A Detailed Guide to Soilless Three-Dimensional Vegetable Cultivation
AbstractAeroponics: It mainly uses a spraying device to atomize the nutrient solution into small droplets, which are then sprayed onto the plant roots to provide the water and nutrients needed for plant growth. It is a soilless cultivation technique. Aeroponics helps increase yield, which is several times that of soil cultivation. Deep flow technique: It is a hydroponic technique belonging to the flowing nutrient solution layer type. Nutrient film technique: It is a hydroponic method in which plants are grown in a shallow flowing nutrient solution layer.
I. Aeroponics
1. Spray cultivation is also called aeroponics or spray culture. It mainly uses a spraying device to atomize the nutrient solution into small droplets, which are then sprayed directly onto the plant roots to provide the water and nutrients needed for plant growth. It is a soilless cultivation technique.
2. Crops can be suspended in a sealed growing trough, box, or bed, while the roots need to be exposed inside the growing device, and the nutrient solution can be atomized by the spraying device and then sprayed onto the root surface.
3. Among all soilless cultivation techniques, aeroponics is a form that solves the water-air contradiction in the root system relatively well. It is also easy to automate, control, and carry out three-dimensional cultivation, improving the utilization rate of greenhouse space.
4. Aeroponics can increase crop yield, but because this device requires continuous circulating liquid supply, if a power outage lasts more than 30 minutes, or if the water pump fails, it cannot circulate in time, so problems easily occur.
5. The various aeroponic cultivation methods introduced in the past are all used for growing leafy vegetables and melon and fruit vegetables. Their common feature is that the harvested products usable by people are all the aboveground branches, leaves, and fruits.
6. With aeroponic cultivation, it is not only beneficial to the development of roots and tuberous root stems, but harvesting is also very convenient. Harvesting can be done in batches at any time, or selectively according to standard specifications. For some plants whose roots are harvested for medicinal use, it is even more conducive to the formation of well-developed root systems, greatly increasing crop yield.
7. Growing these crops aeroponically is the same as with other leafy vegetables and melon and fruit vegetables: it helps increase yield, which is several times that of soil cultivation. Moreover, its underground parts can be inspected at any time, which is more conducive to observing and studying the growth of the underground parts, and provides more field data for growers to formulate management measures and for cultivation technique research. For example, when applying paclobutrazol as a foliar spray, its effect on potato tuber development is more convenient and intuitive to observe than in soil cultivation.
8. For soil-cultured plants, when harvesting the underground parts, it is generally a one-time digging harvest, resulting in uneven plant sizes and poor quality. In contrast, with aeroponic cultivation, when harvesting the underground parts, it is like picking melons and fruits: harvesting can be done in batches and selectively. The harvested tuberous roots and bulbs are high in quality and yield. Using this method, the overall economic yield ratio can be increased several times compared with one-time harvesting. This may be related to less nutrient waste in the plants and the ability to fully convert biological yield into economic yield.
9. From the perspective of the technique itself, aeroponics is also more convenient in operational production. The growth and development of the underground parts can be inspected at any time, and nutrient solution regulation can be carried out at any time according to growth conditions. 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 relatively uniform, showing relative consistency in morphology.
10. During the growing period, there is no need for weeding, loosening soil, hilling soil, or preserving soil moisture. Root tubers and stems can develop in the mist without any obstruction, and the yield is several times or several dozen times that of ordinary soil cultivation.
II. Deep Flow Technique
1. Deep flow technique (DFT) refers to a hydroponic technique in which the plant root system grows relatively deeply and in a flowing nutrient solution layer. A 5-10 cm, or even deeper, nutrient solution can be placed in the growing trough, and then the crop roots are placed in the trough. At the same time, a water pump is intermittently turned on to supply liquid so that the nutrient solution circulates and flows, in order to supplement the oxygen in the nutrient solution and make the nutrients in the nutrient solution more uniform.
2. Deep flow hydroponic facilities are mainly composed of growing troughs, planting nets or planting boards, liquid storage tanks, and circulation systems. It belongs to the earliest soilless cultivation technique developed for commercial crop production. It can grow fruit vegetables such as chieh-qua, sponge gourd, melon, watermelon, tomato, cucumber, and pepper, as well as leafy vegetables such as choy sum, lettuce, water spinach, chives, and bok choy.
3. In the deep flow technique, the nutrient solution layer is relatively deep, and the roots extend into the deeper liquid layer. Each plant occupies a relatively large amount of liquid, so the nutrient solution concentration, dissolved oxygen, pH, temperature, and water volume are not prone to sharp changes, providing the root system with a relatively stable growth environment.
4. The plant is suspended at the level surface of the nutrient solution so that the root crown of the plant leaves the liquid surface, while the extended roots can still touch the nutrient solution. Because the root crown will rot if submerged in the nutrient solution, causing the plant to die, measures for suspending the plant must be done well.
5. The circulation and flow of the nutrient solution helps increase the dissolved oxygen in the nutrient solution and eliminate the local accumulation of harmful metabolites on the root surface, eliminate the concentration difference between the nutrient solution on the root surface and outside the root, and enable nutrients to be delivered to the root surface in time, more fully meeting the needs of the plants.
III. Nutrient Film Technique
1. Nutrient film technique, abbreviated as NFT, is a hydroponic method in which plants are grown in a shallow flowing nutrient solution layer. After 1979, this technique was rapidly promoted and applied worldwide. Traditional soilless cultivation techniques require relatively deep growing troughs and place solid substrate or nutrient solution in the troughs to grow crops. The growing troughs need to be made of materials such as cement, bricks, wooden boards, or metal, which are both bulky and expensive, and at the same time the oxygen demand of the root system is difficult to solve.
2. The nutrient film technique does not use solid substrate. In inclined growing 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 root system is immersed in the shallow flowing nutrient solution, while the other part is exposed to the moisture in the growing trough, which can relatively well solve the root system's demand for oxygen for respiration.
3. However, because this device has poor buffering performance in the root environment, the temperature around the rhizosphere is greatly affected by the outside. Since the nutrient solution layer in the growing trough is relatively shallow, 5-10 mm of nutrient solution can be placed in the growing trough, and the total amount of nutrient solution in the growing system is relatively small.
4. Therefore, the concentration and composition of the nutrient solution are prone to sharp changes. Liquid must be supplied continuously in circulation, and energy consumption is relatively large. If a power outage lasts a long time or the water pump fails, it cannot circulate in time and problems easily occur. 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. If supply is not timely, the plants are likely to wilt.