Before renovating a turf area, it is critical to assess why the grass declined. The following are potential causes for turf deterioration.
Causes of turf deterioration
The first step in lawn renovation is to correct the primary cause of turf deterioration. Such things as drought, excessive shade, tree root competition, poor drainage, soil compaction, inadequate fertility, acid soils, weed or insect infestation, disease, thatch build-up, improper mowing, poorly-adapted grass species and cultivars, and others may contribute to poor turf. Most of these problems can be corrected by renovation, proper turfgrass selection, and improved maintenance practices.
Shade problems may require removal of some trees, pruning, and planting turfgrass species that are adapted to shaded conditions. Tree roots may need pruning to reduce competition with grasses for water, air, and nutrients.
Drainage problems can often be corrected by breaking-up compacted soil or through installation of drainage tile. Where surface drainage is insufficient, the site may have to be regraded so that water is removed from the site.
Soil fertility and acidity
Inadequate fertility or acid soils which can limit turf growth can be determined by testing the soil. Soil testing services are available from the Soil Testing Laboratory at the University of Delaware or through private laboratories. Kit for the soil tests are available at a nominal fee from the cooperative extension office in your county. Soil test laboratories will provide recommendations for the amounts of fertilizer and lime that need to be applied to the lawn.
Pests that cause serious turf damage need to be identified and controlled. If you cannot identify these pests, take fresh samples to your county extension office or another knowledgeable source to have them identified. The most common pest problem causing decline in Delaware turf is grubs (severa species of beetle larvae such as Japanese beetle).
Thatch is a tightly intermingled layer of partially decomposed grass stems and roots which develops beneath the actively growing green vegetation and above the soil surface. Thatch decreases the vigor of turfgrasses by restricting the movement of water, fertilizers, and pesticides into soil. Turfgrass roots also grow into the thatch and may become desiccated as the thatch dries. Thatch builds up over a period of years and must dealt with. The best approach to managing thatch is core aeration that brings some soil up into the thatch layer. The soil will have microorganisms in it that can help the thatch to decay. Thatch removal equipment can usually be rented from garden centers or rental outlets however this is a temporary solution usually
Mowing on most lawns should be at two inches or above and on a regular basis as long as the grass is growing. How frequently the grass is mowed depends on the growth rate of the grass. No more than one third of the total leaf surface should be removed at a given mowing. Thus, if the turf is cut at two inches, it should be mowed when it reaches a height no greater than three inches. Clippings do not need to be removed provided the lawn is mowed on a regular basis. All mowing equipment needs to be sharpened and adjusted periodically.
Species and management
Unadapted species and improper management are perhaps the most common causes of turfgrass deterioration. Species and management must be adapted to the conditions present at the site. Other problems include the use of inferior turfgrass cultivars and poor quality seed. Once the reasons for lawn deterioration are recognized and steps are taken to correct the problems, the renovation program can begin. The following three programs are designed to fit most renovation situations. Some operations may need to be altered or omitted depending on the individual situation.
Information adapted from a fact sheet from Penn State University http://cropsoil.psu.edu/Extension/Turf/pdf/ec412.pdf