Nutrients such as calcium, magnesium
and sulfur, are required in smaller quantities, while tiny amounts of
other nutrients are also vital but rarely deficient in garden soils. One
exception is alkaline soil, which is unable to release manganese and
iron, and causes yellow leaves on acid-loving plants. A general-purpose
fertilizer has equal amounts of the major plant nutrients, together with
other nutrients that are not always readily available in the soil.
- Nitrogen (N) encourages lush leafy growth, and is the main ingredient
in spring lawn fertilizers. It is highly soluble and quickly washes out
of free-draining soils.
Potassium (K) promotes flowering and fruiting; it is sometimes listed
as potash. Fertilizers for tomatoes and summer container plantings are
rich in potassium.
- Phosphorus (P) promotes healthy root growth, and is essential for young plants whose roots are developing. There is usually plenty in garden soil in the form of phosphates.