Suppression of soil borne pathogens through soil solarization
Authors: LALITA LAKHRAN¹ , NARESH KUMAR¹ AND ANITA BURDAK^2
1Department of Plant Pathology, S.K.N. University of Agriculture, Jobner, Jaipur (Raj.)India 303328.
²Department of Plant Breeding and Genetices, S.K.N. University of Agriculture, Jobner, Jaipur (Raj.)India 303328.

INTRODUCTION

Solarization is a safe , economic, cheapest, simple, and effective method that has been used with field, vegetable and flower crops and in orchards. Soil Solarization is claimed as a novel techniques for treatment of soil by solar heat. It is a hydrothermal treatment. If moistened soil is covered under transparent polyethylene film (about 25 μm thick) during summer to prevent dissipation of the trapped solar heat the temperature of the soil rises sometimes 13⁰c higher than the temperature outside reaching 50-55⁰c at 8cm depth. This kills most fungal, bacterial and nematode propagules as well as weed seeds. It is an environmentally friendly method of using solar energy for controlling soil- borne plant pathogens by covering the soil with transparent plastics so that sun rays will increase the soil temperature to levels that kills the pathogen. Katan(1976): First reported on the use of soil solarization for control of soil borne disease. In India Gujarat Agriculture University first adopted this technique.

Mechanism:

Soil solarization is based on trapping solar radiation by tight covering the soil, usually with transparent polythene sheets, this result in significant increase (10- 15⁰c) above normal temperature of soil, up to the point where most pathogens are susceptible to heat effects.

Important points:

• Soil solarization is most effective when done in June and July.
• However, depending on geographic locality, it may also be effective in May, August and September.
• Solarization is most effective when the weather is hot and cloudless.
• Solarization leaves no chemical residues and is a simple method.
• The process changes, physical, chemical and biological properties and thereby improves soil health.

Procedure of soil solarization: It consist of four steps

• Plough the soil and dispose of dead plants and other debris that might harbor pests.
• Level and smooth the soil surface.
• Irrigate the soil to enhance its heat conductivity.
• After watering the field, immediately it should be covered with transparent polythene sheets and there should be a minimum distance between plastic sheets and soil. Left it as such for 4-6 weeks during the summer months to allow the soil to heat to the greatest depth possible generally goes to 5cm depth. After some weeks plastic is removed and the soil is allowed to dry to workable texture.

Effect of soil Solarization:

• Reduces soil borne diseases : Damping off, root rot, stem rot, wilt, blight caused byPythium spp., Phytophthora spp.,Fusarium spp., Sclerotinia and Verticillium spp.
• Reduces weed population.
• Nematode control.
• Increased plant growth response : Some important nutrients like N, Ca, Mg may be increased and their availability to plant root increased.
• Increased colonization of beneficial soil organism : many soil borne pathogens are killed by soil Solarization but many beneficial soil organisms are able to either survive Solarization or recolonize that soil very quickly afterwards. Important among these are the mycorrhizae fungi and pathogen antagonistic bacteria and fungi.

Conclusion : soil Solarization is very effective practices there was a large reduction in population of both pathogens due to solarization in both dry and irrigated condition, it also reduces nematode population and weed growth. The large difficulty in consistently achieving weed control but soil Solarization is very effective for weed control and reduces soil borne pathogens. Soil solarization is extremely effective and is a popular method used in organic gardening because it doesn’t require any chemical pesticides.




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