How much water does grass need?
The main objective is to get the soil moist where the grass roots are located. This depends on the type of grass, how well the lawn is thriving, and the health of the soil, even mowing height. It’s a good practice to keep the soil moist 4 inches deep, but also giving enough time to dry out to prevent disease. The watering schedule depends on the type of soil. In New Jersey, we have sandy and clay regions. Factoring whether a property is flat or on a slope will change a watering schedule as well.
If too much water is applied, nutrients will leach through the soil faster, taking nutrients past the root system in order for grass to benefit from. Grass won’t be as green, disease may occur, and it will encourage weeds to thrive in that area when too much water is being applied.
Not enough water will cause grass to go dormant and turn brown, eventually leading to death. Depending on the age and type of grass, sometimes grass can survive a drought. In order for grass to survive a drought, nutrient and pH levels need to be at optimum levels. Grass needs a couple of years, once the soil has optimum conditions, in order for the roots to get fully established. So if you have a fairly young lawn, make sure grass is taken care of during the summer months until the roots are well entrenched into the soil.
*Schedule is for an irrigation system that is properly installed/adjusted with good water pressure.
**Sprinkler heads on an irrigations system that rotate a full 360 degrees, require twice the amount of time.
SANDY SOIL: Water leaches through the sand much faster than other soils. This requires less water than other soils to get the soil moist four inches down where the roots extend. Unfortunately, sandy soil dries quicker than other soils. Instead of increasing the time the lawn is watered, just water more frequent. When temperatures are in the 90’s and above, you may need to be watering twice a day, 15-20 minutes each zone. In cooler weather, water once a day for the same amount of time.
CLAY SOIL: You have to use heavy watering to get where the roots extend moist. When temperatures are above 90 degrees, you may need to water once a day, 30-40 minutes each zone. Below 90 degrees, water once every other day, for the same amount of time.
SLOPE: See sandy soil. This will prevent water runoff.
Areas that recieve shade from the sun may not require as much water.
Every lawn should be watered as early as possible, 4-7 am is ideal. If you have to water twice in one day, water a 2nd time 12 hours later. Watering in the afternoon, when the sun is at its strongest, could lead to a waste of water. Evaporation will happen faster on a hot, sunny day, possibly too fast for grass to reap the benefits.
If an in-ground sprinkler system is being used regularly, DO NOT assume it’s watering your lawn perfectly! Sprinkler heads have to be properly adjusted every year. If browning occurs on an irrigated lawn, check to see how the heads are spraying. A sprinkler system is only as good as it sprays! It can be such a fine adjustment, not even noticeable unless studied, that can make a world of a difference. This is may only be a problem during the hot and dry months. Lawns with optimum levels for soil pH and nutrients, a well balanced lawn care program, and properly irrigated should not have browning! In just about every heat stressed lawn you can find disease and more often than not, turf disease is brought on as a result of the heat stress. Once grass is hit with one stress, it is very susceptible to other stresses (disease). Please compare these two photos.
Photo A, no bueno! Notice the difference between A and B, the vertical spray. In photo B, from the start of the sprinkler head to where the water ends, grass is getting wet and it is noticeable. If you cannot see the mist between the top of the spray and the grass, it is not enough water! That mist should be easily visible or it will be inadequate. The condition of the sprinkler head and the proximity of the sprinkler heads will play a role into creating an effective irrigation system, but water pressure is the most important. Photo A will also cause issues when seeding in the fall time! Unfortunately, a high percent of irrigation systems lack the quality needed. A $15 manual oscillating sprinkler is recommended when an irrigation system isn’t present or is ineffective.
SIGNS OF HEAT STRESS
Gradual browning in-between brown spots is a clear indicator of heat stress. Textbook disease still has green around brown spots. Now, you will always find disease in heat stress. When grass is stressed out, it can easily get sick, like us! Take a look at pics below, sections of brown, then sections of green. The pics have the same amount of sunlight throughout, why is disease in just one spot? The type of grass does play a role and small sections of certain types of grass can have similar browning, but that is not the case in these pictures. If you have these issues, don’t increase the duration of your watering schedule! Over watering will cause more problems. Adjust the heads, check the water pressure and make sure sprinkler heads are not too far apart. This is, by far, the most common problem in summer months, especially during long, hot periods with no rain.