Aoi.T(2000₯10₯13)Phytoremediation by Kenaf in the Tone River Basin, Proceedings of the 2000 International Kenaf symposium Hiroshima,pp51-54
1.Introduction
It has recently been suggested that a plant called "kenaf" may help prevent
global warming and help
conserve forest resources. Kenaf(Pic.1) is a ligneous and
annual plant. It grows quickly and has a stem which
contains mainly cellulose. Kenaf grows actively either
hydro-ponically or in soils. Therefore, kenaf will absorb
carbon dioxide from the air and remove nutrient salts from
water, thus helping environmental conservation. But a
sufficient knowledge has not been obtained on the water
purification ability. Either the concrete report on unit area
yield point in Japan has not been done.
The Tone River is the biggest river with the
drainage area in Japan, and the Tone River supplies
drinking water to almost 26,000,000 people in the
Metropolitan area. By the development of the
metropolitan area, the importance of Tone
River strengthens more. But the water quality
of the Tone River is getting worse to
eutrophic, because the sewage treatment
plants in the upper and middle stream region
of Tone River does not remove nutrient salts.
In this study, hydroponic culture test
using household polluted water was carried
out, and the water purification ability was
examined. Then unit area yield point at each
cultivation condition was measured.
Hydroponic culture test using the
farm pond water which was polluted by
household drainage and open-field culture
test were carried out in the same time
(Pic.2,Pic.3,Fig.1) . At first kenaf seeds were
cultivated on rock wool using household waste
water. Then the seedlings were transplanted
and grown in the cultivation bed. Water
culture bed used by this experiment is a
shallow water channel made by wood board
and canvas sheet which gained any
inclination. Since kenaf grows as high as 4m
height in the autumn, fixations for the kenaf
stem are necessary in the hydroponic culture. Then, the frame made of the pipe ( the 1m height
) was installed with horizontal pipes, the fall down prevention was done. The residence time of
the experiment was as short as 40 minutes. For example, entrance T-N 2.61mg/l were reduced
to 2.09mg/l in effluent, also entrance T-P 0.22mg/l were reduced to 0.16mg/l in the exit(Fig.2).
It seemed that removed N,P
were mainly used in
synthesis of plant body and
partly denitrification .
It is known that the kenaf
does not receive the rate-limiting
of growth over T-N
concentration 0.5mg/l.The
kenaf grew to the 3.5m height
in the autumn.
culture(Pic.4), wet weight and
water content of the kenaf
which matured in the winter
were measured. And the yield
point per unit area( dry weight
kg/ha ) was calculated by the observation of
planting density.Nutritional factor of the
cultivation pond, time of the seeding, planting
density, etc. influence the yield point.At the
hydroculture, the transfer of seedings were easy,
so in the place of the dense planting, the yield
point reached to as high as 100t/ha from
50t/ha(Table1). On the open-field culture, yield
point reached to 40t/ha in the maximum on the
fertile land(Table2). In the place of the nutrient
deficiency like volcanic ash, yield point was as
small as 5t/ha.
To the others, it has also been proven that
the kenaf chip is suitable for the culture medium of
some mushroom cultivation. Takamura and
Sameshima et.al has already tested the kenaf
chip(partly blended) for the cultivation of
Lentinus edodes(Japanese name: shiitake).
As Gunma Prefecture is a main mushroom
growing district in Japan, if it can be used for
the mushroom production, effective
utilization of the kenaf core becomes
possible.
Recently, many kinds of mushroom
are produced industrially in-bottle cultivation
with wood-chip(broad-leaved tree), rice bran
and wheat bran as the culture material. Two
kinds of mushroom(Pleurotus ostreatus
(Japanese name: hiratake) and Lyophyllum
decastes (Japanese name: simeji) )were used
as an object of the experiment. These
mushrooms have features with the fast
growth. And so it is convenient for the
experiment, because it can be harvested within
1 month.
In the mushroom cultivation test with
kenaf chip(Pic.7,Pic.8,Pic.9), only the kenaf
chip was used as a raw material instead of
broad-leaved tree chip. Hypha growth
increment in kenaf culture medium was
greater than the usual culture medium. As
the result, the cultivation period from the
inoculation to the harvesting was able to be
shortened . It was confirmed that the kenaf
could be effectively utilized for the
cultivation of Pleurotus ostreatus and
Lyophyllum decastes as a substitute of the
broad-leaved tree chip.
