The solarization is the method that we get a soil disinfection by solar radiation completely environmentally friendly way. If we learn to combine this technique with some products (or not), we can achieve levels of disinfection comparable to other much more expensive methods.
BRIEF INTRODUCTION TO SOLARIZATION
Formerly, in traditional agriculture, techniques such as crop rotation, fallow and nutrient restoration were carried out with which good results were achieved. Currently, in the XXI century with intensive agriculture, not many producers cannot afford to leave the land uncultivated. With the repetition of the cultivation, pests and diseases often appear that carry out part of their cycle in the soil, generating problems for the following productions.
WHAT IS SOLARIZATION?
Solarization is based on covering a portion of the land with a polyethylene mulch in order to heat a moist or warm soil and reduce the microbiotic load.
THE SOLARIZATION PROCEDURE
Before proceeding to mulch the ground, a series of procedures will have to be carried out. The first of these is to carry out a deep work with subsoiler followed by a pass to break up the clods or large pieces of earth.
To carry out solarization, the land must have sufficient humidity. In the event that the plot is dry, drip or flood irrigation will be carried out. Then the plastic will be placed correctly, avoiding gaps and burying it correctly so that it cannot be torn off by actions of the wind.
The specific duration of this technique should be at least 30 days, with an optimal recommendation of 45 days .
AT WHAT TIME DO I SOLARIZE?
As it is a procedure for heating the soil by the effect of solar rays, the best season to do it is in summer. The months of July and August are the best indicated to perform this technique. In the event that for calendar reasons it cannot be carried out in the optimal summer months, by means of a sum of procedures, such as the use of manure or fumigants, good results can be achieved from May to October.
Let’s see an example of the temperatures achieved with solarization and its comparison with a test without a sheet.
Single sheet test
- At a depth of 8 cm in the hours of maximum sun (12 a.m. to 4 p.m.): 42.5º C
- At a depth of 16 cm in the hours of maximum sun (12 a.m. to 4 p.m.): 37.5º C
- At a depth of 32 cm in the hours of maximum sun (12 a.m. to 4 p.m.): 35º C
- At a depth of 8 cm in the hours of maximum sun (12 a.m. to 4 p.m.): 47.5º C
- At a depth of 16 cm in the hours of maximum sun (12 a.m. to 4 p.m.): 43º C
- At a depth of 32 cm in the hours of maximum sun (12 a.m. to 4 p.m.): 40º C
- At a depth of 8 cm in the hours of maximum sun (12 a.m. to 4 p.m.): 35º C
- At a depth of 16 cm in the hours of maximum sun (12 a.m. to 4 p.m.): 31º C
- At a depth of 32 cm in the hours of maximum sun (12 a.m. to 4 p.m.): 29º C
The difference in temperatures throughout the day, with a variation between night and day of 20º C contributes to a «pasteurizing» effect. High temperatures reduce the burden of pathogens in the soil, until the disease is completely eliminated in situations of high temperature and sudden changes at night.
Furthermore, the system does not work solely due to the change in temperatures. In the event that the land has organic matter, fermentation phenomena occur with temperatures. An environment is created with an accumulation of gases such as ammonia, which are toxic to fauna. This is a method for areas where high temperatures are not achieved on the ground, or for example, if it is practiced in less hot months (May, June or October).
With the incorporation of between 2.5 and 5 kg / m 2 of manure or compost , the fermentation process discussed above is obtained.
If the ambient temperature is too cold, better temperature ranges are achieved with double layer solarization.
The problems of this method are not related to the process that it carries out, but to the maintenance of the sheet in the field. The layer must be prevented from having holes, cracks or breaks where the heat escapes. Likewise, depending on the color of the sheet, it can cause animals to consider the layer as water and approach the plot, especially in the case of birds, whose control is very difficult. For the rest of non-flying animals, it is solved with the installation of a perimeter rope around the sheet, by means of stakes.
It is necessary to avoid the shadows of the surroundings, originated by trees, mountains or houses.
The effects of solarization at the edges of the plot are very low, because high temperatures are not achieved. Optimal temperature values are achieved 1 meter from the edge.
The plastic must be well tensioned, avoiding air pockets that reduce the effectiveness of the technique. Also avoid the opposite case, which are holes or holes in the ground.