Most vegetables will grow best when the soil is slightly acidic. According to Ohio State University, the pH level for vegetable garden sites should fall into the range between 6.0 and 6.8 pH level. There are basic elemental chemicals that are amended into the soil to lower the pH levels. Organic materials are also available, but these materials may take a longer time period to break down and acidify the soil. Regardless of the materials utilized, improving the soil's acidity begins with a soil test.
Conduct a soil test of the garden area by taking several small soil samples. Mix the soil together. Allow the sample to completely dry. Send the soil sample to your local agricultural extension service. The results generally take up to three weeks. Use the results to adjust the pH level of the soil.
Layer up to 3 bushels of organic material such as sphagnum peat per 1,000 square feet of soil area. Work this material into the soil using a rototiller or a shovel. The peat will not only lower the pH level, but will add water retention capacity to sandy-type soils. The peat will have a varying effect on the pH level. Sphagnum peat, taken from around the country, will have different levels of acid. Retest the soil pH level after the peat has had a chance to set in the soil for two weeks.
Follow the exact recommendations from the soil test and amend the soil with either ammonium sulfate or sulfur-coated urea. These two types of materials are both acid agents and fertilizers. In most all cases, the soil test results will explain how many pounds of the material are required to lower the pH level to the desired acidity. Both ammonium sulfate and sulfur-coated urea are available at most garden centers or farm stores. The dry ingredients are fully labeled on the front of the packaging.
Lower the pH level only, with no fertilizer amendments, by the addition of elemental sulfur. In most soil applications, adding 1 pound of elemental sulfur per 100 square feet of area will lower the pH level by 0.5. The sulfur must be worked into the soil to a depth of at least 6 inches. Elemental sulfur is a powder product available at most garden centers and farm stores. The package may be labeled as either elemental sulfur or garden sulfur.