Soil pH

The acidity or alkalinity of your soil ultimately determines a plant's absorption of nutrients.

Here is a succinct chart that represents the most important plant nutrients and the pH at which they are available.

Most plants are fine at a neutral pH, but some like a bit more acidity, some like an alkaline environment. This shouldn't be too much of an issue, unless you make a mistake with fertilizer, or you are not amending correctly according to your soil type.

To lower your soil's pH (make it more acidic), simply add more compost and/or peat moss.

To raise the pH from acidic to alkaline, adding lime can work. There are two types of lime available for this: agricultural lime made from ground calcium carbonate, and dolomitic lime made from ground limestone. Each should be added at least 6 weeks before planting to take effect on the soil. Though there are other types of commercial lime such as slaked lime or quick lime, they pose a high risk of burning and are not suitable for the home garden.