AN ECONOMIC APPRAISAL OF “BAMBOO PLOT-FISH” FARMING

Minh Kwan-houng

Asian-Pacific Regional Research & Training Centre
for Integrated Fish Farming, Wuxi, China

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AN ECONOMIC APPRAISAL OF “BAMBOO PLOT-FISH” FARMING

Minh Kwan-houng

ABSTRACT

Fish farming in China is characterized by integration. There are many systems of integration with fish culture to make a maximum utilization of wastes for the production of protein-rich food. “Bamboo Plot-Fish Pond” is another example of fish farming long practised. The farmers, in Pearl River Delta particularly, have gained age-old experiences and found that the economic returns are high and the inputs low. The bamboo shoots are sold to the market as food. Processing the bamboo shoots into canned food provides 25–30% by-products which can be utilized as food or pond manure. The space between rows of the bamboo shoots can be used for cabbage production which can satisfy the food needs of 85–90% of the fish at a production rate of 250 kg/mu.

INTRODUCTION

Use of bamboo shoots as human food has a long history in most parts of the world. People in the Pearl River Delta in Guangdong Province carry out bamboo production from backyard scale to large scale production which is economically managed and integrated with fish farming which is called “Bamboo Plot-Fish Pond”. The old Chinese saying that “fish farming with bamboo production benefits a lot” indicates the benefits from this historic practice.

Bamboo shoots are rich in nutritional value and contain about 18 amino acids. The vitamin and trace elements in bamboo shoots cannot be substituted by the other vegetable plants. For comparison, Table 1. shows the nutritional values of bamboo shoots and some other vegetables.

Table 1. The nutritional aspects of bamboo shoots, carrot and lettuce.

Bamboo production techniques in “Bamboo Plot-Fish Pond” system

1. Cultivation

Normally, three methods, plant division, sowing and nursing, are adopted in the cultivation of bamboo.

Plant division : The perennial roots of strong adult plants are dug out to remove the weak stems that appear on the ground. The roots with new buds are used for replanting. Before planting, the land should be well-tilled with a sufficient quantity of basal manure. This method helps early production and less mutations. The bamboo buds are planted at a density of 2,250–3,000 plants/ha. Low densities are preferred to ensure of good ventilation and sunlight penetration. The experience Zhangchuo Town in the Guangdong Province of China is that because of the small size of plots, good moisture, high humidity and easy operation of pond, use of mud as fertilizers for the plot, the yield is normally 25–30% higher than the bamboo shoots that are planted densely.

Sowing : This method is seldom used because it requires a large amount of seeds the supply of which solely depends on costly importation.

Nursing : The cuticle of the seeds contain a thick wax which is not easy to absorb the water for swelling. 100 g of chemicals (50% Duojunlin) and 25 kg of water are used to immerse 10 kg of seeds for 3 weeks. When 10% of seeds start sprouting sowing is conducted. After 20–40 days of sowing sprouting is complete.

2. Management

The plant is still young when. Its small size and limited covering area facilitates the growth of weeds but if the space between plants and corner plots are used for short maturing plants such as legumes, carrot, cabbage and fodder grass to be harvested before October, the land utilization becomes higher. The bamboo shoot needs small quantity of water. The plants are watered every 10 days. If possible, pond mud is used as a supplementation of both water and fertilizers. Zhangchuo Town obtains pond mud 4–5 times a year for use in bamboo shoot plots. This is the main source of fertilizer. It is estimated that a fish pond of one mu* with 500 kg of fish yield, can accumulate 10–20 cm thick pond mud annually due to the large application of feeds and manures, which amounts to 100–190 metric tons/mu. The fertility is varied with the type of manure and feeds. Table 2 shows the fertility of pond mud. Based on the minimum limit, half of the 100 tons of pond mud available is used.

1 mu = 1/15 ha

Table 2. Pond mud fertility.

One-half is for fertilizing the pond water and the other 50 tons are dried into a 25-ton, mass which contains the equivalent of 50 kg N, 45 kg P, and 250 kg K. The normal NPK refinement of one mu of bamboo shoots for a production of 400 kg/mu is 11.2 kg N,. 7.25 kg P and 10 kg K. Part of the pond mud applied into the bamboo plot can well supply the needs of plant fertilizers. But due to the complexity of pond mud, the N. P. K. cannot be completely utilized by the plants, some are volatilized, some need further decomposition by micro-organisms. However, the removal of the excessive pond mud can effectively prevent the outbreak of fish diseases and oxygen depletion.

3. Collection

The bamboo shoots can be collected in 3 years. Highest production is achieved in 3–5 years. The maximum production is 1500–1750 kg/mu. The season for shoot collection is from late June to late September. The bamboos should be cultivated and manured if possible after each collection to facilitate growth of new shoots. At the end of each year, one strong stem is kept which serves as the main plant for shoot production in for years while a 2-year old stem is cut off. In one plant, there are only two stems as “father and son”, which are allowed to grow together. Having 3 generations is strictly avoided to maintain a higher production and quality of shoots. Zhangchuo Town employed this method for hundreds of years and maintains a high production.

The bamboo shoots should be collected at the proper time to avoid loss of nutrients. A difference of 5–10 days in collection gives a strikingly different nutritional values (Table 3). Protein is one of the important indicators in appraising the food value. Since sprouting out of the ground, protein content decreases from 2.5–2.1% every five days. It decreases further with the passage of days. Tyrosine at five days is 3.51% but increases to 4.8% at 10 days. In canning the shoots, the tyrosine becomes milky white in colloidal form to be settled, which affects the preference of the consumer. Lysine, at 5 days is 0.68% but decreases to 0.53% in 10 days.

The drastic reduction is in Methionine, from 0.35%–0.29%. In any type of food, a deficiency in these two kinds of amino acids will seriously affect the absorbtion of other amino acids. Table 3 shows that the crude fibre is greatly increased. P and Ca, as an example are reduced by 25% and 43.8%, respectively, from 5 to 10 days. Therefore, the shoots should be collected in time, not too late but not too early either as the nutrients are not yet complete. The collected shoots should not be piled up for long periods. The ripe shoots lose the water content very quickly, 5–6 hours after the collection. This will certainly reduce the edible part.

Table 3. Nutrient changes at 5 and 10 days old after the sprouting.

4. Processing and Utilization

The bamboo shoots are placed in air-tight cans filled with water. When they are collected, it is not necessary to peel off the old husks. The collected bamboo shoots are immediately transported to the processing factories and boiled for 20–30 minutes before instant cooling by immersing in the cold water. When taking off the husks of the shoots, a bamboo knife is preferred with careful handling as the top head of the shoots may break. Grading is important in canning the bamboo shoots which are placed in water for 1–3 days with the water changed three times. Exhaustion and sealing are necessary before steaming or immersing in the boiling water for 9–10 minutes.

The by-products of bamboo shoot processing serve as food for fish. Experience in the Zhangchuo Town Processing Plant shows that in the processing, 25–30% comes as waste which can be consumed by fish and served as compost materials. Aspartic acid which imparts pleasant flavour exists largely in the bamboo shoots which are good for both fish and animals. The waste water in processing is a nutrient for primary producers in the ponds.

At the production rate of 360–400 kg/mu, 12–13 kg of fish can be produced using the by-products. Production in the Zhangchuo Town is higher, 49–57 kg of fresh fish, with herbivores as dominant species in the fish production.

Fish Stocking in “Bamboo Plot-Fish Pond”

As stated above, the by-products from bamboo shoot processing can produce a good quantity of herbivores fish. But the detritus and spilled parts are completely consumed by the filter feeders and omnivores. The spaces between the plots of bamboo shoots are used for fish feed production, particularly, in one or two years at the beginning of cultivation. The total area between the rows is almost 50% of the total area and can be used for growing cabbage 3–4 times a year. Production is as much as 8,000 – 12,000 kg per mu which enables a production of 130–195 kg of fresh fish. With additional amount of shoot husks, a production of 220 kg of fish can be achieved. If 15–20 kg of barley or wheat bran is used as a supplementation of commercial food, a yield of 250 kg/mu of fish can be obtained. Table 4 shows the stocking practice.

Table 4. Stocking practice with herbivorous fish as the main species at the rate of 250 kg as final production in “Bamboo plot-fish pond” systems.

GC. WF. SC. BH. CC. CrC refer to grass carp Wuchang fish (Blunt snout) silver carp, bighead carp, common carp and crucian carp.

“Bamboo Plot-Fish Pond” system provides a very limited quantity of by-products for fish farming and Zhangchuo Town also raises pigs to supplement the food production even though there is a large area of bamboo plots. The farmed species are mainly filtering fish. Table 5 shows the stocking practices with filtering fish as the main species.

Table 5. Stocking practice with manure-fed fish as the main species at the rate of 200 kg as final fish production in “Bamboo Plot-Fish Pond” system.

From Table 5, the by-products from bamboo shoot processing in Zhangchuo Town is almost sufficient to meet the needs of herbivorous fish. To achieve the normal amount of fish production, 6300 kg of manure is additionally needed.

Economic appraisal of “Bamboo Plot-Fish Pond”

Bamboo shoots can be sold fresh but are mainly processed into preserved form for export. Some countries earn a lot of foreign exchange by the export of bamboo shoots. It is reported that Thailand earned $80 million worth of bamboo shoots, in both fresh and preserved forms, in 1984. In Taiwan Province, export of bamboo shoots was $25 million in 1977, in 1982 the value was doubled to $50 million. In China, the annual production of bamboo shoots reaches about one million tons, some are used for domestic consumption but a major part is sold in the international market. The actual performance of Zhangchuo Town practice shows one mu can give a production at ¥ 3,000 ($100 = ¥372 Aug. 1988) and a net profit of ¥ 2,000; fish production at the same time can be as high as 1,000 kg/mu. If a private sector or a family manages one pond (3–5 mu) and one bamboo plot (2–3 mu), the income is even higher.

When the bamboo shoots, are harvested 3,500–4,500 kg of bamboo sticks and dried branches are also collected which can either serve as firewood or as a raw material for paper making or as building materials for simple types of livestock pens.

In China, with long years of practice from which the farmers have accumulated rich experience, the farmers, from Pearl River Delta in particular have developed various forms of such production systems such as “Mulberry Plot-Fish Pond”, “Sugarcane Plot-Fish Pond” and “Bamboo Plot-Fish Pond”. Many specialists have worked hard on the economic aspects of the “Mulberry Plot-Fish Pond” and found that it is profitable and beneficial to the farmers. But there is a large demand of man-days which is considered to be the main input for its production. Ma Shi-Jun (1987) reported that “Mulberry plot-Fish Pond” (4:6) demands about 72 man-days per mu annually, but 75% of the labour is for mulberry production which consumes about 54 man-days. In comparison, even if the “Bamboo Plot-Fish Pond” demands the same number of work days, the mulberry leaves from “Mulberry Plot-Fish Pond” cannot be accepted in the market which should go to sericulture. Hu Baotong (1983) reported that 50 kg of mulberry leaves can produce 4 kg of cocoon and as the per mu production of mulberry leaves is about 2,500 kg it enables production of 200 kg of cocoon. It has also been reported that one man-day is just able to produce 1.7 kg of cocoons and the total amount of the cocoons from one mu of mulberry plot demands 118 man-days. Therefore, if an able-bodied man assures 300 man-days for annual production, he can at the most manage only 2 mu of mulberry plots. In contrast, the bamboo shoots from “Bamboo Plot-Fish Pond” can be immediately accepted in the market. Based on 54 man-days for the plot cultivation each able-bodied man can manage 3–4 mu of bamboo plots, which accords with the actual practice of Zhangchuo Town farmers.

ACKNOWLEDGEMENT

I wish to express my thanks to NACA and NACA Coordinator, Mr. Chen Foo Yan, IDRC and to Dr. P.V. Flores who worked with IDRC before becoming President of Silliman University in the Philippines, for their encouragement and support of this study. I am grateful to Prof. Hu Baotong and Prof. Guo Xianzhen for their valuable suggestions on this report.