Detailed Explanation of Key Technical Points for Earthworm Farming in Greenhouses
With the development of the farming of famous and special aquatic products such as rice field eel and spiny frog (stone frog), the use of earthworms as bait and fresh feed is increasing day by day, and the area of supporting earthworm farming at breeding farms is continuously expanding. However, because some farms have not mastered earthworm farming techniques well, their farming results are not ideal. Especially under conditions without shade-providing greenhouses and with improper management, the number of earthworms often drops sharply, making it impossible to guarantee the needs of famous and special aquatic product farming. The relevant greenhouse earthworm farming techniques are summarized below for reference in farming in various places.
Biological Characteristics
① Living habits. The temperature for normal activity of earthworms is 5°C-35°C, the suitable temperature for growth is 18°C-25°C, the suitable moisture content of the worm bed base material is 30%-50%, and the suitable pH value is 6-8. "Taiping No. 2", introduced from Japan in the late 1970s, also belongs to this variety. It generally has a body length of 50-90 mm, a body width of 3-5 mm, and an adult earthworm weight of 0.45-1.12 grams. Its body color is purplish red, but the shade of body color also varies with feed, moisture, and light. This type of earthworm grows and develops quickly, has a high reproduction rate, is easy to raise at high density, and has the advantage of high yield per unit area, making it the preferred variety for artificial farming. ② Earthworm reproduction. Earthworms are hermaphroditic, but they must mate with another individual to reproduce. Sexually mature earthworms (that is, those with a clitellum) each lay eggs one week after mating, but the egg-laying frequency is greatly related to humidity, temperature, and so on. When the temperature is 18°C-25°C, the humidity is 30%-50%, and ventilation is good, they generally lay one egg every 3-5 days; when the temperature is higher than 35°C or lower than 13°C, the number of eggs laid decreases significantly. The suitable temperature for cocoon hatching is 18°C-25°C. At this time, the hatching time is short, about 20 days, and the hatching rate is high. Each cocoon generally contains 2-4 young earthworms, as few as 1, and as many as 5-6. Newly hatched young earthworms are thin and white like threads, and after 40-50 days of rearing and growth they reach sexual maturity. The peak reproduction period of earthworms is about 8 months, and after 1-1.5 years they begin to age and die.
Construction of Earthworm Farm
The site for an earthworm farm should preferably be chosen in a place with abundant livestock and poultry manure, convenient drainage, and a water source. For small-scale rearing, some idle sites can be fully used. When the farming area is large, water pipes or automatic sprinklers need to be installed. In addition, 1-2 manure storage tanks, a water storage tank (or deep well), and a manure piling site need to be built. The greenhouse for earthworm farming is similar to a vegetable greenhouse. The greenhouse width is generally 5 m, the greenhouse length is 30-60 m, and the central walkway is about 0.7 m. If a dump truck is used to deliver material, the width is 1 m. The walkway is filled to a height of about 0.3 m, and the two worm beds on both sides are 2 m wide. Ditches are dug on the outer sides of the two worm beds to facilitate drainage.
Fermentation of Manure Material
Cow manure is piled for 5-10 days for fermentation, during which it is turned and mixed evenly 1-2 times before use. The moisture content is required to be 30%-40%. Pig manure needs to be evenly mixed with 5%-10% (wet weight) chopped rice straw (or other grass material), then piled into a pile about 1 m high for fermentation (moisture content same as cow manure). Be careful to prevent the pile from being too compact. After 7-10 days, turn the pile and continue fermentation. Generally, after 2-3 turnings, the pig manure can be fermented and decomposed, becoming loose in texture. At this point, it can be used as manure material for raising earthworms. The quality of manure fermentation is directly related to the yield level of earthworm rearing, so this work must be taken seriously.
Stocking Earthworms
After the worm bed is prepared, put the fermented pig and cow manure into the worm bed. The pile height is about 20 cm. Leave 20 cm of space on the side near the central walkway for stocking earthworm seed. Before stocking earthworm seed, first moisten the worm bed, then place the earthworm seed with manure on its side next to the pig and cow manure in the worm bed. There is no fixed requirement for the stocking of earthworm seed. However, do not stock earthworm seed after filling the worm bed with pig and cow manure, so as to avoid losses of earthworm seed.
Feeding and Management
① Adding material in a timely manner. Adding material in a timely manner means that when 20%-30% of the feed remains in the worm bed, decomposed manure material should be added promptly after harvesting earthworms. The main methods of adding manure material are the side-adding method and the strip-adding method on top. In the high-temperature summer season, pig manure can be fermented by adding water in the manure storage tank to form a paste, then directly poured in strip form onto the manure material in the worm bed. If material is not added and water is not sprinkled for a long time, the earthworm body will shrink, and the earthworms will be unable to survive and will die by autolysis.
② Maintaining moisture and ventilation. In high-temperature summer weather, try to sprinkle water once every afternoon. Where conditions permit, deep well water or low-temperature water is best, combined with covering with rice straw to maintain moisture. In spring and autumn, sprinkle water once every 3-5 days. In winter, it depends on the specific situation. When sprinkling water, make it even and fine, and the impact force of the water should be small. In addition, in the high-temperature summer season, open the film around the greenhouse to facilitate ventilation, air exchange, and cooling.
③ Loosening the manure material. In addition to loosening the manure material when harvesting earthworms, the manure material also needs to be checked for caking, and the soil should be loosened once a month. When using an iron rake to loosen the soil, the movements should be gentle, and try to avoid turning the cocoons in the surface layer into the bottom of the manure material, so as not to affect the hatching rate of the cocoons.
④ Summer cooling. In the high-temperature summer weather of July-August each year, some cooling measures should be taken, and every effort should be made to lower the temperature of the manure material in the worm bed to within 30°C, so as to facilitate the normal growth and reproduction of earthworms. The measures taken are: first, building a shade canopy, using blue plastic film in summer and then covering it with a straw-woven curtain or shade net; second, covering the worm bed in the greenhouse with a layer of rice straw; third, watering every afternoon to cool down, and absolutely do not use rice field water that has been heated very hot by the sun.
⑤ Winter insulation. Before winter arrives, do a good job of sealing the greenhouse for warmth. Cover the worm bed in the greenhouse with rice straw. Where conditions permit, cover the straw with a layer of film as well. Strive to keep the minimum temperature of the manure material above 10°C-15°C, so as to facilitate the normal growth and reproduction of earthworms.
Prevention and Control of Natural Enemies
After several years of earthworm rearing, it has been found that earthworms have few diseases. The main issue is preventing and controlling certain natural enemies. For example, mole crickets are quite harmful to earthworms. They first eat cocoons, then eat small earthworms. When loosening soil and harvesting earthworms, once they are found, they should be killed promptly. In autumn and winter, some birds, having nothing to eat in the wild, often come to eat cocoons. In addition, rats, snakes, ants, and others are also natural enemies of earthworms.
Earthworm Harvesting
Reasonably arrange earthworm harvesting according to the rearing density and production needs. In principle, catch the large ones and keep the small ones. The main harvesting method is to use a specially made small iron rake with flat spikes to shovel out and loosen the manure material in the worm bed, then pick out by hand the manure material containing more earthworms and pile it on plastic film. Because earthworms fear light, after 15-20 minutes the earthworms gradually move downward until they reach the plastic film. Then gradually scrape off the surface layer of manure material and put it back into the worm bed. What remains at the end is clean earthworms. This method is relatively simple and practical.