Alongside traditional horticultural cultivation methods, other techniques of cultivation without soil, or hydroponic cultivation, have been developed. However, the joint application the general concepts of hydroponics and the advanced techniques applied to traditional horticulture, such as localized irrigation through geotextile exuding hose, has permitted the appearance of what is called "semi-hydroponic" cultivation. This technique also provides an improvement in the environmental impact in comparison with traditional technology or hydroponic techniques, because it takes advantage of the best of both systems.
It takes the water where the plant needs it
The attainment of an increase in productivity in traditional horticulture has required for many years the use of an enormous quantity of natural resources. It is because of this that in the last two decades there have appeared a great number of new techniques whose main purpose has been to increase productivity whilst reducing production costs and the environmental impact of traditional horticultural production.
One of these techniques is that of localizes irrigation using a non-labyrinthine geotextile hose, whose main purpose is to supply the water where the plant needs it, by moistening a continuous strip of land, thus avoiding the loss of water. In comparison with other methods of localized irrigation, this technique also permits:
- the use of saturated calcareous and ferruginous water, as the salts are not deposited inside the hose.
- a cost reduction because drippers do not need to be checked.
- a reduction in fertilizer consumption.
- a reduction in plant health product consumption.
- a reduction in the pressure requirements.
- the elimination of flooding, as the system provides the amount of water demanded by the osmotic pressure of the soil.
The purpose of cultivation without soil, a technique that was consolidated in the 1960s, is to give the plant the best conditions of fertilization and irrigation, and to avoid the diseases transmitted by the soil in traditional horticulture.
This technique can use different sorts of substrates (peat, sand, pine bark, glass wool, perlite, moisturizing gels, etc.) or even no substrate, as is the case of the NFT method. However, all types of CHS have in common a strict quantitative control of the nutrient solution that is provided to the plant with the water. The drawback of this technology, in addition to its cost and technical complexity, is that it has a high environmental impact, both in the process of obtaining some of the substrates and in the product washed off with the water. The inert substrates also generate an important volume of residues at the end of the cycle.
The continuous search for new techniques to improve productivity, reduce costs, and generate an added value by minimizing the environmental impact has led to the appearance of the so-called "semi-hidroponic" cultivation, which was first put into practice by Greek producers.
This new cultivation system is based on the reuse of the plastic cases - grooved containers - used for transporting flower bulbs, the use of a non-inert recyclable substrates and the use of a localized irrigation system using PORITEX geotextile exuding hose.
After disinfection and filling with a substrate chosen by the producer, the plastic cases are placed in the greenhouse, and the irrigations system mentioned above is installed.
The surplus waters that are filtered along the grooves of the cases can be withdrawn and reuse after analysis and reloading with nutrient. The cases, or production units, are withdrawn from the production system at the end of the growing cycle, and are replaced by sown or germinated cases from other installations. The substrate can be reused after disinfection or after undergoing a fermentation process.
What is interesting in this new production system is that provides the positive aspects of both advanced traditional horticulture and CHS, whilst minimizing the environmental impact of horticultural production. Furthermore, it provides a new final use for plastic cases. The most important advantages include:
- I does not need a high level of technical knowledge on the part of the horticulturist.
- It does not require investment as it uses non-returnable containers.
- It does not require specific substrates.
- The production units are easy to handle.
- It is possible to prepare (sow and germinate) the containers outside the production greenhouse.
- Both containers and substrate can be reused.
- Uniform plantation.
- Reuse of nutrients.
- Absence of flooding and guaranteed ventilation of the roots, thus reducing root pathologies.
- Application of an irrigation system with a lower energy consumption, or even by gravity.
- It is possible to install the production units on non-arable lands or contaminated lands.
- A new final use for the plastics containers.
- Recycling of the irrigation water and nutrients, thus reducing the pollution of the soil.
- An overall energy saving through the improved use of the nutrients.