Fertilisers: Introduction

Fertilisers are substances that are added to soil to promote plant growth. Plants need essential nutrients to grow and thrive, and these nutrients are often in limited supply in the soil. Fertilisers provide these nutrients, helping to increase crop yields.

Types of Fertilisers

There are various types of fertilisers, but two common categories are those containing ammonium salts and those containing nitrates.

Ammonium Salts as Fertilisers

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

The chemical equation for the formation of ammonium nitrate can be represented as:

$$NH_4(aq) + HNO_3(aq) \rightarrow NH_4NO_3(aq)$$

Nitrates as Fertilisers

Nitrates, such as calcium nitrate ($Ca(NO_3)_2$) and potassium nitrate ($KNO_3$), are also important fertilisers. Plants absorb nitrate ions ($NO_3^−$) from the soil. Nitrate is also a key source of nitrogen for plant growth, and it's often a preferred form of nitrogen uptake by plants because it's less likely to be lost from the soil through leaching.

Table Summarising Ammonium and Nitrate Fertilisers

Fertiliser Type	Chemical Example	Nutrient Provided	Plant Uptake
Ammonium Salts	Ammonium Nitrate ($NH_4NO_3$)	Nitrogen	Ammonium ions ($NH_4^+$)
Nitrates	Calcium Nitrate ($Ca(NO_3)_2$)	Nitrogen	Nitrate ions ($NO_3^−$)

The use of ammonium salts and nitrates in fertilisers is crucial for modern agriculture, enabling higher crop yields and supporting food production worldwide.