Soil Solarization is an environmentally-friendly method of using solar power for controlling disease agents in the soil by [[mulching-In agriculture and gardening, mulch is a protective cover placed over the soil, primarily to retain moisture and encourage micro-organisms to generate nutrients into the soil. Mulching in gardens and landscapes, mimics leaf cover on forest floors.

]] the soil, usually with a transparent polyethylene cover. It may also describe methods of decontaminating soil using sunlight or solar power.

Soil disinfestation

Soil solarization (also referred to as solar heating of the soil in early publications) is a relatively new soil disinfestation method, first described in 1976 by Katan et al., for controlling soilborne pathogens and weeds, mostly as a pre-planting soil treatment. It was achieved by covering (mulching, tarping) the soil with transparent polyethylene during the hot season, thereby heating it and killing the pests. The publication described in detail the method, its principles and potential in disease and weed control under field conditions. It presented the results of studies initiated in 1973 as presented at a meeting of the Phytopathological Society of Israel in February 1975.

Soil decontamination

A 2008 study used a solar cell, to generate an electric field for electrokinetic (EK) remediation of cadmium-contaminated soil. It was found that a solar cell could be used to drive the electromigration of cadmium in contaminated soil, and removal efficiency achieved by solar cell was comparable with that achieved by conventional power supply. ^[1]

In Korea in order to evaluate the potential use for ex situ remediation, a solar-driven, photocatalyzed reactor system was constructed and applied for the treatment of soil slurry and groundwater contaminated with benzene using selected advanced oxidation processes (AOP) processes. The remediation method was trialled at a contaminated gas station site and achieved 98% degradation, and lead to a substantial increase in the removal of benzene. ^[2]

History

Attempts were made to use solar energy for controlling disease agents in soil and in plant material already in the ancient civilization of India. In 1939, Groashevoy, who used the term "solar energy for sand disinfection," controlled Thielaviopsis basicola upon heating the sand by exposure to direct sunlight.

Soil solarization is the third approach for soil disinfestation; the two other main approaches, soil steaming and fumigation; were developed at the end of the 19th century. The idea of solarization was based on observations by extension workers and farmers in the hot Jordan Valley, who noticed the intensive heating of the polyethylene-mulched soil. The involvement of biological control mechanisms in pathogen control and the possible implications were indicated in the first publication, noticing the very long effect of the treatment. In 1977, American scientists from the University of California at Davis reported the control of Verticillium in a cotton field, based on studies started in 1976, thus denoting, for the first time, the possible wide applicability of this method.

It should be emphasized that the use of polyethylene for soil solarization differs in principle from its traditional agricultural use. With solarization, soil is mulched during the hottest months (rather than the coldest, as in conventional plasticulture which is aimed at protecting the crop) in order to increase the maximal temperatures in an attempt to achieve lethal heat levels.

In the first 10 years following the 76 publication soil solarization was investigated in at least 24 countries (today - more than 50), mostly in the hot regions, although there were some important exceptions. The studies demonstrated the effectiveness of solarization with various crops (vegetables, field crops, ornamentals and fruit trees) against many pathogens, weeds and a soil arthropod. Pathogens and weeds which are not controlled by solarization were also detected. In parallel, the biological, chemical and physical changes taking place in the solarized soil during and after the solarization process, interactions with other methods of control and many other topics, were investigated. Some findings, e.g. long-term effects, biological control and increased growth response were verified in various climatic regions and soils. This demonstrates involvement of general mechanisms in solarization.

Computerized simulation models were developed, and can be used as a guidelines by researchers and growers which are interested to employ solarization, and are not sure whether the ambient conditions in their place are suitable for solarization.

Studies of the improvement of solarization by integrating it with other methods or by solarizing in closed glasshouses, or studies concerning commercial application by developing mulching machines were also carried out.

The use of solarization in existing orchards (e.g. controlling Verticillium in pistachio plantations) is an important deviation from the standard preplanting method and was reported as early as 1979.

Resources

• http://www.agri.huji.ac.il/~katan/applic.html
• http://solar.uckac.edu/

References