Fertilisers: Introduction

Fertilisers are substances that are added to soil to promote plant growth. Plants need essential nutrients to grow, and these nutrients are often in low concentrations in the soil. Fertilisers provide these nutrients, ensuring healthy plant development and increased crop yields.

Types of Fertilisers

There are various types of fertilisers, and they can be broadly classified into organic and inorganic fertilisers. This section focuses on inorganic fertilisers, specifically ammonium salts and nitrates.

Ammonium Salts as Fertilisers

Ammonium salts, such as ammonium nitrate ($NH_4NO_3$) and ammonium phosphate ($NH_4PO_4$), are commonly used as fertilisers. Plants can readily absorb ammonium ions ($NH_4^+$) and nitrate ions ($NO_3^$) from the soil. Ammonium is an important source of nitrogen, which is a key component of amino acids, proteins, and nucleic acids  all essential for plant growth.

The nitrogen in ammonium salts is converted to nitrate in the soil through a process called nitrification, carried out by bacteria. This conversion makes the nitrogen more readily available to plants.

Nitrates as Fertilisers

Nitrates, such as calcium nitrate ($Ca(NO_3)_2$) and potassium nitrate ($KNO_3$), are also widely used as fertilisers. Plants absorb nitrate ions ($NO_3^$) directly from the soil. Nitrate is another crucial source of nitrogen for plant growth, playing a vital role in chlorophyll synthesis and overall plant vigour.

Fertiliser Type	Chemical Formula (Example)	Nutrient Provided	Plant Uptake
Ammonium Salt	$NH_4NO_3$	Nitrogen	$NH_4^+$ (converted to $NO_3^$ in soil)
Nitrate	$KNO_3$	Nitrogen	$NO_3^$ (direct uptake)

Using fertilisers can have environmental impacts, such as water pollution from excess nutrients running off into rivers and lakes. Sustainable fertiliser use is important to minimise these impacts.