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The
invasive aquatic fern Azolla filiculoides can be put to potentially good
use as a biofertiliser. This study reports on the response of wheat to soil
fertilisation with varying proportions of A. filiculoides subjected to
three pre-treatments. In a preliminary study, treated Azolla was mixed
with acid-washed sand at three application rates. Results demonstrated that
pre-heated A. filiculoides added at 80% (v/v) resulted in the highest
wheat above-ground biomass, but that the use of dried Azolla had a
similar effect. In order to differentiate between the effects of fertilising
nutrient-poor soils versus effects that could be expected from the
fertilisation of field soils a second study was conducted applying dried A.
filiculoides in various proportions to acid-washed sand and topsoil. Wheat
performance in response to fertilisation was assessed by monitoring yield of
grain, leaf areas and above-ground biomass. Wheat grown in acid-washed sand and
fertilised with 80% (v/v) air-dried A. filiculoides significantly out
performed other treatments. When added to topsoil, 20% and 80% (v/v) A.
filiculoides, and the N, P and K fertiliser treatments resulted
in higher wheat yields than the control treatments. The potential contamination
of water-bodies with A. filiculoides spores was also tested. It was
found that A. filiculoides spores germinated from mixtures of air-dried A.
filiculoides after a period of four months. A. filiculoides, an
invasive water-weed, can thus be put to agricultural use under dry-land
conditions, but may be a potential source of contaminating spores, perpetuating
it as an invasive.

South African Journal of Botany 2003, 69:
295–300