What is soilless culture?

Soilless culture can be broadly defined as a planting method that does not use soil but uses nutrient solutions to grow any plants. Since the soilless culture method needs to dissolve the nutrients required by the crop in the nutrient solution to absorb the roots of the plant, it is also called a hydroponic system. The research report shows that the use of soilless cultivation can significantly increase the yield of crops, which may increase the yield by more than tenfold ^[1], and can effectively control the growth conditions and environment to prevent harmful substances from being produced in the soil. It makes crop quality relatively stable.

Precautions for using soilless cultivation methods:

The formula, concentration, and temperature of the nutrient solution.

In the nutrient solution formula used in the soilless cultivation method, it is necessary to add the nutrient elements originally provided by the soil to the plant. These elements are mainly composed of 6 main mineral elements and 7 kinds of trace elements: nitrogen (N), phosphorus (P), potassium (K), calcium (Ca), magnesium (Mg), sulfur (S), boron (B), chlorine (Cl), copper (Cu), iron (Fe), manganese (Mn), molybdenum ( Mo), and zinc (Zn), respectively^[4]. After the nutrient solution is configured and planted, as the plant absorbs nutrients, the concentration of the nutrient solution (EC) will decrease. During the cultivation process, the concentration (EC) of the culture medium needs to be checked regularly to prevent changes in the concentration (EC) from hindering plant growth. In addition, the temperature of the nutrient solution needs to be controlled within the optimal range of 18-25 degrees Celsius to prevent root rot.

Maintain the pH Value

The soil has the function of adjusting the pH value. Plants need to absorb nutrients from the nutrient solution at a specific pH value.^[2] To prevent the pH value of the nutrient solution changes in the cultivation process during the soilless period, botanists choose to use the biological buffer as an important component in the nutrient solution to maintain the pH. There are many kinds of buffers that can maintain and adjust pH. After many experiments, it is found that MES Buffer is the best choice. MES Buffer is biologically inert and non-toxic to plants, and it has very low metal-binding constants, It can stably maintain the pH value of the nutrient solution without affecting the metal ions of the nutrient solution ^[3].

If you want to find other backup buffers, you must pay attention to the following^[3]：

• Inorganic buffers may be phytotoxic
• Solid carbonate cannot prevent pH from rising
• The exchange resin may affect the magnesium (Mg) and manganese (Mn) in the nutrient solution

Further reading: Aseptic culture methods and biological buffers

Further reading: MES Buffer used in Hemp

Supply of oxygen

One of the most important keys to the healthy growth of plants is oxygen. Soilless culture systems are mainly divided into open systems—DWC (Deepwater culture) systems or closed systems—NFT (Nutrient film technique) systems. In the DWC system, because the plant roots are soaked in the nutrient solution tank with a high water level for a long time, it is easy to cause the plant to die due to lack of oxygen. It is necessary to use a pump to supply oxygen to the water tank to provide oxygen for the roots ^[6]. In the closed system—NFT system, the root system is cultivated in the nutrient solution conveying pipe at shallow water level. In addition to part of the root system that can directly contact the air, the continuously flowing nutrient solution can also bring oxygen back into the nutrient solution ^[1]for absorption by plant roots.

There are many benefits of using soilless cultivation methods, not only can increase the yield and quality, but also reduce the waste of water resources, and achieve the effect of recycling ^[1], it can also solve the problems of land urbanization and food shortage ^[5]. The future trend of soilless cultivation is unstoppable. However, the initial capital investment cost is high priced, and many instruments and equipment are required to control the state of the planting environment such as water quality, pH value, and oxygen content. Compared with soil cultivation, more professional knowledge and a high degree of environmental control technology are required, which results in some difficulties in popularization.

Reference:

^[1] Soilless Culture System to Support Water Use Efficiency and Product Quality: A Review https://doi.org/10.1016/j.aaspro.2015.01.054

^[2] Fertilizer and Cultivar Selection of Different Vegetable Crops and Evaluation of Different Ph Buffers in Hydroponics https://shareok.org/handle/11244/300316

^[3] An evaluation of MES (2(N-Morpholino)ethanesulfonic acid) and Amberlite IRC-50 as pH buffers for nutrient solution studies https://pubmed.ncbi.nlm.nih.gov/11539688/

^[4] Complete Guide for Growing Plants Hydroponically

^[5] Hydroponics as an advanced technique for vegetable production: An overview DOI: 10.5958/2455-7145.2018.00056.5

^[6] REVIEW ON SOILLESS METHOD OF CULTIVATION: HYDROPONICS http://www.recentscientific.com/sites/default/files/15726-A-2020.pdf