Soil Solarization: Concept and Benefits

Pests and soilborne diseases always cause severe damage to horticultural and field crops. With their presence, the desired output is greatly reduced, posing a heavy economic loss to farmers and growers. Hence, they must be eradicated. Several methods have been tried and practiced to address this issue. There are chemical applications like soil-applied pesticides that control weeds, nematodes, fungi, bacteria and soilborne diseases. However, the use of chemical pest controls are viewed undesirable because of their unfavorable effects on both humans and animals, the toxic residues they generate, and the high cost and complexity of their treatment. To avoid negative consequences, a number of nonchemical methods for controlling diseases and pests have been studied and applied. One such method is soil solarization. (image source)

Soil solarization is a pest and disease control technique that uses the radiant heat from the sun to eliminate many soilborne pathogens. In this process, the soil is mulched and covered with a tarp, usually a transparent polyethylene cover, which traps solar energy. It is much the same as greenhouse. Since heat is captured and used, this method causes some physical, chemical, and biological changes in the soil in the most natural way. These changes result to control or suppression of pathogens and soilborne diseases.

This technique works best in areas with lots of sun and high temperature. However, recent modifications have proven that it can also work in cooler areas and for cooler times of the year. 

Here are the noted benefits of soil solarization:

Disease Control.  Soil solarization does not totally eradicate pathogens and diseases on the soil. However, studies have shown that pathogens would reinfest solarized soil at slower rates than nontreated soil.

Weed Control. Several weed species can be controlled by soil solarization since many of them are sensitive to soil moisture and high radiation. This aspect is often evident after a year of treatment. Some of the weeds that can be partially controlled by soil solarization include sweet clover (Melilotus alba), yellow nutsedge (Cyperus esculentus), purple nutsedge (C. rotundus), purslane (Portulaca oleracea), and crabgrass (Digitaria sanguinalis).

Nematode control. Partly, soil solarization can reduce nematode populations. Nematodes are those families of parasitic worms that include the hookworm and pinworm, and normally found in soil. Since nematodes are generally heat-tolerant, solarization is more effective and economically feasible for shallow-rooted crops and gardens.

Increased plant growth response.  Studies have shown that plants grown in solarized soil grows faster and produce yield superior in both quantity and quality. This can be attributed to three reasons. First, major pathogens and pests are controlled which obviously favor better growth of plants. Second, some soluble nutrients like nitrogen (NO3-, NH4+), calcium (Ca++), and magnesium (Mg++) may be increased and made more available to plants in solarized soil. Lastly, some beneficial microorganisms like mycorrhizal fungi, actinomycetes, and good bacteria survive the solarization process and consequently recolonize the soil. In turn, this helps biological control of pathogens and pests, as well as to stimulate plant growth.

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