It is essential to begin watering new turf grass sod within a half hour after it is laid on the soil. Apply at least 1in (2.5cm) of water so that the soil beneath the turd is very wet. Ideally the soil 3 to 4 inches. (7 to 10 cm) below the surface will be moist.

Watering Tip #1: Pull back a corner of the turf and push a screwdriver or other sharp tool into the soil. It should push in easily and have moisture along the first 3 or 4 in (7 to 10 cm), or you need to apply more water. 

Watering Tip #2: Make absolutely certain that water is getting into all areas of your new lawn, regardless of the type of sprinkling system you use. Corners and edges are easily missed by many sprinklers and are particularly vulnerable to drying out faster than the center portion of your new lawn. Also, areas near building dry out faster because of reflected heat and may require more water. 

Watering Tip #3: Runoff may occur on some soils and sloped areas before the soil is adequately moist. To conserve water and insure adequate soak-in, turn off the water when runoff begins, wait 30 minutes to an hour and restart the watering on the same area, repeating as needed. 

For the Next Two Weeks: (Or until the turf is well rooted), keep the below-turf soil surface moist with daily (or more frequent) watering of approximately one-quarter inch (0.6 cm) each. Especially hot, dry or windy periods will necessitate increased watering amounts and frequency. 

Watering Tip #4: as the turf starts to knit its new roots into the soil, it will be difficult, impossible, and/or harmful to pull back a corner to check beneath the turf (watering tip #1) but you can still use a sharp tool to check moisture depth by pushing it through the turf and into the soil. 

Watering Tip #5: Water as early in the morning as possible to take advantage of the daily start of the grass’s normal growing cycle, usually lower wind speeds and considerably less loss of water because of high temperature evaporation. 

Watering Tip #6: If the temperature approached 100 degrees F (37 degrees C), or if high winds are constant for more than half of the day, reduce the temperature of the turf surface by lightly sprinkling the area. This sprinkling does not replace the need for longer, deeper watering, which will become even more critical to continue during adverse weather conditions. 

During the remainder of the growing season: Most lawns will do very well with a maximum total of one inch of water a week, coming either from rain or applied water. Soil conditions may dictate that the amount be applied in two settings, approximately two to three days apart. This amount of water, properly applied, is all that is required for the health of the grass, providing it is applied evenly and saturates the underlying soil to a depth of 4 to 6 in (10 to 15 cm). 

Watering Tip #7: Infrequent and deep watering is preferred to frequent and shallow watering because the roots will only grow as deeply as their most frequent available water supply. Deeping rooted grass has a larger “soil-water bank” to draw moisture from and this will help the grass survive drought and hot weather that rapidly dries out the upper soil layer. 

Proper Watering techniques are a critical aspect of lawn watering, equal in importance to the issues of when to water and how much to water. Here are several key factors to proper technique.

Avoid hand sprinkling because it cannot provide the necessary uniformity. Most people do not have the patience, time, or “eye” to adequately measure what is being applied across any large areas of lawn. The only possible exception to this guideline would be the need to sprinkle the surface of grass to cool it, or to provide additional water near building or other heat-reflecting surfaces. 

Understand the differences between sprinkler designs because each type has its advantages and disadvantages. Its proper use will be determined by the type of sprinklers you select.

In-Ground systems require professional design and installation and they require routine adjustments and regular maintenance to be most efficient and effective. The greatest mistake made with most in ground systems is the “set it and forget it” philosophy that fails to account for the changing seasonal water requirements to maximize turf growth or even allowing the system to operate during or following a multi-inch rain storm. Another frequent problem is when heads get out of alignment and apply water to the sidewalk, street, or house-siding, rather than to the lawn. 

Hose-End Sprinklers range in complexity, cost, and durability, but are highly portable and can provide uniform and consistent coverage, when properly places on the yard and adequately maintained.

Sprinklers that do not throw the water high into the air are usually more efficient as are larger drop generators because prevailing winds are less disruptive of distribution patterns, the potential for evaporation loss is reduced and trees, shrubs, and other plants do not block the pattern (or are very noticeable if they do). Several times during growing/watering season, routing maintenance is important to check for blocked outlets, leaking or missing gaskets, or un-aligned sprinkler heads, regardless of the sprinkler design.

Verifying water uniformity can be accomplished with a very simple and inexpensive method that uses only 4 to 6 flat-bottomed, straight-sided cans (tuna fish, cat food, etc.), a ruler and a watch. Follow these steps:

Step #1: arrange the cans at random distances away from any sprinkle, but all within the area you assume is being covered; 
Step #2: run the sprinkler for a specific amount of time, say a half-hour OR run the water until a specific amount of water is in at least one can, say 0.5 in. (1.3cm). 
Step #3: measure the amount of water in each can, checking for uniformity. Some variation is expected, but a difference of 25-30% or more between any two cans must be addressed by replacing or adjusting the sprinkler or relocating the system.

This measuring method should be used across an entire lawn that has an in-ground irrigation system to assure maximum coverage or uniformity. Watering difficult areas such as slopes and under trees require some special attention to achieve maximum benefit and a beautiful lawn. 

For areas under and near trees you need to know the water requirements for the specific trees, as well as for the grass. Despite having deep “anchor” roots, trees take-up moisture and nutrients from the top six inches of soil… the same area as the grass. Trees and turf will compete for water. Watering sufficiently for the grass may over-water some varieties of trees and under-water others. A common solution is to not plant grass under the drip-line of trees, but rather use that area for perennial ground covers, flower beds or mulch beds.

How Much water is needed and applied

The amount of water your lawn requires and receives will determine it overall health, beauty and ability to withstand use and drought. Keep in mind that too much water can ruin a lawn just as fast as too little water. 

One Inch (2.5cm) a week is watering “rule of thumb” suggested for most lawns; however, this will vary between different turf species and even among cultivars within a specie. There will also be varying water requirements for seasonal changes and still more differences brought about because of different soil types. Look at your lawn to determine its water needs. Grass in need of water will have a grey-blue cast, rather than a blue-green or green color. Also, foot prints will still appear after a half hour or more on a lawn in need of water, while on a well-watered lawn, foot prints will completely disappear within a few minutes. Inspecting your lawn frequently will help you detect water requirements and to avoid over or under watering. 

Verify watering quantities with the same measuring can method described above, except you will want to note the time it takes for the cans to collect a specific amount of water. For example, if 0.25 in. (0.6cm) collects in 30 minutes, you can easily calculate that it will take one hour to apply 0.5in (1.3cm) of water and two hours to apply 1 in. (2.5 cm) of water. 

Water timers can help provide consistency and even be programmed or set to turn on and off when no one is awake or at home. Some timers measure just the amount of time water is flowing through the device, while others measure the number of gallons of water flowing through it. Read the directions with the timer to determine how it operates.