During spring, it’s vital to acclimatise turf to achieve ideal growing conditions and to minimise future problems.

The arrival of spring reminds us that we need to make preparations for summer. Once we’ve ensured that the irrigation system is operating correctly, the most critical issue is conditioning the turf.

Aerating the Root-zone

New Zealand’s temperate climate generally results in wet winters with minimal drying. By spring, the root-zones on most (if not all) turf facilities will be at field capacity or wetter (e.g. >40-50% Volumetric Moisture Content). The implications of this are that:

• Soil aeration has declined and is worst deeper in the profile.
• Roots have shortened to a depth where adequate aeration occurs.
• Wet or waterlogged root-zones will be cooler and will take longer to warm up. This has major ramifications on how quickly spring growth occurs (i.e. recovery of heavily worn areas) and delays the green-up of warm season grasses.

Having checked that the irrigation system is working correctly, Turf Managers have 2 choices when considering irrigation during late spring:

Path One: No conditioning

Once the first few days of windy and/or dry conditions occur and the dews have stopped (typically mid–late October), it’s common to start turf irrigation. In the absence of rain, watering will generally occur daily thereafter, until autumn. This approach of maintaining high soil-moisture levels throughout the year is less than desirable and contributes to many problems:

1. Aeration is poorer than desired and generally gets worse as soil temperatures increase over summer. This encourages disease such as Anthracnose and thatch accumulation. Air in the root-zone is necessary for the roots to function properly.
2. Shallower roots mean more frequent watering is required to support the plant over summer. This increases the likelihood of over-watering and knife-edge management. (Most root development of cool season grasses occurs in soil temperatures of 10-18°C during spring. As temperatures increase over summer, the turf plant is less able to develop a deep root system).
3. Plants are more succulent and less able to tolerate summer stresses (For more information, refer to NZTMJ Autumn 2012 ‘Water: Less is best.’ by Dr Bingru Huang).
4. The soil profile remains too wet all year and goes into winter at field capacity (or wetter) resulting in poorer winter drainage.
5. Poorer playing conditions.
6. Higher maintenance costs associated with purchasing and pumping water.

The irrigation system needs to function correctly and the growing environment must be conditioned, ready for summer.

Deep root development is encouraged by good aeration.

Path Two: Conditioning the turf

This preferred option requires a ‘managed moisture stress’ programme to be applied to the turf during spring, thereby allowing the root-zone to partially dry at depth.

This ‘drying down’ of the profile earlier in the season also coincides with the greatest period of root activity and thereby encourages a deeper root system with the associated benefits going into and during summer.

Wet soil (41% VMC)

Sand top-dressed (43% VMC) profiles coming out of winter.

Research (Ref.3) has shown that ‘managed moisture stress’ causes the turf plant to undergo physiological changes. Simply stated, it becomes less succulent thereby requiring less water over summer and is better able to tolerate summer stresses.

The programme doesn’t mean stopping all irrigation. Instead, ‘deficit irrigation’ will likely be required during late spring. Based on regular visual assessment and moisture meter sampling, the key goals are:

1. To apply short irrigation cycles (approx. 1–2mm of applied water) as required to maintain some surface moisture (thus reducing the risk of disease and surface crusting).
2. Delay deeper watering until some drying occurs at depth (as illustrated below).

Minimising Dry Patch

When preparing irrigated turf surfaces for summer, dry patch can be a challenge – more so the later it gets identified and treated. For many Turf Managers, the problem is a surface issue and easy to manage, whilst dry zones deep in the profile can be more of a problem for others.

Many dry patch issues result from the operation and/or effectiveness of the irrigation system. Prior to summer, check and fine-tune it. Where dry patch is an on-going problem, test the uniformity of the irrigation system using a catch-can test.

A lack of resources for hand watering is often cited as the reason for applying extra water or commencing irrigation early. This reduces the risk of dry patch occurring, however for the reasons previously stated it is less than ideal. Greater emphasis on both preventative management and fine-tuning the irrigation system (Ref.4) is recommended to help reduce the incidence and severity of dry patch.

The key is to ensure the profile is uniformly re-wetted to depth by October/early November at the latest!

Lack of dew in areas during winter–spring indicates dry patch.

Identification

Getting on top of dry patch early is crucial to long-term success:

• Map any problem areas from previous summers as this enables a preventative approach to be adopted. Dry patch typically reoccurs in the same places every year.
• During winter/spring (on a sunny day and dewy morning), walk over the greens and look for areas where the dew doesn’t form. Not only are these areas already dry, but they will also be your problem areas in the coming summer.
• Sample and treat known problem areas in spring (even winter) whilst regular rainfall is occurring. Dry patch problems are easier to resolve at this time of the year.

To check whether an area is water repellent (dry patch) or is just dry, take a sample. Place a series of water droplets along it and if the water doesn’t soak in within 10-15 seconds, water repellence is a problem. The longer it takes, the more severe the dry patch problem.

Management

The goal is to provide uniform infiltration across the irrigated surface. The approach will be site-specific and include an appropriate renovation and top-dressing programme to manage thatch, layering, surface sealing and the like, while also pulsing of water cycles (especially on undulating greens).

Ideally treat dry patch with penetrant-type wetting agents and water in well. Shallow spiking prior to treatment is recommended, but take care not to spike/core too deep (through the ‘dry zone’), otherwise the turf will not respond due to the uneven wetting of the root-zone.

Take a plug from the area again 2 days later to see how deep the re-wetting is in the profile. Hand water again, as needed, until the profile is re-wetted to the required depth.

Take Action Early

Spring is an important period. It is the time to acclimatise turf so it’s better able to tolerate and survive summer stresses, and manage compromising root-zone issues, such as dry patch, which limits the effectiveness of irrigation.

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.

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