Testing your soil is a relatively simple task and should be done at least every other year or so. You can do it yourself with soil testing kits which are readily available at a garden supply store or online. For a detailed soil test and report, contact your local cooperative extension service who can refer you to someone that provides this service. Cooperative Extension offices are usually a function of your state land-grant universities which can be found on the web under your state "Cooperative Extension Offices".
A professional test will disclose information relating to pH levels as well as salinity and nutrient levels which are more problematic in arid conditions. The test should also discover if nematodes or noxious perennial weeds are present in the soil. Some testing companies will often furnish you with recommendations on how to correct the problems, if any, and improve your garden soil.
Using a shovel or a trowel, take several samples from the areas you need to be tested. Remove any debris from the soil and set the soil aside to dry. Place the samples in a clean container such as a zip lock bag and label the bag with the location where the sample came from in your garden. Prepare the samples according to the instructions included with the kit or the testing lab.
The test will tell the condition of the soil and you what you will need to add to the soil in the form of amendments. The usual information includes the Ph level, nitrogen level, potassium level and the phosphorus level which are the four most important nutrients needed in your soil. These nutrients can easily be added to the soil to achieve an optimum balance.
A high pH (over 7.0) means the soil is alkaline or sweet and needs acidic amendments such as sulphur based products, wood ashes and lime to reduce the alkalinity. Most plants dislike high alkaline soil preferring a neutral Ph level. A low pH (under 7.0) may require applications of ground dolomite limestone. The ideal is a soil in the (6.5-6.8) range.
Low nitrogen can be corrected by adding fertilizer but that has recently become a dangerous practice due to over use of high nitrogen fertilizers which are creating a major ecological problem. Runoff from the millions of lawns, farms and gardens has caused dead zones in the Gulf of Mexico the size of New Jersey and these zones occur worldwide. The best remedy is to use blood meal, compost and manure and to grow crops such as legumes that put nitrogen back into the soil.
Another remedy is to plant fallow ground with a cover crop of winter-hardy rye, Fava beans, hairy vetch or clover and till in the following spring.