dc.description.abstract | In order to reduce the irrigation run-off
and contamination of the underground water,
effects of different nutrient levels were
investigated in Spathiphyllum “Sensation”
grown in an ebb and flow system, and
comparison on the growth with hand-watering
was also determined. Environmental and
economical concerns had generated interest in
the development of substitutes to peat, under
the conditions of this study, coir-based media
was also used in the experiments to compare
the growth responses of Spathiphyllum
“Sensation” under the ebb and flow system.
Plants grew equally well from a range of
1/4 to full-strength of Johnson’s solution in
the ebb and flow system, indicating the
possible luxury consumption of plants was
grown in the full-strength treatment,
moreover, full-strength treatment produced
more necrotic leaves and reduced the root
growth. However, the chlorophyll content was
lower in the 1/4-strength treatment and leaves
showed chlorotic spots symptoms. In the full
strength treatment, a high EC of 7.19mS/cm
was measured in the upper portion of the
medium measured at the end of the
experiment, whereas for the 1/4 strength
treatment, EC at the root zone was maintained
at 0.79mS/cm, which was considered to be
save for the plant growth. These results
indicated that a range of 1/4 to half strength of
Johnson’s solution was optimum for the
growth of Spathiphyllum“Sensation” in the
ebb and flow system.
From September, 1997 to April, 1998,
there were no difference in the plant growth
between irrigation methods at the same
irrigation frequency, however plants grown in
the ebb and flow system had the fewest
number of chlorotic and puckered leaf. From
May, 1998 to January, 1999, plants growth in
the ebb and flow system was better than that
of the hand watering treatment. In additions,
the ebb and flow system could save water and
nitrogen use by 33% and increased the water
use efficiency by 40%.
Coirdust had a lower air-filled porosity
and water holding capacity than Canadian
sphagnum peat. Growing mix containing 33-
60% of coirdust with perlite and treefern
exhibited desirable physical properties, the
pH of coirdust was desirable but EC was
higher than that of peat. Na and K were tested
to be 6 and 3 times higher than peat
respectively, however, the P, Mg, Ca content
of coirdust was less than optimum range.
No difference was observed in plant
growth among various medium mixture
containing either 33-50% of coirdust or 33%
of peat. However, the coirdust content higher
than 50% could reduce plant growth. In
another experiment with medium composed
of 50% of perlite and various proportions of
coirdust and peat, results indicated that
coirdust content up to 25% gave lower root
dry weight. All these suggested that the
chemical properties would affect the root
growth of Spathiphyllum“Sensation”.
Maximum growth was observed in 8mMN
applied in the ebb and flow system by using
peat-mix as the media, while plants grown in
coirdust were equally well with the ebb and
flow by 4-8mM-N treatment. As a medium in
the ebb and flow system, it appeared that
coirdust could be a good substitute for peat.
For either peat or coirdust-based medium, the
optimum nitrogen requirement for
Spathiphyllum “Sensation” in the ebb and
flow system was 8mM. Plant dry weight
decreased and necrotic symptoms occurred
when nitrogen concentration exceeded 16mM
in all treatments, and root dry weight
decreased sharply especially in the ebb and
flow treatment. Increasing nitrogen
concentration paralleled increased the no of
necrotic leaves, and root growth foliar N
content, while K, Ca and Mg content was
decreased. Due to the absence of leaching in
the ebb and flow system, it was suggested to
reduce the nitrogen application rates in order
to maintain good quality of Spathiphyllum
“Sensation”.
Fertigation using once in every 3 days
was shown to be optimum for peat and
coirdust-mix in the ebb and flow system,
while increasing the frequency to once a day
was unnecessary. Coconut husk-mix had a
poor water retention capacity, but the problem
could be solved by increasing the fertigation
frequency to once a day, suggesting that
coconut husk is suitable for constantly
irrigation. | en |