Soil Testing

When preparing your garden, one of the most worthwhile investments you will make is to have a professional soil test done. This will probably cost you less than $10 and will give you a great deal of information about the condition of your soil. This will save you money by directing you more accurately to what your soil really needs, and what it doesn’t.

Soil testing can be done through specialist laboratories. Search the Internet or ask at your garden center for contact details for a local lab. Local labs are best because the recommendations will be specific to your climate and soil type. When you contact the lab make sure they can tailor their soil recommendations to a garden setting. Often, labs test soil for farmers and their results will come in the form of “per acre”, which can be difficult to work with at a garden level. However, if the mathematics doesn’t daunt you, you can do the conversion from pounds/acre to pounds/1000 square feet by dividing the original figure by 43.

Be sure also to let the laboratory know that any specific recommendations they make should preferably be organic soil additives rather than agricultural-standard chemicals.

What does the test indicate?

You will get results for pH level, percentage content of organic matter, and nutrient levels.

A pH level of between 6.2 and 7.0 is ideal for most flowers and vegetables. This is slightly acidic but creates the best conditions to make the widest possible variety of nutrients available to the roots.

If your pH is too low – that is, if your soil is overly acidic – the lab will probably recommend a lime additive. Not all lime additives are the same, however, and the results of your soil’s magnesium levels will give a better indication of the kind of lime most suited to your soil. If magnesium levels are reported as adequate, the lab will likely recommend calcitic lime. If your soil is magnesium deficient, the recommendation will probably be dolomitic lime, which adds both alkaline lime and magnesium.

If, on the other hand, you have a high pH, meaning your soil is too alkaline, sulfur is the normal additive used to lower soil pH. Just make sure not to buy ground sulfur. The dust is so fine that you will need to wear special protective gear.

Along with magnesium, most laboratories will test levels of sulfur, calcium, phosphorus and potassium. Nitrogen is not typically tested because its levels vary dramatically. If you want the test done anyway, specify that when making your arrangements. You’ll probably have to pay a little bit extra.

Labs will also test for some important micronutrients, essential plant nutrients that are only necessary in tiny amounts. Minerals are the main soil  components and the easiest way to add them to your soil is through mulching and composting. If your soil is unmulched and there is evidence of problems, make sure you ask the lab to test for micronutrients.

Taking a successful soil sample

Taking a soil sample is not as simple as scooping some dirt! Follow these steps to get the best possible sample and therefore the most meaningful results.

  1.  Get yourself a bucket and a trowel. These must be free of rust and should not be make of galvanized metal. Either of these will interfere with your test results.
  2. Scrape away organic materials such as leaves and mulch from the top of your soil, and then use your trowel to cut out a wedge about 8 inches deep. Set it aside.
  3.  Dig a half-inch portion of soil from the bottom of the hole you just created, and pour that into your bucket.
  4. Repeat 2 and 3 at least six times from different areas of your garden, so that all areas are represented in the sample you present.
  5. Mix the soil in the bucket thoroughly.
  6.  Fill the sample container or bag that has been provided to you by the lab, make sure all your paperwork is correct, and sent it off for testing.

Remember, there is much to learn from a professional soil sample and if you take the time to get one done well in advance of planting, you have the best opportunity to create a really healthy organic soil that will result in healthy and thriving plants.