Detailed Explanation of Key Techniques for Greenhouse Cultivation of Water Bamboo (Zizania latifolia) in Open Fields

Water bamboo, also known as gaogua, gusun, gushou, jiaosun, and gaosun. It is a perennial rhizomatous herbaceous plant of the genus Zizania in the grass family (Poaceae). It is divided into double-cropping water bamboo and single-cropping water bamboo (or classified as one-harvest jiao and two-harvest jiao); double-cropping 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 were called gu rice or diaohu, and it was one of the "six grains" (tu, shu, ji, liang, mai, gu).

Morphological characteristics of water bamboo

Plant height 1.6-2 m. The roots are fibrous roots, arranged in a ring at each node of the tillering nodes and stolons, 20-70 cm long and 2-3 mm thick, mainly distributed in the soil layer 30 cm below the surface, and numerous. It is a perennial emergent aquatic herbaceous plant. It has rhizomes, and the aboveground stems can produce 2-3 rounds of tillering. Forming clumps of tiller branches, the culms are erect and stout, with adventitious roots at the base. After the main stem and tiller branches enter reproductive growth, if the base is parasitized by the water bamboo smut fungus, they cannot grow normally and form oval or nearly round fleshy stems. The leaves are flat, long lanceolate, 30-100 cm long and about 3 cm wide, with awn-like acuminate tips, slightly contracted or gradually narrowed at the base, generally rough on the upper surface and margins and smooth on the lower surface, with the midrib raised on the back. The leaf sheaths are long and thick, clasping each other to form a “false stem”. The flowering and fruiting period is autumn and winter; the panicle is large, 30-60 cm long, much branched, ascending or spreading. The caryopsis is cylindrical. It is often cultivated as a vegetable. Plants whose culms are not parasitized by the fungus are called wild water bamboo, also known as male water bamboo or jiao'ercai. It is found wild in the Shanghai area.

Greenhouse cultivation techniques for water bamboo in open fields

1. Variety selection

Choose varieties suitable for local cultivation that have high yield and good quality, relatively strong tillering, good stress resistance, white and smooth jiao flesh, thin skin, fine and tender texture, good marketability, good economic returns, and are highly favored by the market.

2. Field selection

It is advisable to choose low-lying fields with fertile and loose soil, high organic matter content, a deep plow layer, convenient irrigation and drainage, good water quality, no industrial “three wastes” pollution, and where water bamboo has not been planted continuously.

3. Select and retain excellent seedlings, and plant at a reasonable density

Select water bamboo clumps with neat plant type, high jiao-bearing rate, plump jiao flesh, low jiao-setting position, no male water bamboo or gray water bamboo, low tillering node position, and uniform maturity for seed retention. At the end of March and the beginning of April, dig up seed clumps and divide the seedlings for temporary planting, 1 seedling per hole, with a temporary seedling density of 30×40 cm, and a seedling field to main field ratio of 1:10. Begin transplanting in early July, with a transplanting density of 100-80×50 cm, 2 plants per hole, 1500 holes/mu. If the leaves of the transplanted seedlings are too long, the upper leaves should be cut off in time to reduce nutrient consumption by the plant. For a 6 m wide greenhouse, leave 70 cm at the film edge and plant 6 rows in total.

4. Clean the water bamboo field and apply sufficient base fertilizer

By mid-December, cut off the aboveground residual plants and dead leaves level with the soil, clean the field, and burn them in a centralized manner to reduce the overwintering base of insects and pathogens. For water bamboo fields with many weeds, 5-6 days before building the greenhouse, drain the standing water in the field and spray with 1 kg of 10% glyphosate aqueous solution mixed with 40 kg of water. Two to three days before building the greenhouse, fill with shallow water and apply 120-150 kg of special organic fertilizer for water bamboo per mu or 50 kg of ternary compound fertilizer.

5. Build the greenhouse for insulation and manage carefully

At the end of December, around the winter solstice, build the greenhouse and cover it with film to prevent frost damage. Water bamboo greenhouses mainly use bamboo-frame greenhouses; the bamboo-frame greenhouse is 6 m wide and 1.8-2 m high, with a central post, and the length depends on the field. Choose 0.08 mm thick, 8 m wide multifunctional drip-free film. During the year, the greenhouse should mainly be kept sealed for insulation. After the beginning of spring the following year, the temperature changes sharply, so it should still be kept sealed for insulation at night, and checked and observed frequently during the day. When the weather is mild, ventilate at both ends; when the weather is clear and the temperature inside the greenhouse exceeds 32°C, uncover the side film and ventilate at both ends; during continuous rainy weather, ventilation should also be strengthened, which is beneficial for strong seedlings and reduces the jiao-bearing rate of small seedlings. Generally, all film is removed around Qingming.

6. Thin and finalize seedlings, and skillfully apply topdressing

At the end of February and the beginning of March, the temperature begins to rise and water bamboo plants grow rapidly. When the plant height is 30-40 cm, thin the seedlings inside the greenhouse, leaving about 20 strong seedlings per clump, so that the effective seedlings per mu can reach about 30,000. When thinning seedlings, weeding can be combined with field cultivation to remove weeds at the field edges and improve soil aeration. At the same time as field cultivation, mud can be pressed around the root zone of the water bamboo clumps to mound the roots, so that tillers spread out and the nutritional status is improved. On the premise of doing a good job of thinning seedlings, apply stem-strengthening fertilizer in time according to seedling color, generally 25-30 kg of compound fertilizer per mu. At the end of March, water bamboo gradually flattens its culms and begins bearing jiao. When 30% of the plants are bearing jiao, skillfully apply jiao-bearing fertilizer according to leaf color, with 5-6 kg of urea per mu, to ensure the nutrients needed after jiao bearing and ensure plump and white jiao flesh.

7. Mound mud to protect the jiao and harvest in time

At the end of March and the beginning of April, water bamboo has begun bearing jiao one after another. At this time, it is necessary to harvest and manually mound mud to protect the jiao. Mounding mud should be done in stages; for each clump, when 1 plant is seen bearing jiao, mound mud for that 1 plant, and as the water bamboo continues to elongate, continue mounding mud. Generally, the mounding height is 5-20 cm and must not exceed the water bamboo eye. Because plants bear jiao at different times, it is necessary to harvest while mounding mud to promote enlargement of the individual water bamboo. When the water bamboo grows until the central leaf contracts, the leaf cushions on the left and right sides contract to the same level, and the middle swells to slightly expose the heart, harvest in time.