fish cum poultry culture.

INTRODUCTION
In modern concentrated animal
farms, a lot of manure arises which
contains dissolved and undissolved
organic material in large
quantities. This secondary product
can be used in plant cultures or in fish ponds. This utilization
procedure has several steps. The
organic material disposed in the
pond is transformed by micro-
organisms under aerobic
conditions. The resulting organic material is nutriment for algae.
Algae transform this inorganic
material into organic plant
material by using solar energy. The
algal biomass thus resulting is food
for the next consumption level for zooplankton. Phyto- and zooplanktons together
form plankton biomass which is the
natural food for fish. Utilization of organic fertilizers in
fish culture has a long tradition. It
is an accepted practice in Far
Eastern countries where climatic
conditions result in rapid metabolic
processes. Considering the allegation of
Wohlfarth (1978) the manure can
be a fodder replacing feed, it would
be negligent not to exploit this
source. Only a part of the huge amount of
pig manure accumulating in pig
farms is utilized in the fields, so the
excess, which contains high
amounts of direct and indirect
proteins (Moav et al., 1977), can be well used in increasing natural
nutrient content of fish ponds. Schroeder and Hepher (1975) found
that manure load causes a
profound change in the natural
nutrient cycle of fish ponds, coming
about by the organic matter
decomposing activity of bacteria and protozoa. Micro-organisms
getting into the water with the
manure also become fish feed.
Water bacteria of 20-30 m m size
are also consumed by pelagic fish
(Kuznetsov, 1977). The optimal utilization of manure
depends greatly upon the stocking
structure. Yashow (1971)
demonstrated that on the influence
of feeding interaction there is a
nutrient movement among the different specific zones in
polycultural fish ponds. The
findings of Wohlfarth (1978)
unequivocally proved the yield
stimulating nature of polycultural
fish pond management. Leventer's (1981) studies also confirmed it
when he proved that algal
production is higher in poly cultural
than in mono cultural fish ponds.
Put the yield is influenced by the
way manure is used as well, for example, to preserve use ful
compounds by keeping them away
from air. It is also important to
ensure the proper balance between
loading and decomposition of the
manure in a pond: therefore, we followed the practice of daily
disposal proposed by Moav et al. (1977) and Schroeder (1974). 2. MATERIALS AND METHODS
The aim of our experiment
performed in 1980 was to find the
optimal dose of manure ensuring
the highest yield of fish as well as
the best water quality. In 8 earthen
experimental fish ponds of 0.17 ha each, we applied different manure
loadings. The liquid pig manure
from a nearby pig farm was rather
diluted, due to the great amount of
water used in the management
regime. Dry matter content was about 1 percent. The composition
of the manure was regularly
analysed. The total nitrogen
content was 8 g/l, while the total
phosphorus was 1.2 g/l. In each pond an identical stocking
structure was used, with a
dominance of silver carp.
Considering the feeding
competition between common and
big head carp, the stocking rate of the former was only 27 percent.
The third member of the structure
was grass carp. One and two year
old silver and common carps were
stocked in order to get an answer
to the question as to which age group could better tolerate the
new conditions. In a follow-up experiment in 1981,
the aim was to find the optimal
stocking structure. Six
combinations of stocking structure
were employed in 8 experimental
ponds, with 2 fish species only, silver and common carp, the
former in varying numbers. The
optimal amount of manure applied
(with 1 percent dry matter content) was 1 035 m3 in 1980. Since the manure used had 4
percent dry matter content, this amount was 200 m3 in 1981. Nitrogen content was 8.6 g/l and
phosphorus was 1.4 g/l. In the
control ponds, inorganic fertilizer
was applied containing only 150
kg/ha nitrogen and 20 kg/ha
phosphorus. The aim of the third year's
experiment in 1982 was to
compare the polycultural and
bicultural systems. We wanted to
get an answer to the question of
which stocking structure was better in respect of water quality
and fish production. 2.1 Short Description of Technology The liquid manure from the pig
farm was transferred in tank
vehicles into a tank, from which it
was pumped to the sprinklers
through aluminium pipes and then
sprayed into the ponds. Clean water for rinsing the pipes was
taken from the water supply
channels of the ponds. The pump
had two forks, one for the manure
and the other for cleaning water. 2.2 Equipment and Facilities The CSN-301 type revolving pulley-
pump has two main parts: a
flexible rubber cylinder and a
re volving metal pulley sucker. The
pump is suitable to transfer pulpy,
fibrous material of high, viscosity. By changing the rpm its carrying
capacity can be controlled between 4.5 m3/h and 16 m3/h. The pump operates according to the
volumetric displacement principle. 3. RESULTS Two factors were considered when
establishing the optimal dose of
liquid manure applied. One was the
highest fish yield, the other the
quality of effluent water (Figure 1).
Taking the yield of the control pond as 100 percent, we reached 109 percent when using 1 030 m3 liquid manure, which corresponds
to a net yield of 2.4 t/ha. The net
yields of the other treatments
were far behind this value. Similar
yields were obtained with 1 or 2
years old common carp, with the exception of one pond where the
lack of feed was obvious, i.e. 560 m3 liquid manure was insufficient. Both age groups showed very good growth rate at 1 030 m3 manure loading. The highest or
lowest doses did not favour the
growth rate of the 2 years old
group. Grass carp showed the best growth
rate in ponds with a low amount of
liquid manure. Due to good light
conditions, the well growing
macrophytes ensured the specific
nutrient demand of grass carps, but the increase of manure loading
did not result in increased yield at
the same light conditions. There
was a considerable mortality when
we increased the manure loading,
especially with the 1 year old silver carp. The loss with the 2 years old
stock was far less. During the
regular pilot harvests, we
investigated the gill and general
health condition of all the fish. No
ill or deteriorated fish could be seen. Based on experience obtained in
1981 (Figure 2/a), further work is
needed to; find the optimal rates
and stocking structure. A yield of 1
000 g fish was obtained only at a
very low stocking rate (1 500/ha), which should be increased. While
the weight of common carp was
above 1 000 g in each combination
at a stocking rate of 1 000/ha, the
weight of grass carp decreased
along with the increase of stocking rate (Figure 2/b). The highest net
yield was obtained with the
treatment resulting in the lowest
individual growth rate. However,
silver carps had not even doubled
their original weight. In 1982, the best net yield of 2.5 t/
ha was obtained in a bicultural
pond (Figure 3). The population
was of good quality and healthy.
Comparing the yield of the 4
bicultural and 4 polycultural ponds with identical stocking structure,
the bicultural form proved to be
better, with an average net yield of
2064 kg/ha. The yield of the pond
with polycultural stocking was 1
444 kg/ha. The quality of effluent water did
not show any difference with the
two stocking structures applied.

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