288
D — Other problems with pond fertilization
The water retention time
in a pond has a pronounced influence upon pond
fertilization
and
the
residual effect
of lime
applications. If water
flushed rapidly through ponds, fertilizer.nutrients
may be discharged
they
stimulate
phytoplankt0n_ There
hasÏ been
no
research
to
quantitative relationships between water exchange rates and the effectiveness
of
pond fertilization,.but experience.suggesté that fertilizers produce the
best results
in ponds
with
water retention
times of
1 month or more.
Aquatic weeds compete with phytoplanktoh for nutrients. Therefore, weed—
Î
infested ponds may
respond to fertilization. Grass carp may be used as a
biological control agent; or herbicides
may be applied. If weeds are brought
under control, a fertilization
program normally
will make
the water turbid
enough With plankt0n to prevent reoccurrence of weeds.
_
In waters with high pH and high calcium concentrations, phosphate may be
precipitated
quickly as insoluble calcium phosphate. The rate of application
of phosphate
fertilizer must
be increased
in such
waters.
There
is
also
evidence that
nutrients
in
addition to
nitrogen and
phosphorus may limit
plankton growth and fish production in SOme ponds.
Turbidity from high concentrations of suspended clay particles restricts
light
penetration
in water
and prevents
optimum growth
of phytoplankt0n.
Ÿ
Treatment
with
aluminum
sulfate
(alum) or
calcium
sulfate
(gypsum)
will
remove
clay
particles. Alum
treatment
the most
efficient means
(Boyd,
1979b). Treatment rates usually range from 25 to 50 mg/l. The alum rate for a
‘particular
pond can
be
determined
by treating 1,000 ml samples
of turbid
with a range
of alum
concentrations.
The lowest
concentration
that
affects the
removal of
clay particles
should
be applied to the pond. Alum
must be
dissolved in water and
sprayed over the
destroys
one half
its weight
of alkalinity, and
the alum rate should never be
more
than 1.5 times
the total alkalinity expressed in milligrams CaCO3 per liter.
Unles$ the source of the
removed, turbidity may reoccur.
: and… excessive… turbidity : from… suspended
j Ê
quality problems are more freduent and severe in'
intensive
Ê
food
culture
Sport fish culture; Fish feeds are often
and
most
result
;
pollution by
of fish and
.…
_
g
l,
«";
“{
…“ ‘,
:
…
‘;;
“J
of
role of. feeding
(1985)‘3develôÿedÏ
demandŸ
d18301vedæ oXyge (DO) over amgr0wing Season for three Hëhannël
GatfiSh ponds. Details
afe
,
presented in
Table
addition to rainfall and runoff, l90 cm
water
were applied fromèea‘
':
:_seeÿagez.
oration; Each
,.
f*fish Frequi;red
à::veed‘ÿa and
tô
;
the ÈW3ËË‘—Ê* : '«-îin-v=metabolic
;. 7 .2
; , ad
1 i‘1î“kË
kg of fish
…to
59 :kg
con
in
@
Fish harveät
(
\
\
'
\
D — Other problems with pond fertilization
The water retention time
in a pond has a pronounced influence upon pond
fertilization
and
the
residual effect
of lime
applications. If water
flushed rapidly through ponds, fertilizer.nutrients
may be discharged
they
stimulate
phytoplankt0n_ There
hasÏ been
no
research
to
quantitative relationships between water exchange rates and the effectiveness
of
pond fertilization,.but experience.suggesté that fertilizers produce the
best results
in ponds
with
water retention
times of
1 month or more.
Aquatic weeds compete with phytoplanktoh for nutrients. Therefore, weed—
Î
infested ponds may
respond to fertilization. Grass carp may be used as a
biological control agent; or herbicides
may be applied. If weeds are brought
under control, a fertilization
program normally
will make
the water turbid
enough With plankt0n to prevent reoccurrence of weeds.
_
In waters with high pH and high calcium concentrations, phosphate may be
precipitated
quickly as insoluble calcium phosphate. The rate of application
of phosphate
fertilizer must
be increased
in such
waters.
There
is
also
evidence that
nutrients
in
addition to
nitrogen and
phosphorus may limit
plankton growth and fish production in SOme ponds.
Turbidity from high concentrations of suspended clay particles restricts
light
penetration
in water
and prevents
optimum growth
of phytoplankt0n.
Ÿ
Treatment
with
aluminum
sulfate
(alum) or
calcium
sulfate
(gypsum)
will
remove
clay
particles. Alum
treatment
the most
efficient means
(Boyd,
1979b). Treatment rates usually range from 25 to 50 mg/l. The alum rate for a
‘particular
pond can
be
determined
by treating 1,000 ml samples
of turbid
with a range
of alum
concentrations.
The lowest
concentration
that
affects the
removal of
clay particles
should
be applied to the pond. Alum
must be
dissolved in water and
sprayed over the
destroys
one half
its weight
of alkalinity, and
the alum rate should never be
more
than 1.5 times
the total alkalinity expressed in milligrams CaCO3 per liter.
Unles$ the source of the
removed, turbidity may reoccur.
: and… excessive… turbidity : from… suspended
j Ê
quality problems are more freduent and severe in'
intensive
Ê
food
culture
Sport fish culture; Fish feeds are often
and
most
result
;
pollution by
of fish and
.…
_
g
l,
«";
“{
…“ ‘,
:
…
‘;;
“J
of
role of. feeding
(1985)‘3develôÿedÏ
demandŸ
d18301vedæ oXyge (DO) over amgr0wing Season for three Hëhannël
GatfiSh ponds. Details
afe
,
presented in
Table
addition to rainfall and runoff, l90 cm
water
were applied fromèea‘
':
:_seeÿagez.
oration; Each
,.
f*fish Frequi;red
à::veed‘ÿa and
tô
;
the ÈW3ËË‘—Ê* : '«-îin-v=metabolic
;. 7 .2
; , ad
1 i‘1î“kË
kg of fish
…to
59 :kg
con
in
@
Fish harveät
(
\
\
'
\