Soil Improvement

The best way to know what your soil needs is to test it every two or three years.
Soil tests that are commonly offered include:
pH - determines the acidity of your soil and estimates how much lime is needed to
adjust the pH to an optimal level.
Nutrients - determines the levels of available plant nutrients. Often, labs don't
bother to test for nitrogen, since this test is often misleading. Around our area you
can assume your soil needs moderate inputs of nitrogen every year. Some labs test
for calcium. This is unnecessary too, since you will be adding lime (calcium
carbonate) for pH balance anyhow.

Organic matter - determines the percentage of organic material in your sample.

Soil texture - determines the percentages of sand, silt and clay in the soil and
classifies it by texture according to the USDA system (ex. silty loam). Since your
soil texture is not going to change, you have to request this test only the first time.

Heavy metals - determines whether your soil contains abnormally high levels of
toxic heavy metals. Sometimes the test is strictly for lead, the most common garden
heavy metal contaminate. Usually if levels are elevated, recommendations will be
included on steps to take to counteract the danger.
Whatever test you do the procedure for taking the sample is the same. Each area
where the soil looks different or has been treated differently should be tested
separately. Don't sample in abnormal spots like right next to a fence, driveway,
sidewalk or building.
Don't sample a soil that has just been fertilized or limed. Make sure your shovel and
bucket are not contaminated from the last time you fertilized. Any of these things
could throw the results way off.
There will be variations even within a rather homogeneous area, so the sample you
send should be a mix of several samples. Using a clean trowel or spade, take thin
vertical slices of soil from about 10 locations within the area they are to represent.
Put them in a clean bucket and mix thoroughly. From this, take the cup or whatever
amount your lab requests. For most purposes you will want to sample the top 6-8
inches. For fruit you should go down to 8-10 inches.