Dear Student,
Fertilizers and Pesticides are used to improve the crop yield. However, on Excessive usage, they have numerous harmful effects as follows:
Excessive use of fertilizers over a long period may affect the alkalinity or acidity of the soil thus the chemical propertis of the soil are altered. This may adversely affect the crop production.Pesticides when get accumulated in soil, they harm soil biota and hinder microbial processes. Also water soluble pesticides mix with groundwater and contaminate the same. .Excessive use of fertilizers and pesticides decreases the soil fertility over a period of time. They reduce the self regeneration capacity of the soil. Hence the soil is able to naturally make up its nutrient content. . Over a period of time water holding capacity of the soil and its texture also changes. Some natural flora and fauna of the soil are destroyed due to overuse of these chemicals.
Regards