Solarization is a method of hydrothermal disinfection. This is done by covering moist soil with transparent polythene sheet and exposing it to direct sunlight during the hottest period of the year.
Methods of solarization:
1. Nursery bed
The nursery bed for raising seedlings is to be levelled and pebbles present on the surface removed before solarization. Incorporate the required quantity of organic manure in the soil and irrigate at the rate of 5 litres per m2. Cover the beds with 100-150 gauge transparent polythene sheets. Seal the edges of the sheet with soil to keep it in position in order to maintain the temperature and moisture inside the polythene mulch. Adequate care is also to be taken to see that the sheet is in close contact with the surface of soil to prevent the formation of air pockets between the soil and polythene sheet. Keep the sheet in this way for 20-30 days. Protect it from stray animals and birds. After the period of solarization, remove the sheet and the bed is ready for sowing and transplanting.
The required type of potting mixture is to be prepared as per the recommended practice. Spread this mixture on a levelled ground to a height of 15-20 cm. Moisten with water using a rose-can and cover the soil with polythene sheet and solarize for 20-30 days as described above. After solarization, the soil can be used for sowing/planting. This method is found to be very effective to raise disease free pepper cuttings.
3. Main Feild
Solarization can also be effectively used for the control of soil borne diseases in the main field. The land used for planting is initially prepared to a fine tilth and pebbles removed. Solarization and planting can then be done as already described. All the other agronomic practices are to be followed as per the package of practices recommendations. Biopesticides and fertilizers can be incorporated in soil after removing the polythene sheet.
Importance of soil solarization
Soil solarization is a non chemical method to control the soil borne pathogens, insects, nematodes and weeds. Soil solarization is effective for short season crops. The effect of the solarization will last up to 3 to 4 months. The damping of seedlings in nursery can be managed by soil solarization.
The hard weeds like Cyperus (Nutsedge) can be controlled with this method. The solarization is to be done during the hottest period of the year. Apart from the above the solarization helps in breaking the organic matter in the soil there by making the nutrients available to the plants easily.
The quality of the produce will be better if grown in solarised soil.
If solarization is perfect no weeds will grow under the plastic cover. Under good solarization conditions, weeds, even nutsedge, will be killed soon after they come up.
The effect of the solarization will be maximum in the soil surface so that the micro organisms in the soil will be active immediately after the soil solarization process is finished.