Hydroponic is soilless system, which allows a production of plants in degraded and for traditional horticulture inadequate areas. The advantage of hydroponics is economical and environmentally friendly water management, as waste water is recycled and reused. There are several systems of hydroponics, such as deepwater culture, float hydroponics, nutrient film technique, aeroponics and aquaponics. Crucial part of successful production in hydroponic system are growing media or substrates. Substrates are mixture of various inert materials that create a living space for the plant. Each substrate has its own physical and chemical properties, which are crucial for normal growth and development of plants. Substrates take over the role of soil, so it is important they have good water-holding capacity, adequate aeration and enable constant flow of nutrients from media to rhizosphere. Growing media can be divided into mineral, organic and synthetic. Literature on growing substrates lists some of the facts supported by experiments. A growing media with coconut fiber and crushed stone is better choice for aquaponic systems than a phenolic foam, because the first one has better water-holding capacity. An experiment with substrate mixtures with different proportion of vermiculite and pine bark showed that a higher proportion of vermiculite affects on lower water-holding capacity of the substrate. The last study is about salt accumulation in relation with irrigation rate in closed hydroponic system. It concludes that with higher irrigation rate we affect on slower accumulation of salt in the rhizosphere.
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