Most plants prefer the soil to be a little acidic in order to be the most productive. Slightly acidic soil provides the plants in your garden with the most and best nutrients. If your soil is dry or in need of composting, it may be too alkaline. By adding an element or two to your soil you can make it more acidic.
Test your soil using a litmus test or a pH testing kit. To determine whether your soil needs to be more acidic, note that levels under 7.0 are acidic and levels over 7.0 are alkaline. Most plants grow best at pH levels of 6.0 to 6.5. Some plants, such as blueberries, require even more acidity.
Decide which materials you would prefer to use to increase the acidity of your soil. Sulfur and aluminum sulfate are common soil additives to increase acidity. However, compost, manure and peat moss will also help lower pH. Sulfur and aluminum sulfate are the quickest ways to lower the pH, making the soil more acidic. Peter Bennett, a soil adviser for TM Organics, recommends a mixture of chicken manure, cedar wood chips and elemental sulfur as the quickest and best way to make your soil more acidic.
Calculate the texture of your soil and amount of soil you need to treat to determine how much sulfur or aluminum sulfate to use. If you have a high content in your soil, you will need more sulfur; if you have sandy soil, you will need less. The existing pH, the amount of soil and the desired pH are all factors you need to consider to know how much sulfur or aluminum sulfate to add.
Spread sulfur or aluminum sulfate onto your soil with a fertilizer spreader. While aluminum sulfate will change your acidity immediately, sulfur and organic materials will take several months to lower the acidity level of your soil. Use a tiller or pitchfork to work materials into your soil for the best results.