How can we grow greener watercress?

Watercress, scientific name watercress, is a cruciferous vegetable. It originated in Europe or northern Asia and has been introduced to China for a hundred years. It is one of the main leafy vegetables planted in autumn and harvested in winter and spring in Guangdong Province. Watercress is planted out of season in summer in Guangdong Province, and in Shuikou Town, Yangshan County. The key points of cultivation are as follows-

1. Growth characteristics: watercress likes cold, cold and heat. Generally planted in autumn, harvested in winter and spring. The optimum temperature for watercress growth is 65438 05 ~ 25℃; It grows rapidly at about 20℃ and has good quality; /kloc-growth is slow below 0/0℃, easy to freeze below 0℃, difficult to grow above 30℃, and easy to die at high temperature. Shallow water and air wetting are needed, and shallow water with a depth of 5 ~ 7 cm is needed at the peak of growth. If the water layer is too deep, the plants will grow white, with many adventitious roots and yellow stems and leaves. The water layer is too shallow, and the new stems are easy to age, which affects the yield and quality. Watercress needs plenty of sunshine during its growing period, and clay loam and loam are the most suitable. It is required that the topsoil is larger than 10 ~ 12 cm, the soil is neutral, and the optimum pH value is 6.5 ~ 7.5, so continuous cropping is not suitable.

2. Breeding and planting: At present, there are two varieties of watercress cultivated in Guangdong and Guangxi: one is that it can't blossom and seed under normal circumstances, and it depends on nutrition to reproduce; The other can blossom and bear seeds. For example, varieties cultivated in Zhanjiang and Baise suburbs of Guangxi can be propagated through seeds. However, due to the difficulty in seed collection, only a small number of seeds remain, and most of them still rely on nutrition to reproduce.

Asexual propagation of watercress requires a large number of seedlings. Seedling propagation is carried out in cool autumn, and watercress seedlings that spend the summer in dry land are transplanted to shallow ponds or low-lying fertile fields for propagation in August and September. Before planting, 500 ~ 1000 kg of decomposed human excrement and urine should be applied as base fertilizer per mu, and the land should be finely raked until the water depth does not exceed the mud surface. Leave a 0.5-meter-wide working line for management every 4 meters. Breeding seedlings are generally planted in a single plant, with a spacing of 3 cm and a row spacing of about 5 cm. When transplanting seedlings, the seedlings should be slightly fixed on the mud surface to prevent floating. Keep wet at seedling stage and strengthen management. When the seedlings grow to 15 ~ 20cm, the tender stems should be cut and transplanted into the field.

Watercress grows rapidly, has strong tillering ability, has many ramets and needs a lot of fertilizers. If planted in ordinary rice fields, sufficient base fertilizer must be applied to obtain high yield. In the suburbs of Guangzhou, watercress is planted in fields near cities, towns, industrial and mining areas or residential areas. These fields are often irrigated with fertilizer and water, and the flow process can adjust the microclimate in the soil, and the soil temperature is low, which is suitable for the growth of watercress.

Before planting watercress, the site should be leveled, the water surface should be consistent, and the water depth should not exceed the mud surface. After the field work is completed, the seedlings are inserted into the field in the form of border rows with a spacing of 3 cm and a row spacing of 10 cm. Leave rows 0.5 meters wide every 4 meters. When planting, make the seedling base shallow buried in the soil so that it does not float. After planting, shallow water irrigation should be carried out to keep the water layer 3 cm. When the plants enter the peak growth period, gradually deepen the water layer to 5 ~ 7 cm.

3. Growth management:

(1) Choose strong seedlings and plant them at suitable time: watercress is usually planted in autumn and harvested in winter and spring in South China, so the suitable planting period is from late September to 10. When planting watercress, strong seedlings with thick stems, short internodes and green leaves should be selected as seedlings, and the two bases and roots should be obliquely inserted into the field to facilitate survival.

(2) Scientific land selection and proper close planting: Try to choose fields close to towns, industrial and mining areas or residential areas. These fields are often irrigated with rich water, and the soil temperature is low, which is suitable for the growth of watercress. At the same time, these fields are rich in organic matter and have sufficient fertility, so there is generally no need to apply base fertilizer, or no or little topdressing. Watercress is a small plant with little growth, so it should be planted closely. The planting density is row spacing10cm, and the plant spacing is 3cm.

(3) Adjust the water level and control the temperature reasonably: Leave a shallow layer in the early stage of watercress planting to facilitate rooting. When the plant enters the vigorous growth period, the water layer gradually deepens to 5 ~ 7 cm. After watercress is planted, it often encounters high temperature above 25℃ or even 35℃, which causes the water temperature to rise and burns the seedlings. After winter, the low temperature below 15℃ is easy to occur, causing plant freezing damage.

(4) Topdressing by stages to prevent and control pests and diseases: When planting watercress in ordinary paddy fields, topdressing should be applied every harvest except applying sufficient base fertilizer, and an appropriate amount of nitrogen fertilizer can be used. Generally, decomposed human excrement and urine fertilizer 1000 kg is applied per mu, diluted 5 times with water, or 0.3% ~ 0.5% urea solution can be applied. The main pests in the growth period of watercress are aphids, Plutella xylostella and striped flea beetle. In order to control aphids, 3% Nachongding rice 2000 times solution, 25% Cicadae Suspension Concentrate (thione Isocarba) 600 times solution or 20% dichlorvos EC (synergistic) 1000 times solution can be sprayed alternately. Plutella xylostella and striped flea beetle can be controlled with 24% Wei Shui EC 2000 times solution (propitiazem) or 25% Cicada SC 500 times solution or spinosad (note: the safe period from spraying to harvesting should be more than 10 day).

4. Harvest: When the stem is 25 ~ 35cm high, the watercress can be harvested and marketed. It usually takes only 20 ~ 30 days from planting to harvesting. In southern China, the temperature is high in winter, and plants grow constantly. The harvest of 1 165438 began in late June or early mid-October, and then it was harvested every 20-25 days until April of the following year. * * * It can be harvested for 5-6 times, and the yield per mu is 750- 1200 kg. There are two ways to harvest watercress: one is to harvest buds one by one; Another way is to harvest the mud in separate beds, collect one and leave one, remove the residual roots and old leaves after harvesting, and put them on the market after classification and bundling. The former is time-consuming and laborious, but the product quality is high, the plant loss is small, the recovery is fast, and the time to enter the second harvest is short. The latter has less labor and high yield, but the post-harvest finishing is labor intensive, the quality is slightly worse, and the post-harvest recovery period is longer.

5. Seed reservation: There are two seed reservation methods for asexual propagation of watercress, that is, seed reservation for old stems, that is, seed reservation in situ and seed reservation for transplanting in dry land. In South China, when the temperature exceeds 25℃ in the middle and late April, watercress will no longer be harvested and can be stored.

The method of keeping seeds in situ is: choose a well-drained and cool watercress field, drain the field water in the middle and late April, and keep seeds in situ. When crossing Xia Hou, only the old stems and roots at the base can be kept for seed.

The method of keeping seeds in dry land is to transplant plants to dry land in mid-April in time, and water them every day after planting until they survive.

Cabbage is not resistant to high temperature, and whether it can spend the summer safely is the key to the success or failure of planting. No matter which method is adopted, the management of fertilizer and water should be strengthened in summer. After Tomb-Sweeping Day, the temperature gradually increased, the weather was hot, and plants were prone to wither and even die. Therefore, first of all, we should build a cool gauze curtain shed in time to keep out the shade.