To achieve a uniform, dense, healthy and low maintenance lawn, proper soil preparation is essential. Lawns require appropriate amounts of sunlight, air, water and nutrients. Too much of one or not enough of another often results in stressed lawns. However, when given the right proportions, the grass will flourish. Well prepared soil encourages deep roots and result drought resistant, dense lawns. A dense lawn crowds out weeds and better resists insects and disease.
Soil provides three of the above requirements; air, water and nutrients. Soils with high amounts of clay are poorly drained are easily compacted which can prevent air and nutrients from reaching the lawn’s roots. Sandy soils, on the other hand, are too well drained causing water and nutrients to leach through the soil. Loams, sandy loams and loamy sands, with a pH of 6.0 to 7.0 are the ideal soils for growing healthy lawns.
Begin soil preparation by removing any visible rocks and debris. Next, till the soil to a depth of about 2 inches. This will most likely uncover more stones (and possibly old tree roots) which should be removed. Tilling will loosen compacted soil and allow air, water and nutrients to penetrate the surface. Using grading rakes, remove any weeds and sod which has been dug up as a result of tilling. Give the area a rough grade to avoid any drainage problems. Be sure to grade the lawn away from the house and patio. Add topsoil and organic humus to a depth of 6 inches and grade the area once again.
Test the soil pH with a chemical soil test to determine its acidity. Acidic soils (pH of 6 and below) can be improved with the addition of lime. The type (or source) and total amount of applied lime will be determined by the level of acidity and should be based on the recommendations of nursery of lawn service. Alkaline soils (pH of 7.5 and higher), on the other hand, can be improved with the addition of sulfur or gypsum.
Apply "starter fertilizer" at a rate recommended for the particular product. this fertilizer should be worked into the top 3-4 inches.
Roll the area with a lawn roller to firm and look for any low spots which may have been revealed. These should be filled and leveled to the grade of the surrounding soil.
The area is now ready for seed or sod.