Most lawn stress is usually brought on by temperature, drought, disease, or insect stresses, but there are many other stresses on your yard that can influence the growth of grass. Some of these stresses are; shade, compaction, and thatch.
Shade Stress on Grass
It is estimated that as much as 25% of the turfgrass grown in the United States is shaded to some extent. The leaves from the trees block the grass only allowing 5% of sunlight to reach the grass. This lack of sunlight makes it difficult for the grass to conduct photosynthesis properly. Low light intensities restrict the rate of photosynthesis and therefore the plant does not grow as much and in consequence restricts it from storing reserve carbohydrates. In return other stresses such as cold, heat, and drought increases when the plant has an insufficient supply of storage food.
Trees do not only block valuable light for photosynthesis but they also compete with the grass for water and nutrients. Grass may suffer from moisture and nutrient deficiencies because trees require large amounts of water and the same amount of nutrients that the turfgrass needs. Competition and low light are not the only factors contributing to shade stress. Cooler temperatures and moist soils that shade causes creates an environment that is ideal for the development of grass disease.
Shade stress cannot be totally avoided but they can be managed. A valuable tool for the prevention of shade stress is to use grass seed for shade which are tolerant to shade. These grasses can grow well under shade because they require less light to conduct photosynthesis at their optimal level. Some examples of shade tolerant grasses are; St. Augustine, and some varieties of fine fescue. Using shade tolerant grasses is a good management practice for dealing with shade stress, but the best management practice is to simply avoid shade stress by implementing a good landscape design.
Soil Compaction on Grass
A compacted soil is a soil in which the mineral particles have been pressed together so tightly that they do not allow air, water, and nutrients from grass fertilizer to penetrate the soil easily. In effect, the grass suffers because the roots of the grass cannot obtain the essential nutrients, air and water that are needed to grow vigorously. Like shade, compacted soils can intensify other stresses such as salinity, drought, and temperature. Therefore, maintaining a healthy and spacious root zone is required for a pleasing aesthetic grass surface.
There are several methods to use to alleviate soil compaction. Some of the best methods are avoiding excess traffic, aerification, and maintaining a proper soil particle balance. A proper soil particle balance is the optimal balance between clays, organic matter, and sand. Too much of one substance can decrease the quality of the soil, but specifically too much clay in a soil can and will cause soil compaction. This is why adding soil amendments such as gypsum, organic matter, and sand is crucial to assist in avoiding soil compaction. Excess traffic such as golf carts and people walking are sometimes hard to avoid but with a good maintenance schedule, the negative effects can be reduced. This is where aerification comes in. Aerification is the process of removing cores from the soil surface to promote good air ventilation, water and nutrient absorption. Simple maintenance practices can help reduce the risk of soil compaction. One of these practices is keeping machines off your lawn when wet.
Thatch build up occurs when the production of plant tissue is greater than the decomposition rate. The build up of thatch can lead to water infiltration problems, poor playing surfaces, and provides an ideal environment for disease organisms and insects. Because of thatch build up, the grass roots are more likely to surfer from cold, heat, and drought injury because the lack of insulation provided by thatch. A thick layer of thatch can also make the grass surface uneven leading to scalping during mowing.
There are two major ways to deal with thatch. The most common and widely used method is verti-cutting. Verti-cutting is the vertical thrashing of blades that physically tear out plants and thatch. Visit the De-thatching Lawns to Revitalize Your Grass post for more. The complimentary method to verticutting is to top-dress the surface with a light amount of sand. This replaces the thatch with inorganic matter suitable for root growth.
All of these three stresses discussed in this paper influence and accelerate other stresses that can lead towards turf death. With sound soil science and proper planning of the landscape and good lawn care practices, most of these stresses can be avoided or controlled to a minimal level.