Heat is on for moisture stress – Unlock & Play trial update
The Syngenta Unlock and Play trial at STRI is examining integrated turf management techniques and their impact on summer stresses such as simulated golf wear, drought, heat, and light stress.
A dry period has pointed the latest discussion towards drought stress and moisture management, reports STRI Research Operations Manager, Dr Christian Spring.
Whilst the trial is not suffering from drought conditions currently, the surface is beginning to dry out. With a largely dry week forecast for next week, moisture levels should begin to fall.
Moisture conditions in the trial so far have relatively benign. No irrigation has been applied to the trial area since, at present, it has not been required. However, that can change quickly in the UK climate.
This brings us on to an important point. Many turf managers tend to over water surfaces.
Depending on soil type, moisture is retained in the rootzone for some time before the plant starts to suffer from symptoms of drought.
Moisture content fluctuates more in soils with higher sand content. Newly constructed greens tend to be built with a sandy soil and moisture content needs to be managed closely. Older greens constructed on indigenous soils typically have a higher clay content and retain more moisture.
The best way to approach irrigation strategies is to take measurements of moisture content. A good rule of thumb is to try to maintain volumetric moisture content above 15 % in dry periods.
There are many devices on the market that measure moisture content. In this trial we are using a theta probe from Delta T, which measures volumetric moisture content as a percentage at a depth of 60 mm. This the depth of rootzone that the main mass of plant roots inhabits.
Management of soil moisture is made easier with the use of surfactant technologies.
Commonly known as wetting agents, these products help to balance moisture content in soils by breaking down hydrophobic films on soil particles, providing the means for soil to absorb moisture and allowing moisture to pass through the profile in wet conditions.
The Unlock and Play trial is using Qualibra, a wetting agent from Syngenta, to optimise moisture content in the rootzone. Qualibra has demonstrated good efficacy in a large body of trial work conducted at STRI and across the globe.
In dry conditions, Qualibra has improved visual turf quality, density and colour and maintained good surface characteristics for play (surface hardness ball roll), compared to untreated turf.
Qualibra trials at STRI
Previous trials at STRI have looked at the performance of Qualibra, along with other wetting agents, in drought conditions (<20% VMC) and at conventional greens moisture levels, held at 25 to 30% VMC.
The results of repeated research, on both sandy loam and sand rootzones, with bentgrass/AMG and fescue/AMG swards, has shown that under moisture stress conditions Qualibra has maintained optimal surface firmness and imporved surface consistency (below). Standard penetrants and wetting agents resulted in extrenmely hard surfaces in low moisture situations, even more so than untreated.
However, where surfaces were held above 25% Volumetric Moisture Content (VMC) with standard or high irrigation rates, the use of Qualibra, or any other wetting agent, did not lead to any softer green surfaces than the untreated.
What's in the Unlock and Play trial?
The Unlock and Play trial, at STRI in Yorkshire in association with ICL, is running throughout the summer, when play on golf courses is at its peak.
A summer stress management programme is being applied to trial plots in combination with standard management and compared to standard management alone.
- Standard management: Qualibra applied monthly @ 20 l/ha and ICL Greenmaster Liquid 25.0.0 applied at low rates 19 l/ha every fortnight.
- Summer stress management programme: Syngenta bio-stimulant @10 l/ha, ICL Sportsmaster WSF Seamax @ 1 kg/ha and Ryder @ 0.5 l/ha. Applied every fortnight.
In addition to this, the Primo Maxx II programme used in the lockdown trial continues:
- No Primo
- Primo applied @ 0.4 l/ha every 7 days
- Primo applied @ 0.4 l/ha every 50 Growth degree days
- Primo applied @ 0.4 l/ha every 100 Growth degree days
The products in the summer stress management programme have been chosen for the ability to improve turf health and wear tolerance, without applying an excess of nutrient to turf.
No irrigation will be applied to the trial area, but it will be left uncovered to the elements. Simulated golf wear will be applied weekly to simulate a busy golf course.
Visual assessments of turf quality, colour, live grass cover and evenness are being made weekly along with measurements of sward height, NDVI and light intensity.
Results from the trial so far have been positive. Primo Maxx II continues to regulate growth and evenness of turf effectively. The summer stress programme has increased turf colour and turf quality compared to standard management, whilst plots treated with standard management remain in good health.