Detailed Explanation of Key Points for High-Yield Cultivation Techniques of Water Bamboo
Water bamboo, also known as gaogua, wild rice shoot, wild rice hand, jiao shoot, and gao shoot. It is a perennial herbaceous plant with persistent roots of the genus Zizania in the grass family. It is divided into double-crop water bamboo and single-crop water bamboo (or divided into one-harvest jiao and two-harvest jiao). Double-crop water bamboo (two-harvest jiao) has higher yield and better quality. The ancients called water bamboo “gu”. Before the Tang Dynasty, water bamboo was cultivated as a grain crop. Its seeds are called wild rice or diaohu, and it is one of the “six grains” (tu, shu, ji, liang, mai, gu). Later people discovered that some gu plants, infected by the smut fungus, did not send up ears, and the plants showed no signs of disease; the stems kept swelling and gradually formed spindle-shaped fleshy stems. This is the water bamboo eaten today. In this way, people used the smut fungus to prevent water bamboo from flowering and fruiting, and propagated this diseased, malformed plant as a vegetable. It can also be used as medicine. In the world, only China and Vietnam cultivate water bamboo as a vegetable. In Baizhuangzi, Xintai, Shandong, water bamboo is known as one of the three treasures (the three treasures are water bamboo, spring buds, and wild duck eggs), a tradition passed down since ancient times. It mostly grows in the Yangtze River lake areas and is suitable for growing in fresh water.
Site selection
Water bamboo has a well-developed root system and a large growth volume. It is suitable for cultivation in clay loam or loam with sufficient water sources, soft soil layers, rich organic matter, and strong water and fertilizer retention. Farmers in the south have the habit of growing water bamboo in shallow water at the edges of lakes, ponds, and ditches. For cultivation in low-lying land and paddy fields, generally plow the first time 7 to 10 days before planting; 2 to 3 days before planting, apply sufficient base fertilizer and plow the second time; after plowing, harrow immediately to level, achieving level fields and muddy soil.
Crop rotation
Water bamboo can be rotated with rice, mat grass, lotus root, water chestnut, arrowhead, and gorgon fruit, and can also be co-cultured with yellow eel, loach, crab, or other fish. In continuous cropping of water bamboo with rice, water bamboo uses two-harvest jiao varieties. After the summer jiao is harvested, plow and harrow the field, apply sufficient base fertilizer, and transplant single-season rice or double-cropping late japonica rice. The growth periods of the two crops complement each other, and both can achieve high yields. This method is suitable for paddy fields with higher ground temperature. Continuous cropping of water bamboo with mat grass: after the autumn water bamboo harvest, prepare the land, apply fertilizer, and plant mat grass.
This method is suitable for low-lying land with relatively flat ground temperature and shallower water layers. Co-culture of water bamboo with yellow eel and loach: when raising yellow eel and loach in water bamboo fields, the surrounding field ridges must be reinforced, and the ridge height should be 50 cm above the highest water level in normal years; cement wall ridges are best to prevent escape; the mud layer in the field should be thick, water bamboo should be planted in wide and narrow rows, and cross-shaped open spaces should be left in the field; before stocking seedlings, quicklime should be used to disinfect the pond. Co-culture of water bamboo with crabs: when interplanting water bamboo in crab ponds, set up anti-escape and anti-theft walls around the outside of the pond, dig wide ditches around the inside of the pond, and dig “cross”-shaped ditches in the middle, with a suitable ditch depth of about 1 m; the silt layer should not be too thick, water bamboo should be planted sparsely, and the plant-row spacing can be 40 cm × 100 cm; before stocking crab seedlings, quicklime should be used to disinfect the pond.
Variety selection and cultivation season
It is advisable to choose varieties with good quality, many effective tillers, few gray jiao and male jiao, strong stress resistance, and high yield for cultivation. Water bamboo likes a warm and humid climate, and after frost the water bamboo leaves wither and die. The north has a short frost-free period, so one-harvest jiao is mainly planted, and one-harvest jiao is suitable for spring planting. The south has a long frost-free period and sufficient water sources, so both one-harvest jiao and two-harvest jiao are suitable for cultivation. In the Jiangsu, Zhejiang, and Anhui areas, one-harvest jiao is planted from Qingming to Guyu; summer and autumn two-harvest jiao can be divided into spring planting and autumn planting, with spring planting around Guyu and autumn planting around Liqiu. In southern regions, two-harvest jiao varieties should be the main focus, and the cultivation season should be based on a one-year cycle.
Planting
For spring planting around Guyu, when tiller seedlings grow to 30 to 50 cm and have 3 to 4 leaves, dig up the seedlings with soil at 3 to 5 cm from the jiao clump, and use a sharp knife to divide them along the trend of tiller growth into 7 to 12 small clumps. Each small clump is required to carry old stems and stolons and have 3 to 5 healthy tillers. Dig, divide, and plant as you go, preferably in the evening or on cloudy and rainy days. If introducing seedlings from other places, maintain a certain temperature during transport, cut off the leaf tips before planting, and leave a plant height of 30 cm to reduce water evaporation and prevent wind from shaking the plants after planting, which affects the survival rate. Planting density should be determined according to variety and soil fertility.
For fields with medium fertility, use a plant spacing of 40 to 50 cm and a row spacing of 85 to 95 cm, with 22,000 to 25,000 hills per hectare. For poor and low-fertility fields, density should be appropriately increased, with 30,000 to 37,000 hills per hectare. For transplanting, if the previous crop is early lotus root, mat grass, early rice, etc., early-maturing jiao varieties should be used for autumn planting. Jiao seedlings are raised during Qingming to Guyu in lotus root fields or around ponds, and transplanted around Liqiu (no later than August 15). At this time, the seedlings are already more than 1 m tall and have many tiller seedlings. Before planting, pull apart the tillers of the seedling clumps one by one by hand along their direction, lift the seedlings clump by clump, keep 1 to 2 seedlings per plant, and cut off about 50 cm of leaf tips. Because summer and autumn temperatures are relatively high, choose cloudy days or afternoons for planting. For planting density, the row spacing is 40 to 45 cm and the plant spacing is 25 to 30 cm, with about 60,000 hills per hectare. Lift seedlings and plant them the same day, planting to a depth of 10 to 15 cm, with the degree of planting just covering the stem tube.
Water and fertilizer management
Water bamboo plants are tall and have a long growth period. They prefer organic fertilizer and require sufficient base fertilizer to obtain high yields. Generally, base fertilizer should account for half of the total fertilizer application. The amount of fertilizer applied to jiao fields is mainly related to soil fertility, planting density, and planting time. Where soil fertility is high, planting is early, and density is high, apply less; where soil is poor, planting is later, and jiao seedlings are sparser, increase the amount of fertilizer. Generally, for two-harvest jiao or one-harvest jiao planted in spring of the same year, in plots with medium fertility, apply 30,000 to 37,000 kg of decomposed pig manure or other farmyard manure of corresponding fertility per hectare when preparing the land. For topdressing, adopt the fertilization principle of heavy, light, heavy: 12 to 15 days after planting, apply 50,000 to 25,000 kg of human excrement and urine or 220 to 300 kg of urea (called seedling-promoting fertilizer) to promote effective tillering; at the peak tillering stage, apply fertilizer according to seedling conditions to prevent premature aging, generally 450 to 1,500 kg of urea per hectare; around mid-August before jiao pregnancy, the topdressing amount should be large to promote expansion of the fleshy tender stems and increase water bamboo yield per unit area, generally 22,000 to 30,000 kg of human excrement and urine or 220 to 300 kg of urea per hectare, called jiao-promoting fertilizer.
The jiao-promoting topdressing must be applied carefully and timely. If applied too early, the plants have not yet become pregnant with jiao, increasing ineffective tillers; if too much is applied, it causes excessive growth, the plants remain green, effective tillers are few, and jiao formation is delayed, and in severe cases the whole field becomes male jiao; if too little or too late, it cannot meet the needs of jiao pregnancy, the jiao is small, quality is poor, and yield is low. Generally, apply 5 to 7 days before the first batch of jiao pregnancy. For autumn-planted two-harvest jiao, the growth period in the same year is short, so the base fertilizer must be sufficient, generally 37,000 to 60,000 kg of farmyard manure per hectare, and 10 to 12 days after planting, apply 30,000 to 37,000 kg of human excrement and urine or 3,700 to 4,500 kg of urea per hectare in one application to promote early and uniform tillering and to become pregnant with jiao before the temperature falls below 25°C. For old jiao fields in the second year after planting, the fertilization method for one-harvest jiao is the same as above, but for two-harvest jiao summer jiao, because there are only 3 months from sprouting to jiao pregnancy, fertilization technology is key to striving for high yield. Before Qingming, apply 30,000 to 37,000 kg of farmyard manure per hectare. Topdressing should mainly be quick-acting fertilizer, applied heavily in 2 applications: when seedlings grow about 10 cm tall, apply 37,000 to 45,000 kg of human excrement and urine or 300 to 370 kg of urea; 5 to 7 days before jiao pregnancy (generally after Lixia), apply 22,000 to 30,000 kg of human excrement and urine or 220 to 300 kg of urea for the second topdressing. For both new and old jiao fields, topdressing should mainly be quick-acting organic fertilizer; only if human excrement and urine are insufficient may urea be used as a substitute. When fertilizing, appropriately lower the shallow water layer, and 2 to 4 days after fertilization add water back to the original water level to facilitate fertilizer absorption into the soil. When fertilizing, prevent burning the leaves. In water layer management, spring-planted water bamboo follows the irrigation principle of shallow, deep, shallow. From after planting to the early tillering stage, maintain a shallow water layer of 3 to 4 cm to help raise water temperature and promote root development and effective tillering. At the middle tillering stage (more than 20 tiller seedlings per jiao clump), deepen the water layer to 8 to 10 cm to suppress ineffective tillering.
In midsummer when high temperature exceeds 35°C, appropriately irrigate deeply to lower temperature and change water regularly to prevent root rot caused by soil oxygen deficiency. However, the highest water level should not exceed the “jiao white eye”, because the tissue there is relatively tender and disease can easily invade. In addition, if the water level is too high, the stem tube will elongate and the plants will easily lodge. From the late tillering stage to before jiao pregnancy, maintain a water layer of 12 to 15 cm to lower water temperature, control late tillering, and promote early jiao pregnancy. During the jiao pregnancy period, deepen the water layer to 18 to 20 cm to prevent direct sunlight, ensure the water bamboo is white and tender, and improve quality. Entering the harvest period and overwintering period, jiao fields should maintain a shallow water layer of 3 to 5 cm or a moist state. When planting autumn water bamboo and during the seedling recovery period, maintain a shallow water layer of 3 to 5 cm; at the tillering stage, deepen the water layer to 8 to 10 cm; during the jiao pregnancy period, maintain a water layer of 15 to 18 cm; water and fertilizer management during the harvest period and overwintering period is as above. Water layer management for old one-harvest jiao fields is similar to the above spring-planted new jiao fields. For old two-harvest jiao fields, from the spring sprouting stage to the tillering stage, maintain a water layer of 3 to 5 cm; from the late tillering stage to the jiao pregnancy stage, maintain a water layer of 8 to 10 cm, and at the same time remove excess small tiller seedlings.
Jiao field management
In the early growth stage of water bamboo, temperatures are low, growth is slow, and aquatic weeds grow densely. Before tillers close the rows, cultivate and weed 2 to 4 times. After seedlings emerge in old jiao fields or after planting in new jiao fields, replant promptly if dead or missing seedlings are found. If tiller seedlings in the field are too many and too vigorous at the middle tillering stage, remove overly dense small tiller seedlings so that the number of tiller seedlings per clump is controlled within 25. At the late tillering stage, remove yellow leaves in time, pull out small tiller seedlings, and tread them into the mud to enhance ventilation and light transmission in the jiao field. When removing old leaves, do not pull hard enough to injure the plants. When harvesting autumn jiao in the first year, mark gray jiao and male jiao plants whenever found, and after Cold Dew and Frost's Descent, dig out the gray jiao and male jiao together with their roots. After entering winter, cut off dead leaves level with the mud so that seedlings emerge neatly and uniformly the next year. In rural areas of the south, there is a custom of burning dead leaves on jiao clumps after Lidong, believing that this can avoid gray jiao and male jiao the following year. In fact, to thoroughly eliminate gray jiao and male jiao, they must be dug out together with their roots, and the jiao clumps burned. After digging out gray jiao and male jiao in old jiao fields, fill in missing seedlings at early spring sprouting. If old jiao clumps have too dense seedlings, thin out small and dense tillers during Qingming and Guyu, leaving one robust tiller seedling per 8 to 10 cm square, and at the same time press a piece of mud into the middle of the jiao clump, with the degree of coverage such that jiao seedlings spread outward around it.
Pest and disease control
Diseases mainly include rust, rice blast, sheath blight, sesame leaf spot, and small sclerotium disease.
Rust occurs on both sides of leaves and on leaf sheaths, and is obvious on the remnants at the cracked edges of the epidermis. In the late growth stage, telial piles form, gray to black, elongated, not exposed.
Rice blast diseased leaves initially show strip-shaped or spindle-shaped lesions, and later the entire leaf withers and scorches; in severe cases the whole field looks as if burned by fire. Sheath blight is most likely to occur from the peak tillering stage to the jiao pregnancy stage of water bamboo. In the early stage of the disease, water-soaked dark green oval lesions first appear on the leaf sheaths, and then expand into cloud-patterned lesions. When the disease is severe, jiao leaves wither and die, and the jiao flesh becomes dry and thin.
In the early stage of sesame leaf spot on leaves, pinhead-sized brown small spots appear, then gradually expand into round, oval, and spindle-shaped lesions, with edges light brown to dark brown, centers yellow-brown to gray-white, sometimes slightly concentric-ringed, and with a yellow or light yellow halo around the outside. In the later stage, lesions can heal together into blocky death, mostly dying gradually from the leaf margin or leaf tip along the outer edge downward, or becoming withered white. There is an obvious brown exposed layer on both sides of the lesions, sometimes also concentric-ringed.
Small sclerotium disease mostly lives saprophytically or parasitically on leaf sheaths in the late growth stage of water bamboo, harming leaf sheaths and causing water-soaked discoloration. After obvious lesions form, they turn withered yellow, and a large number of small granular sclerotia grow inside the sheaths.
The above diseases are all caused by high temperature and high humidity. Eliminate sources of inoculum, such as cultivating disease-free varieties, burning jiao clumps during overwintering, removing diseased plants and diseased leaves, and changing fields, etc.; increase base fertilizer and phosphorus and potassium fertilizer, and apply less nitrogen fertilizer in the middle and late stages, etc.; plant at a reasonable density, irrigate shallowly in the early stage, and drain the field appropriately in the middle stage, etc.; and control at the early stage of disease onset. For sheath blight and rice blast, carbendazim wettable powder or thiophanate-methyl 500 to 800 times can be used, with continuous control 2 to 3 times within 10 to 15 days; for sesame leaf spot, 40% isoprothiolane 600 times solution can be used, with continuous control 2 to 3 times within 10 to 15 days; for rust and small sclerotium disease, 80% zineb wettable powder 800 times solution can be used, with continuous control 2 to 3 times within 10 to 15 days. Pests mainly include large rice borer, striped rice borer, aphids, and leafhoppers. Large rice borer and striped rice borer larvae bore into the jiao flesh during the young jiao stage, feeding on the heart leaves and jiao flesh, causing deadheart seedlings and unmarketable water bamboo, with 3 generations per year.
The biological control method is to promptly remove weeds at the field edges, cut off withered and yellow stems and leaves level with the ground in winter and burn them in a concentrated manner to eliminate overwintering larvae; the chemical control method is to apply 3 kg of 50% fenitrothion emulsifiable concentrate per hectare, add 60,000 to 75,000 kg of water, and splash it on, or 2 days before the peak hatching of ant larvae, use shachongshuang or shachongling for spray control.
Aphid damage shows as water bamboo leaves curling after being damaged. The control method is to spray 40% dimethoate emulsifiable concentrate 2000 times solution at the early stage of occurrence. Leafhopper adults and nymphs gather on water bamboo leaves to suck sap, causing leaves to wither and yellow. You can use 40% suhua 203 emulsifiable concentrate 1,000 to 1,500 g, add 1,000 kg of water, and spray.