1. INTRODUCTION
Aquacultural rotation (AR) is a production method developed for unproductive soils. It allows mutual and beneficial biological effects on cultures of different types. With the help of AR, the most economic utilization of sodic soils can be achieved, by producing foods rich in protein (fish, duck, rice) and high quality forage crops (alfalfa, red clover) ameliorating, at the same time, the structure and quality of soil.
1.1 Application of AR
In Hungary, this method offers possibilities for production of important foods on flat soils of the poorest quality. Its introduction into areas where fish and rice are essential foods may be desirable. Protein production per unit area achieved by "fish-cum-duck" rearing is much higher than that achieved with any other land use. During the dry phase the pond bottom is utilized, its hygiene is improved and at the same time reconstruction of ponds may be carried out. Leguminous plants are the best crops for preparing the soil for rice production.
1.2 Conditions for Application of AR
AR may be adapted for any flat area where the soil is suitable for fish farming or rice cultivation, but areas not suitable for agriculture can also be used for this purpose. Ponds under 1 ha cannot be used for AR (wintering ponds, rearing ponds, etc.). The optimal size of ponds in Hungary is 20-30 ha.
Dikes of fish ponds should be constructed in such a way that the thin layer of fertile soils on the pond bottom will remain intact. Inner sides of the dikes are to be constructed with a moderate slope (1:5, 1:4) thus assuring their protection.
The filling and drainage system of every pond must be independent, using irrigation water of good quality and a drainage system by gravity. The pond bottom should be large enough for rice fields of 2-3 ha. Within the rice fields the bottom level differences should not exceed ± 5 cm, sloped to allow inundation and drainage through each other. Within the ponds, one or two artificial islands should be constructed and planted with trees for the purpose of duck breeding.
2. DETAILED DESCRIPTION OF AR
2.1 First Phase - Double Meat Production
Young ducks are prepared and trained for living under natural circumstances. This training has three steps. During the first step, ducks are held in warm rearing rooms on a wire-screen 1 m above the floor (mesh size 15 × 17 mm) at a temperature of 28-30°C. Ducklings are fed with pelleted starter feed 3 mm in diameter, ad libitum, and drinking water is supplied by a flow-through system. After the arrival of the one-day old ducks, the temperature is lowered by 2°C every day. On warmer sunny days (20-25°C), 2-3 days old ducklings are allowed to enter the open run and to bathe in the bathing channel after 4-5 days. During the first step 30-50 ducklings are kept on a 1 m2 wire screen.
In the second step, ducklings of 8-10 days are transferred to cool rearing rooms, which may be heated in cold weather (+ 5-15°C). Here they are kept in a density of 20-30/ m2, and are fed pellets made with less protein. Healthy, well developed ducklings are kept in the open run and in the bathing basins, which are deeper than those of the first step.
For the third step, ducks of 12-14 days are kept on illuminated rearing ponds 24 hours a day. In extremely bad weather they can enter a shelter. Feeding is carried out by the use of self-feeders and pelleted feed. During this procedure, weaker ducklings are lost (2-3 percent), which is more economical than losses occurring at a later stage.
In summer, the ducks are transferred to the fish ponds at 16-18 days old, while in early spring (March), they are transferred at 21-22 days, their average weight being 750-900 g at that time.
The self-feeders are situated on the wind-protected sides of the islands. They have to be 20-30 cm above the water level and, consequently, their height should be adjustable. Ducks are fed ad libitum with feed of low protein content. The rest of their growing period (totalling 45-46 days) is spent on the artificial island and on the water surface. Losses caused by predators (weasels, foxes, etc.) are minimal (0.5-1 percent). On a fish pond of 20-30 ha, 5 000-6 000 ducks may be kept at the same time, and this can be repeated 3 to 4 times a year.
In good weather, well fed ducks spend half of their time on the water surface, thus manuring the pond in an ideal way. They control the growth of undesirable water weeds, which serve as natural food for them. Average weight of marketed ducks of 45-46 days is between 2 600 and 2 800 g, and of first quality.
2.2 Effects of Duck Breeding on Fish Farming
Ducks can be reared on any fish pond where the weight of fish stocked has reached or surpassed that of 5-10 g. Natural fish yields doubled in those ponds where duck rearing had been practised for 2-3 years.
Production Results (kg/ha)
|
|
1 |
2 |
3 |
4 |
|
Increase in weight of fish |
950 |
1 090 |
1 540 |
1 410 |
|
Natural yields |
299 |
488 |
580 |
571 |
|
Increase in weight of ducks |
420 |
1 529 |
1 960 |
2 107 |
|
Total increase of weight |
1 370 |
2 619 |
3 502 |
3 517 |
The effect of duck breeding was studied in an experiment conducted in the experimental ponds of the Fish Culture Research Institute at Horvátpuszta. Two similar ponds (E-9 and D-9) of 8 ha each were stocked with 6 920 one summer-old carp and 530 two summers-old silver carp. During the growing season, both ponds were treated in the same way (feeding, artificial fertilization, inundation, etc.). Pond E-9 served as a control, while on pond D-9 13 274 ducks were reared (1 659/ha).
At the end of the experiment, the following result was obtained. In the control pond (E-9) 1 654 kg was the increase in fish weight per hectare, out of which 498 kg/ha was the natural yield. At the same time, pond D-9 produced a 2 334 kg/ha increase, the natural yield being 1 185 kg/ha. As a result of duck breeding, the natural yield was 687 kg/ha higher than that of the control pond. Total meat production (duck and fish) of pond D-9 surpassed that of pond E-9 by 3 680 kg/ha, being 5 334 kg/ha (322 percent), while 1 654 kg/ha (100 percent) was produced in the control pond.
Beneficial effects of duck breeding on the production of marketable fish in polyculture are also illustrated by the data of pond No. 10 at Horvátpuszta.
Results Achieved in Fish Pond No. 10 at Horvátpuszta
|
Stocking |
| |
|
|
Number of fish/ha |
2 141 |
|
|
Total weight kg/ha |
468 |
|
Harvesting |
| |
|
|
Total weight kg/ha |
2 542 |
|
|
Increase in weight kg/ha |
2 074 |
|
|
Natural yield kg/ha |
1 308 |
|
|
Weight of ducks kg/ha |
2 374 |
|
|
Total meat production kg/ha |
4 448 |
During the growing season from March to October, in addition to organic fertilization by ducks, artificial fertilization and feeding is carried out. The quality of feed is determined by daily control.
The percentage of monthly amounts of feed is given below:
|
Month |
Feed consumption Percentage |
|
|
|
|
April |
5 |
|
May |
12 |
|
June |
22 |
|
July |
26 |
|
August |
30 |
|
September |
5 |
|
Total |
100 |
Fish are fed cereals (maize, wheat, rye, corn, etc.), and fry are fed pellets.
Chemical studies proved that, as an effect of fish-cum-duck farming, the organic material content of the pond bottom increases significantly, and the content of easily soluble phosphorus as well as easily soluble potassium increases.
2.3 Second Phase - Forage-Crop Production on Pond Bottoms
Organic matter and mud deposited during the first phase of AR (5-6 years) offer an opportunity for agricultural crop-production on the dry pond bottom. Experiments were carried out with 27 different plants, selected on the following bases:
- Which species or varieties give the highest yields on dried pond bottom.
- Which crops offer the highest incomes.
- Which crops improve the quality and structure of the soil.
- Which crops best secure the conditions for rice production in the third phase of AR.
It was found that leguminous plants, particularly a red clover mixture, proved to be the best.
The results were as follows:
|
|
|
Ton/ha |
Ton/ha |
|
1. |
Red clover |
85.05 |
16.00 |
|
2. |
Alfalfa - red clover mixture 1:2 |
74.74 |
14.95 |
|
3. |
Alfalfa - red clover mixture 1:1 |
70.69 |
14.49 |
|
4. |
Alfalfa - red clover mixture 2:1 |
63.42 |
13.32 |
|
5. |
Alfalfa |
54.91 |
11.53 |
|
|
Smallest SD5 percent |
4.83 |
9.65 |
In 1965, new experiments started with leguminous plants in pond No. 6 at Horvátpuszta. This pond was used for fish-cum-duck production for the previous three years. Five varieties of clover and the best variety of alfalfa were used, and even in the first year the experimental area yielded 260/346 t/ha in green weight.
Production data of the second year are given below:
|
|
Green weight |
Hay value |
|
Red clover of Tápió |
106.23 |
21.25 |
|
Red clover of Táplán |
105.57 |
21.11 |
|
Red clover "0" |
102.35 |
20.47 |
|
Red clover of Fertód |
101.95 |
20.39 |
|
Red clover of Táplán 120 |
101.09 |
20.22 |
|
Alfalfa of Martonvásárhely |
74.67 |
17.92 |
It was found that poliploid red clovers (Hungaropoly Táplán 120) secured higher yields than those of diploid red clovers and adapted very well to pond bottom conditions.
Harvesting of leguminous crops can easily be mechanized. They can be used in the green stage for feeding of duck breeders and herbivorous fish species, or they can be preserved and utilized as components of fish and duck feeds.
Experiments showed that during the second phase of AR, the production of leguminous crops are the most suitable. Among these, the alfalfa and red clover mixture proved to be the most economical because results of the first harvestings are secured by the red clover, while, particularly in dry years, those of the last harvestings by the alfalfa. With irrigation, polyploid red clovers provide the highest yields. The soil is enriched in nitrogen and calcium by alfalfa.
2.4 Third Phase - Rice Production on Pond Bottom
The structure of pond bottom soil considerably improves during the first two phases of AR, increasing its organic matter content and nitrogen level significantly. This richness of nutrients can be favourably utilized for rice production.
This third phase lasts for three years. Highest yields of rice were obtained following production of alfalfa and its mixtures. Yields were by 0.7 to 1 ton higher than those following sunflower, sorghum and maize production. Channels and structures of fish ponds are also of good use for irrigation and drainage of rice fields. Dams of rice fields are constructed along the contour lines after sowing, so that level differences will not exceed ± 5 cm within one sector.
The sectors of the rice field within the fish ponds should be situated in such a way that inundation and drainage are possible through one another.
In this phase we achieved yields 50-100 percent higher than the average yields of our country. The highest yield was achieved in a 16 ha fish pond. After three years of rice production, the dams of the rice fields are levelled and fish-cum-duck production starts again.
3. CONCLUSION
Fish ponds utilized for AR assure higher income than those utilized for fish farming alone, producing a variety of products at the same time. The production structure of AR is more adaptable to changing demands of the market. In comparison with fish farming, production of commodities takes a shorter time (duck meat produced in 46 days; fodder production 3-4 times a year). Consequently, incomes are more balanced during the year.
AR is a successful method of utilizing soils of poor quality. Besides improving the quality of the soil, high yields are achieved by AR.
AR may be introduced not only to areas of sodic soils in Hungary, but also to those countries with climates favourable for fish farming and rice production.
4. REFERENCES
Dyke, J.M. and E. Green, Jr. 1974, Interrelations of agriculture and aquaculture in multicropping rice and fish. Il Riso, 13(4):365-71
Fábry, I.,1975, A szarvasi vizes forgóban kezelt halastavak talajainak kémiai vizsgálata (Chemical analyses of pond soils treated with aquacultural rotation in the Fish Culture Research Institute). In Halhustermelés fejlesztése, edited by Fish Culture Research Institute. Szarvas, Hungary, Fish Culture Research Institute, vol. 3:1-35
Müller, F.,1975, A szikes talajok hasznositásának gazdaságossága vizes forgóval (Economics of utilization of alkali soils by aquacultural rotation). In Halhustermelés fejlesztése, edited by Fish Culture Research Institute. Szarvas, Hungary, Fish Culture Research Institute, vol. 1:1-19
Ribianszky, M., 1967, A halastó talajának müvelése (Agricultural cultivation of soils of fish-ponds). Halászat, 3(5):162-3(5):162-3
Tevjasova, L.E., 1975, Agrobiologicseszkaja meliorácija i ee vlijanie na fiziko-himicseszkie szvojsztva gruntov rübovodnüh vodoemov (Agrobiologic melioration and its influence on the physical and chemical properties of soils of fishponds). Rybn. Khoz., Mosk., (7):14-7
