Want to grow vegetables with soilless culture? You need to master these three techniques

Soilless culture replaces the soil environment with an artificially created crop root environment, which can effectively solve the contradictions in the supply of water, air and nutrients that are difficult to resolve in traditional soil cultivation, keeping crop roots in the most suitable environmental conditions, thereby giving full play to the yield-increasing potential of crops. At present, more than 100 countries and regions around the world have adopted soilless culture technology. As the cultivation technology has gradually matured and developed, its scope of application and cultivation area have also continued to expand, and the level of management and technical expertise has risen to unprecedented heights, achieving intensive, factory-style production and attaining the goals of high quality, high yield, high efficiency and low consumption.

Aeroponic cultivation

Aeroponic cultivation is a soilless culture technique that uses a spray device to atomize the nutrient solution into fine droplets and spray them directly onto the plant roots to provide the water and nutrients needed for plant growth. The crops are suspended in a sealed cultivation device (trough, box or bed), while the roots are exposed inside the cultivation device, and the nutrient solution is atomized by the spray device and sprayed onto the root surface.

Animated demonstration of aeroponic cultivation

It is the form that best resolves the water-air contradiction of the root system among all soilless culture techniques, and it is also easy to automate and to carry out vertical cultivation, improving the utilization rate of greenhouse space. It can multiply crop yields. However, because this device requires continuous circulating supply of solution, if there is a prolonged power outage (more than 30 minutes) or a water pump failure, and the solution cannot be circulated in time, problems can easily arise.

The various aeroponic cultivations introduced previously were all used for growing leafy vegetables and fruiting vegetables, and they share a common feature: the harvestable products that people can use are all the original above-ground leaves, stems and fruits. In fact, adopting aeroponics is even more favorable as the best cultivation method for plants grown for their roots or various tuber and rhizome types. It not only benefits the development of the root system and tuberous roots and rhizomes, but also makes harvesting extremely convenient, allowing harvest in batches at any time, or selective harvesting according to standard specifications. For some plants grown for their roots for medicinal use, it is even more conducive to the formation of well-developed root systems, greatly increasing the economic yield.

So what advantages and conveniences does aeroponics offer for underground-use plants such as lilies, potatoes and sweet potatoes?

First, when these crops are grown aeroponically, just like other leafy vegetables and fruiting vegetables, the rate of biomass formation is greatly accelerated, several times that of soil cultivation;

Second, their underground parts can be inspected at any time, which is more conducive to observing and studying the development of the underground parts, providing more field data for people to formulate management measures and research cultivation techniques. For example, the effect of foliar spraying of paclobutrazol on potato tuber development is more convenient and intuitive to observe than in soil cultivation;

In addition, for soil-cultivated plants, when the underground parts are to be harvested, most are harvested by a single digging, resulting in products of uneven size and inconsistent quality. With aeroponics, harvesting the underground parts is like picking fruits and vegetables: batch harvesting and selective harvesting can be carried out, and the harvested tuberous roots and bulbs can fully achieve consistency in size and quality. Using this method, the overall economic yield can be increased several times compared with one-time harvesting. This may be related to less nutrient waste by the plant and the ability to fully convert biological yield into economic yield.

In addition, from the perspective of the technology itself, aeroponics is also more convenient in operational production. The development of the underground parts can be inspected at any time, and the nutrient solution can be regulated at any time according to the development situation. More importantly, underground development is completed in the air, and its morphological development is not affected by the mechanical resistance of soil. Individual development is extremely uniform, showing relative consistency in morphology. For example, potatoes appear as consistent round or oval shapes, truly like eggs of uniform size. Management labor is also greatly reduced: no need to hoe weeds or loosen soil, no need to earth up or preserve soil moisture. Root tubers and rhizomes can develop in the mist without any obstruction, allowing their varietal potential to be maximized. The yield is several times or even dozens of times that of ordinary soil cultivation.

Deep flow trough cultivation

Deep flow technique (DFT) refers to a hydroponic technique in which plant roots grow in a relatively deep and flowing layer of nutrient solution. The planting trough holds about 5-10 cm or even deeper nutrient solution, with the crop roots placed in it, while a water pump is turned on intermittently to supply solution so that the nutrient solution circulates and flows, to replenish oxygen in the nutrient solution and make the nutrients in it more uniform. Deep flow hydroponic facilities consist of planting troughs, planting nets or planting boards, solution storage tanks, circulation systems and other parts. It is the earliest soilless culture technology developed for commercial crop production. It can produce fruiting vegetables such as tomatoes, cucumbers, peppers, hairy gourd, sponge gourd, melons and watermelons, as well as leafy vegetables such as choy sum, bok choy, lettuce, water spinach and chives.

Dynamic demonstration

Its characteristics are shown in:

The nutrient solution layer is relatively deep, and the root system extends into the deeper solution layer. Each plant occupies a larger amount of solution. Therefore, the nutrient solution concentration, dissolved oxygen, pH, temperature and water volume are not prone to sharp changes, providing a relatively stable growing environment for the root system.

The plants are suspended at the level of the nutrient solution surface, so that the root crown of the plant leaves the solution surface, while the extended roots can still touch the nutrient solution. Since the root crown would rot if submerged in the nutrient solution and cause the plant to die, the work of suspending the plants should be done well.

The nutrient solution circulates and flows. This increases the dissolved oxygen in the nutrient solution and eliminates the local accumulation of harmful metabolites on the root surface, eliminates the concentration difference of nutrients between the root surface and the nutrient solution outside the roots, so that nutrients can be delivered to the root surface in time and meet the needs of plants more fully.

Shallow flow cultivation

Shallow flow (NFT): Its characteristic is that the circulating nutrient solution flow is film-like, with only a shallow flow a few millimeters thick passing through the bottom of the cultivation trough. The bottom of the root mat of hydroponic crops contacts the shallow flow to absorb water and nutrients, while the upper part is exposed to moisture to absorb oxygen, thus better resolving the contradiction between root water absorption and oxygen absorption. However, it has shortcomings such as shallow solution flow, unstable solution temperature, plants easily wilting once power or water is cut off, and poor stability of the rhizosphere environment, which limit its further development. This method is widely used on some crops such as lettuce and tomatoes. The composition of hydroponic facilities mainly consists of five parts: the nutrient solution tank, the cultivation bed, the solution supply system, the drainage system and the circulation system.

Animated demonstration of shallow flow cultivation technology

Compared with it, shallow flow cultivation technology does not use a solid substrate. In inclined planting troughs requiring a certain slope (about 1:75), the nutrient solution flows through the crop roots only as a thin layer several millimeters deep. Part of the crop roots is immersed in the shallow flowing nutrient solution, while the other part is exposed to the moisture in the planting trough, which can better solve the root system's oxygen demand for respiration.

However, because the buffering performance of the root environment of this device is poor, the temperature around the rhizosphere is greatly affected by the outside. In addition, because the nutrient solution layer in the planting trough is relatively shallow, with the planting trough holding about 5-10 mm of nutrient solution, the total amount of nutrient solution in the planting system is relatively small. Therefore, the concentration and composition of the nutrient solution are prone to sharp changes, and the solution must be continuously circulated, resulting in relatively high energy consumption. If there is a prolonged power outage or a water pump failure, and the solution cannot be circulated in time, problems can easily arise. During high temperatures and the peak crop production period, the plant leaves have a large transpiration rate and consume a large amount of nutrient solution, and if supply is not timely, it can also easily cause plants to wilt.

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