Soil Nutrients and Fertilisers

Soil Nutrients and Fertilisers

All plants require nutrients in different amounts. 
Micronutrients are needed in trace levels and are usually found in garden soil. 
The three more important are Macronutrients, which are vital for plant health, are Nitrogen (N), Phosphorus (P) and Potassium (K).

Nitrogen (N) for healthy leaves/foliage 

Nitrogen is essential for plant development. It plays a fundamental role in energy metabolism and protein synthesis. Nitrogen is absorbed by the plant in the form of a nitrate. Most growth you see above ground, stems and foliage, is governed by Nitrogen.

Phosphorus (P) for strong roots and plants

Phosphorus is involved in stimulating root growth. Above ground, it helps with flowering. A shortage of Phosphorus results in late, deficient flowering, browning and wrinkling of leaves and a lack of vigour.

Potassium (K) for fruit & flowers

Potassium is involved in the regulation of water and the transport of the plant’s reserve substances. Potassium stimulates flowering and fruiting and supports the synthesis of carbohydrates and enzymes. A lack of Potassium reduces the plant’s tolerance to dry spells and frosts and to a fungus attack. This, in turn, results in a lack of balance among other micronutrients. When there is a Potassium deficiency, dark spots appear on the leaves.

What does the N,P,K ratio mean?

Fertiliser packaging lists three numbers indicating the percentage values of Nitrogen (N), Phosphorus (P) and Potassium (K) in the product. They are always displayed in this form.
For example, Tomorite, a fertiliser high in Potassium, used to aid flower and fruit development in tomatoes, has an NPK of 4-3-8, 4 % Nitrogen, 3 % Phosphorus and 8 % Potassium. 

Balanced fertiliser
Most plants benefit from a ‘balanced’ fertiliser (one that contains equal amounts of all three macronutrients). If an unhealthy plant displays the symptoms of a lack of one particular nutrient, such as yellow foliage and nitrogen deficiency, it is good practice to apply a balanced fertliser as all three macronutrients work in tandem.

Dig for Victory
During the height of the Second World War, German submarine activity limited the amount of food entering the country. The government instituted a ‘Dig for Victory’ campaign and arranged the supply of a good standard fertiliser at a reasonable price. It was called National Growmore Fertiliser (now branded Growmore) and contained equal amounts of 7% Nitrogen, 7% Phosphorus and 7% Potash.

Always follow the manufacturer’s instructions when applying fertiliser, otherwise plants  can be easily damaged.


View more categories in the category Plants