Organic Matter: Organic matter is plant and animal residues, soil organisms (microscopic,) and living plant roots.* Organic soil also includes humus* matter, which is highly decomposed organic material. Good lawn soils should have at least 2% of organic soils. Organic soil matter helps your plants by supplying usable nutrients and nitrates for growth. Organic matter also helps establish a soil with various crumb sizes (composed of 3 types of soil) of 1 to 3 mm (.025 to .10 in.) This is the best soil structure in which air, nutrients, and water can produce healthy grasses.
For lawn purposes, your concern should not be the fertility of the soil, but rather how the makeup of the soil affects its ability to hold water and to allow air to pass through it. You may need to improve sandy soils by adding organic matter (heavy soils) and clays or clay-loams. For a clay soil, you should add organic matter (light soils) and sand or sandy loams.*
The organic matter may be materials such as peat, manure,* old sawdust, straw, seed hulls, and other materials. You should thoroughly mix the organic matter with your soil to a depth of 12.75-15.25 cm (5-6 in.) Add extra nitrogen if high quantities of organic matter are added so as to replace the nitrogen that is tied up in the decomposing materials in your soil. Fertility can be improved through the addition of fertilizers and lime (use sulfur if the soil is alkaline.)
Using Soil Tests
Soil Tests Reduce Fertilizer Guesswork
Soil tests reduce the guesswork involved in deciding what kind and how much fertilizer to use. Your soil may contain an adequate level of one mineral nutrient and be quite low in another. A test of your soil will enable you to determine the correct amount of each mineral nutrient to apply. Soil tests are done by laboratories at colleges and universities and by private labs. A soil test result will give you the levels of nutrients in your soil and the recommendation for how much fertilizer your plants will need each year. You don't need to test your soil every year--testing every three to five years is adequate. To get useful results from a soil test, take a soil sample that represents your lawn and provide information about the types of grass you're considering on the form provided by the soil test lab. When collecting a soil sample, take samples from a depth of 15.25-20.25 cm (6-8 in.) from at least ten spots in your yard. Avoid sampling areas that are not typical of your yard. Mix the samples together well and take a sub-sample to send to the lab. Next...