Soil application of Chemical

The purpose of chemical soil treatment is to eradicate or reduce the inoculum density of soil-borne plant pathogens. However, complete eradication of pathogens from soil with chemical treatments is neither feasible nor desired. One cause of failure of chemicals to completely eradicate pathogens from soil is their rapid degradation by physical, chemical and biological conditions of soil. Most fungicidal soil treating , chemicals have the ability to diffuse through soil particles. In the control of nematodes volatile soil fumigants are used. The chemical soil treatment can be done in any of the following ways.

1. Drenching of soil with solution of suspension: Chemicals are applied to soil surface in quantities sufficient to wet 10-15 cm depth of the soil. The treatment can be applied before or after planting of seeds.

2. Broadcasting of dusts, powders of granules: Non-volatile fungicides are mixed with soil or fertilizers and broadcast on the soil surface. Light ploughing or harrowing is done to mix the chemical in sufficient depth. This method of soil treatment is too expensive.

3. Furrow application: Furrow application is most common practice followed to apply dusts and granules. This method is possible in crops planted in furrows such as potato and sugarcane.

4. Fumigation: Soil fumigation is usually done to control plant parasitic nematodes. The chemicals used for this purpose are usually volatile and on coming in contact with soil moisture release gases which diffuse in the soil and kill the larvae of the nematode. Application of these highly toxic volatile substance is recommended some days or weeks before actual planting of the crop. Special equipments are required for their application.

The success of soil treatment depends on many factors. Proper ploughing of the land is necessary before-treatment. The soil should be well pulverised and should be neither too dry nor too wet. If organic manures are to be added that should be done after fumigation. Many soil fumigants are not effective in soils containing high organic matter content.