There are a dozen or more chemical elements which are essential for healthy plant growth including Carbon, Hydrogen and Oxygen which plants absorb from their surroundings (air and water).

The other major elements are Nitrogen (N) Phosphorous (P) and Potassium (K). These three are shown on most fertilizers as the N:P:K ratio. Secondary elements including Sulphur, Calcium and Magnesium are required in smaller amounts than the major elements but are still necessary.

Trace elements like Iron, Copper, Zinc, Chlorine and Molybdenum will only affect plant growth if they fall to extremely low levels. The major elements (NPK) are generally supplied by fertilizers and organic matter and need to be in sufficient quantities throughout the growth cycle of plants. The major and secondary elements are predominantly absorbed through the root system of the plant and here the influences of the pH of the soil are most important for nutrient uptake.

With a neutral pH of 6.5 to 7.5 all nutrients are readily available for most plants and grasses but outside this range (see chart) nutrient uptake decreases.

This means fertilizers can be wasted if the pH is too low or too high. There are certain exceptions with some plants like azaleas and camellias which like more acid conditions and some vegetables like peas and celery which prefer more alkaline soils. 132030

If in doubt about a particular plant check in a good gardening guide, it will have the requirements of the plant, including the best pH level. pH affects the "availability" of nutrients not their "presence" in the soil, as the pH balance changes, nutrients get locked up in the soil structure. The addition of extra fertilizers to soils which are out of balance will not help.

Increase the pH level in the soil to make it more alkaline by adding lime or dolomite.