygen available in the water, lignins can be oxidised to humic acids
and other humic substances.

****These humic substances occur naturally in many waters and it has
been shown that, when sunlight shines onto water which contains
dissolved oxygen, in the presence of humic substances, hydrogen peroxide
is formed*****

. Low levels of peroxide are known to inhibit the growth of algae and
experiments have shown that sustained low concentrations of hydrogen
peroxide can have a very similar effect on algae to that of straw.
Peroxides are very reactive molecules and will only last in water for a
short time. However, when humic substances are present, peroxides will
be continuously generated whenever there is sufficient sunlight. The
slow decomposition of the straw ensures that humic substances are always
present to catalyse this reaction. "

The cut out section with the asterisks is what I am interested in, can
this happen and does this happen?



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