Fixing Grade and Drainage Problems
Before planting a new lawn any drainage problems should be identified and corrected. If you know that there are serious drainage problems, hiring a professional grading contractor to correct the problem is heavily recommended. Professional graders will use a laser transit to ensure proper drainage. Too, you can tell the grader to pile up top soil removed from any surface areas for later use when finish grading
If you have a smaller lawn area, and will be doing the job yourself, fix any existing grade problems before adding ammendments. Although grading often requires help from a landscaping contractor with heavy equipment, minor problems can be fixed by the ambitious do-it-yourselfer. Small versions of earth-moving equipment are often available for rent.
The first rule of grading is that the ground should slope away from your house in all directions so that it drops at least 2 or 3 inches for every ten feet. Sometimes this is not possible to achieve, so just make sure that the grade slopes away from your house. The finished grade should also end up matching the level of existing fixtures, such as permanent walks and patios, as well as areas of lawn that are not being replanted. This takes some figuring. If you will be replanting with seed and adding one inch of amendments, grade so that the level is one inch lower than fixtures.
When grading, first focus on any problem areas; low and high spots. Make adjustments by scraping away high areas and filling in low areas. Keep a pile of good topsoil around to spread over any areas where sub-soil has been exposed. Spread two inches of the reserved topsoil over the subsoil, and till in to a depth of two inches. This will help prevent drainage problems between the two layers of soil.
The maximum slope in a lawn should be 12 inches for every 4 feet. If the drop is greater than 12 inches, you should plan to build a low retaining wall or cover the slope with a hardy ground cover or low-growing shrubs.
Ammending Poor Soil
If your soil is hard-packed, non-porous and of poor quality, tilling in 2 to 4 inches of a screened native top soil to a depth of at least 6 inches is recommended for peak performance. And remember, once the job is done, it's done - and your poor soil will have been conditioned for a lifetime. If you need to add topsoil, buy a screened topsoil that's free of debris, such as roots or stones. A landscaping rake (hard rake) is the best tool for working soil to the proper grade if you're doing it yourself.
If you're lucky, the soil in your yard will be porous and of good planting quality. If so, there will be no need to add or till in native screened topsoil, or soil conditioners.
Either way, tilling in a layer of compost, such as composted cow manure or Mushroom Compost, at a rate of 3 to 4 cubic yards per 1,000 square feet is also recommended. For large lawns, the cost of adding these ammendments could be quite hefty. At a minimum, broadcast a pelletized chicken manure product, or Milorganite over the area at a rate of 50 pounds per 2,500 square feet to add beneficial organic matter.
Broadcast pelletized lime over the entire area at a minimum of 40 pounds per 1,000 square feet. NOTE: Centipede lawns do not require lime.
Ensure even application of amendments by dividing the recommended amounts in half and applying half while walking in one direction and the other half while walking in a perpendicular (opposite) direction. Once you have applied the amendments, till them into the top 6 inches of soil.
Till in top soil and any other ammendments.
