Sterilizing Soils

Plant Characteristics

Origin:	✈	?

Cultivation

Exposure:	☼	?"?" is not in the list (sun, part-sun, shade, unknown) of allowed values for the "Exposure" property.
Water:	◍	?"?" is not in the list (wet, moist, moderate, dry, less when dormant) of allowed values for the "Water" property.

Scientific Names

Read about Sterilizing Soils in the Standard Cyclopedia of Horticulture

Sterilizing Soils. Greenhouse and plant-bed soils are specially liable to infection by disease organisms, as they are intensively cropped and not exposed to the action of frost and weather. Careful growers now resort to methods of artificial sterilization. In practice, the sterilizing is accomplished either by heat applied by live steam, or by a chemical process employing a formalin drench. In either case, the work must be thoroughly performed if satisfactory results are to be expected; it will be required at least as often as every other year, and the situation is safer if sterilizing is practised annually. Steam sterilizing is of two methods: by buried perforated pipes, and by a pan inverted over the soil and under which the steam may be conveyed. The latter is probably preferable in most cases. In either case, live steam should be applied for an hour or more. "The perforated pipe method appears to consist, at its best," according to Selby and Humbert in Circular No. 151 of the Ohio Experiment Station, "in a system or set of perforated pipes, with crosshead and high-pressure boiler connection. These pipes are connected and buried in the soil of the bed, either with or without partial banking up of the soil; the surface of the bed is then covered with canvas or other covering and the steam passed into the system for such a period as is required to heat the soil to the necessary temperature. This temperature for best results is 180° to 212° F. maintained for a period of an hour or more. The time required to reach this temperature will vary with the boiler area, the pressure and other steam and soil factors. The length of pipes of the system will be adapted to the beds, being one-half or one-third the total length of large beds. Generally, 1 1/2-inch pipe is used with 1/8-inch holes bored in a straight line about 1 foot apart. These pipes are buried in the beds 12 to 16 inches apart." For the inverted pan method, "The apparatus consists," according to W. W. Gilbert, "of a galvanized iron pan, 6 inches deep and 6 by 10 feet in size, which is inverted over the soil to be sterilized and the steam admitted under pressure. The pan is supplied with steam hose connections, has sharp edges, which are forced into the soil on all sides to prevent the escape of steam, and is fitted with handles for moving it from place to place, the weight of the entire pan being not over 400 pounds.” Remarking on the formaldehyde or formalin drench method, Selby and Humbert say that Soils to be treated by any method of sterilization should be prepared as for use by addition of manure so that the latter is incorporated with the soil before treatment. The soil after spading or plowing is ready for treatment, whether by steaming or drenching. For the work of drenching it is rather difficult to make exact estimates as to cost of appliances, as well as labor outlay, since the appliances are the usual watering devices of greenhouses or coldframes, and the labor will be somewhat variable according to the effectiveness of these devices. The appliances used may be extremely various, though usually some form of sprinkling-can, a force pump with hose and nozzles or application through the overhead Skinner watering system. For outside beds the hose and force pump offer a convenient method. The best strength appears to be three to three and one-half pints or pounds to each fifty gallons of drench applied at the rate of seven-eighths to one gallon to the square foot of surface." CH The above text is from the Standard Cyclopedia of Horticulture. It may be out of date, but still contains valuable and interesting information which can be incorporated into the remainder of the article. Click on "Collapse" in the header to hide this text.

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References

• Standard Cyclopedia of Horticulture, by L. H. Bailey, MacMillan Co., 1963

External links

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