Here is Lesson 4 - "Watering and Mowing" in our Lawn Challenge Series from the University of Illinois. terry
"Watering Lawns the Right Way
How much water does a lawn need? In general, cool-season grasses need about one to 1.5 inches of water per week is needed to maintain green color and active growth, and naturally slow down in growth and may go dormant in hot weather. Factors such as the soil, weather, and management practices all have a role in water needs of lawns. Here are a few general rules to follow:
* Decide before summer to either water lawns consistently as needed throughout the season, or let lawns go dormant as conditions turn warm and dry. Do not rotate back and forth. In other words, don't let the grass turn totally brown, apply enough water to green it up, and then let the grass go dormant again, as breaking dormancy actually drains large amounts of food reserves from the plant.
* When is it time to water? The first few warm days of summer does not automatically mean to water lawns. In fact, allowing lawns to start to go under mild drought stress actually increases rooting. Watch for footprinting, or footprints remaining on the lawn after walking across it (instead of leaf blades bouncing back up). Grasses also tend to turn darker in color as they go under drought stress. Sampling the root zone soil could be another option.
* In general, water as infrequently as possible. Water thoroughly so moisture gets down to the depth of the roots. Exceptions to this general rule would be for newly seeded lawns where the surface needs to stay moist, newly sodded lawns that have not yet rooted into the soil of the site, or when summer patch disease is a problem. Otherwise, avoid frequent waterings that promote shallower root systems and weeds (e.g., crabgrass).
* Given a choice, water early in the day when lawns are normally wet from dew. Avoid midday due to evaporation, and at night due to potential increased chances of some diseases.
* Spread the water uniformly across the lawn. Sprinklers vary in distribution patterns, and require spray overlap for uniform coverage. Placing coffee cans or similar straight-sided containers on the lawn can help measure water application rates. Avoid flooding areas, or missing other spots. On heavy clay soils and slopes, watch for excessive runoff; it may be necessary to apply the water in two applications to assure it soaks in.
* To help conserve water use, mow higher, avoid excess nitrogen as warm weather approaches, limit traffic over the lawn, improve turf rooting, control thatch and soil compaction, and avoid pesticide use on drought stressed lawns.
Importance of Proper Mowing
Although often overlooked, mowing has a major impact on lawn appearance and health. Follow a few simple guidelines to assure lawns are mowed properly:
* Don't make the common mistake of mowing too short. For most lawns in northern Illinois, a mowing height between two and three inches is suggested; with the upper range best for summer. Lawns mowed at higher heights tend to have deeper roots, less weed problems, and look much better. Mowing too close invites problems such as weed invasions. Simply raising the mowing height can have a major impact on the quality of many home lawns. A mowing height of two inches would be fine when grasses are rapidly growing, but the height should be raised as growth slows, stress increases, and when the lawn is in the shade.
* Base mowing frequency on the rate your lawn is growing. Do not remove more than one-third of the grass leaf in any one cutting. Mowing on a regular basis as the lawn needs it is essential. Don't mow when the grass is wet.
* As long as the lawn is mowed on a regular basis and the clippings readily filter back down into the lawn, clippings do not need to be collected. Returned in this manner, clippings readily decompose (contain 75 - 80 percent water) and do not cause thatch (thatch is discussed later in Thatch and Lawn Renovation). Clippings also recycle nutrients, in particular nitrogen, so less fertilizer is needed.
* Selecting a mower can involve a number of factors, many being personal preference. A study at the University of Illinois showed mulching mowers did not provide any additional benefit over conventional rotary mowers returning clippings, assuming proper mowing frequency and lawn fertilizing was followed. Regardless of the type of mower, blades need to be kept sharp.
* Mow in the direction that is safest. Periodically change directions if desired, although mowing the same direction each time should not be a problem on taller grass of home lawns."