Zeolite as a substrate for growing plants – Hydroponics

Zeolites are natural mountain minerals from the group of aqueous aluminosilicates of alkaline and alkaline earth elements. Crushed zeolite tuffs have good porosity, high ion-exchange and adsorption capacity, air and water permeability, significant content of nutrients such as potassium, magnesium and calcium. Zeolites do not contain nitrogen and phosphorus, which must be applied with mineral fertilizers. Due to the high exchange capacity of cation absorption (1-5 meq / g), zeolites can retain significant amounts of potassium and ammonium ions introduced with fertilizers and available to plants. These properties of zeolites allow them to be used as an excellent substrate for greenhouse crops.

Certain agricultural plants exhibit specific requirements for the nitrogen content of the substrate. Cucumbers and especially tomatoes give a high yield on all substrate modifications. The fertility of the substrate does not decrease after the first harvest, which is confirmed by the harvests of crops planted again.

From an agronomic and industrial point of view, zeolite substrates have the following advantages:

• great potential of mineral nutrition elements;
• good physical properties, high air capacity;
• duration of operation;
• no weeds;
• sterility and good aesthetic appearance.

Good physical properties of the substrate favor gas exchange and ensure the formation of a robust root system and aerial parts of plants, which contributes to faster development and earlier fruiting. The use of zeolite substrates changes the technology of growing plants. A large supply of nutrients ensures normal plant nutrition during multiple harvests.

Plant products are distinguished by good taste. Laboratory studies have shown that its chemical composition meets international standards, and nitrates and nitrites are not found in excessive amounts.

In the production of seedlings of vegetable crops, the substrate shows a number of advantages – faster germination of seeds, the formation of a strong root system and aerial part, which, to a certain extent, predetermines the receipt of a high yield.

Zeolites are used in pure form or with some additives (perlite, coconut). When grown on zeolites, excessive accumulation of nitrates in the product does not occur. When working with zeolite substrates, one should pay attention to the presence of silicon in the solution and the entry into the plant.

The presence of a fine fraction of zeolite (0-2 mm) should be avoided. Its share increases during the operation of the zeolite.

Basic requirements for the agrophysical and agrochemical properties of zeolite, which is suitable and used as a hydroponic substrate:

• mass fraction of clinoptilolite not less than 60%;
• mass fraction of impurities (clay) no more than 10%;
• the zeolite must be water and mechanically strong;
• used fraction 3-8 mm;
• bulk density 0,80-1,10 g / cm³;
• solid phase density 2,30-2,40 g / cm³;
• overall duty cycle 57-60%;
• water holding capacity (PIV) 25-35%;
• air capacity 25-35%;
• the ratio of solid, liquid and gaseous phases – 40%: 28%: 32%;
• the pH value should be close to neutral;
• absorption capacity 1,0-1,5 meq / g (determined by the sum of exchangeable cations);
• specific electrical conductivity (EC, EC) of water extract, not more than 2 mS / cm.

Zeolite containing excessive amounts of sodium, chlorine, bicarbonates must be rinsed with water before use.

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