PRIMARY STUDIES ON FREQUENCIES OF FERTILIZATION OF FISH PONDS

by

Zhu Yun, Yang Yejin, Wan Junhua, Hua Dan
Asian-Pacific Regional Research and Training
Centre for Integrated Fish Farming
Wuci, China

Network of Aquaculture Centre in Asia
Bangkok, Thailand
January 1987

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PRIMARY STUDIES ON FREQUENCIES OF FERTILIZATION OF FISH PONDS

Zhu Yun, Yang Yejin, Wen Junhua, Hua Dan
Asian-Pacific Regional Research and Training
Centre for Integrated Fish Farming
Wuxi, China

INTRODUCTION

One of the common practices in traditional Chinese fish culture is the utilization of animal manure in farming fish. Although qualitative and quantitative studies have been done on the principles of fish culture in manure-loaded ponds (1, 3, 4, 5), further research on the relationship between the methods of manuring and/or fertilizing and fish yields will be of help in furts er maximizing fish production.

MATERIALS AND METHODS

Eight newly-dug 300 m² earyhern ponds were stocked with silver carp (S.C.), bighead carp (B.H.), common carp (C.C.) and crucian carp (Cr. C.) of the same size and at an initial stocking density of 6,333 ind/ha (Table 1).

Table 1. Initial fish stocking of fish ponds.

Manure and Fertilizer Application

Fermented pig manure and chemical fertilizer, given in four treatments and replicated twice, were used in this experiment. Manure was applied daily to P4, weekly to P3 and every five days to P2, with the cumulative amount of manure similar for all ponds during the grow-out period. For P1, only chemical fertilizer, urea plus calcium superphosphate, was applied once a week.

The rate of manuring over the culture period was 32,066 kg/ha in wet weight base, or 4,810 kg/ha in dry matter base (water content of fermented pig manure was 85). The daily rate of manuring was 278.8 kg/ha. in wet weight base and that of chemical fertilizer, 1.80 kg/ha/d. for urea and 3.78 kg/ha/d. for calcium superphosphates.

Pond Water Quality Measurment

In each month during the experiment, water quality of all ponds was measured for seven continuous days. Parameters measured included water temperature, transparency, pH, DO, COD, BOD, ammonia, PO³₄-, phytoplankton, zooplankton, primary productivity and bacterial growth.

Measurement of the first eight parameters above was carried out by using the standard method for water quality analysis. Qualitative analysis of phyto- and zooplankton and quantitative analysis of zooplankton were performed under microscope. Phytoplankton was quantitatively analysed using chlorophyll a method. Oxygen method (with light and dark bottles) was used for measuring primary productivity. Measurement of bacterial growth was done by measuring the rate of microbial digestion of cotton cloth stripes suspended in pond water as described by Schroeder(5).

Culture period covered 115 days from 30 June to 22 October 1986.

RESULTS AND ANALYSIS

Fish Yields

Table 2 shows fish yields at harvest from two ponds which received the same treatment.

The total net fish yield in P4 during the culture period was 1,418.2 kg/ha and daily net weight gain (7.4 kg/ha/d.) of the main species, S.C. in P4, topped that of other species. In P3 the total net yield was 1,016 kg/ha and daily net weight gain of S.C. was 5.3 kg/ha/d. In P2 the total net fish yield and S.C. daily net weight gain were 904.2 kg/ha and 5.2 kg/ha/d., respectively. Total net fish yield of P1 was 667.6 kg/ha. S.C. exhibited the lowest daily net weight gain of 3.3 kg/ha/d (Fig. 2).

Highest yield of Cr. C. was also derived in P4, which was 68% and 82% higher than that of P2 and P3, respectively. All the manure-loaded ponds gave higher fish yield compared to the ponds which received chemical fertilizer only.

Yield of C.C. in P4 was higher than that of P3 and P2 by 19% and 110%, respectively. The high mortality of C.C. in P2 had a bearing on the very low yield of C.C. in P2.

Changes of the Ecological Factors

The experiment went through summer and autumn and the water temperature ranged from 20 to 29°C. From the pond water temperature records, the temperature in manured ponds was 0.3-1.0°C higher than that in ponds receiving inorganic fertilizers, and no distinct thermal difference was found between manure-loaded ponds. Since the stocking density of ponds was not high the DO level was kept around 5 mg/l on the average in manured ponds. The chemincally fertilized ponds had even slightly higher levels of D.O.

Figures 3–6 show the fluctuations of content of nutrients (ammonia and phosphorus), COD and BOD of pond water.

Figure 1 Total net fish yield of ponds of different treatments	Figure 2 Daily net weight gain of silver carp in ponds of different treatments
Figure 3 The changes of COD,  BOD and nutrients (NP) content in P4	Figure 4 Changes of COD, BOD and nutrients (N.P.) content i P3.

Figure 7 Fluctuations of phytoplankton occurrence in differently treated ponds as indicated in content of chlorophyll -a.

Figures 3–6 indicate small ranges in the fluctuation of COD, POD and concentration of nutrients, ammonia and prosphorus in P4. Concentrations of ammonia and phosphorus in P4 were kept comparatively constant. Average concentrations of ammonia were 0.98 mg/l; phosphorus, 0.08 mg/l; COD and 24 hour BOD were on the average 12.4 mg o/l and 3.9 mg o/l, respectively.

On the first day of manure aplication, the manure added into P2 and P3 were 5 and 7 times that going into P4, and thus the peak concentrations of ammonia and phosphorus in P2 and P3 were then attained. After 4–5 days, the concentrations of ammonia and phosphorus in P2 and P3 declined to the level before adding manure, which was close to the level in P4. In addition, COD and BOD of P2 also obviously increased on the day of manure application. Average COD in P2 and P3 were 13.1 mg 0/1 and 13.2 mg 0/1, respectively and 24-hours BOD were on the average 4.2 mg 0/1 in P2 and 4.0 mg 0/1 in P3.

Plankton Fluctuation

The dominant species of phytoplankton in manure-loaded ponds included Euglena, diatoms and Entophysalis. Euglena dominated the phytoplankton in ponds receiving only chemical fertilizer. The occurrence of filamental algae in addition to Euglena was however observed in July.

Though the amount of manure application was kept the same in each pond, the differently-treated ponds exhibited different patterns of phytoplankton fluctuation resulting from distinct differences in nutrients concentation fluctuation (Ffig. 7). The content of chlorophyll - a of pond water averaged 100 mg/m³ or so.

Morever, the peak occurrence of phytoplankton in P3, P2 and P1 was observed on the third day after manuring, coinciding with the COD curves of these ponds. In P4, however, the occurrence of phytoplankton fluctuated calmly, showing no obvious peaks. This also coincided with the changes of nutrient and COD of the pond water. The standing stock of phytoplankton in P4 was not very high, and this might be attributed to the harvesting of fish.

Primary productivity of water in P4 and P2 was higher than that in ponds receiving chemical fertilizer. Low transparency of water due to high mud content was responsible for the low primary productivity in P1 (Table 3).

Bacterial Growth

The high digestion rate of cotton cloth stripes suspended in water manifests the luxuriant growth of bacteria, and vice versa. Table 3 shows that manure-loaded ponds had higher bacterial growth than ponds receiving only chemical fertilizers. Bacteria was found most abundant at the sediment-water interface and secondly in the upper water column (50 cm under water surface). Bacterial growth in the middle layer of water was relatively low. Average digestion rate of cotton cloth stripes in P4 was 10.4% which is 2.7 times that in P3 and P2 and 4.6 times that in ponds added with chemicals.

Table 3. Bacterial growth (indicated in the rate of digestion of cotton cloth stripes) and plankton density of pond water

Notes: Number in brackets refer to the number of data and the numbers above the line refer to averaged value.

DISCUSSION

Compared with fish yields of ponds with manure added at 5- and 7- day intervals, the total fish yield in daily manured ponds was 30–40% higher. By species, yield of S.C. was 40% higher; Cr. C, 75% C.C, 5.3% and B.H, 31%. When the quality and total amount of manure application are similar in each group of ponds, the fish yield increase should be attributed to differences in the methods of manure application. Daily input manure can raise the efficiency of the conversion of manure into fish body protein via both auto-and heterotrophic food webs.

It will also ensure a continuous supply of nutrients that will keep the pond water abundant with plankton and bacteria algae fluctuating gently. Thus it is favourable to the growth of fish and S.C. in particular.

Morever, daily adding of manure increases the suspension period of organic matter of manure in the water. Bacteria requires organic matter such as nutrients and substrates for growth, and therefore organic particles in water are always found colonized with numerical bacteria forming cotton-like aggregates which serve as good food for fish. Half of the fish yield is derived from the heterotrophic production of, mainly, bcteria (Schroeder 5). Bacterial growth in daily-manured ponds was more vigorous than that in other ponds. The results of this experiment are in accord with those of Schroeder (1978). Raising the frequency of manure application also enhances the utiliation of above said aggregates by fish.

Common carp grew better in daily manured ponds than in others, and this seemed related to the most luxuriant growth of bacteria at the sediment surface of such treated ponds. The enormous bacteria in daily-manured ponds growing on suspended organic were partially ingested by fish and the rest sank gradually to the pond bottom as the bacterial communities developed. Therefore the bacterial communities at the pond bottom would further proliferate, eventually becoming the best food for common carp.

Due to the short duration of the experiment, P3 and P2 differed from each other by only 7 times of manuring, and they gave similar fish yield results by the end of 115 days of culture. Whether there are distinct differences in fish yield needs confirmation in experiments of longer culture periods.

CONCLUSION

Keeping the accumulated amount of manure going into each pond equal (about 4,810 kg/ha in dry base), we compared the effects of manuring ponds daily, weekly and at 5-day intervals.

The results of the experiment of 115 days of grow-out culture showed that daily-manured ponds demonstrated fish yields 30–40% higher than that in ponds manured at 5-day and 7-day intervals.

Daily manured ponds were found with less fluctuation of nutrients concentration of pond water and average concentrations of ammonia and phosphorus were 0.98 mg/l and 0.08 mg/l, respectively. The N/P ratio was 12:1 and plankton changed in small range. Water of daily-manured ponds was abundant with bacterial growth as indicated in the rate of digestion of cotton cloth stripes which averaged 10.4%, which is 2.7 times that in ponds with manure added at 5-day and 7-day intervals.

Daily application of manure into ponds raised the efficiency of conversion of manure into fish body protein, leading to higher fish yield. Daily application then of manure into fish ponds is superior and of value for extension to fish farmers.

REFERENCES

1. Li, S. H. et. al 1956 Proliferation of phytoplankton by applying organic manure Acta Hydrobiologica sinica. 201–207 (in Chinese)

2. He Z. H. 1985. On Biological Indicators of water qualities of water qualities of fish culture from the experience of “observing water.” Acta Hydrobiologica Sinica. Vol. 9 No. 90–98 (in Chinese)

3. Hu. B. T. 1981 Food Webs Formed in Manure-loaded Fish Ponds. Fisheries Science and Technology Information. 1981. No. 6 (in Chinese)

4. Buhbept. T. T. (Trannslated by Zhang Zhongshe) 1965 Biological Fundamentals of the application of innorganic fertilizers in fish pond. On Fertilization in fish Pond. Pg. 1–44 Science Press. (in Chinese)

5. Schroeder. G. L. 1987 Autotrophic and Heterotrophic production of microorganisms in intensely-manured fish ponds, and related fish yields. Aquaculture (14) 303–325.

6. Rom Moow et. al. Intensive Polyculture of fish in Freshwater Ponds. I. substitution of Expensive Feeds by Liquid Cow Manure. Aquaculture 10 (1977) 25–43.

ACKNOWLEDGEMENT

The authers offer deep thanks to the International Development Research Centre (IDRC) for financial support, to Dr. F. Brian Davy for his warm help, in coordination with IDRC, and to Mr. Chen Foo Yan, Coordinator of NACA, for his valuable suggestions.