Understanding Soil

Nutrients

The four major nutrients are Nitrogen (N), Phosphorus (P), Potassium (K) and Magnesium (Mg). Ideally, all four should be present in order to achieve a balanced soil.

Nitrogen
This is the main growth nutrient and is required for the growth of leaves and stems. Deficiencies manifest themselves through weak, stunted growth and yellowing of older leaves. However, excess nitrogen can also be detrimental to the plant causing such effects as disproportionate leaf growth at the expense of other parts of the plant e.g. flowers.

Phosphorous
This is the principal nutrient concerned with plant growth and development. Deficiencies may be seen through stunted root systems whilst the leaves on some plants may also exhibit a dull green or purple colouration.

Potassium
This nutrient performs an important photosynthetic function within the plant, whilst also promoting flower and fruit development. Deficiencies may be seen through the yellowing and death of marginal (and older) leaf tissue, whilst low levels also make the plant more susceptible to diseases.

Magnesium
This nutrient is a constituent of chlorophyll, the green pigment which enables plants to photosynthesise. Magnesium deficiencies may be noted by the interveinal yellowing of the plant’s older leaves.