Hydroponics and soil-less system
Hydroponics and soil-less system consist of not using soil as substrate for crop production. It has been widely used for production of tobacco and vegetable seedlings. The major advantage with such a system is the absence of weeds and other soil- borne pests, no toxic pesticide residue, better use of water, better control over nutrient and oxygen, increased crop quality and yields.
An example of these methods is the opened hydroponics, where the solution with nutrients is not always recycled.
Seedling production through this system is carried out in plastic pools of 10 m long, 1,20 m wide and 10-15 cm height. It is important that the land in the pools be well levelled covering the surface with a layer of 2 cm of sand to avoid punctures in the plastic. The borders can be built with diverse materials (wires, plywood, bricks, others). The covering of the internal part of the pool is carried out with black plastic of no less of 200 microns. The pool is full with clean water until it reaches 3-5 cm of the superior border. The pool is protected by a micro-tunnel of transparent plastic UV of 150 microns, which is kept by iron arches of 6 mm diameter. The plastic was fixed to both ends by stakes placed one meter of the head of the pool. The pools have to be opened often. The dimensions of the pools can be changed according to the size of the greenhouse.
Crop planting is carried out in Styrofoam trays with 288 small cells per tray, previously filled in with a sterilised substratum. Pelletized seeds are used, which favours better distribution at the time of planting. Trays are placed in the pool and left floating during 60-80 days until the seedlings are well developed. During this period the seedlings are regularly checked, especially the whole pool system ventilation (open during the day on the lateral up to 15 cm of height and closed at night), maintaining constant the level of water, fertilising the water (15N 10P 15K or 20N 10P 20K), using foliar treatments for disease control, treating water with copper hydroxide, and pruning the plants three times.
The pools of supported trays system are smaller (4 x 1 x 0,5 m) than those used in common floating trays. Its walls are built with bricks. In this system plastic tray of 50 x 33,5 x 0,5 cm, with 150 cells each one, is used. The pool is filled in with water and due to the fact that plastic trays do not float, it is supported by the plastic, immerses in a volume of water that arrives to 2 cm height. The reposition of water to keep the required level is constant.
The handling and managing procedures of the supported tray and floating tray systems are basically the same thing, with very few variations, such as in the supported trays it is carries out only two prunings.
Of soil-less systems, the system of supported plastic trays presents additional advantages, such as the seedling development cycle is shorter (10 days), seedlings with better root system, easy removal of seedlings from the trays, better managing of the trays, smaller storage space and bigger durability.
Such methods have been applied for growing tomatoes, strawberries, cucumbers, peppers, eggplants, and ornamentals.