Soil Testing and Labs

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The first step before implementing any new landscaping should always be to take a soil test. A soil test will tell you exactly what your lawn or garden needs so you can add only those nutrients that are necessary.  You send a sample of your soil to a soil testing laboratory, and they send a report on the chemistry of your soil with specific recommendations of what types of fertilizers and nutrients to add to optimize the soil for what it is you want to grow.

The report lists the pH and organic matter content of your soil, and how much available nitrogen (N), phosphorus (P), and potassium (K) the soil has. Soil can also be tested for the minor (but important) nutrients magnesium (Mg), calcium (Ca), sulfur (S), boron (B), manganese (Mn),  and zinc (Zn), as well as toxic heavy metals like lead (Pb), arsenic (As) and cadmium (Cd). The most important values are the pH and following macronutrients: nitrogen (N), phosphorous (P), potassium (K)

The report also lists recommendations for soil management based on what you are planning to grow, for instance a lawn or a vegetable garden.  Suggestions may include increasing or decreasing the pH of your soil, or adding some of the above nutrients, usually in the form of fertilizers or compost.  The recommendations will specify how many pounds of each nutrient to add per 1,000 square feet.

When you fill out the form for your soil test be sure to request the percentage of organic matter in your sample, which should be at least 3.5 percent or more, along with organic recommendations. Your state land grant university or experiment station offers soil analysis for a small fee, or in some cases for free. You can indicate the type of plantings you have in mind, and the appropriate recommendations will be made. Fertilizing and liming, particularly of lawns, should always follow the soil test recommendations. Don’t fall into the habit of just adding a little more nitrogen or phosphorus, as over-fertilizing can cause pollution and lawn problems.

The benefit to using organic fertilizers and soil amendments is that their nutrients are released slowly and in a ratio that the plant can absorb. Organic is defined here as having no synthetic or man-made materials in the formulation. A balanced organic fertilizer will add the major plant nutrients: nitrogen (N), phosphorus (P) and potassium (K) along with micronutrients and trace minerals. All these amendments are important for plant growth and a healthy soil, which is alive with beneficial microorganisms, worms and insects which keep it aerated and fertile.

Plants growing in healthy soil develop strong roots, stems and leaves and are better able to resist disease and insect damage. Organic fertilizers will often have an N-P-K ratio in the range of 4-3-3, a relatively low analysis. If an “organic” fertilizer contains either N, P, or K near the 10 range, chances are it contains a substance prohibited in an organic program, and you risk run-off of excess nitrogen. Study the label carefully. Avoid synthetic ingredients such as superphosphate and harmful "natural ingredients" such as nitrate of soda which contains excess salts.

Synthetic chemical fertilizers, such as 10-10-10, are usually highly water soluble, releasing ALL their nutrients within a short time. Excess nutrients are washed into our groundwater, polluting our lakes, streams and drinking water with nitrates and phosphates. After a few weeks the synthetic fertilizer has completely dissolved and is no longer available to the plant. These petroleum-based chemical fertilizers also tend to kill off beneficial soil organisms.

Organic compost is a wonderful soil amendment and the best source of minerals, nutrients and beneficial organisms. Follow soil test recommendations for the use of compost. It can be applied at any time, but spring and late summer top-dressings of 1/4" depth are preferred. Read labels carefully and avoid any product that contains sewage sludge (also referred to as biosolids), which may contain harmful heavy metal contaminants. Wetting agents (synthetic polymer additives) in compost should also be avoided. The soil testing laboratory in your state can analyze compost samples using the same testing as for soil samples. Organic compost can be purchased at local garden centers and sometimes from your town’s municipal recycling facility. You can also make your own with leaves, yard clippings, and kitchen waste.

Where to Get a Soil Test

Connecticut

OR

Massachusetts and Rhode Island

Maine

New Hampshire

New York

Biological Testing