Plants use nitrates as a supply of nitrogen, which is needed to make proteins for healthy growth. Plants absorb nitrates in water through their roots. Nitrates are present in high levels in plant fertilisers. Without nitrates, the amount of chlorophyll in leaves reduces.

When should plants use nitrogen?

Typically, you need to add nitrogen to the soil if there is a deficiency or your plants are hungry and require a lot of nitrogen to flourish. So how can you spot a deficiency? A typical sign is stunted growth or yellowing leaves, but these may also be a sign of disease or pest infestation.

How do you know if a plant needs nitrogen?

The first way is to take a look at the leaves. If the leaves are yellowing, this can be a sign of chlorosis — which could also be a sign that your plant is in need of nitrogen. Keep in mind, however, yellowing leaves can also indicate a few other issues (like overwatering). The second way is to perform a soil test.