ISSUE 1 Better Frost Decisions

ISSUE 1 | AUGUST 2021

BETTER FROST DECISIONS Knowledge to inform grower and adviser decisions for pre-season planning, in-season management and post-frost event responses

IN THIS ISSUE Seasonal frost risk update Frost work in the regions

Will this season be frosty?

Some years are frostier than others and there seem to be frostier and less frosty decades. This newsletter article addresses the year to year variability in frost.

In issue 2, due in September, SARDI climate applications will combine with CSIRO colleagues to discuss how minimum temperature varies across the landscape (spatial variability). In issue 3 we will analyse the weather maps for the frost events in 2021.

Why is historical minimum temperature data important?

In the last decade there has been an explosion of NRM and on-farm weather stations and many of these are now networked. The lower cost and availability of temperature loggers such as Tiny Tags and iButtons provide further local information.

This is valuable information, but unfortunately it is all recent. Even 10 years of measurement is a small sample to try and understand year to year variability. In the future there may be clever ways to connect the on-farm weather data with the long term data. At the moment we rely on BoM sites for long term records.

Continued...

WELCOME Welcome to the first issue of the "Better Frost Decisions" newsletter brought to you by the GRDC Frost Extension project in the southern region.

This four part newsletter series will keep you updated on frost extension activities and events as well as checking in on the weather and responding to frost events as they may unfold.

Our regular contributors will include Peter Hayman and the team from SARDI Climate Applications and farming systems groups AIR EP, UNFS, MSF, BCG and SFS. Read on to learn more from the regions.

Next issue due mid September.

These long term records are the only way to 1) rank the frostiness of a season like 2021 to better interpret the demonstration trials, 2) make long-term comparisons of the frostiness of regions, 3) check the impact of climate drivers like negative IOD, 4) check on how frost risk is changing over decades and 5) analyse ‘optimal’ or ‘safe’ flowering windows.

Measuring and ranking the frostiness of a season or a region is somewhat similar to what we do with deciles for rainfall.

Dryland farmers would agree that a statement like “the growing season was a decile 3 season” tells us more than “it was a dry season, not the worst season, but dry”.

What do you mean by Optimal Flowering Windows?

In addition to ranking a given season, historical information on frost risk is important to identify the optimum flowering window.

This is a “window“ of days in spring that balances the risks of frost, heat and moisture stress.

At recent frost workshops organised by MSF and GRDC we asked farmers and agronomists about "what date in spring would you drive past a crop in head and think it was too early and pushing against frost risk?

What date would you think a crop was a bit late to be in head and prone to heat and moisture stress?”

Further discussion covered how the targeted flowering window might shift earlier or later depending on the risk appetite of the farmer and the frostiness of the paddock.

It is obviously a mistake to determine the Optimal Flowering Window after a single year, or even a three year project; we need to use long term climate records.

How can farmers access local info on frost and heat?

The APSIM model behind Yield Prophet captures the dynamics of crop development and how critical stages interact with the risks of heat and frost but also rainfall, crop water use, nitrogen supply and the other driver for modelling biomass, radiation.

Of course, deciles for the growing season don’t cover everything. The statement of a decile 3 season might be followed with “a late break but the rain came just as the crops were flowering”.

A great tool for farmers and a agronomists to freely access climate data is the CliMate App

Deciles as a way to rank the rainfall of the season are only possible because we have reliable long-term records of rainfall. We have fewer temperature records and even when we do have good records, it is more difficult to provide a frostiness decile.

A user of CliMate can set the percent chance of reaching a cold or hot threshold. For example the 10% chance of being warmer than zero degrees and the 30% chance of being cooler than 30 degrees.

Candidates for ranking years include the number of frosts, date of last frost, coldest night, accumulated nights or ‘frost sum’ under a threshold of 2 degrees or 0 degrees and simulated damage from frost using a crop model like APSIM (YieldProphet).

We will explore different ways to measure frostiness for recent years, including 2021 in issue 3.

A recent GroundCover article gives a good example of using CliMate as one input into managing frost risk 'Dodging frost a numbers game'.

Kenton Porker discussing time of sowing impact on flowering date and yield for different varieties.

Farmers and agronomists in the room were able to tell us based on their experience, local trials and because they had attended presentations at recent GRDC updates, for example Stabilising the flowering time of wheat .

They were also quick to point out that hitting the optimum flowering window with different varieties and sowing times isn't always easy, especially if a season is warmer or cooler than usual.

Because this is only based on frost and heat it is better understood as a user defined ‘safe flowering window’.

Unless farming in a highly frost prone area, the Optimal Flowering Window is usually earlier than the Safe Flowering Window.

This is because earlier flowering minimises the risk of moisture stress as well as heat stress.

Continued...

What to expect in 2021 The very late break to the season in 2021 has meant that even dry sown crops didn’t emerge immediately post sowing and hence crops will generally be later and likely to be more prone to heat stress than frost.

The Bureau of Meteorology has declared a negative Indian Ocean Dipole (IOD) Climate Driver Update (bom.gov.au).

A negative IOD is associated with warmer waters to the north west of Australia and wetter conditions.

The increased cloud cover and wetter conditions are generally less conducive to frost. However, analysis conducted by SARDI Climate Applications for key sites in South Australia shows a minor decrease in the number of frosts over the season (not consistent at all sites) and even less impact on late spring frosts.

Unfortunately, late spring frosts remain a random low frequency but high consequence event.

The negative IOD suggests a swing towards wetter conditions, but only a small shift towards slightly lower frost risk.

The last negative IOD was 2016, and this was a wet spring with relatively low frost incidence.

However, there were some damaging frosts, especially in the Clare region.

Experienced SA Mid North agronomist Mick Faulkner made the important point that frost in a drought adds insult to injury, but the main damage to the farm enterprise is the low yield due to the lack of rain.

Contributed by Peter Hayman, Dane Thomas & Bronya Cooper, SARDI Climate Applications.

The cost of a frost in a good season is much greater. Another problem of a frost in a wet spring is that cutting hay is more challenging and finding a profitable market can also be difficult.

Is the risk of frost and heat changing?

Farmers and agronomists with long experience across the state have observed more frost damage and in many cases, earlier heat events.

There is a paradox whereby in a warming world, we seem to be getting more frost, or at least noticing more frost damage. If we compare the risk for the last 20 years (2001 to 2020) with the risk in the previous 20 years (1981-2000) we find that days over 30 degrees C are occurring earlier. The red line showing risk in decades is shifted above and to the left of the brown line for a number of locations.

The risk of frost is also much greater in the last 20 years. It is hard to say whether this is a permanent shift, but it supports local experience that recent decades have had damaging frosts at a critical period. This timing may also contribute to stem frosts.

Kyancutta

Lameroo

Right - The chance of at least one day in seven measured being zero degrees or colder and 30 degrees or warmer in the last 20 years from 2001 to 2020 (blue line and red line) or the previous 20 years from 1981 to 2000 (grey line and brown line).

Ararat prison

Two tiny tags for temperature monitoring and a rain gauge are located at the site, with weekly observations taking place from Ag Innovation & Research Eyre Peninsula GS31 to October.

Reducing the impact of frost with variety selection

The treatments include: 1. Vixen - early 2. Rockstar - mid late 3. Denison - late spring 4. LR Awnless wheat 5. Mixture Did sowing a mix of maturities in a 6. Spartacus - barley single crop reduce the impact of 7. Mace - early mid

Did sowing wheat varieties of different maturities sown on the same date reduce the impact of frost?

frost?

EP growers are encouraged to These are the questions that will be follow Air EP news and events with addressed at the demonstration site site visits planned in September. at grower Tim Zacher's site at Trial updates to follow in issue 2.

Tooligie, EP in 2021.

For more info contact The demonstration was sown 26th May by EPAG Research and will be Naomi Scholz harvested for yield and grain quality. eo@airep.com.au

What is the risk of frost and heat at Kyancutta?

Tooligie site pictured 3rd August with plants at G30.

Tiny tag temperature monitoring is adjusted to canopy height.

Figure 1 - chance of a single day measured at Kyancutta BoM station being zero degrees or colder (blue line) and 30 degrees or warmer (red line).

It is difficult to find representative weather stations for frost on EP. Many sites are too coastal and sites closer to the trial at Tooligie show very limited frost risk. Kyancutta is a site with high quality data.

Figures 1 and 2 show the risk of being colder than zero degrees and warmer than 30 degrees for Kyancutta.

The X axis of both graphs is the day of year and the Y axis is frost risk presented as a percentage. The difference is that Fig. 1 is the risk for a single day whereas Fig. 2 is the risk at least one day in seven.

The very sensitive stage of wheat to frost is at least 7 days during flowering. The chance of one frosty night over 7 days or one hot day over the week is much higher than the chance of a frost or heat on a single day.

Figure 2- the same thresholds as Fig 1 but chance of at least one day in seven meeting the threshold.

Creating frost zone maps for timely decision making Upper North Farming Systems

The Murray Town site in the Upper North will demonstrate the use of Precision Mapping using elevation map to establish likely zones of frost impact.

Finally a prescription map is created for any management actions, for example, to input into a Topcon display for accurate hay cutting or to define areas to leave for grazing or harvesting.

Tiny Tag temperature sensors Map of paddock showing Tiny Tag location in different zones

The site at Todd Orrock's has been selected because of its frost history, and because it has three good data years from 2016-18.

Precision Ag Advisor Jess Koch will partner with Agronomist Dustin Berryman to source canopy temperature data from sensors and ground truth frost events and frost impact.

Zoning using historic data can also provide opportunities to manage risky frost zones differently.

Change detection maps will be developed using NDVI pre and post frost events.

If zones can be accurately mapped, it is possible to manage and reduce frost impacts through variety selection or input management.

All data layers are then combined to create a scouting map for Dustin to assess impacts.

A field day will be held at the site in spring to demonstrate tools and the impact on decision making.

What is the risk of frost and heat at Booleroo?

For more info contact Morgan McCallum morgan@unfs.com.au

Figure 1 - chance of a single day measured at Booleroo station being zero degrees or colder (blue line) and 30 degrees or warmer (red line).

The Upper North cropping region has limited temperature recording stations, especially stations that are appropriate for frost.

Temperature data is not recorded at Booleroo, but the data is calculated from the nearest recording stations with correction for altitude. This is the same data that is used in CliMate and YieldProphet for Booleroo.

Figures 1 and 2 show the risk of being colder than zero degrees and warmer than 30 degrees for Booleroo.

The X axis of both graphs is the day of year and the Y axis is frost risk presented as a percentage. The difference is that Figure 1 is the risk for a single day whereas Figure 2 is the risk at least one day in seven.

The very sensitive stage of wheat to frost is at least 7 days during flowering. The chance of one frosty night over 7 days or one hot day over the week is much higher than the chance of a frost or heat on a single day.

Figure 2- the same thresholds as Fig 1 but chance of at least one day in seven meeting the threshold.

Frost response turns to Facebook Mallee Sustainable Farming

An innovative approach will be piloted in the Mallee in 2021 to help growers work through the steps of monitoring frosted crops and making decisions following damaging frost events in Spring.

The impacts of frost can never be underestimated. We are aware the emotional toll can be high following a damaging frost event.

This platform will not only offer technical support when it comes to a 'frost response' but will also provide a community of growers dealing with a similar situation, with similar questions and decisions that need to be made.

A Facebook discussion group will be sharing information and giving you access to experts to answer your questions on assessing frost damage, options for a frosted crop, harvesting a frosted crop, agronomic considerations for next season and long-term frost management strategies.

Through this group, we will give you the information you need at the time you need it from the time the frost occurs, right through until pre-sowing next year.

QR code sign up to Frost Response group to receive a Facebook invitation and updates upon Spring launch

What is the risk of frost and heat at Lameroo?

We’ll look to launch the group in spring, but if you’d like to register your interest now, you can sign up using the QR code to receive notifications.

For more info contact Tanja Morgan tanja.morgan@msfp.org.au

Figure 1 - chance of a single day measured at Lameroo BoM station being zero degrees or colder (blue line) and 30 degrees or warmer (red line).

Figures 1 and 2 show the risk of being colder than zero degrees and warmer than 30 degrees for Lameroo.

The X axis of both graphs is the day of year and the Y axis is frost risk presented as a percentage.

The difference is that Figure 1 is the risk for a single day whereas Figure 2 is the risk at least one day in seven.

The very sensitive stage of wheat to frost is at least 7 days during flowering. The chance of one frosty night over 7 days or one hot day over the week is much higher than the chance of a frost or heat on a single day.

Figure 2- the same thresholds as Fig 1 but chance of at least one day in seven meeting the threshold.

Mitigating frost risk in a mixed farming system Birchip Cropping Group

BCG has established a larger frost trial site that will aim to assess the impact and economics of variety selection and management on production in a frost prone environment.

The trial established at Watchupga is comparing six varieties with a spread of maturities, established at two different sowing times.

Simulated grazing is also being compared as a strategy to delay the flowering.

Lawn mower simulated grazing

The treatments include: 1. Illabo - mid developing winter 2. DS Bennett - slow developing winter 3. Scepter - fast developing spring 4. Razor CL Plus - fast developing spring 5. Vixen - fast-mid developing spring 6. Catapault - mid developing spring The first time of sowing was 15 April and as conditions were dry early sown plots were irrigated.

The second time of sowing took place on 7 May with a follow up rainfall event of 7-10mm.

As early season growth was slow and early grazing unviable, grazing will be compared at different timings beginning at stem elongation. This is known as a "reset strategy" and has been investigated in other environments to manipulate flowering date by 7-15 days.

What is the risk of frost and heat at Birchip?

Grazing occured on all early sown treatments on 21 June.

In the coming months grazing and biomass cuts on the second time of sowing will be completed and phenology monitored for all varieties.

Hay cuts will be taken to assess hay biomass and quality as well as frost induced sterility assessments. Multiple crop walks will be held at the site.

For more information contact Tom Draffen tom.draffen@bcg.org.au

Figure 1 - chance of a single day measured at Birchip PO being zero degrees or colder (blue) and 30 degrees or warmer (red).

Long term temperature data is not available for Birchip but data is calculated from the nearest recording stations with correction for altitude.

This is the same data that is used in CliMate and YieldProphet for Birchip.

Figures 1 and 2 show the risk of being colder than zero degrees and warmer than 30 degrees for Birchip. The X axis of both graphs is the day of year and the Y axis is frost risk presented as a percentage.

The difference is that Figure 1 is the risk for a single day whereas Figure 2 is the risk at least one day in seven.

The very sensitive stage of wheat to frost is at least 7 days during flowering. The chance of one frosty night over 7 days or one hot day over the week is much higher than the chance of a frost or heat on a single day.

Figure 2- the same thresholds as Fig 1 but chance of at least one day in seven meeting the threshold.

Developing an Economic Frost Calculator Southern Farming Systems

At the pre-season frost risk workshops a simple Economic Frost Calculator was used to compare paddock and farm scale management for varying levels of frost risk.

Agronomists attending the autumn workshops found the tool valuable, particularly when working with clients as the tool was used to identify different seasons of varying frost intensity based on historical scenarios and focusing on the relative risk and impact of the enterprise mix going forward.

Over the next few months SFS will work with Research Agronomist Michael Moodie as initial calculator designer and Federation University and the Food Agility CRC to refine the calculator and improve its functionality so that agronomists and advisors can use the tool with clients when farm planning.

When complete the new calculator will be launched at AgriFocus - a main event on the SFS calendar.

Half day workshops will also be scheduled with agronomists and advisors to train them in how to use the calculator and generate important discussions with farmer clients.

An instructional video on how to For more information contact use the calculator will also be Michelle McClure developed and made available mmclure@sfs.org.au online.

Growers and advisers at the pre season frost risk workshop

What is the risk of frost and heat at Ararat?

Figure 1 - chance of a single day measured at Ararat station being zero degrees or colder (blue line) and 30 degrees or warmer (red line).

Figures 1 and 2 show the risk of being colder than zero degrees and warmer than 30 degrees for Ararat. The X axis of both graphs is the day of year and the Y axis is frost risk presented as a percentage.

The difference is that Figure 1 is the risk for a single day whereas Figure 2 is the risk at least one day in seven. The very sensitive stage of wheat to frost is at least 7 days during flowering. The chance of one frosty night over 7 days or one hot day over the week is much higher than the chance of a frost or heat on a single day.

Figure 2- the same thresholds as Fig 1 but chance of at least one day in seven meeting the threshold.