What Does a Fertiliser’s NPK Ratio Mean?

Every fertiliser normally carry an NPK value which tells you the relative proportions of the three most important nutrients needed by plants – nitrogen, phosphorus and potassium. Different plants have different nutrient requirements and the type of soil in your garden can affect the amount of each nutrient that is naturally available. This makes it really important to pick a fertiliser with the right balance of nitrogen, phosphorus and potassium for your specific needs as each has its own vital part to play in helping you produce healthy plants.

Nitrogen (N)

Arguably the most important of all plant nutrients, nitrogen is normally absorbed by plants in the form of nitrates or ammonium ions through their roots. Nitrogen is one of the basic elements of all proteins so is vital for plant growth. It is also a major component of chlorophyll making it essential for photosynthesis and giving plants their green colour.

Plants that don’t get enough nitrogen will tend to turn yellow as they are unable to produce enough chlorophyll. Ultimately this means they will be unable to effectively turn sunlight into usable energy in the form of sugars, leading to sickly plants which will eventually wither and die.

Phosphorus (P)

Like nitrogen, phosphorus is vital for photosynthesis as it is needed to produce one of the basic chemicals plants used to produce and store energy from sunlight, adenosine triphosphate (ATP). Plants also use phosphorus in the production of DNA and cell membranes as well as all oils, sugars and starches, making it especially important when growing fruit and vegetables. It also encourages healthy roots, rapid growth and maturation of the whole plant and helps flowers to bloom.

A plant that isn’t getting the right amount of phosphorus will usually show much slower than normal growth and have dull yellow foliage.

Potassium (K)

The forms of potassium used in fertilisers are sometimes referred to as potash. It is essential for plant growth and is required in larger amounts by most plants than any other nutrient except nitrogen. Like nitrogen, potassium is essential for making proteins and photosynthesis. Potassium helps regulate the rate at which photosynthesis occurs and is important for controlling the way plants respire, taking in carbon dioxide and giving out oxygen. Potassium also helps make plants more resistant to disease and effects the quality of any fruit plants produce.

Plants suffering from potassium deficiency will tend to have yellow or purple tinted leaves with browning at the edges and will generally not flower or fruit well.

If you’re not sure what sort of fertiliser is best suited to your requirements, we will be happy to offer our advice on both lawn feed and general fertiliser. Simply call 0117 311 1217 with your query or Ask John.

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