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When to Water
The best time to water your lawn is before 10:00 AM and all watering should be completed before this time. There are several good reasons for this.
Watering early in the day covers the grass with a layer of water, which allows the turf to remain cooler further into the day. Water film tends to form better in the morning hours, where there are cooler temperatures, less direct sunlight, and less wind to drive surface evaporation.
If for some reason the morning hours are not available, late afternoon hours are reasonable times to water. You want to complete all watering before 6:00 PM.
However, there will be significantly more evaporative loss. Not to worry, drying of the leaf surfaces is preferable, since a damp lawn overnight can lead to other problems (see below).
Related Article: Best Time To Aerate Your Lawn
How Much to Water
A good watering typically means moistening the soil to a depth of 6-8 inches. Most turf grasses do well with 1.0-1.5 inches of water per week. There are exceptions; see below.
A 30-minute watering will lay down about 0.5 inches of water, so a 20-25-minute watering 2-3 times per week will do. Take care not to waterlog the soil.
Despite what you may have heard, plants do not breathe carbon dioxide. They fix carbon dioxide, but they breathe oxygen just like you do.
Healthy soils typically are about 40-60% air space, because roots need to breathe. Waterlogging will drown grass roots and kill the plants.
Excess watering can also train grass roots to grow shallowly, which will result in a lawn that is not resilient to water stress and will tend to dry out easily.
So, how do you determine how much water is enough? You measure it. There are several easy techniques to determine if your lawn is getting too much, not enough, or just the right amount of water.
Water the lawn for 10 minutes, turn off the sprinkler, and jab a long screwdriver vertically down into the soil. The screwdriver should be longer than 6 inches.
If the screwdriver can easily penetrate 6 inches of soil, watering is sufficient for a healthy lawn. If not, repeat the test in 10-minute increments until the screwdriver can penetrate 6 inches of soil.
Tuna Can Test
Position your sprinkler where you typically place it. Place empty tuna cans around the yard and record the amount of time required to fill the cans with 1.0-1.5 inches of water.
Calculate the average time required to fill all the cans to at least 1 inch. This amount of time, broken into 2-3 applications, will provide adequate moisture for your soil per week.
Measure it: Calculations – Standalone Sprinkler (flow meter)
Measure the area of your lawn and multiply by 0.62 gallons. This is the equivalent to 1 inch of water/square foot.
Using a water flow meter which measures water flow in hundreds of gallons will allow you to calculate a watering time which will apply the correct amount.
If you find standing water at the end of this time, break up the water time to 2-3 increments.
Water Requirements Of Different Turf Grasses
Bermuda grass, buffalo grass, and zoysia tend to thrive in temperatures >80°F and grow slower in cooler daytime temperatures. If the grass is growing and still must be occasionally mowed, continue to water at 1.0-1.5 inches per week.
Kentucky bluegrass, rye grass, and fescue grows well in cooler temperatures (<70°F) and tend to grow mostly in the fall months after a summer of dormancy. During the fall growing season, water these grasses to 1.0-1.5 inches per week until the first frost.
Choosing The Right Sprinkler
Watering is not just about the amount, but the way you water is also important. Pulsing sprinklers tend to be resistant to wind shear effects that would deflect the projected flow. Use these sprinklers for mature lawns instead of oscillating sprinklers.
Oscillating sprinklers are more appropriate for new lawns or seeded soils that need watering. Pulsing sprinklers send out high pressure projectiles of water, which tend to be too rough for newly-established lawns and certainly will disturb the surface of seeded soils.
Oscillating sprinklers are much more gentle for these applications. Water new turf 15 minutes/day for its first two weeks and twice a day if sod is laid down in hot summer weather. Just be certain to avoid waterlogging the soil.
Necrotic ring spot.
Cause: Overwatering or watering at night. Caused by fusarium blight fungus, which produces patterns resembling rings of dead grass. This disease is typically seen in cool-season grasses.
Solution: Reduce watering and only water either in the morning hours (before 10 AM) or late afternoon (before 6 PM).
Cause: Overwatering or watering at night. Caused by brown patch fungus, which leaves large patches of brown dead grass with irregular borders.
Solution: Reduce watering and only water in either the morning hours (before 10 AM) or late afternoon (before 6 PM).
Hard soil (compaction).
Solution: Reduce watering.
Cause: overwatering or soil needs aeration (soil is compacted).
Solution: Reduce watering and/or aerate soil.
Dry lawn after watering.
Cause: Excessive overwatering causing the root bed to grow shallow.
Solution: Reduce watering and elevate mower height. Grass height is closely related to root depth.
Cause: Soil needs more organic matter and cannot retain water.
Solution: Add an organic fertilizer (peat moss, humus, compost, etc.) to the turf with a spreader.
Cause: Excessive fertilizer has been applied causing nitrogen burn.
Solution: Rake away the brown turf. Pull back the turf and inspect the roots. If the roots are dry, the sod must be replaced. Otherwise, the soil must be waterlogged to remove excess fertilizer solutes.
Solution: Reduce watering.
Cause: Overwatering may have caused beetles to lay eggs in the soil; if grubs are present, they are damaging the roots.
Solution: Reduce watering, water at the proper times, and treat the lawn with an anti-grub insecticide such as Acelepryn.
Thinning and browning.
Solution: Increase watering.