Growing in a generally results in stunted growth after a few years of use. Indeed, mono-cropping or lack of crop rotation necessarily causes soil fatigue, a build-up of pests and diseases and a high salt content. The amateur is relatively free from these types of problems because he does not often have the necessary tools to properly disinfect the soil. Preventive control requires the best possible crop rotation.
Let us not forget that the greenhouse can be used to grow other plants than tomatoes or peppers!
How can the health of the soil be maintained?
Preventive:
- Apply the crop rotation rule.
- Grow different crops throughout the year.
- Water the soil well when it is no longer being grown to flush out salts.
- If possible, let the frost penetrate after a major root ball cultivation in winter.
- Never let the soil dry out. Dry soil is dead soil.
- Avoid weed growth.
Curative:
- Steam disinfection
- Chemical disinfection
Salt saturation
With every crop there is a tendency to smoke the soil. In contrast to the open ground where the weather (especially rain) washes away the soil and the water drags your harmful elements into the garden greenhouse where they are stored in the soil. The sometimes inadequate watering only worsens the concentration of salts. Some plants are sensitive to excessive salt content, for example lettuce remains yellow and does not grow.
Control
11 will therefore be necessary: washing the soil in the greenhouses. To be able to do this, you only need to create a dam in front of the doors and flood the garden greenhouse with water. When the soil is then dried out, you can start growing again. Fungal attacks: mold, seedling melting, root rot, (rhizoctonia), pythium, fusarium, botrytis, phytophthora, scierotinia, etc.
Preventive control
- After each crop, eliminate waste (plants, ropes used for staking, etc.).
- Clean the greenhouse, wash the windows and frames. The use of bleach diluted to 10% can be considered.
- Disinfect cutting and sowing equipment
- Use new equipment (pots, terrines, etc.)
Curative control
- Steam disinfection: it requires special and expensive equipment that the amateur cannot get. It is necessary to call on a horticulturist or specialized companies.
- Chemical disinfection: spraying with fungicides: propamocarb – benomyl, maneb; this technique can already solve some problems. Usually, the treatment is carried out by spraying the soil and the pots or terrines before the crop is installed.
More specific disinfection with products
Often, the products of the trade are not approved for the amateur. An approval is required for their use. It is therefore advisable to contact a horticulturist, who usually has this permit.
Dazomet: is used to control nematodes, cryptogams and soil insects. It has a secondary action on weeds. It is applied dry to stirred soil, then incorporated and then sprayed with 10 liters per m². The soil is then covered with plastic to prevent the product vapor from spreading. Rate of use: 40 to 50 g of active substance per m². The ideal temperature will be 12 X and more. Leave the plastic cover for at least 15 days. Then the greenhouse must be aerated for a few hours before using it, then remove the plastic and let the soil aerate. This can be facilitated by using a strawberry to promote aeration. The greenhouse can be grown 4 weeks after treatment. 11 take the precaution of carrying out a watercress test.
Watercress test; take treated soil from a pot and sow watercress: the pot is then closed well. Do the same in another pot with untreated soil to ensure that the watercress can grow well. If the watercress germinates and grows well in both pots, no problem. If it dies in the pot with treated soil, wait a few days and repeat the test.
Formaldehyde treatment
Formaldehyde is an old product that is less commonly used, but can be obtained from a chemist. Formaldehyde can be useful for removing foam. In this use, a 10% dilution is used. The dry foams are then sprayed. After treatment, the foams die and dry. They must then be brushed to eliminate them. This treatment can be carried out on ashlar etc. The excavated soil is sprayed with 10 litres of a 2.5% solution of commercial formaldehyde per m² and then covered with plastic for 15 days. Then aerate as above and carry out a cress test before cultivation.
N.B.: tools, pots and terrines can also be disinfected with formalin.
Toxicity of formaldehyde:
Produces a gas that irritates the eyes. Wear a mask to avoid inhaling the fumes. Calcium cyanamide can also contribute to some disinfection while providing calcium. Cyanamide has a herbicidal and insecticidal effect. Dose 5 kg per are.