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CHOOSING THE RIGHT SUBSTRATE FOR GROWING MICROGREENS
One of the most critical aspects in growing microgreens is the choice of the cultivation substrate, which plays a fundamental role in determining the productivity and finally the quality of these small vegetables. Furthermore, this choice determines the sustainability of the entire production process.
In order to ensure a good germination and optimal growth of the seedlings, a good substrate must have physical characteristics such as to ensure a porosity greater than 85% of the total volume. It must ensure a correct ratio between macro and micro pores to allow a good water retention capacity (55-70% of the total volume), and a good level of aeration of the root system.
Due to the chemical characteristics, a good substrate for growing micro-vegetables should also have a pH between 5.5 and 6.5 and be clearly free of heavy metals and pollutants. To avoid sanitation problems, it is advisable to choose substrates that have undergone sterilization treatments. Numerous solutions are available on the market and the choice of substrate is generally based on the availability locally, its cost, togheter with its physical, chemical and biological properties.
ORGANIC SUBSTRATES VS. INORGANIC
It is possible to distinguish the cultivation substrates in organic, that is made up of natural and biodegradable materials (for example peat), and inorganic generally inert, such as perlite.
The cultivation substrates most used for the production of micro-vegetables, both commercially and as a hobby, are peat, perlite and vermiculite; either alone or mixed as needed.
By mixing substrates with different characteristics in adequate proportions, it is possible to obtain ideal agronomic characteristics or in any case better than those provided by the single substrates.
An alternative organic material to peat is coconut fiber (coir), which has the advantage of being sustainable and derived from waste materials.
Among the substrates specially developed for the production of micro-vegetables we must mention the specific mats made of recycled fibrous materials. These again can be natural and derived from coconut fiber, jute, cotton and cellulose pulp. Or be inert products made from polyethylene terephthalate. Generally commercially developed mats have standardized agronomic characteristics, with a good balance between water retention capacity and oxygenation.
However, the high cost of commercial substrates has prompted many microgreen producers to seek alternative materials by developing their own growing medium. For example, many micro-vegetable producers buy fibrous waste materials from industrial processes, such as cellulose fiber, cotton and jute at low cost, trying to improve their water retention capacity.