Simple Soil Tests
Charlie Nardozzi of the National Gardening Association shares some tips for simple soil testing.
Sandy soil drains rapidly, but doesn't hold nutrients well. Adding organic matter will help the soil retain both moisture and nutrients.
Clay soil does a good job of retaining nutrients, but its dense texture is difficult for roots to penetrate. Clay is difficult to work when moist, and once it's dry, it often forms a tough, impenetrable surface.
To determine whether your soil is sandy or high in clay, try the ribbon test. Take a handful of soil, and roll it back and forth in your hand. The object is to make it stick together.
If the soil doesn't hold together, it's probably sandy. If it holds tightly together, it contains a lot of clay.
The key to amending your soil is organic matter such as straw, hay, leaves, manure or grass clippings. These materials improve your soil's texture and its ability to retain water and nutrients.
Manure, for example, is an excellent amendment that not only supplies some nutrients, but also improves soil texture. You can apply manure to the soil in late fall and turn it under in spring – or incorporate rotted manure at any time. If manure isn't available from a nearby farm, you can buy it at garden centers. Commercially available manure has been composted or sterilized and is easy to handle, with very little odor.
After amending the soil, you may wish to have a soil test done to determine whether it's lacking any nutrients. A professional soil test, performed by your county agricultural extension service or a local garden center, is more accurate and may be cheaper than using home-testing kits. Private laboratories may charge between $5 and $50, depending on the number of tests performed. The test results will indicate whether you need to add other nutrients or minerals to the soil.
Your soil test may recommend the use of a balanced, or complete, fertilizer. The three numbers on a package of balanced fertilizer indicate the percentages of nitrogen, phosphorus and potassium it contains. Plants need all three elements for growth.
If your soil is deficient in a specific nutrient, the test results will tell you how much of it to add. Cottonseed meal, for example, is an amendment that's relatively high in nitrogen; another choice is ammonium nitrate. Make sure to use only as much as the test results recommend. Too much of any fertilizer or amendment can cause problems.
Fruit trees, shrubs and trees can be fed with fertilizer spikes. Put an end cap on each spike, and pound it into the soil around the drip line (the outer edge of the leafy top part of the plant).
Container plants respond well to a slow-release fertilizer such as Osmocote, which releases nutrients slowly over a period of several months.