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.