Grass plants are made up mostly of water and to little or too much can be cause for concern. Water is the primary mechanism for transport of nutrients, organic compounds, and gases into turf roots and throughout the plant. While most people think a lack of water will damage their lawn, overwatering may in fact cause more damage to existing turf. To maintain a healthy, dense, and actively growing lawn, it is essential to irrigate the lawn during dry periods. It is easy to overwater a lawn.
The consequences of overwatering a lawn include: increased weed pressure (especially crabgrass), increased disease pressure, shallow rooted turf (think weak), wasted natural resources, and for most, higher water bills. When you irrigate your lawn, it is best to err on the dry side rather than be guilty of overwatering. You can always add more water if the lawn is still dry, but you cannot take excess out of a lawn.
Frequency will vary based on the appearance of your lawn. The first signs of drought stress are a blueish-green color (caused by leaf blades beginning to curl up to conserve energy) and footprints that remain in the turf after walking across it.
Ideally this is the point at which you should irrigate your lawn. There is no benefit whatsoever to irrigating a lawn before this point.
As drought stress increases, your lawn will wilt and have a greyish-green color. At this point, you should irrigate the affected area immediately. Turf in this stage of drought stress can recovery quickly with prompt attention on your part.
Severe drought stress causes the plant to cease all metabolic processes and stop growing. The shoots (leaf blades will turn brown and could die.
Irrigating at this point helps the plant to survive, however it can take up to two weeks to see noticeable improvement and possibly longer to make a full recovery. Patience is your friend at this stage of the game.
Another common irrigation misconception is that lawns should be irrigated on a set schedule. This is not the case, as a set schedule does not take into consideration the needs of the plant, evapotranspiration rates, or other environmental conditions, however it does increase the likelihood of over watering. Also, for those with automatic irrigation systems, you should not run the same programs for the entire season. Irrigation rates and timing should accommodate the needs of the plant at any given time.
Turfgrass species vary widely in their water requirements, with most cool-season grasses using approximately 20% more on average than warm-season grasses. Most turfgrass species will require between 1-1.5” of water per week to maintain a healthy status. Factors that influence water use rates of grasses (and all plants for that matter) are: weather, soil type, slope, etc. It is best to apply this amount of water in a single cycle or two equal applications spaced three to four days apart, rather than through light irrigations daily (if you have newly seeded or sodded turf, then you will need more frequent irrigation at first). During an irrigation event, soil should be wetted to the depth of the deepest root. Shallow, frequent irrigation encourages the plant to produce shallow root systems. A shallow root system weakens the plant when drought sets in or temperatures increase and encourages the proliferation of weeds, notably crabgrass.
Hose-end sprinklers usually apply a small volume of water to a given area and must be left to run for extended periods (2-3 hours) to provide adequate moisture. See the example below:
Automatic systems can deliver larger volumes (depending on system and nozzle configurations) in less time.
If you have an automated system, then you should do an irrigation audit yearly to gauge the efficacy of the system and make any needed repairs. This will keep the system operating at peak efficiency and lower your overall water usage (your lawn and water bill will thank you).
The best time of day to irrigate turf is between 4-8am. There is little wind disruption currently of day, you do not lose water to evaporation, and temperatures are generally at their coolest. Yes, 4-8 am is early and could pose some logistical challenges for most people. The next best time to irrigate your lawn is between 8pm-12am. However, irrigating at this time of day can increase the possibility of soil borne disease that affect turf if humidity levels are high (we live in the South, when aren’t they high in the summer). Irrigation that is preformed during the middle of the daylight hours is ineffective and should only be undertaken as a last resort.
Proper irrigation practices are just as vital to a healthy lawn as fertilizer, weed prevention, or mowing and should not be intimidating. When in doubt about your irrigation practices, remember, you can always add more water, but you can’t take any out.