DFT-Vegetable Soilless Cultivation Technology---Deep Liquid Flow Cultivation

Vegetable Soilless Cultivation Technology---Deep Liquid Flow Cultivation

The deep liquid flow method is the most primitive method of the hydroponic system, which refers to a hydroponic technology in which the root system of the plant grows in a relatively deep and flowing nutrient solution layer. The nutrient solution of about 5~10cm or even deeper is placed in the planting tank, and the root system of the crop is placed in it. At the same time, the water pump is used to intermittently turn on the liquid supply to make the nutrient solution circulate, so as to supplement the oxygen in the nutrient solution and make the nutrient in the nutrient solution more stable. uniform.

The composition of the nutrient solution in the nutrient solution layer of this cultivation method is relatively stable, and at the same time, it also solves the difficulty that the nutrient solution film cultivation system cannot operate normally due to power failure.

1. The characteristics of deep liquid flow hydroponics technology
1. deep

Deep means that the planting tank containing the nutrient solution is deeper, and the nutrient solution layer in the planting tank is deeper.

The root system can extend into the deeper nutrient solution. The total amount of nutrient solution in the whole planting system is relatively large. The composition and concentration of the nutrient solution (including the concentration of various nutrient elements, total salt concentration and dissolved oxygen concentration in the nutrient solution, etc.) , pH, water and temperature are not easy to change rapidly, the root growth environment is relatively stable, and the supplement and adjustment of nutrition are convenient. This is a remarkable feature of deep liquid flow hydroponics technology.

2. flow

It means that the nutrient solution is circulating, the purpose is to:

① Increase the concentration of dissolved oxygen in the nutrient solution;

② Eliminate the "nutrient depletion area" between the root surface and the root nutrient solution when the nutrient solution is left standing, so that nutrients can be supplied to the root surface in time;

③Reduce the harmful metabolites secreted by the root system and accumulated on the root surface, such as organic acids, physiological acidity and alkalinity produced by the root system’s selective absorption of ions, and other metabolites;

④ Redissolve some nutrients lost due to precipitation to supply the needs of crop growth.

3. Hanging

Suspended means that the plants are suspended and planted above the nutrient solution level, the purpose is to:

①Keep the root neck away from the liquid surface to prevent the root neck from being immersed in the nutrient solution and cause rot or even death (except for swampy plants or crops with oxygen transport tissues from the aboveground to the underground;

② Improve the oxygen supply of the root system: Part of the root system can grow in the nutrient solution, while the other part of the root system is exposed to the part of the moist air between the nutrient solution liquid level and the planting board or the planting net frame, so that the nutrient solution The root system in the air and in the air can absorb oxygen, and adjust the liquid layer depth and liquid level of the nutrient solution to the space between the planting plate or the planting net frame according to the growth of the crop and the climatic conditions, so as to adjust the oxygen absorption of the root system.

2. The composition and structure of commonly used deep liquid flow cultivation facilities

The deep liquid flow cultivation facilities include a planting tank, a planting plate or a planting net frame, a liquid storage tank, and a nutrient solution circulation flow system.

1. Planting trough

The width is generally 100~150cm. On the one hand, it is easy to operate, and on the other hand, it prevents the planting board or the planting net frame from being bent, deformed or broken due to insufficient strength when the planting groove is too wide. The depth of the groove is controlled at about 12~15cm, the deepest is no more than 20cm, and the length of the groove is about 10~20m.

2. Planting board or planting screen frame

3. Liquid reservoir

The advantages of setting up an underground liquid storage tank are:

① As a place for nutrient solution adjustment: the adjustment of the pH value of the nutrient solution, the replenishment of nutrients and water, etc. are all carried out in the liquid storage tank.

②Increase the total amount of nutrient solution in the planting system to increase the amount of nutrient solution occupied by each plant, so that the concentration, composition, pH value, dissolved oxygen content, and liquid temperature of the nutrient solution are less likely to undergo drastic changes. The general principle of construction of the underground liquid storage tank is to prevent leakage. During construction, the bottom of the pool should be made of 10-15cm concrete and reinforced, and the wall of the pool should be built with 18-24cm bricks and plastered with cement paste. The cement used for building the pool should be high-grade and corrosion-resistant. At the same time, the surface of the underground liquid storage pool should be 10-20cm higher than the ground and should be covered to prevent rainwater or other debris from falling into the pool, and keep the pool dark to prevent algae from growing.

4. Nutrient solution circulation system

It consists of two parts: liquid supply system and return system. The liquid supply system includes a liquid supply pipeline, a water pump, a valve for regulating flow, etc., and the return system includes a return flow pipeline and a liquid level regulating device in the planting tank. (1) Liquid supply pipeline

Refers to the pipelines at all levels leading from the underground liquid storage tank to each planting tank through the water pump (Note: All pipelines must use plastic pipes, do not use galvanized water pipes or other metal pipes).

(2) Return pipeline and liquid level adjustment device in the planting tank

In order to ensure sufficient oxygen in the nutrient solution, both the liquid supply system and the cultivation tank must be equipped with oxygenation facilities. In addition to increasing the air content during the preparation of the nutrient solution, the method of increasing oxygen can also add compressed air to the cultivation pond, or perform self-circulation of the nutrient solution in the cultivation pond.
3. Management of deep liquid flow cultivation facilities

Taking cement brick structure deep liquid flow hydroponic facilities as an example, we will focus on some problems that should be paid attention to in its management.

(1) Preparation of planting tanks

1. Treatment of new planting tanks

The newly-built planting tanks and liquid storage tanks are made of cement and bricks. Some alkaline substances will be dissolved after soaking in water when they are newly built. At this time, the pH of the aqueous solution after soaking can be as high as pH11. Tanks and reservoirs are treated before use.

(2) Management of the planting process

Select crop varieties with high economic value. Use the conditions of the greenhouse for "off-season" or "wrong-season" production.

(1) Selection of nutrient solution formula

Not only for a certain crop, but also for other crops similar to this crop. However, plants have both commonality and individuality in their nutrient requirements. Some plants or even certain plants in different growth periods require more of one or some nutrients, while others require less.
(2) Adjustment of the liquid level in the planting tank Just after the crops are planted, the liquid level should be kept submerged in the bottom of the planting cup for about 1~2cm. When it is very large and the root system is very developed, it only needs to maintain a 3~4cm liquid layer in the planting tank.

In production, as the plant grows and the root system increases, the nutrient solution level should be gradually reduced, so that part of the roots are exposed to the air. Once the liquid level decreases and the roots produce more hairs, the reduced solution cannot be removed Otherwise, it may cause damage to the root hair or even the entire root system, and may even cause death in severe cases.
However, it is not possible to make the liquid layer in the planting tank too shallow. Generally, it should be ensured that the depth of the liquid layer can maintain the amount of nutrient solution that the plants can still grow normally for 1 to 2 days when there is no power supply and the water pump cannot circulate normally.

4. Advantages and disadvantages of deep liquid flow technology

Compared with other systems, the main advantage is that the nutrient solution has a strong buffer capacity, which can solve the problem that the system cannot operate due to short-term power outages or other failures, and greatly reduces the difficulty of management.

The advantage is that the total amount of nutrient solution is large, the composition and concentration are stable, and short-term water and power outages or equipment failures have no effect on crop growth. The management is more convenient; the root system is partly exposed in the air (except for the full-greenhouse hydroponics technology), and partly submerged in the nutrient solution layer, which can better solve the water-air conflict; the facility is easy to build, durable, and there are few follow-up production materials; suitable for planting Wide range of crops; high nutrient utilization rate, up to 90% to 95%, will not or rarely cause pollution to the surrounding environment.
The disadvantage is that the environment is relatively closed, and the nutrient solution is continuously recycled. Once the root disease occurs, it is easy to cause spread. Moreover, the investment in facilities is relatively large, especially the construction cost of fixed deep liquid flow hydroponic facilities is higher than that of assembled ones. Technical requirements are higher than substrate cultivation