Immediately after breaking ground for a new garden, you should test the soil. You can buy kits to do this, or buy a soil sample pouch at a garden center and send a sample of your soil to a state laboratory for testing.
- To make sure that your test sample represents actual conditions at the plants’ root level, take three or four samples from around the whole garden plot.
- Don’t take a sample from any place that was recently fertilized or limited; it will distort the results.
- To get a clean sample from root level, take a shovelful of soil out of the ground and set it aside, then slice another section, only an inch or so thick, from the side of the hole. With a penknife or scrap of wood, scrape away the top inch or so, and take your sample from a one-or-two-inch-wide vertical section of what remains.
- Mix that small bit with the other samples from around the area to be tested; all roots, leaves, rocks, and other material should be removed, and the test sample should be dry and fully pulverized before mailing.
One of the most critical aspects of a soil test is the pH report, which tells you if your soil is overly acid or alkaline. This is important, because all nutrients are more or less available depending on the pH balance of the soil.
- On a scale of 0 to 14, each whole number represents a tenfold difference from the next whole number. Thus, taking the number 7 as neutral (which it is on the pH scale), a pH of 6 indicates that the soil is ten times as acidic, while a pH of 8 indicates it is ten times as alkaline.
- The soil report will usually include a recommendation of how much lime (to raise the pH) or sulfur (to lower the pH) should be added, and in what form.
- Keep in mind: if the pH of your soil is more than two points away from neutral, you should break the application of lime or sulfur into two or more applications to avoid shocking the resident soil life with too radical a change.
Once an ideal pH of 6.0 to 6.8 (at which the widest range of nutrients is optimally available to most plants) has been established, an ongoing program of manure and compost applications will remove the need for any further attention to soil pH. Except for special conditions, the latest research backs up this belief. Only if your soil is of the most extreme acid or alkaline nature, or your garden is subject to serious acid rain and snowfall, should an ongoing program of pH balancing be necessary.