With Soil Additives. The easiest way to add calcium to your soil is to buy a soil additive, like lime or gypsum, from a garden centre. Some garden crops, such as tomatoes, peas, and beans, have a high calcium requirement but do best in slightly acid soil. Lime will help to raise the pH of your soil, while gypsum maintains its pH. In this case, calcium can be provided in the form of a gypsum soil amendment (calcium sulfate). The way to determine whether you need to add calcium to your soil is a professional soil test. Too much calcium in your garden soil can go hand in hand with a high pH, which means the soil is too alkaline, which then affects the absorption of the macronutrients contained in other fertilizers. The first thing you should do … How to Add Calcium to Soil. Agricultural gypsum is a good source of both calcium and sulfur, yet has little effect on soil pH. Use soil additives to enhance its calcium content. It’s best to do a pH test to see which one will work best for your soil. Adding calcium to your soil can help your plants to absorb water and grow stronger.