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Irrigation - Water Quality

Tuesday 22, Dec 2020

In the final article of this series on water management and irrigation, John Neylan looks at the issue of water quality and availability and assessing the suitability of alternative water sources.

There is little question that the lack of a constant, good quality water supply is the greatest threat to the long-term sustainability of turf areas. Having been involved with turf management and water quality for over 35 years, I have noted that the turf industry has had to increasingly find ways of using water of deteriorating quality.

The Australian Golf Industry Council water survey conducted in 2007 determined that reclaimed effluent is a major source of irrigation water and there were increasing issues identified with water quality including;

  • Increasing salinity;
  • High sodium resulting in increased soil
  • sodium;
  • Moderate to high bicarbonates that require
  • water modification through the use of
  • acidification;
  • Increasing cost;
  • Modifications to irrigation systems;
  • Increased need for renovations; and
  • Potential health issues.

It is not only the quality of reclaimed water but also the deteriorating quality of bore water supplies that is creating additional challenges in turfgrass management. Whether the water supply is reclaimed water, bore water or even storm water runoff, the main water quality parameters that are creating the greatest turf management challenges are total soluble salts (salinity), chloride (Cl), sodium (Na) and bicarbonate (HCO₃)

From my recent experience, the increasing chloride levels appear to be the single biggest change in water quality. As water quality deteriorates there are several factors to consider including the changes in soil chemistry, the direct impact on turfgrass health and the potential environmental impacts. Table 1 summarises the impacts of water quality and the potential treatment options.

As water quality deteriorates the intensity of turf management has to increase to counteract the adverse effects. At the top of the list is undertaking a water testing regime so as to understand the chemical constituents and then developing a water management plan to minimise the impacts of these constituents. The management techniques that can be implemented to create a sustainable system include;

Introducing more salt-tolerant grasses:
There are significant differences in the salinity tolerance of turfgrass species, with some differences between cultivars. The change to a more salinity-tolerant grass may come at the expense of reduced turf quality and presentation. This is particularly the case among the cool-season grasses.

In reviewing the available research, there has been some screening of bentgrass for improved salinity tolerance where Koch and Bonos (2011) identified several creeping bentgrasses as having improved salinity tolerance. In recent correspondence with these researchers there has been little salt tolerance work undertaken since.

In research undertaken by Neylan et. al. (2009), they demonstrated that 27 local selections of bentgrass had better turfgrass quality than the commercially available bentgrass cultivars at the salinity regimes of 4dS/m and 8dS/m. In this research ‘Mariner’ creeping bentgrass had the best salinity tolerance and reflects the breeding of this grass which was bred as a salt-tolerant cultivar.

Warm-season grasses are inherently more salt-tolerant compared to the cool-season grasses and may be the only sustainable option in some situations (e.g. change from creeping bentgrass to a hybrid bermudagrass). Constructing high permeability profiles: Well-drained profiles provide the best opportunity to leach accumulated salts and sodium from the rootzone and to maintain it at a sustainable level. Fine-textured, poorly- drained soils are extremely difficult to manage where there is high salinity and sodium. Subsoil drainage: Having a subsoil drainage system is critical in enabling the removal of salts and sodium as they are leached through the rootzone.

Irrigation leaching fraction: Applying a leaching fraction or water in excess of plant needs is a good management tool for managing high salinity water. It is a well-adopted technique in agriculture but there is often a reluctance to do this in turf management because surfaces may remain wetter and softer. Even using high salinity water will dilute the salts that will accumulate in the upper rootzone.

Application of gypsum and other amendments: In two recent trials that assessed the effects of gypsum, surfactants and other amendments on the impacts of salinity, there were minimal improvements identified. Young (2020) determined that no cultivation practice or product combination was effective at moving salts without applying leaching fractions of irrigation.

Schiavon and Baird (2019) tested 30 commercial and experimental products for their ability to alleviate salinity stress on bermudagrass. These treatments included calcium-based products as well as wetting agents and supplemental nitrogen fertilisation and/or biostimulants. The most effective product consisted of a combination of carboxylic acids and foliar fertilisers. It was thought that the benefits were due to the positive effects on soil characteristics and the supplemental nutrition that the programme provided to the turf.

Soil cultivation to improve permeability: As noted above, soil cultivation is not particularly effective without a leaching fraction or high rainfall event to flush the salts

Water treatment: Desalination or acidification may be the only option for improving quality.

As the irrigation season approaches, there are several important tasks to undertake as it relates to water quality:

  • Testing of all water sources for at least salinity, sodium, chloride and bicarbonates.
  • Take soil samples from representative turf areas to determine salinity and sodium concentrations. Adjust as required (e.g.: apply gypsum to counteract sodium accumulation).
  • Maintain adequate soil permeability through subsoil aeration and thatch control.
  • Irrigate at night to avoid salt burn.
  • Ensure that irrigations are deep and beyond the rootzone to leach salts out of the rootzone and to prevent accumulation.
  • Irrigate with freshwater whenever possible to aid leaching.

As water quality deteriorates and becomes unusable or the volume of water available decreases, there is a need to source alternative water sources or to undertake treatments that improve the water quality. During the Irrigation Workshop at the 2019 Brisbane conference, several case studies were provided that highlighted the planning required so as to understand the viability of the project, the costs associated with it and the implementation strategy. Two of these – Sorrento Golf Club, Vic (superintendent Shane Greenhill) and Cape Wickham, Tas (superintendent John Geary) – we will now look at in more detail.

CLICK HERE to read the full article which originally appeared in Volume 22.5 of the Australian Turfgrass Management Journal.