New GDD calculator aids more accurate decision making

Mark Sandersonin Chemicals & Fertilisers

A new Syngenta GreenCast Growing Degree Day calculator is set to provide turf managers with a more accurate tool to help make better decisions on timing for Primo Maxx II applications and other actions.

Glen Kirby, Syngenta Technical Manager

The GreenCast GDD Calculator will automatically generate a predictive email notification when a user defined Growing Degree Day (GDD) target is approaching - in time for greenkeepers to assess local conditions and to decide what actions to take.

Commenting on the live launch of the GDD Calculator on GreenCast this week (11 May 2020), Syngenta Technical Manager, Glenn Kirby, said: "We know that GDD can be a useful guide to many turf management actions.

"However, from my own and other greenkeepers' experience, the challenge in a busy working schedule is finding the time to regularly record the temperature information and the reliability of that weather data source.

"The GDD Calculator does that all autonomously, and provides easy to interpret information in time to use for every day decision making."

Advancing GDD to a new level, the GreenCast calculator utilises immense data processing capability to compute figures from hourly temperatures throughout the 24-hour period, compared to a simplistic daily high and low temperature conventionally used in GDD calculation.

"That better reflects the duration of growing conditions through the day, for a more accurate assessment of how turf will actually perform," advised Glenn.

Evaluation compared to conventional GDD calculation has highlighted it is more responsive to assess onset of true growing conditions, particularly through early spring, and as growth declines in the autumn.

Users can set their own target GDD figure, or multiple targets if GDD is being used to aid decisions on different aspects of turf management, such as Primo Maxx II intervals, fertiliser programmes or pest risks, for example.

Glenn highlights Growing Degree Days have been shown to be an extremely useful guide for timing of turf management decisions. But he cautions that much of the research and many of the models have been based on US trials, under different conditions and with different grass species seen in the UK.

"The Syngenta GDD Calculator gives far greater flexibility to be able to utilise and interpret a wide range of information resources. But they do all need to be validated against an individual course's specific conditions to see how they can be applied.

Uniquely, the Syngenta calculator allows users to adjust the base temperature used in calculations. Whilst a normal base for the UK is 6°C, which reflects the onset of consistent turf growth, Glenn suggests, many US models work from a base of 10°C - which generates hugely different cumulative GDD figures.

"It is crucial to understand how recommendations have been calculated and the information on which they are based, and then use the GDD Calculator to interpret how that will work on your course," he advocated.

Whilst a GDD of 150 may be appropriate for Primo Maxx II intervals on one specific course, for example, he points out another course with a different management style, turf species or soil types, may find they get better results by repeating applications at a GDD of 140.

The GDD calculator is now being used at STRI in Yorkshire, as part of a new initiative assessing Primo Maxx II applications and intervals to aid turf management under lower intensity lockdown management.

"For the first time, there will be scientifically assessed GDD data for cool season grasses under UK growing conditions, to enable turf managers to better interpret existing turf growth models for their own individual situations," added Glenn.

"It is free and easy to use, so would urge anyone to start gathering the data and assess how it correlates to their own decision making process now, to be able to further integrate GDD in the future,"

The Syngenta GDD Calculator is available for all UK turf managers, agronomists and researchers registered on the GreenCast website.