Plant cultivation technologies: hydroponics and substrate culture methods

Hydroponics allows for maximum yields in greenhouses by creating an ideal balance of air, water, and nutrients for roots. This method solves the main problems of protected ground: soil exhaustion is eliminated, the need for soil preparation is removed, and weed and pest control are simplified. The technology is indispensable for the rapid propagation of valuable specimens, hybridization during the winter season, genetic research, and studying the performance of aerial organs against a backdrop of optimal water supply and nutrition. At the same time, artificial soil fertility depends entirely on the agronomist and requires constant monitoring.

How water-gravel hydroponics is structured and works

The most common method in greenhouses remains water-gravel culture. Plants are planted in waterproof trays filled with gravel, and the nutrient solution is supplied by a pump from a reservoir. After the roots are saturated, the liquid drains back by gravity. The upper part of the substrate is left dry to protect against algae, and the irrigation frequency is adjusted according to the season, plant age, and material properties.

• Thickness of the dry upper layer of substrate — 1.5–2.0 cm
• Frequency of solution supply — from 1 to 5 times per day
• Cycle time for supply and drainage — 30–50 minutes
• Minimum solution concentration level — 50% of the initial value
• Frequency of chemical analysis — 1–2 times per week

1. Monitor the pH of the medium daily and adjust it: add alkali when acidifying, and acid when alkalizing.
2. Perform an analysis of the nutrient solution for nutrient content 1–2 times per week.
3. Completely remove the spent solution from the reservoir every 1–2 months.
4. Flush the substrate with clean water to remove accumulated salts before introducing a new batch of nutrients.

Requirements for substrates and nutrient solutions

The physical and chemical properties of the substrate directly affect the development of the root system of plants. A high-quality soil substitute must be chemically inert, neutral, and not release toxic compounds. Durability is critical: as the substrate crumbles, its particle size decreases, which impairs root aeration. Based on their ability to retain moisture, all materials are divided into two main groups.

• Porous substrates (expanded clay, vermiculite, perlite) — have high water-holding capacity, retain water well, and adsorb nutrients. This will protect plants from dying during temporary failures in the irrigation system.
• Dense substrates (sea gravel, granite crushed stone) — have low water-holding capacity, therefore requiring more frequent irrigation, but they guarantee excellent air exchange.

In scientific research, to ensure experimental purity, glass beads, granulated polyethylene, or polystyrene are used instead of gravel. These inert granules do not stick to the roots, allowing the root system to be extracted entirely without damage. Extracting roots without losses from ordinary sand or soil is practically impossible.

To simplify care as much as possible, aeroponics is used — growing plants in humid air without a solid substrate. Roots are periodically sprayed with a fine mist of nutrient solution in enclosed chambers. This approach allows for full automation of all technological practices in the greenhouse.

Aeroponics, aggregatoponics, and plastoponics: features of the technologies

Aeroponics allows for maximum access of air to the plant roots. They are secured in perforated cups with a small volume of granular substrate, and the root system hangs freely in a dark, airtight reservoir. Automation regularly sprays the roots with a fine mist of nutrient solution from above and below. In practice, this method is used primarily for precise control and study of the gaseous regime of the root system.

• Root spraying interval — every 10 min
• Duration of solution supply — 5–7 s
• Complete renewal of the solution in plastoponics — every 2–4 weeks

Aggregatoponics is based on the use of solid granular materials that are periodically saturated with a nutrient solution. This method gives the agronomist flexibility in choosing a substrate for a specific crop and farm conditions. Depending on the origin of the root-inhabited environment, the technology is divided into several categories:

• organoculture — growing on natural organic substrates (peat, sawdust, moss);
• lithoculture — use of solid mineral or plastic substrates;
• aerohydrolithic culture — combined systems that integrate the positive properties of three soilless cultivation methods;
• wick culture — growing on thin hydrophilic films that are moistened through the capillary rise of water and nutrient solution.

In plastoponics, the root-inhabited environment is a hydrophilic, physiologically neutral foam plastic. This material can initially contain the macro- and microelements necessary for nutrition or actively absorb them during irrigation. The method is attractive due to its technological simplicity but has significant operational limitations.