It’s easy to consider water shortages an overseas problem yet New Zealand is not exempt. Those not convinced that water is a precious, increasingly scarce resource in this country need to recall that:

• The Auckland water shortage of 1994 saw severe restrictions imposed.
• During 2013, the West Coast had but a few days’ water supply left. Fortunately, it rained just in time.
• Many other New Zealand regions, for example North Canterbury, suffer some level of restrictions each year.
• Even if your facility does have an adequate water supply, better year-round playing surfaces and lower costs are very good reasons for using it efficiently.

To satisfy your plants’ requirements whilst keeping wastage to a minimum (i.e. not overwatering), try following these tips this summer:

1. Optimise Your Irrigation System

Conduct an annual check of your irrigation system, ensuring that it’s operating correctly and uniformly over the target area. Now is a good time to do this, rather than waiting until summer! Cost is often cited as a reason for not making any changes, however some minor adjustments can be made cheaply with one’s time being the only outlay. In many cases, this can make a big difference.

A simple checklist:

1. Inspect all solenoid control valves to ensure there are no leaks. Manually operate each valve to ensure it’s opening and closing correctly.
2. Inspect and adjust all sprinklers:
   – Are there any obvious leaks or breakages?
   – Are sprinklers perpendicular?
   – Are all sprinkler models and nozzle types on a given irrigation station the same? (This is important because each sprinkler brand/model will typically have a slightly different application rate.)
   – Are all the ‘sprinkler operating arcs’ on a given irrigation station or control valve the same? (A common mistake is to mix 180° and 90° sprinklers.)
3. Check that all filters (in the sprinklers and the irrigation system) are clean?
4. Conduct weekly checks during the dry season to ensure the irrigation system is still operating correctly.

Ensure sprinklers are perpendicular.

Check that sprinklers are installed at the correct depth and trimmed so that grass doesn’t interfere with their operation.

2. Hand-water Known Dry Areas

No irrigation system provides perfect coverage, so hand-water the known dry areas to avoid overwatering other parts that are adequately wetted up. On less resourced facilities, prevention is better than cure; it is vital that dry areas are identified early and wetted to the full depth of the root-zone. Lack of time or budgets are often given as reasons for not doing any watering by hand. However, where there’s a will there’s often a way, i.e. many part-time or sole turf managers are doing a great job with hand-watering.

Hand-watering provisions are cheap and valuable tools to avoid overwatering.

3.Condition Turf Plants for Summer

Good management practices during spring will result in a turf plant that can better tolerate summer stresses and use less water.

For all turf plants

Following winter, root systems will typically have shortened up to a depth within the profile where adequate aeration occurs. However for the best summer performance, the deeper the root system the better. Spring is the period when substantial root development or extension occurs and good management now will result in a much stronger root system. As we move out of the winter rainy period when minimal evaporation losses occur, the root-zone is either saturated or close to this. Consequently it is important to allow for some partial drying down of the profile to depth. This drying down will –

• Increase the aeration status within the root-zone.
• Encourage aerobic microbes (good guys) to do their beneficial jobs (e.g. organic matter recycling & nutrient release).
• Encourage deeper root development.
• Cause the turf plant to undergo physiological changes as it gradually gets used to tolerating drier conditions. Simply stated, the plant adapts, becoming less succulent so it requires less water over summer and is better able to tolerate summer stresses.

Saturated soil profiles and shallow root development make for a difficult summer.

Encourage a deep root system to reduce stresses faced during summer.

For warm season grasses

Couch and Kikuyu have considerably better drought tolerance than cool season grasses so don’t irrigate during spring until the cool season weeds (particularly Poa annua) have died. For most areas in New Zealand, irrigation is unlikely to be required before December at the earliest! This practice will also provide improved root-zone aeration status for the newly developing root system and enable the soil profile to warm up more quickly, hastening green-up and recovery from winter wear.

To Achieve Adequate Drying Down

During spring, allow the profile to dry down to quite low moisture levels (still without stressing the grass) e.g. approximately 20% Volumetric Moisture Content (VMC), before commencing deep watering programmes. This means that during October – early December (approx.) whilst the profile is drying at depth, concentrate on infrequent and shallow watering to maintain some moisture in the surface and thereby reduce potential issues with disease and dry patch. Additionally, hand-water ‘hot spots’ rather than adopting full scale irrigation. This means that the automatic system should only used when the entire area requires watering, rather than just a small area.

4. Ensure the Soil Profile Can Take Up Water with Minimal Runoff

Key steps to achieving this are:

1. Identify and uniformly re-wet dry or dry patch-affected areas to at least 100-150mm (approx.) prior to the end of October. Confirm the areas you need to target by:
   – Sampling known dry patch areas during winter.
   – Looking for areas where dew doesn’t form during late winter and spring.
   – Completing a droplet test on plugs taken from suspect areas (if in doubt as to whether dry patch is the cause). Where dry areas or dry patch are an issue, completely re-wet the area by using a combination of closely spaced and shallow spiking, hand-watering and localised applications of a penetrant wetting agent. Follow up over successive days with hand-watering to ‘push’ the penetrant deeper into the profile and assist with complete rewetting.
2. Promote uniform infiltration of applied water into the root-zone. The exact approach will be site-specific and depend on thatch content, the presence of layering, etc. The main considerations are to: – Generally limit the spring aeration treatments to the depth where most of the roots (effective rooting depth) are found. Excessively deep renovation treatments (especially in dry climates) can result in water bypassing the root-zone. – Adopt an ‘as intensive as is practical’ renovation pattern to encourage more uniform wetting up of the root-zone.
3. Manage excessive thatch and layering so they don’t limit both root development and water movement within the profile (i.e. restricting infiltration from irrigation or capillary movement from deeper in the profile up into the root-zone).

Closely spaced coring promotes more uniform infiltration.

Poa annua invasion following winter in a Couch field. Don’t irrigate until the Poa annua dies!

5. Understand Your Irrigation System

Run time

Do you know the average time taken for a typical 360° sprinkler to complete a rotation? This is important to find out so you can set realistic light watering programmes. A common industry standard of 10-15 minutes of irrigation is, in many cases, not a light watering! Table 1: Guideline reduction in application rate, relative to the slope of a turf surface (Adapted G. Connellan).

Ponding

Do you see water ponding during the irrigation cycle? On your worst green or turf area (i.e. with the steepest slope or poorest drainage), do you know how long you can to run the irrigation system before ponding or run-off occurs? This information is vital as it determines the maximum run time for your sprinklers (see Table 1).

Dry patch is present in the areas where dew is not forming.

Layered profile (left) limiting water movement. Well-managed profile (right) providing more uniform moisture and water movement.

6. Understand Your Turf Facility

Any turf facility is more likely than not to be made up of several micro-environments i.e. areas with different levels of exposure (wind, shade), soil types (sandy vs. heavy clays) and drainage potential (poor vs. well-drained). Turf managers need to adjust the watering programme to meet the needs of each one. For example, a shady or poorly drained area will generally require only 50% (approx.) of the water that an exposed micro-environment will require.

7. Sample, Sample, Sample!

Guessing the amount of irrigation required is a poor substitute for regular sampling that enables you to genuinely –

• Work out existing soil moisture content.
• Work out existing soil moisture content.
• Quantify how much water is required.
• Monitor the effectiveness of your irrigation programme.
• Fine-tune your watering practices.
• Better predict problems (such as dry patch) before they become noticeable, severe and difficult to restore.

Consider the photo below. At what VMC would you start irrigating?

Visual assessment of moisture levels in a silt loam soil and the impact on irrigation requirements. (Note: VMC values are based on FieldScout moisture meter and NZSTI calibration work).

We recommend you develop some guidelines for your specific turf area. Sampling can be completed by:

1. Taking plugs to the depth of your effective root-zone and estimating the moisture content by feeling how wet the soil is and/or noting how dark it is. Also, it is important to take a visual note of the grass condition at each sampling as matching the two will determine watering requirements.1. Taking plugs to the depth of your effective root-zone and estimating the moisture content by feeling how wet the soil is and/or noting how dark it is. Also, it is important to take a visual note of the grass condition at each sampling as matching the two will determine watering requirements.
2. Using a good quality soil moisture meter for accuracy but be aware that each meter uses a different mechanism or scale, and so needs to be calibrated, i.e. when does a different grass show signs of moisture stress, what moisture levels are adequate and what moisture levels are too high? Once it’s been calibrated to suit your facility, a meter will enable you to apply less water with more confidence and thereby minimise the risk of over-watering.

Note

All the VMCs in this article are based on NZSTI’s calibration work using the FieldScout moisture meter.

Confidence is gained by active sampling. Here’s a Ryegrass sportsfield at 14% VMC yet still growing happily. In absence of monitoring, it would have been watered well before now!

8. Change the Irrigation Programme as Required

It’s common to see a single irrigation programme being applied throughout the season. The only adjustment might be to add repeat cycles during the drier parts of the summer. Yet if you truly want to optimise water use, then it’s important to adjust your irrigation controller settings based on visual or moisture meter sampling of the soil profile.

When you start to actively manage the application of water, make sure –

• Changes are made gradually.
• There’s monitoring done after adjusting (reducing) the water application to make sure you haven’t gone too far to the ‘dry side’.
• Make changes early enough in the week (at least initially) to allow correction if necessary, i.e. starting a dry down programme on Friday is unnecessarily risky!

Heavily shaded areas (above) require significantly less water than exposed areas (below).

Advice Grounded in Experience

The above recommendations have evolved from years of trial and error. Once a turf manager has fully implemented them, this is the sort of feedback NZSTI receives:

“When we started using a moisture meter daily (during the summer), we used the results to fine-tune our irrigation programme. Once it was correctly adjusted to suit the conditions, we were delighted to see more consistent playing surfaces, no reduction in plant health and a major saving in water use. It was a win-win all round.”

References

Pearce, D. Checked your sprinklers yet? Spring 2013 NZ Turf Management Journal

NZSTI. Irrigation management. Summer 2013 Turf Notes.

Huang, B. Water: Less is best. Autumn 2012 NZ Turf Management Journal.

NZSTI. Dry patch management. Spring 2012 Turf Notes.5. Connellan, G.  2013. Water Use Efficiency for Irrigated Turf and Landscape.

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