Irrigation

Introduction to Irrigation

Properly watering a lawn is key to maintaining it in a healthy condition. Most lawn problems are related to irrigation. Failing to apply sufficient water will result in dry areas, which will turn brown and ultimately die if left too long. On the other hand, excess water can lead to disease.

The key to proper irrigation is learning to recognize the signs of a thirsty lawn. Turfgrass indicates its dryness by wilting, which is expressed through changing color from its typical green to a slightly blue-gray tint; closer inspection of the turf will show that it is limp and will not bounce back if stepped on. Testing for lack of water can be done by probing the soil with a knife or screwdriver in the wilted area and in a green area. More difficult penetration in the wilted area is confirmation of lack of water.

Usually, certain sections of the lawn will repeatedly show wilting before others. These areas likely receive the least water due to poor irrigation uniformity, top of slope or the most direct sunlight. Check for uniform sprinkler coverage by placing empty cans in the wilted area and green area. After running the sprinklers for about fifteen minutes check the amount of water in each can. If it is not the same, sprinkler adjustment or an additional sprinkler may be necessary. Sloped areas will require shorter more frequent irrigation cycles. Full sun areas should not be on the same irrigation valve as part sun areas.

Watering New Sod

To help understand the underlying concepts behind our quick guidelines for watering new lawns, consider the following analogy. Think of the roots of your newly installed lawn as straws through which the plant drinks water. The roots grow into the soil, which can be considered a glass of water for this analogy. Now imagine yourself drinking from a very tall glass with a straw that will only reach 1/2 inch deep. In order for you to get enough daily water, you will need to fill the glass with small amounts of water numerous times throughout the day. As time passes, your straw gets longer and you can access water from deeper in the glass. The longer your straw, the less often you need to fill the glass. Ultimately, your straw can reach the bottom and you are able to fill your glass with the full amount of water once every other day.

This is very close to what is going on with your new lawn. At first, the roots are very shallow and cannot access the deeper water. To keep the lawn hydrated you will need to water 3 times per day for short periods of time. In the second week, the roots have begun to penetrate deeper into the soil and you can water less often (2 times per day). In the third week the roots are even deeper and you can water once per day. Ultimately your lawn will be established and you should be able to water every other day if you increase the time appropriately.

New Sod Watering Schedule:

Water Sod lightly after each 200 square feet are installed, to prevent wilting. After all the sod is down and rolled, turn on your sprinklers and let them run until the sod is good and soaked. To keep it that way, water according to the following general guidelines:

Daily Watering Schedule

Week 1:	7:00 am	11:00 am	2:00 pm
Week 2:	7:00 am	2:00 pm
Week 3:	7:00 am

Watering Time

Look for signs of wilting due to lack of water. If you observe wilting, water immediately and increase the irrigation time on your clock.

Adjust according to weather – increase water during warm/dry or windy weather.

Watering New Lite Sod

Marathon Lite is grown in an organic mat, which has been designed for its moisture holding capacity. The Marathon Lite mat holds more water than soil and therefore needs less frequent irrigation during the early establishment period. Once the turf begins to root into the soil, irrigating Marathon Lite is the same as the field-grown Marathons.

As a general rule, you can water the Marathon Lite once per day for the first three weeks. If dry spots appear in the lawn during the afternoon, the irrigation time should be increased. If dry spots persist, an irrigation uniformity problem is likely, and an additional sprinkler head may be required. After the first three weeks, you should begin to taper back to once every two or three days, depending on how quickly the sod is rooting. Generally speaking, as the root system grows deeper, irrigation frequency should be reduced.

Watering Established Sod - Rules of Thumb

After a lawn has become established (approximately 6 to 8 weeks), water according to the following guidelines:

Water as infrequently as possible. In the cooler months, this would be once or twice a week; in the warmer months, it could be three or more times per week.

Water for as long as possible to deeply penetrate the soil (up to 30 minutes). Cycle irrigation may be necessary if runoff occurs within a short time; i.e., water until runoff occurs, then stop and wait for the water to penetrate the soil (usually 1 -2 hours). Repeat watering and waiting until water deeply penetrates the soil.

Water as early in the day as possible (first thing in the morning). Do not water lawn between 4 pm and 2 am.

Do not water shaded areas of lawn as frequently as areas that receive full sun.

Note of Caution: Be sure to watch out for a blue-gray tint and/or limp areas in the lawn. This is not a fungus; rather, it is caused by dehydration and indicates that immediate watering is needed. Such spots usually occur on tops of mounds, or in areas where sprinkler coverage is not adequate. (Watering in full sun is acceptable and will not burn the blades.

Watering Established Sod - The Specifics

To Determine the correct sprinkler run time, you must first determine the sprinkler’s precipitation rate and uniformity. Follow the directions below. Alternatively, go to the WaterSmart.Toro.com to learn about the latest technology that makes lawn irrigation easy and water efficient.

How to Measure Your Precipitation Rate

To measure your precipitation rate and uniformity, place a grid of equal sized containers around your lawn as shown in the photo. It is best if you use containers with vertical or near vertical sides. You should also take measurements at the same time of day your sprinklers normally operate. This will reduce errors from variation in water pressure throughout the day. Measurements should be taken on a calm, windless day.

To Determine Your Precipitation Rate and Uniformity:

Evenly place measuring containers on lawn, using a minimum spacing of 10 feet.
Turn on your sprinkler system for 15 minutes
Turn off your sprinkler system
Keep measuring containers in place
Measure and record the inches of water in each container
Note the containers with the lowest and greatest amount of water.

Uniformity:

If the difference between the lowest and greatest amount in the containers is more than twenty percent, it indicates an inconsistency in your irrigation pattern. Adjust wet areas to receive less water and dry area to receive more water until your lawn is provided with a consistent pattern of irrigation. If you’re unable to adjust your sprinkler system to provide a consistent pattern of irrigation, you may need to add or change sprinkler heads, or call a landscape professional.

Calculation of Precipitation Rate

Take the measurement from the container with the least amount of water and multiply by four. (i.e. 1/2 inch x 4 = 2 inches per hour). This is your hourly precipitation rate. Use this number to determine your watering requirements. Be sure that you are providing a uniform irrigation pattern to your lawn as described above.

Note: Precipitation rates are typically greater than 0.25 and less than 2.5. If your calculations are outside this range, we suggest that you check your calculations to ensure you have computed the correct rate.

Enter the hourly precipitation rate into Schedule Calculator:

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