Prime objective of this lecture is to present on Fertilisers and Pesticides. Fertilizer use to grow properly, plants need nutrients (nitrogen, potassium, calcium, zinc, magnesium, iron, manganese, etc.) which normally can be found in the soil. Pesticides means: Herbicides, Insecticides, Fungicides, Bactericides etc. This lecture also briefly present on Biochemical Oxygen Demand (BOD) and Bioaccumulation. A high BOD means lots of organic material and aerobic microbes.