The DWC system is a soilless cultivation system that enables plants to grow efficiently by providing the plant roots with a nutrient solution environment of suitable depth, a stable supply of nutrients, and sufficient oxygen. This system can effectively overcome problems that may occur in traditional soil cultivation, such as uneven soil fertility and soil-borne pests and diseases. Moreover, it can precisely control the composition of the nutrient solution and environmental conditions according to the needs of different plants.

The Deep Water Culture (DWC) system mainly consists of the following parts:

• Planting bench
  This is the container for crop growth. It is a rectangular structure made of hot-dip galvanized pipes and covered with a layer of waterproof film. The depth of the planting bench is usually around 15-20 centimeters to ensure there is sufficient nutrient solution to support the growth of plant roots, enabling the nutrient solution to fully immerse the roots.
• Nutrient solution circulation system
  Reservoir: It is used to store the nutrient solution. Its size depends on the planting scale and crop requirements. Usually, it is a large-scale container either underground or above-ground. It needs to hold an adequate amount of nutrient solution to meet the growth needs of the crops for a certain period, thus avoiding frequent replenishment of the nutrient solution. For example, in a small indoor DWC system, the reservoir may only have a capacity of several tens of liters, while in a large-scale commercial planting system, the reservoir capacity can reach several thousand liters.
  Water pump: It is the power source for the circulation of the nutrient solution. The water pump transports the nutrient solution from the reservoir to the planting bench, ensuring that the plant roots can continuously obtain the nutrient solution. Its flow rate and head should be selected according to factors such as the size of the planting system, the length of the pipeline, and the resistance.
• Pipeline system
  It includes the inlet pipe and the return pipe. The inlet pipe is responsible for transporting the nutrient solution from the reservoir to the planting bench, and the return pipe returns the excess nutrient solution in the planting bench to the reservoir. The pipeline materials are generally required to be corrosion-resistant and non-toxic, such as PVC pipes. The diameter of the pipeline should be determined according to the flow rate of the nutrient solution and the system pressure.
• Planting board and planting cup
  Planting board: Usually, it is a foam board with planting holes, placed on the planting bench. Its function is to fix the plants, keeping the basal parts of the plant stems in the appropriate position and preventing the plants from lodging.
  Planting cup: It is a container for placing plant seedlings, generally made of plastic, with many small holes on the cup wall. These small holes allow the nutrient solution to enter the planting cup and provide nutrients for the plant roots. The size of the planting cup depends on the size of the plant seedlings. For example, when planting leafy vegetables such as lettuce, the diameter of the planting cup is about 5-8 centimeters.
• Oxygen-increasing device
  Since plant roots grow in the nutrient solution and need sufficient oxygen for respiration, the oxygen-increasing device mainly includes an air compressor and a microporous aeration pipe. The air compressor compresses the air and then injects tiny bubbles into the nutrient solution through the microporous aeration pipe, increasing the dissolved oxygen content in the nutrient solution.
• Water chiller
  It can optimize the root growth environment. For example, the optimal water temperature for hydroponic lettuce cultivation is between 18-22°C. In summer, when the temperature is relatively high, the water body is likely to heat up and exceed the suitable range. The chiller can lower the water temperature through its refrigeration system, preventing the roots from being affected by high-temperature-induced hypoxia, which could otherwise impact their absorption function. This ensures the health of the roots and improves the absorption efficiency of nutrients and water.

Driven by the water pump, the nutrient solution enters the planting bench from the reservoir, providing nutrients for plant roots. Plant roots absorb nutrients while being immersed in the nutrient solution. The air pump injects air into the nutrient solution through the aeration devices, forming a dissolved oxygen gradient to ensure aerobic respiration of the roots.

As plants absorb and consume the nutrients in the nutrient solution, the circulation system will regularly or according to the detection results, return part or all of the nutrient solution in the planting bench to the reservoir for supplementation and adjustment, such as adjusting the chemical properties such as the pH value and electrical conductivity (EC value) of the nutrient solution, as well as physical properties such as temperature.

I. Excellent Nutrient Solution Supply and Buffering Capacity
Stable Nutrient Supply
In the DWC system, the nutrient solution layer is relatively deep, usually around 10-20 centimeters. This results in a relatively large total volume of the nutrient solution. For example, in a larger DWC planting trough, the sufficient nutrient solution reserve can continuously provide plants with all kinds of essential nutrient elements, such as macronutrients like nitrogen, phosphorus, and potassium, as well as micronutrients like iron, manganese, and zinc. It's like a "nutrient warehouse" that can meet the growth needs of plants for a long time.

The circulating system of the nutrient solution further ensures the even distribution of nutrients. Through equipment like water pumps, the nutrient solution is circulated between the planting trough and the storage tank, allowing plant roots to evenly come into contact with various nutrients and avoiding poor growth caused by local nutrient deficiency or excess.

Buffering Environment
The relatively deep nutrient solution layer can also play a certain buffering role for environmental factors such as the composition and temperature of the nutrient solution. For instance, when the outside temperature changes, the large amount of nutrient solution can absorb or release heat, making the temperature change of the nutrient solution relatively slow and providing a relatively stable temperature environment for plant roots. It's similar to a natural "air-conditioning system", reducing the damage to plant roots caused by temperature fluctuations.

It also has a buffering effect on chemical properties such as the pH value and electrical conductivity (EC value) of the nutrient solution. If there are fluctuations in the pH value or EC value due to plant absorption or changes in the nutrient solution composition, the relatively large amount of nutrient solution can dilute these changes to a certain extent, providing a relatively stable chemical environment for plant roots.

II. Superior Root Growth Environment
Adequate Oxygen Supply
In the DWC system, an air pump is generally used to supplement oxygen to the nutrient solution. Due to the relatively deep nutrient solution, a good dissolved oxygen gradient can be formed in the nutrient solution. The oxygen content is high near the air pump, and in the slightly farther areas, as oxygen diffuses and is consumed by plant roots, the oxygen content gradually decreases, but it can still ensure that the roots have enough oxygen for respiration.

This dissolved oxygen environment is conducive to the aerobic respiration of plant roots, promoting root growth and nutrient absorption. For example, for leafy green vegetables like lettuce in the DWC system, their roots will grow whiter and stronger because of the sufficient oxygen supply. Compared with traditional soil cultivation, the root vitality and absorption efficiency are higher.

Spacious Root Expansion Space
The deep liquid layer provides a broad growth space for plant roots, enabling the roots to stretch and grow freely. This is very beneficial for some plants with developed root systems, such as tomatoes and cucumbers. Their roots can continuously extend in the nutrient solution, absorb more nutrients and water, and then support the vigorous growth of the above-ground parts.

III. Easy to Manage and Maintain
Visualized Management
The DWC system usually has relatively transparent or semi-transparent planting containers, which allows growers to directly observe the growth status of plant roots, the liquid level of the nutrient solution, and its clarity. For example, by observing, problems such as whether the roots are diseased, whether the nutrient solution is contaminated, or whether the liquid level is too low can be detected in time.

Convenient Cleaning and Disinfection
Compared with some complex substrate cultivation methods, the planting troughs and nutrient solution circulation systems of the DWC system are relatively easy to clean and disinfect. After the end of a planting cycle, the nutrient solution can be drained, and then special disinfectants can be used to clean and disinfect the planting troughs, pipes, etc., preparing for the next round of planting. Moreover, due to the absence of substrate residues and complex medium treatment processes, the possibility of pests and diseases breeding and remaining in the substrate is reduced.

IV. Suitable for Cultivating Multiple Kinds of Plants
Ideal for Leafy Green Vegetables
For leafy green vegetables such as lettuce, spinach, and bok choy, DWC deep flow cultivation can provide sufficient water and nutrients, enabling them to grow rapidly. These plants can quickly absorb elements such as nitrogen and phosphorus in the nutrient solution, promoting the growth and development of their leaves. Moreover, by adjusting the formula of the nutrient solution and environmental conditions, the quality of leafy greens can be effectively controlled, such as the thickness, color, and taste of the leaves.

Also Applicable to Some Fruit Vegetables
For fruit vegetables such as tomatoes and peppers, the DWC system can also provide good growth conditions during their early growth and fruiting stages. In the early growth stage, strong roots can be quickly established in the nutrient solution, laying the foundation for the subsequent growth of the above-ground parts and flower bud differentiation. In the fruiting stage, a stable nutrient supply helps with fruit development and quality improvement.