Choosing the right nitrogen type

Various nitrogenous fertilisers are available. Your choice will depend on environmental considerations, cost, availability, and so on, writes Bill Kerr.

- Bill Kerr

Ammonium sulphate is often used where the soil pH is on the high side. In this form, the ammonia will need to be converted to nitrate before it is released from the attachment to the soil colloids into the soil solution where the plants can take it up. This process will be greatly slowed down in cold conditions, as the bacteria that are responsible for this conversion are rendered inactive in the cold.

We also have to consider that all nitrogenous fertilisers have an acidifying effect on the soil. For instance, 1kg of ammonia requires 6kg of calcium to neutralise it. This needs to be taken into account when using ammonium sulphate on soils that are not alkaline.