Now is a good time to have the soil from gardens, lawns, flowerbeds or fields tested if you haven’t already done so. A standard soil test will tell you the level of major nutrients such as phosphorus and potassium, the pH, soil type, and the nutrient holding capacity of the soil. Based on these levels, a computer-generated recommendation will tell you how much fertilizer is needed to grow a good crop of vegetables, grass, trees, shrubs or flowers.
Remember that, except in very rare circumstances, the level of nitrogen in the soil will not be tested. Nitrogen is very water soluble and moves through the soil quickly. Therefore, to test it today would give results that would probably be different tomorrow. So, the ultimate recommendations will be based on the typical needs of the crops being grown and not on the amount existing in the soil.
A good soil sample must, above all, be representative of the area being tested. Never go to just one place, dig up some soil and call that a sample. That one spot may be totally different from the rest of the area and will result in an inaccurate recommendation. It may be the best or the worst spot in the area being tested and would give skewed recommendations.
To collect a good sample, use a clean plastic pail and a trowel or shovel. For a lawn, garden or flower bed, go to at least 6 different spots and dig down about 6 inches (or the root zone depth of the plants to be grown) and place the soil in the pail. Mix all of the soil from the subsamples together thoroughly in the pail. This will represent one sample for the plot.
Always allow the sample to air dry for a few days if the soil is wet when you collect it. Many times, samples are submitted in cardboard containers so wet soil may soak through and cause a mess.
Separate samples should be taken for different crops such as a lawn and a vegetable garden. Also, if one part of the yard is sand and another major part is clay, that should be two samples. Be sure to label the soil taken from each area separately since the fertilizer recommendation will be unique for each plot and proposed crop.
Take about a pint or so of soil to your local County Cooperative Extension Service Office. There are also commercial soil testing labs available in some areas. It is better to bring too much than to have too little for the lab to test. The sample will be sent off to your land grant university for testing and there will be some type of charge.