Nitrogen

The subject of nitrogen and different vegetables requirements is quite complex and I'm only just starting to get my head around it.

Of course it's not just nitrogen but also phosphorus and potassium too which make up the NPK balance shown on fertiliser packets.

When you buy fertiliser you will see an analysis of the NPK content. An equally balanced fertiliser may be described as 5:5:5 - 5% Nitrogen, 5% Phosphorus and 5% Potassium. You may also see Potassium described as Potash.

Nitrogen is used by the plant to produce leafy growth and formation of stems and branches. Plants most in need of nitrogen include grasses and leafy vegetables such as cabbage and spinach. Basically, the more leaf a plant produces, the higher its nitrogen requirement.

Here are the nitrogen requirements of various vegetables.

Very High Nitrogen Requirement	High Nitrogen	Medium Nitrogen
Brussels Sprouts Cabbages Rhubarb	Beetroot Celery Leeks Spinach	Broccoli Calabrese Cauliflower Lettuce

Low Nitrogen	Very Low Nitrogen	No Nitrogen
Asparagus Runner Beans Parsnip Swede Onion	Carrots Radish	Peas Broad Beans

Tomatoes need some nitrogen but can't make their own so they have to be fed regularly. The NPK of Tomorite, for example, is 24% 27% 48% which is twice as much potassium than nitrogen.

Confused? You will be! More on this as we go.