Acids exist in our food, drinks and the very dirt around us. In fact, some plants grow better in soil that contains high levels of acid. These plants, often referred to as ericaceous plants, include rhododendron and heather flowers. Many composting products are designed to balance the acidity level in the soil, but lowering the acidity can kill ericaceous plants. Ericaceous compost is designed to provide nutrients without lowering acidity; mix this type of compost to keep your ericaceous plants healthy.
Pour equal parts peat and sand into a bucket or barrel for mixing. The amount of ingredients you need for your compost will vary depending on the size of your garden, but the peat and sand must be in equal parts. Mix these well with a shovel or other mixer.
Add twice as much loam as you did peat and sand, so that your mixture consists of two parts loam, one part peat and one part sand. Mix them all together thoroughly. These ingredients will help to fertilise the plants and drain the soil without lowering acidity.
Add 600 g (1 1/3 lbs) of sulphur fertiliser and 1.2 kg (2 1/2 lbs) of superphosphate fertiliser per 1 cubic metre (35 cubic feet) of the mixture. These added fertilisers will provide needed nutrients to the ericaceous flowers; in other fertilisers, these nutrients are provided by substances like lime, which lower acidity.
Apply the compost as you would a regular fertiliser, mixing it into the soil to a depth of between 2.5 to 5 cm (1 to 2 inches).
Find peat, sand and other materials at garden centres or nurseries.