The excessive use of fertilizers and pesticides can contaminate the reduces the quality and produces of plants, and makes the plant inedible Usually of pesticides occurs in soil for two reasons: 1) over application to the crops , or 2) the repeated application of a material that persists for long periods in the soil. pesticides in the soil may be useful for insect and disease control, for it prolongs the protection. However, it may not be desirable, since it can damage some send plants