A Detailed Guide to High-Yield Cultivation, Harvesting and Storage Methods of Water Chestnut

Water chestnut is also known as horse's hoof, water chestnut, fuci, wuyu, puji, dili, etc. It is a clump-forming aquatic herbaceous plant of the genus Eleocharis in the sedge family. Its underground corms are used for food; the flesh is crisp, rich in starch, and it can be used as a fruit or vegetable, or made into canned goods, starch, or preserved sweets, and is deeply favored by consumers. So how is water chestnut planted for high yield? How is it harvested? What storage methods are there?

I. Production area distribution of water chestnut

Water chestnut originated in India. There are about 150 species worldwide, widely distributed across the world, mostly in tropical and subtropical regions. China has records of cultivation as early as the Western Han Dynasty. At present there are more than 20 species and some varieties, mainly distributed in low-lying areas of Guangxi, Jiangsu, Anhui, Zhejiang, Fujian, Guangdong, Hunan, Hubei, Jiangxi, Guizhou, etc., and also in parts of Hebei. Baihu Town, Lujiang County, Anhui Province, is rich in high-quality water chestnuts and is China's largest “hometown of water chestnut”. Qingshan Town, Lipu County, Guilin City, Guangxi, is a state-recognized “hometown of horse's hoof”. Lechang water chestnut in the Shaoguan area of Guangdong is famous for its large size, thin skin, tender flesh, abundant moisture, clear sweetness without residue, and crisp, pleasant taste. In addition, Maoli Town, Shayang County, Jingmen City, Hubei Province, is also a water chestnut production area, and its products have long been exported overseas and are widely renowned.

II. Growing environment of water chestnut

Water chestnut prefers to grow in ponds or is cultivated in paddy fields. Propagation uses corms, also called fruit balls, for asexual reproduction. It likes warmth and moisture and fears freezing, and is suitable for growing in loam with a soft plough layer and firm subsoil. In cultivation, a plough layer of 20-25 cm is required, which is beneficial to the growth and development of the corms, prevents the corms from drilling too deep, keeps individual development uniform and consistent in size, and also facilitates digging and harvesting. If the plough layer is too sticky, it is unfavorable for corm swelling; if there is too much humus, the sugar content of the corms decreases and the sweetness is poor. It is suitable for growing in shallow water. In terms of nutrient requirements, it needs less nitrogen fertilizer and more phosphorus fertilizer. Throughout the entire growth period, it requires sufficient light.

III. Seedling-raising techniques for water chestnut

1. Selection of seed corms: Water chestnut reproduces through stolons. Before sowing, select one by one corms with unbroken skin, robust and sound terminal and lateral buds, dark brown skin, a single corm weight of more than 15 grams, and characteristics of the cultivated variety as seed corms. Before sowing, soak them in a 500-fold solution of 50% carbendazim wettable powder for 18-24 hours to kill surface pathogens. About 15-20 kg of seed corms are needed per mu of field.

2. Seedling-raising time: The seedling-raising time for water chestnut depends on the transplanting period. For early-water water chestnut, because the early temperature is low, seedling raising begins 40-45 days before transplanting (late March to early April). For late-water water chestnut, because the temperature during seedling raising is higher, seedlings are raised 20-25 days before planting. In the middle and lower reaches of the Yangtze River, seedlings are generally raised from Qingming to Guyu. Before raising seedlings, sprouting is first carried out indoors, and then sowing and temporary planting are carried out in paddy fields.

3. Sprouting of seed corms: The indoor sprouting method is to spread a layer of about 10 cm of rice straw on the ground, arrange the seed corms on the straw with the buds facing upward, stack 3-4 layers, and cover with rice straw on top. Water once in the morning and once in the evening each day. After 10-15 days, when the buds have grown to 3-4 cm, the seedlings can be transplanted into the seedling field for sowing.

4. Seedling field preparation: The seedling field should be chosen in a place with convenient irrigation and drainage and fertile, loose soil. Deeply plough, finely harrow, and level the seedling field. Leave field ditches around it and build surrounding ridges, because during this period the nutrition for water chestnut growth mainly comes from the corms, and the seedling field generally does not need fertilization.

5. Sowing and seedling raising: Arrange the sprouted corms one by one into the seedling pond, and press the corms into the mud 1-2 cm, with a spacing of 6×6 cm. The buds should face upward and be at a uniform height, and the field should maintain a water layer of 1-2 cm. After 15-20 days, when the seedlings are about 10 cm tall and have 5-6 leaf-like stems, temporary planting can be carried out.

6. Temporary planting of water chestnut: Temporary planting of water chestnut means separating the raised seedlings and expanding their spacing to facilitate concentrated fertilization and management, and more importantly, to meet the need in southern regions to plant water chestnut after rapeseed or wheat. The specific method of temporary planting is, 20-25 days after sowing, to transplant corms with leaf-like stems 10-15 cm into the water chestnut seedling field, planting the corms at a spacing of 30 cm×40 cm. This is beneficial for rooting and also expands the nutritional area for the seedlings.

7. Seedling-stage management: After transplanting the water chestnut seedlings, the seedling field is best kept with a shallow water layer of 2-3 cm, which can increase soil temperature and promote seedling growth. About 15 days after transplanting, apply 20 kg per mu of a nitrogen-phosphorus-potassium compound fertilizer. Note that it should be broadcast, not concentrated near the roots, to avoid burning the seedling roots. After 30-40 days, when the seedlings are 35-40 cm tall and the leaf-like stems are more than 0.5 cm thick, the seedlings can be lifted and planted in the field.

IV. Field-planting techniques for water chestnut

1. Land preparation and fertilization: It is best to choose a paddy field with sufficient sunlight, loose topsoil, relatively firm subsoil, a plough layer of about 20 cm, sufficient water sources, convenient irrigation, and clean water. Before planting, deeply plough the field about 15 cm, then apply base fertilizer. The reference standard for fertilization is 3000 kg of decomposed pig manure, 30 kg of superphosphate, 10-15 kg of potassium chloride, and 15 kg of ammonium bicarbonate per mu. Finally, harrow finely and thoroughly so that the field soil becomes muddy.

2. Timely planting: In the middle and lower reaches of the Yangtze River, the planting time for water chestnut can be arranged from late May to early June. Before planting, carefully dig out the seedlings and wash off the soil before planting. The best spacing for water chestnut planting is about 30×50 cm, with 1 plant per hole and 2500-3000 plants per mu. Water chestnut should be planted at an appropriate depth, with 5-7 cm into the soil being suitable.

V. Cultivation techniques for water chestnut

1. Seedling stage: The period from after the plants survive to before tillering and ramet formation is called the seedling stage. Water chestnut is an aquatic crop, and during the seedling stage a shallow water layer of 3-5 cm should be maintained. Water chestnut begins to grow 10-15 days after planting. When the old leaves of the water chestnut seedlings wither, combine weeding by pressing yellowed stems and rotting seed seedlings and weed litter into the field, which is beneficial for the seed corms to grow new roots. At this time, topdress once with urea, generally 10-15 kg of urea per mu, to promote earlier tillering and ramet formation of water chestnut.

2. Vegetative stage: During the tillering stage, carry out 2-3 times of inter-row hoeing and weeding in the water chestnut field. Combine weeding with the second topdressing, applying 5-10 kg of urea per mu to promote corm formation. From the Autumn Equinox to Cold Dew, during the period of vigorous corm growth, the water layer should be deepened, preferably kept within the range of 6-9 cm. During this period, water chestnut stem blight and water chestnut white stem borer often occur. For water chestnut stem blight, 40 kg per mu of a 500-1000-fold solution of 50% carbendazim wettable powder plus an 800-fold solution of 70% thiophanate-methyl can be sprayed for control. The control method for white stem borer is to spray 100 grams of 98% cartap with 50 kg of water.

3. Maturity stage: During the corm maturity stage, that is, about 20 days before harvest, irrigation should be stopped so that the leaves turn yellow and gradually dry up, preparing for harvest. There is no other management during this period; it is only necessary to prevent damage by livestock.

VI. Harvesting methods for water chestnut

1. Harvest time: The water chestnut harvest period can begin from Frost's Descent and last until the Spring Equinox of the following year. Corms harvested early have tender flesh, a bland taste, and thin skin, and do not store well. From the Winter Solstice to Minor Cold, the skin color of the corms turns reddish brown and the taste is sweetest, which is the period of highest sugar content; harvesting at this time is most suitable. Afterward, the sugar content of the corms gradually decreases, the skin thickens, the skin color deepens and turns dark brown, and a layer of yellow coating forms under the skin, so quality deteriorates. Therefore, corms for commercial use should be harvested before overwintering.

2. Harvesting methods: Generally, drain the field water one day before harvest. Because the corms are mainly concentrated in the 9-20 cm soil layer, first scrape away the upper 8-9 cm of soil, then scrape out the lower soil and carefully pinch out the corms by hand (people call this “feeling for water chestnuts”). If rushing to plant the next crop (such as rapeseed or wheat), drain and air-dry the field 10-15 days before harvest, and dig them out with a fork.

VII. Storage methods for water chestnut

1. Jar storage: After the water chestnuts are dug out, spread them on a brick floor for 12-15 days. After proper air-drying, put them into a large indoor pottery jar. The pottery jar should be placed in a dry, ventilated place. Each jar stores about 80-100 kg. Cover the mouth of the jar filled with water chestnuts. It should be noted that water chestnuts stored in pottery jars have vigorous respiration in the early storage period, so the jar lid must be opened to facilitate ventilation. In the cold winter, a layer of rice straw should be covered inside the jar for insulation. In rainy weather, because air humidity is high, the lid should be opened in time to release moisture. In hot, high-temperature seasons, the lid should be put on in time to prevent evaporation of water from the corms and cause dry rot. During storage, the water chestnuts stored in the pottery jar must be turned and checked once every 25-30 days. Stored by this method, water chestnuts can be kept fresh for more than half a year.

2. Cellar storage: If using an old cellar for storage, before storage, spray the bottom and body of the cellar with a 2.5% carbendazim or 40%-thiophanate-methyl 400-500-fold solution for disinfection. Spread a layer of fine soil on the bottom of the cellar. For every 20-25 cm thick layer of water chestnuts placed, sprinkle a layer of dry fine soil on top. In this way, one layer of fruit and one layer of soil, until 20 cm from the cellar mouth. Then seal the mouth with dry fine soil, and seal the top around with 30 cm thick soil, forming a steamed-bun shape that is high in the center and low around the sides, covering the cellar mouth and patting it firm.

3. Sand storage: After the water chestnuts are harvested and dug out, build a burial pit with bricks in a cool room or basement. First spread fine sand 5-7 cm thick on the bottom of the pit, arrange the water chestnut corms on the sand surface, cover with fine sand 3-4 cm thick, then place another layer of water chestnut corms, stacking layer by layer in this way, with the pile height not exceeding 1 meter. This method can also achieve good storage and fresh-keeping results.

4. Solution: Remove debris from the harvested water chestnut corms, clean them, and quickly immerse them in sodium hypochlorite solution for storage. According to experiments, using this method, under a storage environment with a temperature of 0-2℃ and a relative humidity of 90%-100%, water chestnut corms can be kept fresh for up to 10 months, and under storage below 5℃ the fresh-keeping period can reach 6-8 months.

5. Heap storage: Choose a cool indoor earthen floor, and its size can be determined according to the storage quantity. First spread a layer of dry fine soil on the ground, surround the sides with mats, or build a pool shape with bricks, then place one layer of water chestnuts and one layer of dry fine soil, layer by layer alternating.