Chapter 9 ANIMAL RAISING AND PLANT CULTIVATION ON AN INTEGRATED FISH FARM (Contd.)

Plant Cultivation

Proper fertilizers and feeds are essential for high fish yields. Fertilizers are used primarily to propagate natural organisms as fish feed. Various forage grasses, beans, grains, melons, vegetables, and aquatic plants are also good fish foods. Crop production on an integrated fish farm uses the pond dikes, river banks, corner areas, and forage field. The cultivation of grains, beans, pasture grasses, melons and vegetables, and fruit and mulberries should be rationally practiced according to the needs of the fish and the growing seasons of the different crops. Furthermore, the water surface at the edges of the rivers and lakes in the vicinity of the fish farm can be utilized to cultivate aquatic plants; this ensures the availability of high-quality forage throughout the year. This forage and silage can be used not only for rearing fish but also for raising domestic fowl and animals or to fertilize the water for plankton growth.

Pasture Grasses

Perennial ryegrass

Perennial ryegrass (Lolium perenne) belongs to the Gramineae family. It grows rapidly, has a high yield, is nutritionally rich, easy to cultivate, inexpensive, and very adaptable. Ryegrass may yield 5–10 t/mu per year and is a good food for grass carp, chinese bream, and wuchang fish. The cultivation of ryegrass provides a fresh fish food in the early spring, enabling the fish to break their fast early in the year.

Seeding and transplanting — Ryegrass is a late-season plant that can grow in the shade and prefers moist conditions. Seeding is usually performed at the end of September. The land should be prepared by applying 1000–1250 kg/mu of night soil or a layer of silt as the base manure, turning the soil by deep tilling, and pulverizing and smoothing the soil. The amount of seed for broadcast sowing is 2–2.5 kg/ mu. If the weather is dry after sowing, the plot should be watered until the complete emergence of the seedlings. After seedling emergence, another dressing of night soil (same amount as the first application) should be spread over the soil. When seedlings reach a height of 12–15 cm, they are transplanted to a field that has already been tilled and covered with a layer of pond silt as the base fertilizer. Transplanting usually occurs at the end of October or in early November. The leaves of the seedlings should be cut in half to ensure quick establishment and the seedling should be spaced at 18 × 18 cm or 21 × 21 cm, with six or seven seedlings per bunch. After transplanting, a 1:3 dilution of night soil is applied.

Field management — To enhance the growth of the transplants, all weeds must be removed. Weeding should be done before, during and after transplanting. Seedling plots and transplant fields should be kept moist and must be watered during a prolonged period of dry weather. One application of nitrogenous fertilizer is usually given before initial cropping. Organing manure should subsequently be applied at a rate of 250–300 kg/mu after every harvest. Results are better if the soil is loosened before fertilizer application. Some inorganic fertilizers can also be used.

Harvesting — At the height of 30–60 cm, the ryegrass should be cut near the ground. At this stage, the grass is tender and all of it will be consumed by the fish, thus, the utilization rate of the feed is high. In addition, ryegrass grows fast and has a high tillering activity after cutting. In general, when the air temperature is low from October to February, the growth of ryegrass is retarded and only one or two cuttings can be done. From March to May, harvesting can be made approximately once every 20 days. The second and third cuttings must be close to the ground, leaving 2–3 cm “stubbles”. This increases tillering, yield, and promotes quality.

Production of seeds — Ryegrass begins to shoot, bear ears, and flower in April; seeds can be collected in early June. Seeds do not ripen at the same time and will fall to the ground easily; therefore, when the ears turn yellow, seeds should be collected. The seed yield is about 50 kg/mu. Plots reserved for seed production should not be cropped as green fodder.

Sudan grass

Sudan grass (Sorghum sudanese) is an annual plant of the Gramineae family. It thrives in soils of different fertilities, preferring fertile, clayey soils. Sudan grass yields about 10 t/mu, withstands dryness and soil fertility, shows rapid regeneration, high reproductivity, strong adaptability, and superior quality. It is easy to cultivate, a high-yielding crop in the summer and the autumn and therefore suitable for integrated cultivation with ryegrass to provide high-quality fresh food (Table 9.11) to grass carp, Chinese bream, and Wuchang fish from spring through autumn.

Table 9.11. Utilization by fish of Sudan grass at different development stages.

Seeding and transplanting — Sudan grass prefers a damp environment and is vulnerable to frost. Seeding is usually done when the soil temperature is above 10°C. The optimum temperature range for germination is 20–30°C. Strip drilling is suitable for Sudan grass, which is primarily cut for green fodder. The row spacing is 20–30 cm, the depth of seeding is 3–4 cm and the seeded plot should be mulched with a 1-cm layer of plant ash. For dense drilling, about 2 kg seeds/mu is used. Dibbling (nursery seeding) can also be practised. Plant spacing in the nursery is 18 cm and each bunch takes about 10 seeds. When seedlings are 12 cm high, they are ready for transplanting. Before tilling and sowing, a layer of pond silt is applied to the field as base fertilizer and the soil is turned, levelled, and smoothed. When transplanting, plants are spaced at about 18 × 18 cm with four or five seedlings per bunch.

Field management — Seedling emergence is completed 7–8 days after seeding, budding takes place in 70–80 days, and flowering occurs in 80–90 days. The growth period is 100–120 days. Weeding should be done regularly. In prolonged dry weather, the plot should be watered, especially during the seedling period. The soil should be loosened and fertilized after every cutting. The method of dressing and the amount of fertilizer are the same as for rye grass.

Harvesting — When Sudan grass grows to a height of 60 cm, harvesting is feasible. The remaining stubble should be about 10 cm high, otherwise, tillering, regeneration, and yield will be adversely affected. From mid-May to August, harvesting can be done about every 15 days. The growth of Sudan grass slows around September and death occurs with the firsts frost.

Bunch grass

Bunch grass (Symphytum peregroimum) is a perennial plant belonging to the Borraginaceae family and originated in the Iran-Transcaucasia region. It is usually planted in early spring and yields 7–9 t/mu in its 1st year, 10–12 t/mu in its 2nd year, and may reach 15 t/mu. The stems and leaves of this grass are tender, juicy, and nutritious, with a high protein content. On a dry-matter basis, it contains 22–25 per cent crude protein, 4–6 per cent crude fat, 7–13 per cent crude fibre, and 38–40 per cent non-nitrogenous extracts. Therefore, it is an excellent green fodder (Table 9.12).

Table 9.12. Nutritional analysis of dry and fresh bunch grass.

Bunch grass has a well-developed root system with vigorous growth, and is adaptable to environmental conditions. It is susceptible to few pests, easy to grow and propagate, and has a high survival rate. The underground portion of bunch grass can withstand temperatures ranging from -40 to 37.8°C. It is also resistant to drought and disease.

Seedling cultivation and setting — Both aboveground (leaves, pedicles, and rhizome buds) and belowground organs (rhizomes and roots) of bunch grass can be used for seedling culture and propagation. Propagation methods include sucker division, root cutting, longitudinal cutting of root necks, setting buds divided from root, and setting of stalk cuttings. Nursery bed breeding lasts 30–40 days. When the seedlings reach a height of 10–15 cm, they can be transplanted at a spacing of 45 × 45 cm with 2500–2600 plants/mu. In poor soils, the plant density should be increased to about 3000 plants/mu. For dibbling, the plant should be buried up to the neck of the root and thoroughly watered. Bunch grass is tolerant of a wide range of soil conditions, but a thick layer of sandy soil with good drainage is considered to be the most suitable. Plants can be cultivated on spare land around a pigsty or on pond dike slopes. The land should be deeply tilled, well fertilized, harrowed, smoothed, and leveled before setting the plants. In plots with poor drainage, a system of broad, grooved ridges that cross each other must be established so that any excess water will drain away.

Field management — The bunch grass plot should be fertilized once before the grass turns green in the early spring. Roughly 2500 kg/mu of pig manure should be applied. For new seedlings, the soil must be loosened and weeded. After seedling establishment, a second layer of fertilizer will invigorate the settings and promote root development. The soil should be fertilized after each harvest and before over-wintering; this final application will ensure that hardy-plants survive the cold months. When the weather is dry and hot, the plot should be watered; in the rainy season, proper drainage is crucial (water logging will cause root rot). Bunch grass is very pest resistant; however, cutworms usually attack seedlings and control measures should be practiced.

Harvesting — When bunch grass begins to bud and flower in early May, harvesting can start. The remaining stubble should be about 6 cm. Harvesting is done at about 35-days intervals, giving five or six cuttings every year. The proper time for harvesting depends on the amount and colour of the foliage. In general, one planting will last 8–10 years. When autumn arrives, the grass will no longer bud or flower, and usually, cropping stops in late October to retain the year's final coat of leaves for overwintering. Bunch grass is resistant to cold but vulnerable to frost. The roots however can survive temperatures as low as -40°C. To make full use of the land, other fodder crops can be intercropped after autumn.

Beans

Soybean

Soybean (Glycine max) is an annual plant belonging to the Leguminousae family (subfamily Papilinaceae) and is a native plant of China. The yield of soybean is generally 80–130 kg/mu and the soybean seed contains 30–40 per cent protein, 20–24 per cent fat, about 30 per cent carbohydrate, and several kind of minerals and vitamins, giving it a high nutritive value. When ground, it makes an excellent fish food.

From seeding to maturity, soybean passes through various growth stages (e.g., germination — seedling stage, third true-leaf stage); the entire growing period is 120–140 days. The time from germination to blossoming varies with variety: early ripening varieties, 34–43 days; intermediate varieties, 40–60 days; late varieties, 50–60 days; very late varieties, 63–84 days. Soybean is tolerant of a wide range of soil conditions, but soils that are thick and rich in calcium and humus with good drainage are more suitable. Soils with a pH ranging from 5 to 8 are preferred; soybean will not grow in soils with a pH value above 9.6 or below 3.9.

Seeding — When the soybean seed absorbs water (100–150 per cent of its own dry weight), and if air temperature is 10–20°C and there is sufficicent oxygen, germination will occur. With a sufficiently moist soil, the seed will absorb enough water to germinate 1 day. Seedlings grow rapidly when the air temperature averages 20–25°C in the day and, at the least, 15–17°C at night. Seeding time for spring and summer soybeans is from late March to early April and from 1 to 20 June, respectively; 6–7.5 kg/mu of seeds is required. Seeds should be selected by winnowing and screening. The cotyledon emergence of the soybean is relatively difficult; therefore, the soil must be loose. In addition, the germination of soybean requires ample moisture; therefore, the soil should be turned and smoothed to preserve soil moisture and fertilizer. Dibbling is the common method of seeding. Plants are spaced at 15 × 18 cm or 18 × 18 cm, there are 15000 to 20000 dibbles/mu, and each dibble has two or three seeds. After seeding, thin mulch of plant ash or fine soil is applied to facilitate emergence.

Field management — For every 50 kg soybean produced, it is necessary to apply 2.8 kg nitrogen, 5 kg phosphoric acid, and 6.5 kg potassium oxide. Initially, when nodules have not yet formed on the root portion of the seedling or the action of the root nodules is weak, growth is slow. To increase soybean production, the appropriate amount of nitrogenous fertilizer and large amounts of phosphorus and potassium must be applied. In addition to base manure, a little seed-mulching manure may also be used, i.e., high-quality fertilizer like decomposed barnyard manure, high-quality compost mixed with plant ash, or superphosphate to mulch the seedlings. Depending on growth conditions, ammounium sulphate should be applied at a rate of 2.5–5 kg/mu during the seedling stage and 7.5–10 kg/mu during the flowering stage. When soybean seedlings have uniformly emerged, they should be examined. Dibbles without seedling must be replanted. To enable seedlings to grow stoutly and evenly, thinning should be performed after a pair of true leaves appears.

After the seedlings are established, weeding and thinning should be continued. From flowering to pod swelling, soybean requires much water. A rational irrigation scheme will appreciably increase production. When the pods are ripening, a complete weeding will improve interplant ventilation and sunlight penetration, quickening the ripening process and ensure a good yield. The prevention of soybean pests such as soybean aphids, pod borers, and bean hawkmoths, as well as the weed, dodder (Cuscuta), is important.

Harvesting — The spring soybean crop reaches maturity in late or mid July; the summer soybean crop, in early or mid-October. Harvesting should be done when two-thirds of the foliage has turned yellow and fallen, when the majority of the stems and pods appear dark brown with the seeds separated from the inner walls of the pods, when the beans are half-dried, quite hard, or when the pods rattle when shaken. The crop should be harvested within one week and thoroughly dried in the sun for a few days. After removing all impurities, the crop can be stored. In the storage area, the moisture level should be below 13.5 per cent; if moisture level is below 12 per cent, the crop can be stored a little longer.

Grains

Barley

Barley is an annual plant belonging to the genus Hordeum of the Gramineae family. Barley yields 200–300 kg/mu and, apart from being a food grain, it is important in brewing beer, producing alcohol, and making maltose and straw is appropriate for weaving straw hats. The growth period of barley is about 190 days. Its lowest germination temperature is 1–2 °C and its optimum temperature for growth is around 20°C. Barley bears ears in early and mid-April with a milk stage of about 10 days normally followed by a waxy ripe stage of 6 or 7 days.

Seeding — Seeding of barley is generally done in late October to mid-November at a rate of 15–18 kg seeds/mu by broadcast or strip drilling. Most of the root system is distributed within 15–18 cm of the cultivated surface layer; therefore, secondary tillage should be done carefully with the “three-ditch” pattern of drainage. Seeding should be shallow and even. For every 50 kg barley production, it is necessary to fertilize the soil with 1.5 kg nitrogen, 0.62 kg phosphorus, and 1.15 kg potassium. A base manure of grass and decomposed pond silt (6000–7500 kg/mu) or pigsty manure (2500–3000 kg/mu) is also applied. For the intermediate soil layer, 15–20 kg/mu ammonium sulphate and 25 kg/mu calcium superphosphate should be used with 3000–4000 kg/mu seed-mulching manure.

Field management — If seeding is followed by dry spell, the total even emergence of seeds should be ensured by applying fertilizer at the first-leaf stage: 500 kg/ mu night soil diluted with 3000–3500 kg/mu water or 10–12.5 kg/mu ammonium sulphate diluted with water. Alternatively, 5000 kg/mu diluted silt mixed with 30– 40 kg/mu dissolved ammonia or 1500 kg/mu pigsty waste followed by a layer of river silt 5000 kg/mu could be applied. Inter-row cultivation may be done two or three times. Cholraluron may be used for weeding in barley fields. In early February, 7.5–10 kg/mu ammonium sulphate, 20 kg/mu diluted ammonia, or 1000 kg/mu night soil should be applied to revive the seedlings. Ditches must be cleared to ensure proper drainage. Toward the end of February, 12.5 kg/mu ammonium sulphate should be applied to promote growth and the bearing of ears. In the late stages of growth, disease prevention and pest control is important. Spray 90 per cent trichlorfon (1:1000 dilution) to control army worms, 40 per cent dimethoate emulsion (1:2000 to 1:3000) for aphids, and 0.2–0.3 kg carbendazol diluted with 75–100 kg water for red mold and powdery mildew.

Harvesting — Barley ripens in late or mid-May. Harvesting should be performed at the waxy ripe stage.

Corn

Corn (Zea mays) is an annual plant of the Gramineae family. It is a good fodder with a high nutritional value, and has a high yield, 250–300 kg/mu. Its grain contains 8.5 per cent protein, 4.3 per cent fat, and 73 per cent carbohydrate. Therefore, 50 kg corn is nutritionally equivalent to 67.5 kg oats, 60 kg sorghum, or 65 kg barley. The nutritional value of the corn stalk is generally more than double that of the stalks or stems of other crops. The fresh stems and leaves harvested after the shooting of the phalanxes or before the waxy ripe stage are green and juicy. Their nutritional value is very high and they are excellent substitutes for fine feeds. The successful cultivation of corn is important in developing livestock farming.

Corn thrives in warm climates (the lowest temperature at which germination occurs is 10–12°C) but requires only a short photoperiod. At the seedling stage, 22.7 per cent of the total water requirement is needed; at the middle stage, 44.5 per cent; at the late stage, 32.8 per cent. The soil should be rich in organic matter and well drained; a sandy loam soil is also appropriate. For every 50 kg corn grain production, the crop removes 1.24–1.95 kg nitrogen, 0.68–0.91 kg phosphorus, and 1.96–2.07 kg potassium from the soil. Corn varieties can be classified according to growth period (early, 80–95 days; intermediate, 96–115 days; late, 116–150 days) and sowing season (spring, summer, autumn, and winter corn).

Seeding — Before seeding, seeds must be carefully selected. To achieve full germination and even, vigorous growth, the seed should be prepared by sunning and by immersing and mixing with certain chemicals. Seeds of spring corn can be sown when the soil temperature is above 10°C. To maximize the growth period, seeds should be sown as early as possible. Seeds of summer and autumn corn should be sown as soon as the preceding crop is harvested. Seeding is usually done by drilling or dibbling. The seeding rate for drilling is 2.5–4 kg/mu; for dibbling, 2–3 kg/mu. The seeding depth is 3–5 cm. The seeding density for late varieties is 2000–3000 plants/mu; for intermediate varieties, 2500–4000 plants/mu; for early varieties, 3000–5000 plants/mu. When the corn is to be cultivated for fodder (silage or fresh), the planting density may be 20 per cent more than those given. There are many ways of planting corn. The tilling depth should be 21–24 cm and ample organic manure should be applied before the land is tilled. For ridge cultivation, it is important to ensure sufficient moisture in the top soil. In waterlogged or poorly drained areas, bedding cultivating should be adopted. The base manure is the principal source of nutrition for the corn. Barnyard manure, livestock manure, and compost prepared from decomposed stems and stalks which are rich in nitrogen, phosphorus, and potassium, are the best base fertilizers for corn.

Field management — After seedling emergence, thinning should be done. Weak seedlings should be removed, leaving the strong seedlings and ensuring even growth and vitality. Quick-acting-fertilizers such as night soil, ammonium sulphate, urea, potassium sulphate, and plant ash are applied as a top dressing to promote growth during the following three stages: shooting up of stalks, impregnation of ears, and phalanxing.

Harvesting — After pollination, the corn will be fully ripe in 50–65 days. The higher the air temperature, the faster the corn will ripen. The leaves on the stem turn yellow, the cob wrappers dry up and wither, and the grains appear bright when the corn is fully ripe. At this time harvesting should be done.

Sweet Potato

Sweet potato (Ipomoea batatas) is a trailing plant of the Convovulaceae family that originated in tropical America and the Caribbean. It yields 1500–2000 kg/mu and the tuber contains 20–27 per cent starch, 2.3 per cent protein, 0.2 per cent fat, and multivitamins. Besides being used for human consumption, it is also a fine, high-yielding forage crop. The tubers, vines, and residues from processing can all be used as fodder. Its tender, juicy vines and leaves are a good fresh fodder and the value of sweet potato as a feed is higher than that of ordinary forage grasses. In addition, its vines and leaves can be cut during July and August, yielding 1000– 1500 kg fresh vines that can be used as fresh fish feed. From setting to harvesting, the growth period of sweet potato is 110–160 days. Early tuber-bearing varieties can give a harvest in 80–90 days. The plant is very sensitive to cold weather. Growth stops at 15°C and stored tubers will be damaged at 9°C. It is, however, a relatively drought-resistant crop and will thrive in regions with an annual precipitation of 400 mm.

Seeding and transplanting — In sweet potato production, most farmers use the tuber-vine-cutting method of propagation. The final yield is directly dependent on the time of transplanting (the earlier, the better). Spring cuttings should be set from late April to mid-May; summer cuttings, in June. The density of settings should be determined by climate, soil, amount of fertilizer applied, characteristics of the sweet potato variety, length of the growing season, and method of cultivation. Because sweet potato is a tuber crop, it requires a deep, loose soil layer. Therefore, the land should be ploughed to a depth of 12–15 cm and banked in ridges for setting the cuttings. For every 500 kg production, the vines must absorb 2 kg nitrogen, 0.5 kg phosphorus, and 3.1 kg potassium. The most suitable fertilizer for this crop is a compound, N-P-K fertilizer such as barnyard manure and compost. Manures that have more potassium (e.g., plant ash) will increase the yield.

Field management — When the roots of the sweet potato cuttings are established, missing settings should be replanted. Inter-row cultivation and weeding should be performed as needed. After dressing and spraying with fertilizer, tilling and weeding are necessary. Inter-row cultivation should not damage the root system of the plant. Earth banking is a helpful management technique for sweet potato cultivation. It helps to preserve soil moisture and prevent the tuber from being exposed. It also helps to drain excess water as the grooves or furrows are deepened in the process of ridge banking, which is usually done twice during the growth of the vines.

Harvesting — Harvesting should be done when the temperature begins to drop in the autumn, when leaves near the stock have fallen and others are turning yellow and when the tubers are sufficiently swollen and their water content is reduced. Spring-set crops are harvested from late September to early October; summer-set crops are harvested in late or mid-October.

Cabbage and Melons

Chinese cabbage

Chinese cabbage is a biennial vegetable belonging to the genus Brassica of the Cruciferae family. It is a native plant of China. The nutritional value of Chinese cabbage is very high; the deeper the leaf colour, the higher the nutritional value is. Each 0.5 kg of Chinese cabbage contains 5.5 g protein, 0.5 g fat, 10 g sugar, 2 g crude fibre, 4 g inorganic salt, and vitamins, carotenes, and mineral salts. In general, Chinese cabbage yields 1500–2500 kg/mu. It is a high-quality fresh food for herbivorous fish as well as domestic animals and fowl.

The optimal temperature range for Chinese cabbage growth is 15–20°C. For seed germination, the optimum temperature range is 20–25°C. When the seedlings are young, nutritional requirements are not so much; in the intermediate stage when growth is vigorous, the demand for nutrients increases. Nitrogen is the major required nutrient. The soil should be fertile with good moisture retention.

Seeding and transplanting — For spring seeding, sowing and transplanting are conducted from the beginning of February to the end of May. The seeds of Chinese cabbage are directly sown, usually in early February. For summer seeding, sowing and transplanting are conducted from early June to the end of August. For autumn seeding, cultivation lasts from early September to the end of October. For winter seeding, cultivation lasts from early November to the end of January. Seeding rates depend on seeding time: early spring 3.5–5 kg/mu; spring, 1.5–2.5 kg/mu; summer (Pakchoi, Brassica chinensis), 2.5–3 kg/mu; summer (direct seeding), 0.5– 0.75 kg/mu; autumn (sown and transplanted), 0.75–1.0 kg/mu; winter (nursery bed cultivated), 2.5–3 kg/mu. Chinese cabbage seeds are sown by broadcast. Thinning, weeding, manuring, spraying, and pest control should be done after seedling emergence. Field setting is also known as transplanting. Different cultivation seasons have different requirements for setting. Seedlings for transplantation before August are usually about 25 days old; those transplanted in September, 28–30 days old; those transplanted in October, 32–35 days old; those for transplanting in November, 35–40 days old.

Field management — Field management work includes top dressing, watering, and disease and insect control.

Harvesting — The harvesting period for Chinese cabbage depends on the cultivation method. Yound Pakchoi seedlings directly planted in the summer can be harvested in 20 days; those cultivated in the winter, in 80–90 days; those transplanted from mid-September to the end of the month, in 25–30 days; those transplanted in October, in 40 days; those transplanted from mid-October to early November, in 45 days.

Wild cabbage

Wild cabbage (Brassica aleracea cv. Capitata) is a biennial plant belonging to the Cruciferae family and is a native of southern Europe. The variety commonly cultivated in China is the ordinary cabbage. The yield of this variety is 2000–4000 kg/mu and it is rich in nutrients (having proteins, carbohydrates, mineral salts, and vitamin C). Wild cabbage is suitable for human consumption and is a fine fodder for livestock. Because wild cabbage is biennial, only the edible globular top develops in the 1st year. In the following spring, when the air temperature is still as low as 2–6 °C, flowering buds form and the plant blossoms and bears seeds. Wild cabbage will adapt to cold weather, although the optimum temperature for growth is 14– 20 °C. It grows well in a fertile soil that can effectively retain moisture, has proper drainage, and is easily irrigated. During the formation of the globular top, ample fertilizer and water are required. The nutrient most required by wild cabbage is nitrogen; a considerable amount of phosphorus and potassium is also required. The resistance of wild cabbage to disease is good.

Seeding and transplanting — Cabbage can be planted year round. According to harvesting season and cultivation method, there are three varieties of cabbage: spring, summer, and autumn-winter cabbage.

Field management — Spring cabbage usually requires several applications of top dressing at the end of the year. Night soil is applied in 1:2 dilution at a rate of 1500 kg/mu 1 week after the setting of the seedling. The second dressing should be given before January 19 to enhance sprouting in the early spring. The concentration and application rate are the same as for the first dressing. The third dressing should be applied 1 month later: concentration, 1:1; application rate, 2000 kg/mu. The fourth dressing depends on the stage of growth, i.e., when the spring cabbage is forming its globular top in March to early April. The rate of diluted night soil applied is 1500–2000 kg/mu. This dressing solidifies and accelerates the growth of the globular top. Drainage grooves must be dug in the early spring. From the setting of the plants to the closing of ridges by their foliage, tilling is conducted in combination with weeding three or four times. Summer cabbage (Brassica broccoli) usually requires three fertilizer dressings per month. Each dressing calls for 1500 kg/mu of night soil. The first dressing is given in a 1:3 dilution after the set transplants have been established. The second dressing is applied 10 days later in a 1:1 dilution. Before the formation of the globular top, the third dressing is applied in a 2:1 dilution. Fertilization must be stopped when the globular top begins to form, otherwise rotting may occur. Chemical fertilizers can also be applied throughout growth, e.g., aqueous ammonia (1:100 dilution) four or five times at a rate of 25 kg/mu. The soil is generally loosened two or three times. Autumn cabbage generally gets three or four dressing of 15,000 kg/mu of night soil in different concentrations. The first dressing is given in a 1:3 dilution, 3–4 days after the transplants have been established. After 2 weeks, the second dressing is given in 1:1 dilution 2 weeks later. The third dressing is applied in a 2:1 dilution before the formation of the globular top. Cabbage for overwintering should be fertilized lightly in the second and third dressings. In the middle of November, to aid in the formation of the globular top, a dressing of night soil (2:1 dilution) is applied at a rate of 2000 kg/mu.

Harvesting — Spring-grown cabbage are harvested in batches from mid-April to early June, depending on variety. The yield is 2000–5000 kg/mu. The summer varieties are sown in early March and harvested in July or August with yields of 1500–3000 kg/mu. Those seeds sown in early May are gathered in August or September with a yield of 1500–2000 kg/mu. Seeds sowed in early June are collected in September or October with a yield of about 23000 kg/mu.

Squash

Squash (Cucurbita maschata, C. maxima, and C. Melopepo) is an annual plant belonging to the Cucurbitaceae family and is native of the tropics. It is a high-yielding, juicy fodder rich in nutrients, containing a lot of carotene, vitamin C, and glucose. Its stems and leaves can be processed into stalk sugar fodder after drying. Yield generally ranges from 1000–2000 kg/mu. The optimum temperature for the germination of squash seeds is 25–30°C; the most suitable temperature for the development of the fruit is 25–27°C. It requires only a short photoperiod and thrives in dry, hot environment with a soil moisture of about 50 per cent. A fertile, neutral, or slightly acid sandy loam soil is preferable.

Seeding and transplanting — The nursery bed seeding period usually falls between mid-March and early April. Two kinds of seeding are practiced; bunch planting and “broadcast” sowing. In bunch planting, the size of the planting holes is usually 7.5–9 cm² and 9–12 cm deep. Each hole takes an average of two or three seeds. The plot is then evenly mulched with a layer of nutritive fine soil, to ensure that the seeds are not exposed to the air. A thin covering of straw should be placed over the bed to serve as shading and to preserve moisture. Alternatively, a few short bamboo sticks should be used to support a plastic sheet that would act as a cover. Finally, mud is used to seal the edges of the covering. At night, straw mats are used as blankets to prevent the loss of heat and accelerate germination. The other method, “broadcast” sowing, is also known as two-stage breeding. Over the surface of a dressed bed, a layer of plant ash is spread. Seeds are then evenly cast. A fine-nozzle sprayer should then be used to sprinkle fine droplets of water over the plot. The seeds are then mulched with a 2 cm layer of nutritive soil. Finally, a layer of straw or a plastic sheet is spread over the bed and the nursery bed is sealed. At night, straw mats are used as blankets to preserve heat to enhance germination. It is also necessary to maintain proper ventilation, sufficient sunlight, and to control pests in the nursery. When squash seedlings have grown to a height of 9–12 cm with two or three true leaves, they can be transplanted. Seedlings are usually set in late April and are intercropped with other vegetable crops.

Field management — After transplantation, missing transplants must be identified and seedlings reset, holes must be dug to properly orient the plant, vines must be hilled as necessary, and diseases and pests controlled.

Harvesting — Early set squash can be collected 10–15 days after the pistillate flowers have withered. Harvesting in batches at regular intervals begins at the end of July and mass harvesting occurs in early and mid-August.

Aquatic Plants

Water peanut

The water peanut (Alternanthera philoxeroides) is a perennial plant native to Latin America and introduced into China more than 30 years ago. This plant is a high-yielding, easily cultivated aquatic crop that overwinters easily and is very adaptable. The surface of lakes, river bends, ditches, and ponds can all be used for float cultivation. The annual yield of fresh grass can reach 15–25 t/mu, enough to provide 10–15 pigs with silage all year. The stalks and leaves of water peanut contain 2.49 per cent non-nitrogenous extracts, 2.18 per cent crude protein, 0.18 per cent crude fat, 1.19 per cent crude fibre, 1.25 per cent ash content, 0.23 per cent calcium, and 0.03 per cent phosphorus. It can be served either fresh or cooked, and also can be prepared as fermented fodder or dried and ground as fodder for use throughout the year.

Water peanut prefers a warm, humid climate with a long photoperiod. They can grow in a wide range of water depth and grow well in rivers, ditches, and ponds that have slow running or stagnant, fertile water at a depth of 1–1.5 m. Water peanut reproduces asexually through their stalks and vines. As seedlings can germinate and grow on each node, they propagate very fast.

Time for breeding and propagation — The growth and reproduction of water peanut is very fast. Except in mid-summer when it is too hot and in winter when it is bitter cold, the rest of the year is appropriate for cutting, transferring and propagating the stalks. However, if it is to be introduced from another region to a locality for cultivation, the best time is early April when the old stalks are just beginning to germinate. Upon arrival in a locality the introduced cuttings should be placed on the water surface where they are to be propagated within one or two days to promote their early germination. Shelter the cuttings from wind and sunlight to prevent their drying up. Seedlings are best cut for cultivation when new stalks grow to a length of 15 to 30 cm; cuttings can float better this way and are more resistant to wave action.

Method of planting — Two methods are practiced: laying ropes and using lattice frames. Where the current is swift and the water deep, the method of laying ropes is used to prevent seedlings from being scattered by the water and wind; in stagnant water bodies, lattice frames are preferred.

Management

Fertilizer treatment — Water peanut is seldom fertilized. If the water is sheer and seedlings turn yellow, it is necessary to give a top dressing of fertile silt mixed with barnyard manure, or to spray diluted nitrogenous fertilizer in order to sustain a normal growth.

Weeding — This should be done before planting or after cultivation if moss and weeds are observed. Moss can be eradicated manually. If the results are not so good, it is better to spread plant ash or copper sulphate. The application is done in two ways: (1) use 0.2–0.5 per cent copper sulphate solution to directly kill the moss, or (2) crush copper sulphate into small pieces and put them in a small bag hanging on water surfaces densely aggregated by moss. With the gradual dissolution of copper sulphate in surrounding water, moss will be gradually eliminated.

Pest control — Three-spotted plusia occurs in July to September, crawling over and devouring water peanut plants. To control them, use 90 per cent crystalline trichlorfon at 12 ppt for spraying. Allow 3 to 5 days for the chemical to lose its toxicity before harvesting and feeding thet stalks to livestock. Another method is to disperse the plant so that the affected stalks will bend over drowning the pests.

Harvesting — After 30–40 days from planting when stalks and leaves rear 20–30 cm above the water surface, harvesting can be done. Leave 6 cm of stalk above water and retain 3–4 leaves on them. Cuttings can be made about every 10 days. In July and August when the weather gradually becomes hot with abundant rainfall, the water is enriched and growth is fast. Harvesting interval becomes shorter. After every cropping, use a hoe to loosen and separate the seedlings, which will help restore the growth through better spacing. The last harvest is done by the end of October.

Seedling reservation and overwintering — Water peanut reserved for seed should be densely cultivated on sunny leeward ponds. Choice should be made of plants whose stalks and leaves are luxuriant and healthy. Reserves should not be cut after a frost. Stalks and leaves of such seedlings should remain 50 cm above the water surface.

Water Lettuce

Water lettuce (Pistia stratiotes) is a wild aquatic plant belonging to Araceae family. The roots look like a bundle of cotton threads suspended in the water. The stalk is very short and leaves grow in clusters. Each plant has 6–10 leaves arranged in a ring shape. Leaf blades are oval. Its flowers are yellow in colour and the stamens, without pedicels, grow in symphysis but look protruded, while the pistile are like solitary bulbs of oval with single ovary in which are found several ovules. The fruit is a berry.

Water lettuce contains 1.07 per cent crude protein, 0.26 per cent fat, 1.63 per cent carbohydrates and a considerable amount of crude fibre. It can be used as fresh or cooked fodder for pigs. It grows and reproduces very rapidly and yields 10–20 tons/mu. The cultivation of water lettuce is characterized by less labour input lower cost, and easy management. Water lettuce floats, all the water surfaces of rivers, lakes and ponds, etc. can be used for propagation. It grows well in places where the water is fertile and stagnant. On running water, its growth is relatively poor. The suitable water depth for cultivation is 0.7–1.5 m, and the optimum pH value, 6.5–7.5. This plant prefers warm weather, and its resistance to cold is poorer than water peanut and water hyacinth, but its endurance to heat is better. Although it can grow in a wide temperature range between 15–40°C, it grows faster at 22– 35°C. If water, fertilizer and sunlight conditions are favourable, each plant can reproduce 50–60 plants in a month. When temperature is above 35°C or below 18°C, it is unable to divide, or divides only a few times. When it is below 10–15°C, it will just maintain its life activities, and when it falls below 50°C, it dies. It demands an ample supply of nitrogenous fertilizer if it is to grow well. If water quality is poor and no fertilizer is applied, it will not thrive well.

Small pond planting in spring

When air temperature rises above 15°C around mid April, small ponds can be used to plant seedling removed from the nursery beds for the first propagation in order to have enough seedlings for extensive planting in summer. When seedlings are transferred to ponds, be sure that they are crowded together at one corner of the pond so that they will mutually give support to each other and are not able to move about. Every measure has to be taken to prevent filamentous green algae from entangling the seedlings. A fertile, warm, damp and quiet conditions should be ensured to promote their propagation so that cultivation may commence ahead of season.

Large-scale planting in summer

When the temperature of the water surface has risen to about 23°C in mid-May, the growth and reproduction of water lettuce increases conspicuously. It is the right reason to expand the cultivation of this crop. The stocking amount of seedlings is 10–20 kg/mu. When planting, it is necessary to use reed stalks, bamboo poles or straw ropes to form an enclosure for the growing plants so that they may thrive and grow in groups. As the population increases, the enclosure should be enlarged gradually to provide more space for growth, and when the seedlings cover half of the pond surface, the ropes should be removed for free propagation. Later, they can be transferred to other places for production.

Water surface management

Fertilizer treatment — Fertilizer is applied 5–7 days after planting. After that, the dressing is done weekly, each time at a rate of 250–300 kg of night soil per mu or pigsty manure diluted 4- to 5- fold to be splashed onto the leaf surface in the evening.

Prevention and control of weeds — On the initial stage of planting, it is necessary to eradicate all weeds on the water surface. If filamentous green algae is present, the effective method is to plant ash or spray 1 per cent lime water or 0.5 per cent copper sulphate.

Pest control — Use 0.5 per cent 666 powder to spray on the leaves of water lettuce to control aphids early in the morning when the leaf surface is still wet, or use 40 per cent dimethoate emulsion in about 1:2000 dilution for spraying. At the initial stage of the occurrence of yellow wilt, use the Bordeaux mixture containing 160- to 200-fold water for spraying to control it. Crop can be harvested for fodder one week after applying chemicals to avoid poisoning of livestock.

Sprinkling water on leaf surface — In the summer season when the day is hot and dry, it is necessary to sprinkle clear water on the plant leaves 2–3 times at noon to increase humidity and lower air temperature, thereby promoting growth.

Harvesting

Cropping usually commences from mid or late June. First, divide the crop into several square blocks and then scoop up the plants block by block. The harvest amount depends on growth conditions and it should be done gently. After harvesting, the seedlings should be set apart so that they are distributed evenly on the water surface to enhance their propagation.

Seedling protection and overwintering

From late October to early or mid-April, protection of seedlings from the cold should not stop until it is entirely frost-free. The work is done on the nursery beds. Temperature must be constantly maintained at the proper level which is above 15°C. In addition, more sunlight and better ventilation will help the crop to overwinter safely.

Water Hyacinth

Water hyacinth (Eichhornia crassipes) is a perennial aquatic plant belonging to the Pontederiaceae family. The plant floats on the water, growing out creeping branches from its roots to form new branches. The leaves grow straight and are either oval or round in shape varying from 2.5–5.0 cm in width. They are smooth and shiny. The pedicel bulges out on the lower half like a gall bladder, a spongy interior filled with air. The flower is monopedicel with a sheath in the middle portion. It has six petals blossoming on the top in violet and blue. There is a bright yellow spot at the centre of the top petal.

The yield of water hyacinth is very high, reaching 10–16 t/mu. It is also rich in nutrients. Analysis shows that fresh crops contain 1.9 per cent crude protein, 0.25 per cent fat, 1.11 per cent fibre, 2.21 per cent non-nitrogenous extracts, 1.33 per cent ash content and inorganic salts like calcium and phosphorus. The planting of water hyacinth is a good way of providing green forage requirement of pigs. This crop likes warm and damp climate and still or slowly running water. The optimum water depth is 0.3–1 m, but the water has to be fertile. Its adaptability is better than water lettuce; its endurance to poor fertility is higher. It is more cold-resistant than water lettuce; as long as temperature remains at 7–10°C, it can overwinter safely. The river bends and ponds that are not fit for planting water lettuce can be used for cultivating water hyacinth.

Planting time — Water hyacinth is cultivated along the Changjiang River Basin in early or mid-April. When air temperature rises above 13°C and frost is over, the old seedlings that have overwintered start to germinate and sprout. New leaves burst forth with vigour. This indicates that it is the right time to plant water hyacinth.

Method of planting — Small stagnant ponds of less than 1 cm can be directly seeded with water hyacinth seedlings which float and grow freely. In large ones or in slightly running water, planting should be done with the help of bamboo frames or by setting up supports and tying straw ropes to them to enclose an area of the water surface in which the seedlings can be planted. When the enclosure is densely occupied by the plants, it should be gradually enlarged and eventually removed. In this way, the crop will not be dispersed by winds and water current, and so it is advantageous to its growth and reproduction. One mu of water surface needs about 4–6 kg of seedling.

Management

Fertilizer treatment — In fertile ponds, no fertilizer is required, but it is necessary to stir the fertile silt at the bottom to enable nutrients to dissolve in the water. If water quality is poor, the plants will be weak and slender, and leaf blades yellow. In this case, night soil or animal manure need to be applied. The dressing is usually done in the best growing season weekly or biweekly.

Weeding — During the initial stage, weeds can easily interfere with the growth of water hyacinth. It is necessary to eradicate the aquatic weeds and filamentous green algae. Weeding should be stopped only when the growth of water hyacinth is vigorous and when seedlings cover the entire water surface.

Cropping — Water hyacinth begins to grow luxuriantly and reproduce rapidly after 1 or 2 months by which time harvesting can commence. The amount to be harvested is limited to about one-fourth of the whole crop or one third at most. After cropping, it is necessary to set the seedlings apart for speedy reproduction. In summer, it is possible to harvest once every week, but this interval of cropping depends on the fertility of the water, the growth condition of the crop and air temperature. In Changjiang River Basin, the growth of this plant ceases by the end of October when temperature drops below 10°C and leaves begin to turn yellow. At this point, seedlings that are of medium size, look more seasoned and healthy, and free from diseases and pests, are usually chosen as seeds for overwintering. The method involves placing a layer of fertile pond silt at the bottom of large vessels or wooden tubs and filled with water to a depth of 9 cm. Place the selected seedlings into it and place the containers in a nursery. Maintain the temperature inside above 7–10°C. The seedlings should be frequently exposed to sunlight. They can be placed together with water lettuce seedlings in the same nursery for overwintering.