How do fertilisers affect the pH of soil?

Fertilisers can alter the pH of soil, making it more acidic or alkaline depending on their composition.

Fertilisers are substances added to soil to enhance its fertility and promote plant growth. They contain essential nutrients such as nitrogen, phosphorus, and potassium. However, the effect of these fertilisers on the soil's pH, which is a measure of its acidity or alkalinity, can vary depending on their composition.

Nitrogen-based fertilisers, for instance, tend to make the soil more acidic. This is because they often contain ammonium, which when broken down in the soil, produces hydrogen ions. These ions increase the soil's acidity, lowering its pH. Over time, the continuous use of such fertilisers can lead to soil acidification, a condition that can harm certain plants and disrupt the balance of nutrients in the soil.

On the other hand, some fertilisers can make the soil more alkaline, raising its pH. These include lime-based fertilisers, which contain calcium carbonate. When added to the soil, this compound reacts with water to form calcium ions and hydroxide ions. The latter increase the soil's alkalinity. This can be beneficial for plants that prefer more alkaline conditions, but detrimental to those that prefer more acidic soil.

It's also worth noting that the effect of fertilisers on soil pH can be influenced by other factors, such as the type of soil, its initial pH, and the amount of fertiliser applied. For example, sandy soils, which have less buffering capacity than clay or loam soils, are more susceptible to changes in pH. Similarly, applying large amounts of fertiliser can cause more drastic changes in pH than applying smaller amounts.

In conclusion, while fertilisers play a crucial role in enhancing soil fertility, their impact on soil pH should be carefully considered to ensure they don't inadvertently harm the plants they're meant to help.