Step 9 - Watering — Is your lawn dying of thirst, or drowning
How often does your lawn need to be watered? Since Nassau allows watering every-other-day, does that mean you should water every-other-day? What is the best time of day to turn the sprinklers on? And when you do get your sprinklers started, how do you know when to turn them off? These lawn-watering questions have been the source of many debates in Long Island households over the years.
The answers to these questions can be captured by one simple guideline: Water infrequently, but deeply when you do. What follows are the details of how and why to do this.
With water, as with other "inputs" that you add to your lawn like fertilizer, the Goldilocks Rule applies. The right amount of water is neither too little nor too much and the more common mistake is to cause damage by applying too much. As we have reiterated throughout the 12 Step series, understanding the nature of healthy, organically maintained lawns begins with an appreciation of diverse microbial activity. Soil microbes are the foundation of the soil ecosystem that cycles nutrients, maintains soil structure, and provides natural defenses against disease and pests. Just as chemical pesticides can kill microbes in your soil, so too, excessive watering will deprive the microbes of oxygen and create an anaerobic environment, undermining your goals in establishing an organic maintenance program.
Grass needs water to grow, but probably not as much, or as often as you might think. You should only rarely water more than once a week. Twice a week at most, in very hot, dry weather, if you have sandy soil. More lasting damage can be done to a lawn by improper irrigation than by drought. Soils that have been effectively sterilized by chemical applications, and have very little soil microbial life and organic matter are much more susceptible to drought and "browning out." Healthy soil, with sufficient organic matter, will do more to help your lawn through the summer than an expensive irrigation system will. Organically maintained lawns, with grasses such as fescue, and which have more organic matter that retains water between rains are more drought tolerant.
Encouraging deep root growth will further increase an organic lawn's resilience to drought and heat. Some ways to encourage deep roots are to mow high and not take off more than one-third of the grass blade when mowing. Adding compost will improve soil structure and feed earthworms that dig through the soil, lessening compaction, this makes it easier for the grass plants to grow roots deeper. Don't use pesticides, they can kill most of your earthworms. Watering deeply when you do, and not watering frequently lets the top of the soil dry out between watering, this forces the roots to grow longer to reach the moisture in the deep soil. Watering lightly every day or so lets roots be lazy and stay near the surface.
A healthy lawn will not die of thirst in Long Island's climate, but it may need irrigation to avoid going dormant and turning brown in the height of summer. Water only when necessary. Some experts advise watering only when grass begins to wilt; the grass will turn a dull, grayish color. If you are not confident about your skills at identifying if the grass is wilting, then a simple test is to walk across the lawn and check to see if the grass is springing back as you pass, or if you are leaving footprints after you walk over it.
When you do water, you should wet the soil down to the full depth of the root zone, 6 to 18 inches. In the sandy soils of Long Island, that usually means applying about one to two inches of water, but it can vary depending on your soil type. See the link below for a web site can help you determine your soil type. If you don't know the precipitation rate of your sprinkler you can determine it by placing a coffee can within its range and measuring the depth of water until you reach an inch. Make a note of how long it took to reach 1 inch. In the future, simply multiply that time by the number of inches (or fraction of an inch) that you want to apply.
If you really want to be sure how deep you are getting water into your soil, you can stick a shovel or spade into the ground, push it forward, and look behind it to see how deep the moist soil is. (Then with you hand or foot, simply push the turf back into place.) Another method is to poke a long screwdriver into the ground. It should go through moist soil easily, but stop when you hit dry soil. Mark the shaft of the screwdriver where it goes into the soil, and then pull it out to see how deep the moisture has reached.
Be aware of weather conditions. If you water every week, rather than in response to wilting grass, reduce the amount you water by the amount of rainfall in the last week. If you want to get more detailed information about rainfall and evapotranspiration (a measure of how much water is returned to the atmosphere by evaporation and by plants), a weekly report is available from Cornell Cooperative Extension of Suffolk County (see the link below). If you have an automatic sprinkler system, it should have a rain gauge and adjust for the amount of precipitation. Rain gauges may be required on irrigation systems under legislation proposed in Albany.
Be careful not to cause runoff, don't put water down faster than your soil can absorb it. If you see puddles forming in low spots or water trickling down slopes, lower the flow on your sprinkler.
Don't water in the middle of the day, when evaporation loss is greatest. Most sources recommend watering in the early morning, between 4:00 am and 8:00 am. However morning is when your water company has the most demand for water and their system will be taxed. For years, the advice has been to avoid watering at night because it could cause a fungal disease on your turf. However we believe the risk of encouraging fungus by watering at night is often overstated, especially if you are only watering infrequently and mowing high. If you have a timed sprinkler system, you will have better water pressure overnight, between 10:00 pm and 6:00 am.
Do not water too early in the season, and do not water frequently and lightly. Watering in the spring is rarely needed; there is almost always enough rainfall. Light watering, especially early in the growing season, encourages shallow root growth. When the soil is always moist near the surface, the roots don't have to grow deep. These shallow roots will dry out quickly when the weather turns hot and dry. The only time you should not follow this general rule and water lightly daily is when you have put down new seed, which needs to be kept moist.
Do not over-water. Yes, it is possible to over-water, soil saturated with water will deprive the roots of oxygen, suffocating beneficial microorganisms. Overly wet conditions can also encourage disease and anaerobic microbes that produce alcohols and other toxins that will harm your turf Too much water will do more harm to your turf than too little.
Be aware of local restrictions. Nassau County prohibits watering between 10 am and 4 pm, and allows watering only every other day. Houses with odd street numbers may water only on odd numbered days, and even numbered houses only on even days. But remember, just because you are allowed to water every other day, doesn't mean you should.
- Healthy Lawns Clean Water
- Watering Techniques (Safe Lawns)
- Cornell Cooperative Extension of Suffolk County - Growing Degree Day, Precipitation and Evapotranspiration reports
- EPA: Lawn Watering
- My EcoLawn: Smart Irrigation
- Determining your Soil Type
Long Island Organic Landscapers
Although it's easy for the average homeowner to maintain their lawn organically, some may too busy and wish to hire a professional. In that case there are thousands of landscapers on Long Island to choose from, but only a small but growing number of experts who can maintain your lawn and landscape without the use of chemical pesticides. They can be found here.