During the whole seedling raising period, water seedling raising is a kind of seedling raising method based on flooding management. The water layer is used to keep warm, which plays a certain role in preventing cold and weeds in seedlings. Moreover, it is easy to pull out seedlings, with less damage to seedlings, and has the role of salt prevention and seedling protection. However, long-term flooding, insufficient oxygen in the soil, easy overgrowth of seedlings and poor quality of seedlings are traditional methods used in rice growing areas in China, and are rarely used at present.
Generally, attention should be paid to seed quality, seed treatment, sowing quality, optimal sowing date, sowing amount (density), fertilizer and water conditions of rice seedlings, soil permeability, rice seedling management and application of plant growth regulators. Good seed quality means that seeds must have strong viability and strong germination potential, so that seeds can ensure a good seed foundation. After proper treatment (such as drying seeds), the germination rate and seedling rate of high quality seeds can be improved.
2. Wet seedling raising method
Wet seedling raising is a kind of seedling raising method between water seedling raising and dry seedling raising. This seedling raising method is easy to adjust the contradiction between water and air in the soil, has the advantages of quick and orderly seedling emergence after sowing, and is not prone to physiological collapse, which is beneficial to promoting seedling emergence and rooting, preventing rotten buds from dying, and can also promote and control seedling growth through water management. Replacing water for seedling raising has become a basic seedling raising method.
The common method is the wet insulation seedling raising method with plastic film. On the basis of wet seedling raising, after sowing, the surface of the compartment is covered with a film, mostly with low arch. This kind of seedling raising method is beneficial to heat preservation, moisture preservation and temperature increase, and can be sown early in time to prevent bud rot and seedling rot and improve the seedling rate. Sowing in early spring is very necessary to prevent low temperature and chilling injury.
3. Dry seedling raising method
In the whole process of seedling raising, dry seedling raising only keeps the soil moist and does not keep the water layer. Common dry seedling raising methods, such as fertilizer bed (greenhouse) fine soil plastic tray, open-close film dry seedling raising and so on, have become important seedling raising methods for strengthening seedlings, resisting cold, drought and saving water in cold areas and double-cropping early rice.
On the fertile and loose seedbed, dry-raise seedlings with plastic trays and dry-raise seedlings with plastic floppy disks or paper tubes on the fertilizer bed by fine soil method. The sowing date of the seedling raising method is not limited by water source, and the seedling raising operation in dry seedling field is convenient; Suitable for the cultivation of large, medium and small seedlings. Compared with plastic trays, it prolongs the seedling age without stringing roots, which is beneficial to the collocation of high-yield varieties and the expansion of application scope. In addition, this method is convenient for unified seed supply, centralized scale breeding and commercial seedling supply. Plastic tray dry seedling raising is the best seedling raising form suitable for mechanical seedling throwing, with broad prospects.
4. Two-stage seedling raising method
Two-stage seedling raising is to divide the whole seedling raising process into two stages. The first stage is to cultivate seedlings with 3-4 leaves by the method of dense sowing dry or wet seedling raising; The second stage is the seedling delivery stage, in which the seedlings are sent to the seedling delivery field with or without soil according to a certain density, cultivated into multi-tillered and strong seedlings, and then transplanted into the field.
This is a seedling raising technique suitable for late planting of multi-crop seedlings. Its advantages are high seedling rate, low seed consumption, strong early development and adjustable stubble contradiction. It is especially suitable for late planting of middle rice after wheat stubble, double cropping of late rice and long growth period of hybrid rice seed production. Two-stage seedling raising can solve the contradiction of early sowing and late planting, advance the heading date and avoid adverse effects such as high temperature in flowering period or low temperature in filling period.
5, plastic floppy disk seedling method
This method is a seedling raising method evolved from greenhouse seedling raising, which can increase the proportion of seedlings, reduce the cost of seedling raising, facilitate management, have good seedling quality and are not easy to get sick at seedling stage. The cultivated seedlings can be planted by hand, which is more conducive to throwing seedlings.
Floppy disks are commonly used to grow seedlings on calcium plastic floppy disks, which are 58 cm long, 28 cm wide and 2.6 ~ 2.8 cm deep. They are placed on the bed in the field, filled with nutrient soil, watered and sown. Manual transplanting and sparse sowing, 70-80g per plate; Close planting by mechanical transplanting is per tray 100g, and other operations are the same as open-close dry seedling raising. Rice is grown in the field.