Soil solarization is an environmentally friendly method of using solar power for controlling pests such as soil-borne plant pathogens including fungi, bacteria, nematodes, and insect and mite pests along with weed seed and seedlings in the soil by mulching the soil and covering it with a transparent polyethylene cover, to trap solar energy. Soil should be kept moist during solarization to increase the thermal sensitivity of resting structures of soil-born plant pathogens and weeds, and to improve heat conduction.
Solarization is to be done in open field without any shade and summer months are more suitable for solarization.
Method of solarization
a. Nursery bed
Before solarisation, the nursery bed for raising seedlings is to be levelled and pebbles present on the surface should be removed. Incorporate the required quantity of organic manure in the soil and irrigate @ 5 litres per m2 and 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 and also to prevent formation of air pockets between the soil and polythene sheet. After keeping the sheet for 20-30 days, remove the sheet and the bed is ready for sowing and transplanting.
b. Main field
Solarization can also be effectively used for the control of soft rot of ginger and similar soil-borne diseases in the field. The land used for planting ginger is initially prepared to a fine tilth and pebbles are removed. Prepare raised beds as per the recommended practice. Apply organic manure before solarization. Irrigate the bed once (5 litre/m2) and cover with polythene sheet. Leave the bed without any disturbance for 20-30 days. After this period, remove the sheet and plant rhizome bits. Bio pesticides can be incorporated in soil after removing the polythene sheet.
c. Potting mixture
Spread the potting mixture (soil:compost) on a levelled ground to a height of 15-20cm. Moisten with water 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.
Thus, solarization during the hot summer months can increase soil temperature to levels that kill many disease causing organisms (pathogens) like Pythium, Phytophthora, Fusarium, Rhizoctonia etc., nematodes like Meloidogyne, Heterodera, Xiphinema, etc., and weed seeds and seedlings like Cynodon dactylon, Cyperus rotundus, Digitaria ciliaris, Crotalaria muconata, Indigofera hersuita and Noxia sp. It leaves no toxic residues and can be easily used on a small or large scale garden or farm. Plants often grow faster and produce both higher and better quality yields when grown in solarized soil. This can be attributed to improved disease and weed control, the increase in soluble nutrients, and relatively greater proportions of helpful soil microorganisms.
