Question
The front lawn of my home slopes and I have a rather large maple tree in it.  My problem is that the roots of this tree are growing fairly close to the surface and seem be taking the majority of moisture from the lawn cause the grass to thin and dry out (regardless of increased watering).

We have tried adding a few more inches of top soil to the lawn but the problem continues.

Answer
The lack of grass is due to the shade Mianly Some grasses will grow under  shade while others need full sunlight.
Trees and shade create a naturally pleasing environment in the landscape. However, it is difficult to grow grass under trees because not only the quantity but also the quality of the light changes in the shade. In full sun, light is in the "near red" range of wavelengths; in the shade it shifts to the "far red," which is less effective in photosynthesis. In addition, dense canopies, particularly those of conifers, filter out the blue component of sunlight, which is critical for plant growth. The result of these changes is a reduction in photosynthesis and its products, including carbohydrates needed for plant growth.

Leaves, leaf cuticles and stems of plants are thinner in shade. Shoot density decreases and rhizome and stolon numbers decrease. Plant tissues are succulent and there is an increase in susceptibility to environmental stresses and disease. Transpired moisture from trees and grass, and moisture from dew forming under trees, take longer to dissipate, and the additional moisture may contribute to an increase in disease.

Shady conditions in combination with other plant stresses contribute to the difficulty of growing grasses under trees. For example, tree roots compete with turf for water and nutrients, and this competition can further weaken turf growing in shade. Allelopathic effects, such as the inhibitory effect of silver maple upon Kentucky bluegrass, are important between certain species of plants. Excessive organic matter from leaf litter will also inhibit grass. One or more of these factors make it particularly difficult to grow grass under sweet gum, maple and unpruned pin oak. On the other hand, grass is easier to grow under locust and poplar trees.


Select and use grasses that have improved shade tolerance  Most of the fine fescues (hard, sheep, spreading, slender creeping and Chewing's) have very good shade tolerance. Tall fescue has good shade tolerance, while Kentucky bluegrass is the least shade tolerant of the cool-season grasses. Bermudagrass, zoysiagrass and buffalograss should not be used in shady locations. In areas where shade-tolerant grasses fail, consider shade-tolerant groundcovers or mulched beds instead of grass.