By John Fech, Jim Schild and Sarah Browning, UNL Extension Educators
One of the most important differences in the care of turf and all other landscape plants is the placement and operation of an irrigation system. Regardless of whether in-ground or hose and sprinkler equipment is utilized, many options are available in todays' marketplace. The key to success is choosing one which is easily adjusted during various times of the year and that can deliver water with good uniformity to all turf surfaces.
Like any mechanical system with moving parts, irrigation systems need to be properly maintained and regularly checked to determine if they are operating correctly. The first step is to simply turn the system on manually and watch it run. Undoubtedly, several flaws will be noted, such as water spraying into the street, broken or misaligned heads, heads that don't turn to cover the desired area, and leaking valves.
While there are several ways to approach irrigation efficiency, the most common is to fix the biggest problems first. In the audit, many problems are likely to be identified. If money and time are tight, choose those that have the greatest potential to save water to implement first. Other "fixes" can come later. Though changes and improvements can be expensive initially, consider the payback over time in terms of the cost of water saved, and the reduced pressure on municipal and rural water systems.
Once broken components are identified, make appropriate repairs. Next, conduct another irrigation audit to determine how efficiently the system is now delivering water to the turf. The goal is to apply the same amount of water to each part of the lawn.
Because it can be difficult to determine the exact amount of water being applied by simply viewing the operation of the irrigation system,
- Run the system for a short period of time, and place a colored flag near each spray head.
- Set out a dozen or so flat bottom cans - tuna, cat food or coffee cans work well - place a few cans near sprinkler heads, a few between heads and a few in areas of known water stress, and a few in "good areas".
- Run the system for 20 to 30 minutes to partially fill the cans with water.
- Use a ruler to measure the amount collected in each can.
- Compare the amounts in each can.
- If more than a 25% difference exists, reconsider the system components. With hose and sprinkler systems, the most common flaw is placement of the sprinkler device. Experiment with different placements until the percent of application difference is reduced. With in-ground systems, head to head coverage (the amount of water spraying from one head to another) is often inadequate. In these situations, some sections of the lawn are watered less than others. Consider replacement of sprinkler heads, using heads designed to give better coverage of the areas that are not receiving enough water.
- Once the distribution uniformity is improved, consider a 10% reduction in the runtime of each zone or the hose system. This is a good way to save a considerable volume of applied irrigation water.
Water Application Tips
In addition to applying water uniformly, several other factors influence the overall efficiency of the irrigation process.
- It's important to keep the roots moist, not dry or soggy.
- Water to the bottom of the root system; keeping soil moist an inch deeper than the grasses' root system will facilitate root expansion and promote deeper rooting.
- Roots are deeper in spring and fall for cool season turfgrass species and shallower in summer. The opposite is true for warm season species.
- Check water infiltration into the soil with a screwdriver or by digging a hole.
- Water soaks into a clay soil much slower than a sandy one, so water infiltration should be checked often.
- Cool season turfs tend to use more water in the summer than spring or fall.
- If water runs off the lawn due to slope, reduce the zone's run time to the point where no water runs off. Allow the water to soak in, and then re-run the zone to moisten the soil deeply enough to reach the bottom of the root system.
- The best time to water is early morning as less water is lost due to evaporation.