Soil sterilization,soil solarization

In simplest terms soil sterilization consist in getting
rid of the organisms harmful to plant growth or
atleast, in reducing their numbers to a point where
they are no longer of consequence without permanently eliminating or disturbing the balance of those organisms essenstial for fertility.

Soil sterilization is indispensable to modern practice, not only
because it ensures clean soil but because it provides better
nutrition; indeed, it is the basis of the best nutrition.

Basically it is treatment of soil of glasshouses , greenhouse and other horticultural soils in order to kill weed, seeds, plant disease organisms, and pests.

Sterilisation is distinct from disinfection, sanitization and pasteurization in that sterilization kills, deactivates, or eliminates all forms of life and other biological agents.

Example: Molya disease of wheat caused by Heterodera avenae White tip disease of rice caused by Aphelenchoides besseyi . Soil borne pathogens like Fusarium, Rhizoctonia, Sclerotia can be controlled by this.

1. Indira Gandhi Krishi Vishwavidyalaya , RAIPUR COLLEGE OF AGRICULTURE,RAIPUR. Presented To; Presented By; Dr.(Mrs.) SONALI DEOLE SHEKH ALISHA Dept. of Entomology M.Sc. Prev.(Ag.) Entomology ENT-518 Techniques In Plant Protection TOPIC:SOIL STERILIZATION (SOIL SOLARIZATION) SESSION 2018-19

2. SOIL STERILIZATION In simplest terms soil sterilization consist in getting rid of the organisms harmful to plant growth or atleast , in reducing their numbers to a point where they are no longer of consequence without permanently eliminating or disturbing the balance of those organisms essenstial for fertility. Soil sterilization is indispensable to modern practice, not only because it ensures clean soil but because it provides better nutrition ; indeed, it is the basis of the best nutrition . Basically it is treatment of soil of glasshouses , greenhouse and other horticultural soils in order to kill weed, seeds, plant disease organisms, and pests . Sterilisation is distinct from disinfection, sanitization and pasteurization in that sterilization kills, deactivates, or eliminates all forms of life and other biological agents . Example: Molya disease of wheat caused by Heterodera avenae White tip disease of rice caused by Aphelenchoides besseyi . Soil borne pathogens like Fusarium , Rhizoctonia , Sclerotia can be controlled by this.

3. Importance Of Soil Sterilization It creates ideal condition necessary for plant growth and development in the soil . The death of these micro organisms due to sterilization helps to release certain nutrient to the plant such as nitrate which increases plant growth . Soil sterilization leads to high quality in marketing produce. Soil sterilization reduces the population of micro organism that is harmful to crop plant . It helps to control disease outbreak in the soil.

4. SOIL STERILIZATION Under this soil is sterilized in greenhouses or polyhouses and also in nurseries by steam or hot water/air. Soil treated with hot water or steam at about 50°C – To inactivate or kill majority of nematodes, some oomycetes fungi 60-70°C – most of plant pathogenic fungi and bacteria 82°C – Most of weeds and plant pathogenic bacteria and insects . Some heat tolerant weed seeds and virus like tobacco mosaic virus are killed at near boiling point depend upon pressure . It causes their cell structure to physically degenerate . Sterilization can be achieved with one or more of the following: heat, chemicals, irradiation, high pressure, and filtration.

5. SOIL SOLARIZATION Soil solarization is an environmentally friendly method of using the sun’s power to control pests such as bacteria, insects, and weeds in the soil. The process involves covering the ground with a tarp, usually a transparent polyethylene cover, to trap solar energy. The sun heats the soil to temperatures that kill bacteria, fungi, insects, nematodes, mites, weeds, and weed seeds. To solarize your soil: Clear the area of plants and debris . Water the soil deeply until it is wet. Cover the area with clear plastic (such as 1 to 4 mil painter’s plastic). Don’t use white or black plastic; they don’t allow enough heat to get to the soil. Bury the plastic edges in the soil to trap the heat. Leave the plastic in place for at least 4 weeks in the hottest part of the summer. 6. Remove the plastic

6. Soil solarization works best on heavy soils—those containing clay, loam, or mixtures of them. They can hold more water than can light soils, long enough to produce steam every day. Steam is needed to kill nematodes, weed seeds, and insect eggs in the soil. Solarization may be less effective on sandy soil, which drains faster and produces less steam. To maximize the benefit of solarization in sandy soils, lay drip irrigation lines under the clear plastic cover and add water regularly.

7. Solarization The solarization period should be from four to six weeks during the hottest part of the year. The longer the soil is exposed to the heat generated by the solarization process, the greater the kill of undesirable organisms will be. Be sure to restrict the movement of pets across the polyethylene film. Dogs especially will leave holes in the film and allow heat to dissipate from beneath the film. Periodically inspect the film and repair any tears with tape. Add water, if needed, during the treatment period without disturbing the film.

8. Principles of soil solarization The principles of soil solarization  are summarized as follows: 1.Solarization heats the soil through repeated daily cycles. At increasing soil depths, maximal temperatures decrease, are reached later in the day, and are maintained for longer periods   Figure 1. The daily course of soil heating by polyethylene at three soil depths, as compared to nonsolarized (no mulch) soil at a depth of 10 cm. Typical results obtained during July–August in Rehovot , Israel.

9. 2.The best time for soil mulching, i.e., when climatic conditions are most favorable, can be determined experimentally by tarping the soil and measuring the temperatures. Meteorological data from previous years and predictive models further aid in this task; 3.Adequate soil moisture during solarization is crucial to increase the thermal sensitivity of the target organisms, improve heat conduction in the soil, and enable biological activity during solarization . The soil can be moistened by a single irrigation shortly before tarping . Additional irrigation during solarization via drip system or furrow irrigation is usually not necessary, except for very light soils; in addition to which it may reduce soil temperatures unless carried out during the night;

10. 4.Proper preparation of a soil ready for planting is essential. This is the case because, after plastic removal, the soil should be disturbed as little as possible to avoid recontamination; 5.The soil is mulched with thin, transparent polyethylene sheets or other plastic material. Another method of solarization involves a closed glasshouse (or plastic house), provided climatic conditions are suitable and the soil is kept wet. Novel technologies such as the use of sprayable plastics can replace plastic mulching of the soil; 6.Successful pathogen control in various regions of the world is usually obtained within 20–60 days of solarization . Extending the solarization period enables control in deeper soil layers, as well as of pathogens that are less sensitive to heat; 7.Solarization causes chemical, physical, and biological changes in the soil that affect pest control, plant growth, and yield.

11. Procedure Site selection and preparation Solarization can be applied to entire areas (gardens) or to linear rows (beds) that will be cropped using plasticulture techniques. Shady areas should be avoided because temperatures likely will not reach lethal levels. The area to be treated should be well tilled and free of clods and crop debris . Tillage is best applied with a rototiller, but hand spading and raking are also effective. Because wet soil conducts heat better than dry soil, the soil should be thoroughly watered to a depth of 12 inches. This can be done before or after the film is applied. Soaker hose or drip irrigation, installed under the film, can be used to irrigate the soil after application of the film is complete. Water then can be added if needed during the solarization period.

12. Film selection and application Clear polyethylene film of various thicknesses (0.5 to 4 ml) should be used. These can be obtained from home improvement stores, hardware stores, garden centers, or in bulk rolls from agricultural suppliers. Agricultural films for commercial application are often treated with ultraviolet ( uv ) inhibitors to delay film breakdown. Colored films should not be used for solarization because they do not transmit solar radiation, but rather reflect or absorb it, thus diminishing soil heating. Thinner (0.5 to 1 mil) films conduct more heat, but are more susceptible to tearing and have a shorter life than thicker films. The film should be applied as tightly as possible to the soils surface to minimize air gaps and potential damage from wind. The film should be firmly anchored by burying the edges in trenches dug by hand when treating gardens and small plots ,or during bed shaping and film application when using plasticulture . In the treatment of linear rows (beds) using plasticulture , beds are formed and the film and drip tape are applied simultaneously

13. a.Preparation of site b.Level the soil c.Irrigate d.Cover with film and lay the urp

14. ADVANCEMENT IN SOIL SOLARIZATION India is a country of 29 states and consist of humid and arid climatic condition in most of the states. As this strilization technique can easily be used in those areas where there is hot and arid climates,and have direct contact of sunlight. For advancement of this technique research is going on. An article THE ROLE OF SOIL SOLARIZATION IN INDIA:HOW AN UNNOTICED PRACTICE COULD SUPPORT PEST CONTROL was published on sep 2017,in which it is mentioned that trials were conducted in 15 states of india to launch this soil sterilization as an approach to overcome conventional treatment that is chemical usage in plants. As these chemicals have made a huge agricultural pollution and ruined the originality of soil properties. Apart from that the plastic we use for tarping soil is made of polyethylene which is also harmful for environment,so to overcome this biodegradable plastics were suggested.

15. BENEFITS AND LIMITATIONS soil solarization  has advantages and limitations. It is a nonchemical method with less drastic effects on the biotic and abiotic components of the soil; it is simple (and is therefore suitable for both developing and developed countries); and it is frequently less expensive than chemical soil disinfestation. The limitations of this method stem from its dependence on climate and it can therefore be used only in certain climatic regions and during limited periods of the year. In addition, during solarization , the soil remains without a crop for several weeks. Nevertheless, this method has attracted many researchers in more than 60 countries and it is used by farmers, especially in combination with other methods. SOURCE: SOIL STERILIZATION by W. J. C. LAWRENCE O.B.E., V.M.I:l . Head of Department of Physiology and Plant Culture, John Innes HortlculturalIlistitutioll . Hertford.   WEED SCIENCES BASICS AND APPLICATIONS BY T.K.DAS

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