Alkaline soil often is clay, making it heavy, wet and difficult for many plants to thrive in. The pH of alkaline soils is above 7.0. Because many vegetables prefer a neutral or slightly acidic soil pH, adding ingredients such as sulfur to the soil will bring the pH down and make it more acidic. Some vegetables do well in alkaline soil, including cabbage, Brussels sprouts, mustard, turnips, Chinese cabbage and more. Tomatoes won't grow well in alkaline soil, but with all the cabbage family plants that do, perhaps you won't miss them.
Test your soil with an inexpensive pH soil test kit. If the pH is above 7.4, the soil is alkaline. If it is below 7.0, you'll be able to grow most vegetables without amending your soil and changing your pH. Decide if you want to lower your soil's pH: if you're determined to grow tomatoes, for example, you must do so. If you're happy growing mainly cabbage family vegetables, you needn't bother.
Apply sulfur to the soil to lower the pH. Measure your planting area to determine its number of square yards, which will dictate how much sulfur to add. For each square yard, dig in 4.6 oz. of ground rock sulfur.
Add composted leaves and any other plant materials, sawdust, wood chips and peat moss to also help make your soil more acidic. Even if you have decided not to grow acid-loving vegetables like tomatoes, adding these ingredients will benefit all the types of veggies you plan to grow.
Plant vegetables that do well in more alkaline soil after the soil dries out a bit and your final spring frost has passed. Veggies you can expect to grow well in alkaline soil with a pH between 7.0 and 8.0 include cauliflower, cucumbers, celery, cabbage, Chinese cabbage, mustard greens, turnips and turnip greens and Brussels sprouts. If your soil tested slightly acidic (ph 6.0 to 6.8), you'll be able to grow asparagus, kale, broccoli, beets, onions, bok choy, tat soi, spinach and Swiss chard. All other vegetables require soil pH to fall under 6.8.