Most plants prefer pH between 5.5 and 7.5. A simple rule is that if your plants are growing, flowering and fruiting well, the nutrient levels are fine. If you're just starting out or if you aren't satisfied with the growth of your plants, a little testing can help you get to the root of the matter. Too high or too low pH can result in yellow, stunted and unproductive plants. Unhealthy plants are more prone to insect and disease attacks, which translates into more work for you and less satisfaction from your garden.
Testing your soil is like doing home repairs. You can do it yourself or have someone else do it for you. Doing it yourself with a home test kit is simple and gives you a basic pH reading and an estimation of the major nutrients in your soil. You can buy test kits at nurseries and garden centers and they range from extremely simple to elaborate. The more sophisticated tests cost more, but give you more accurate results.
You can also send a soil sample to a lab for testing. You simply take a representative sample of the soil from your garden, fill out a form and mail or take it to the lab. The results are more accurate and detailed that if you do the test yourself with a home kit, plus testing labs can look for things that home kits cannot, such as organic matter and micronutrients. Soil-testing labs can also test for heavy metals and other industrial residues. Soils near heavily traveled roads or on old industrial sites can contain lead and other unwanted metals that you may want to know about before planting a vegetable garden.
Lab reports give you the current levels of nutrients and soil pH and also offer specific recommendations about which nutrients to add to your soil and in what quantity for your plants' optimum growth. Lab tests can get costly, however, especially if you have many different types of plantings, such as perennial flowers, vegetables and lawn and you do separate tests for each type. Check the phone book under "Soil Testing" for private soil labs in your area or contact your state university's extension service. Many state universities test soil for a small fee or can recommend a private testing lab.
Most plants grow best in a pH range from 6.0 to 7.0. Some plants, however, suck as blueberries and rhododendrons, like highly acidic soil (pH below 5.0), so you may need to adjust the soil pH to individual plants.
In general, you add lime or limestone to raise the pH and sulfur to lower it. How much lime or sulfur you need to add depends on the type of soil you have and its current pH. The soil-testing lab will make a specific recommendation based on that information.
When adding lime or sulfur to your soil, remember to wear gloves and a dust mask because this material can be very dusty and irritating if inhaled. You can spread the material by hand or use a drop spreader made to spread grass seed. In the garden, work the lime or sulfur into the top few inches of soil with a rake or shovel after spreading.
Don't expect results right away. Most limestone or powdered sulfur products take a few months to react with the soil enough to change the pH to the desired levels - another good reason to prepare your soil a season before you plan to plant.
