Agriculture and the Chemistry of Soils

Soils receive vast amounts of fertilizers, soil additives (e.g., gypsum and sulfur), pesticides, and 

Apart from agricultural applications, pesticides are applied over large areas for other purposes such as the control of the tsetse fly and locust swarms in Africa. 

The use of sewage sludge as fertilizer on agricultural land is another source of pollution. Heavy metals, nitrates, phosphates, and detergents are all added to soil in this way. 

As mentioned earlier, high salt contents in water (e.g., Na, Ca, and Mg sulfates) in contact with soils produce salinization (i.e., excess salinity). Other causes of salinization include high water tables, high evaporation rates, and low annual rainfall. Excessive salinity makes it more difficult for plant roots to take in water, which considerably reduces crop yields and also degrades the quality of shallow groundwater and of surface water. 

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