Fertilizers & Pesticides

Fertilizers

» These are the chemical substances which are rich in a particular nutrient. They supply nitrogen, phosphorus, and potassium. Continuous use of fertilizer in an area can destroy soil fertility. A chemical fertilizer should be completely soluble in water, easily assimilated by plants, and stable so that elements are retained in the soil for longer duration. It should not disturb the pH of the soil.

» Major nitrogenous fertilizers are ammonium sulphate, calcium cyanamide, basic calcium nitrate, calcium ammonium nitrate, and urea.

» Urea is the best fertilizer as it leaves only carbon Sioxide after ammonia, which has been assimilated by plants. It has 46.6% nitrogen, and it does not alter the pH of the soil.

» Mixture of Ca (CN)₂ and C is known as nitrolim. Commercially, calcium nitrate is known as Norwegian salt-peter.

» Calcium superphosphate, nitro phosphate, triple phosphate, and phosphatic slag (Thomas slag) are some important phosphatic fertilizers.

» The mixture of nitrogenous, phosphatic, and potash fertilizers in suitable amounts, is called NPK fertilizers.

» NP fertilizers are prepared by mixing nitrogenous and phosphatic fertilizers in a definite ratio. Dihydrogen ammoniated phosphate and calcium superphosphate are the examples of NP fertilizers.

Pesticides

Pesticides are the chemicals which are applied to crops, e.g., DOT and Malathion to kill those pests which adversely affect the growth and strength of plants.

Insecticides

Kill those insects which attack crops, livestock, buildings, and human beings.

Fungicides

Control parasitic and saprophytic fungi that live at the expense of growing and stored crops.

Nematicides

Kill eelworms that feed on growing crops.

Molluscicides

Kill slugs and snails and are usually active after ingestion.

Herbicides

These are also commonly known as weed killers and are pesticides used to kill unwanted plants. The first widely used herbicide was 2,4-dichlorophenoxyacetic acid, often abbreviated 2,4-D. Atrazine and glyphosate are other examples. Phenoxy herbicides are often contaminated with dioxins such as TCDD. Researchers have suggested that such contamination results in a small rise in cancer risk after exposure to these herbicides.

Rodenticides

This is a category of pest control chemicals intended to kill rodents. Rodents are difficult to kill with poisons because their feeding habits reflect their place as scavengers. They will eat a small bit of something and wait, and if they do not get sick, they continue. An effective rodenticide must be tasteless and odourless in lethal concentrations and have a delayed effect.