Tips for a Proper Irrigation Regimen

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With the arrival of summer, we have moved out of our rather wet spring and into the typical cycle of long hot days in New Jersey. This is the time of year when attention needs to be paid to turf grass as it has already begun to show signs of inadequate watering. By employing proper techniques to irrigate your lawn while being conservation-minded, you can easily implement an appropriate and cost-effective irrigation plan and keep your turf looking great!

How Much, How Often, and What Time of Day?
These are the most common questions that face property owners and managers and the simple answer is, “it depends.” This is because the needs of your property will always vary from other properties. There are a few key components to assessing the best practices for irrigating your turf and they are comprised of the following:

1. What is the depth of my root zone?
2. What type of soil is present? (sandy vs. clay-based)
3. What variety of grass is present? (Kentucky Bluegrass vs. Tall-type Fescue)
4. How much sun does my turf get (full sun vs. partly to mostly shady)
5. What are the wind conditions of my property? (sheltered vs. exposed to wind)
6. What are the weather conditions?
7. What is the “flow-rate” or watering output rate of the irrigation that is present?
8. What time of day should watering occur?
9. How often should I water?
10. How should my grass be cut to compliment a proper irrigation program?

The Root Zone Depth is Critical to Know
To determine how much we will need to water, we have to determine how deep the root zone is for your turf. The reason for this is that you will need to supply enough water to seep to the bottom of this root zone as this is where your grass plants take-in water. Knowing whether your root zone is being adequately watered is the key to a proper irrigation program.

In this cross-section cut of turf,  the depth of the root zone becomes visible.  This area must receive adequate moisture for the grass plant to thrive.

In this cross-section cut of turf, the depth of the root zone becomes visible. This area must receive adequate moisture for the grass plant to thrive.

To determine the root-zone depth, the easiest method is to take a flat-headed shovel and dig down to pull open a space where you can see the base of the roots. The distance from the base of the roots to the crown of the plant (the part that breaks through the top of the soil) is considered your root zone depth. Proper irrigation requires your soil to contain moisture down to the base of the root zone.

What type of Soil is Present?
The type of soil that you have on your property determines the amount of water that is necessary on a recurring basis to support hydration of the root zone of growth. On average, clay based soils (appear orange-brown in color) need a larger amount of water to reach the root zone. Typically, this can be 1-1½ inches of water per iteration. Sandy soils (typically dark-gray in color) however, aren’t able to hold as much water as clay-based soils and therefore need less water to reach the root zone, generally about ½ inch of water is adequate.

To truly determine how much of your irrigation is reaching the root zone, it is best to check the amount of percolation subsequent to a watering cycle. If you find that the soil beyond the root zone has been saturated, you may reduce the amount of irrigation being applied, conversely a dry root zone means that irrigation should be increased.

The second important aspect of soil type to be aware of is the fact that clay-based soils will typically need less frequent watering than sandy soils as they tend to be better at retaining water. Again, checking the moisture level of the root zone will let you determine if your irrigation program is adequate.

What Variety of Turf Comprises Your Lawn?
The two most common varieties of turf in the coastal region of New Jersey are tall-type Fescue and Kentucky Blue. Oftentimes, however, seed applied to property is a blend of various sub-varieties of both of these two grasses. The reason for this is that the two types of grass are of a very similar color and their differences in growth habit tend to complement each other.
Generally speaking, Bluegrass requires more watering than Fescue because the root system of Fescue establishes itself to a greater depth. Again, a working knowledge of the amount of water necessary to irrigate your root zone is critical.

How Much Sun and Wind Does The Turf Receive?
Turf exposed to full sunlight throughout the day will suffer a greater level of evaporation than turf located in an area that is partly to mostly shady. Additionally, turf exposed to continual wind will experience a greater loss of moisture to evaporation than turf in sheltered areas. Whenever possible, different irrigation zones should be established for each area of a property that vary with regard to their exposure to wind and sun.

Again, if we go back to checking the root zone of various areas of the property for saturation amount, the conditions present will be the best guide to determine if your turf is receiving adequate watering.

Weather Conditions are the Driving Force behind the Need for Irrigation
Most towns in New Jersey require the presence of a working rain sensor on your irrigation system. This is because it is wasteful to water your lawn during times when it is not necessary and over-watering your lawn can create unnecessary runoff which poses a threat hazard to streams and bodies of water in the state. Although many irrigation system controllers have a setting to bypass the rain sensor, there should never be a reason to utilize this setting unless system maintenance or testing is being performed.

During times of frequent rainfall, there should be no need to irrigate your property. However, during times of relative drought, periodic deep-watering may be necessary to maintain turf health and optimal growth rates.

What is the ‘Flow Rate’ of my Irrigation System?
To determine how much water your irrigation system puts onto your lawn during an irrigation cycle, you should place a rain gauge or drinking glass inside of the irrigation zone and allow it to accumulate water from the sprinklers for one cycle of your irrigation system. Once the cycle is complete, measure the amount of water inside of the container. On average, 1 to 1 ½ inches of water are necessary to moisten soil to a depth of six inches. Again, this will change given the variables of soil type from clay to sandy.

What Time of Day Should Watering Occur?
The simple answer is the average time of day when evaporation is least likely to be a factor. For most areas, this would be during the hours of darkness when winds are most calm. It is recommended that watering occur, on average, between the hours of 10:00 pm and 5:00 am. Watering in the middle of the day is a needless waste as the vast majority of the water sprayed from your irrigation system will evaporate before it ever penetrates to the soil.

The typical months in New Jersey that require irrigation supplementation for your lawn’s hydration are the summer months of June, July and August.

How Often Should I Water?
Again, there are variables at play here that drive an appropriate answer to this question. The average answer would be that your turf should be watered properly at least twice during a seven day week. You may, however, need to water more often if your soil is sandy or if there is a hot and dry weather pattern present.

How Should My Grass be cut to Compliment a Proper Irrigation Program?
Most perennial turf grasses, to include Fescue and Kentucky Blue, should be cut between 2 ½ and 3 ½ inches in height. This practice allows grass to thrive and remain dominant over weeds. Cutting grass too short can and reduce its resistance to drought, cutting too high can cause the grass above the soil level to maintain too much moisture and become prone to fungal diseases.

Here, a fungal disease is present in the grass, made obvious by rounded lesions on the grass blades.

Here, a fungal disease is present in the grass, made obvious by rounded lesions on the grass blades.

It is important to keep in mind that certain areas of your turf will always be more difficult to adequately hydrate than others. A very common problem is dehydration of “curb strips” or long thin lines of turf present between a curb line and a sidewalk. Because both the sidewalk and the street that these areas border retain and generate heat, the soil tends to dry very quickly and require a much higher level of attention than a large turf area. Additionally, areas of turf along rock beds or large solid structures that retain heat often suffer from the same problems.

Small strips of turf between two radiant heat sources such as a sidewalk and curb as pictured here, present a challenge to irrigation due to excessive evaporation.

Small strips of turf between two radiant heat sources such as a sidewalk and curb as pictured here, present a challenge to irrigation due to excessive evaporation.

Bringing It All Together To Make Proper Irrigation Decisions
In consideration of all of the above information, one can easily infer that there is no simple answer to the question of how to properly water turf. The best practice is to adapt your irrigation schedule to the needs of your turf. Too much irrigation can be bad for your lawn as it promotes weed growth and increases susceptibility of your turf to fungal diseases. Too little irrigation will force your turf into dormancy.

One pro-tip that I am happy share with you is that turf in need of hydration changes color. Tall Fescue will change to almost a mint-green hue and Bluegrass turns light and dull in appearance. This can most easily be seen if the observer is wearing polarized sunglasses.

If you notice your lawn’s appearance changing as described above, that is your cue to take action and immediately irrigate your turf to the extent that the root zone’s hydration is replenished. Routine attention paid to your lawn’s irrigation needs will be of benefit to your lawn’s health, the environment, and ultimately your wallet.

If you would like more information on considerations for proper turf irrigation, a great resource is the Best Management Practices for Watering Lawns by James A. Murphy, Ph.D published by the Rutgers Cooperative Research & Extension. The PDF of this document can be found at http://njaes.rutgers.edu/pubs/publication.asp?pid=fs555.

Industry News: New Offerings for Conservation of Water
New products from irrigation vendors seek to target the effectiveness of the method of water delivery. A great example is Hunter® who has released a new spray head that it calls the MP Rotator. Rather than spraying a mist which oftentimes blows away from the intended target of irrigation, the MP Rotator projects multiple rotating streams of droplets which more closely resemble rain and promote soaking of the water into the soil. Hunter® claims a 30% reduction in water consumption, “…when compared to traditional sprays and significantly reduces wasteful runoff.” [http://www.hunterindustries.com/irrigation-product/nozzles/mp-rotator] While a great solution for a new irrigation system, the MP Rotator line can be fitted for use to most existing systems by simply changing out the spray heads which is minimally-invasive.

The MP Rotator by Hunter Industries is purported to reduce watering needs by as much as 30%

The MP Rotator by Hunter Industries is purported to reduce watering needs by as much as 30%

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