Rock wool is a lightweight hydroponic substrate made by spinning molten basalt into fine fibers, then forming a series of cubes, blocks, growing slabs and granular products. Since rock wool and other asbestos or mineral wool used in horticulture are derived from rock, many people consider them natural products. Rock wool is a widely used substrate in commercial horticulture for producing a variety of crops such as tomatoes, melons, cucumbers, peppers, strawberries, herbs and cut flowers; however, small hydroponic growers who wish to utilize improved root zone technology can also easily use it. Rock wool earlier started as an insulation material in the construction industry, its lightweight but highly aerated characteristics help keep the inside of buildings warm while being easy to handle, cut and install. In the late 1960s, trials were conducted in Denmark to test the possibility of using asbestos as a substrate for hydroponic plants, and since then, asbestos as a growing medium has been continuously developed and improved. Both large commercial producers and small growers use rock wool. A series of products have also been developed, each with different advantages and applications. In addition to choosing different sizes of rock wool cubes, blocks and blocks for propagation, growing slabs and granular rock wool are also used for producing long-term crops and fruiting plants.
The way molten rock fibers are packed and the density inside rock wool products determine the characteristics of the growing medium, such as water retention capacity, aeration or air-filled porosity, and water gradient from the top to the bottom of the cube or growing slab. By changing these characteristics, growers can use rock wool products for different applications. For example, one product may maintain a slightly drier root zone, helping guide crops to avoid excessive vegetative growth, while another product is specifically designed for ultra-fast root growth and development. This allows growers to choose rock wool products suitable for their system, crop, irrigation strategy and environment to maximize plant growth and development. Standard rock wool products can drain freely after irrigation, and then usually contain 80% nutrient solution, 15% air pore space and 5% rock wool fiber, although these ratios vary slightly between rock wool brands and products. A typical rock wool slab, such as one used for tomatoes and other fruiting crops, although drainage holes can freely drain excess solution.
And one of the other characteristics of rock wool board is that plants can still extract water at very low water tension in the medium to promote growth. This means that when rock wool is saturated due to irrigation, and the rock wool board has dried significantly and lost up to 70-80% of its water content, plants can easily extract water. The water gradient between the top and bottom of the rock wool growing slab, cube or block is one of the important characteristics of the product. After irrigation, the bottom of rock wool has sufficient water, usually at the medium saturation level, while the upper layer of rock wool remains in drier conditions, so sufficient aeration and oxygen can be obtained for root absorption and respiration. It is this water gradient of rock wool material from top to bottom that makes it such a good hydroponic substrate, but at the same time, growers who do not understand this characteristic may mistakenly think that the rock wool surface is too dry, although there is a lot of nutrient solution deep in the roots, and over-irrigate the plants. Rock wool, when properly irrigated, should not sit in a nutrient pool and be completely soaked from top to bottom like a sponge. Rock wool must be allowed to drain completely so that excess nutrient solution leaves the slab or cube under the action of gravity after application. When doing so, fresh air is drawn into the top layer of the material, providing fresh oxygenation for the material. Root zone. By allowing rock wool to drain freely, overwatering becomes more difficult. Therefore, make sure not to over-irrigate plants. On the surface of the slab, rock wool may look dry, but there is a lot of nutrient solution at the bottom.
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