Watering is one of the most often misunderstood aspects of turfgrass culture. Often, watering on turf areas is too frequent and too light. Frequent, shallow watering encourages shallow rooting, soil compaction, thatch accumulation, and weed seed germination.
Ideally, turf should not be irrigated on a regular schedule but on one that is determined by need. An irrigation program cannot be developed to fit every location due to 1) dissimilar water holding capacities of different soil types found in Oklahoma, 2) weekly fluctuations in temperature, humidity, wind, and precipitation, and 3) the influence of management practices, such as mowing and fertilization on turfgrass water consumption. Sandy coarse-textured soils absorb water faster but retain less water than fine-textured soils like loams and clays. Thus, it takes less water to moisten sandy soil to a 6-inch depth than to moisten a clay soil to the same depth. This means more frequent applications of less water are required for turfgrasses growing on sandy soils. Lush, actively growing turfgrasses utilize more water than turfgrasses maintained on the “lean side.”
The ideal time to water is when turfgrasses show the first visual symptoms of water need or wilt, characterized by “foot printing” and a blue-gray appearance. When turfgrasses experience moisture stress, their leaves begin to roll or fold and wilt. Thus, the leaves are slower to bounce back when stepped on. Enough water should be applied in one application to wet the soil to a 6-inch depth. This can be checked by probing the soil. After a few times you should develop a feel for the amount of time and water required for deep watering. If the area begins to puddle and run-off is occurring, stop irrigating and allow the water to soak into the soil. It may be necessary to repeat this cycle several times before proper irrigation is complete. Irrigating only when turfgrasses show the first visual symptoms of water need and then watering deep will encourage deep rooting. Early morning is an ideal time to irrigate.
Warm-season turfgrasses (bermuda) are cut higher in the fall to provide insulation for low temperatures. When they are growing during the summer, they are cut lower to promote lateral spread and a “tight” turf. Cutting turfgrasses below their recommended height will discourage deep rooting. Cutting too low may cause the turf to thin, because it is less able to withstand heavy traffic and environmental stresses such as low soil moisture and extreme temperatures. Cutting bermudagrass above its recommended height may produce a stemmy turf, characterized by leaves being produced near the end of upright stems. This kind of turf is prone to scalping.Turfgrasses grown under shady conditions should always be maintained at a slightly higher cut in order to increase leaf area to compensate for lower light levels.
Ideally, turfgrasses should be mowed on a schedule that is based on the amount of plant growth between mowings. This will depend on the level of soil moisture, nutrients, and temperature and the amount of sunlight. Since these conditions fluctuate from week to week, it follows that plant growth also fluctuates. Therefore, the ideal time to cut turfgrasses is at a point so that no more than about a third of the leaf area is removed at any one mowing. This means cutting U-3 bermudagrass at 1 inch each time it reaches 1.5 inches and cutting Tifgreen bermudagrass at 0.75 inch each time it reaches 1 inch.
It is preferable not to bag grass clippings since collecting clippings removes valuable nutrients from the lawn, grass clippings take up valuable space in the landfill and bagging clippings takes more time than mowing with a mulching mower. Regardless of the type of mower used, it is essential that mowing equipment be kept sharp and in good operating condition. Dull, improperly adjusted equipment bruises leaf tips, reduces growth, and causes a dull-cast appearance over the turf area due to frayed leaf blades.
Other mowing practices should include varying the mowing pattern throughout the growing season to distribute wear, reduce soil compaction, and improve turf appearance. Secondly, make turns on sidewalks and drives or make wide turns to avoid tearing the turf. Lastly, avoid mowing wet grass. It is harder to obtain a quality cut, clippings form clumps on the mower and turf, and disease organisms are more likely to be spread.
Bermudagrass and zoysiagrass are particularly prone to developing an excessive (greater than 0.5 inch) layer of thatch. Thatch is undecomposed roots and stems. Excessive thatch accumulation is caused when the production of plant tissue exceeds its decomposition. This condition can be caused by excessive plant growth or during conditions when plant tissue decomposition is slow. Excessive thatch layers impede the movement of moisture, nutrients, and air into the root-zone soil. This condition leads to shallow root development, which may cause the turf to thin. Thatch formation is retarded through proper mowing, fertilization, watering, and responsible pesticide use.
Determine the thickness of the thatch layer in your lawn by examining a 3- to 4-inch deep plug. If thatch is thicker than 0.5 inch, a dethatching operation is in order. The best time to dethatch warm-season lawns of bermudagrass and zoysiagrass is prior to spring green-up. Dethatch tall fescue lawns in the early fall. Thatch layers are best removed by a dethatching machine or power rake. These machines may be hired or rented.