Why Substrate is Used in Soilless Growing

Hydroponics growing is best known as soilless growing. Plants are grown with natural light or grow lights, water and nutrient solution. Soil is not required or used in hydroponics, but some sort of growing medium generally is. This media or substrate helps anchor plants in place and supports roots. It also helps retain the oxygen and water these root systems need to survive. Only one type of hydroponics does not utilize substrate, and that is the Nutrient Film Technique or NFT system. In this system roots are bathed in nutrient solution directly.

Some common organic substrates used in hydroponics are sawdust, peat or rice hulls. Inorganic substrates may include gravel, sand or rockwool. Certain types of foams or plastic beads may also be used as substrate media in hydroponics.

Why are substrates used at all in hydroponics? The main reason is because the media can serve as a type of buffer. The media creates a reservoir of nutrient solution which keeps both oxygen and nutrient solution available to root systems. This means that irrigation systems need not run continually to keep plants alive as in NFT systems. Without the substrate reservoir, roots would die if irrigation failed and the flow of nutrient solution ceased, or if flooding occurred and oxygen was cut off.

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