Written by:  Simon Leake | Agronomist | 0439 999 173

What a cracking start we have had! Most of my growers in the central and southern wheatbelt have had three good hits of rain since the end of March allowing an awesome early sowing opportunity. These rains caught most of us off guard when we were expecting a drier than average start to the season based of long-term forecasts, luckily for us as we all know long range weather forecasting isn’t too crash hot. Anyway, a good portion of my clients have made a good dent in their Canola program or even finished and are now getting excited about Barley so I thought I would share some ideas to help come up with your plan to not get frosted.

Zone mapping
First of all lets go over your farm and highlight the high-risk areas, this will include low lying paddocks, sandy country and potassium (K) deficient soils and paddocks that have had bad frosts in the past. I’m sure you will have a good memory of which areas of the farm have been subject to it in the past. Once we’ve done this it will help us decide on crop choice/variety selection and time of sowing. Now that we have identified risky paddocks what can we do?

Crop & Variety choice
We all know oats are more tolerant than barley and barley is more tolerant than wheat and we typically seed our mid-short varieties in that order. Now that all the canola is in the ground (or should be) and we’re making headway on lupins and oats how can we take advantage of this early moisture if it’s too early to start seeding Maximus? This would be an ideal fit for long season wheat and barley and exactly why
I always recommend keeping some seed in the silo. This would be perfect timing to seed some Rockstar or Valiant or Kinsei then moving onto some Planet or Laperous or Zena for example. If these options aren’t available try not to get too excited, slow down and remember if you spread out your barley seeding this will reduce your exposure to frost.

There are a number of tools that can help you get the right seeding order by variety. “Flower Power” (Figure 1) which can be found at https://www.agric.wa.gov.au/frost/flowerpower is particularly useful for mapping out potential flowering dates for each variety based of sowing date – this is available for wheat, barley and oats. You can also access varietal frost risk rankings (Figure 2) at https://nvt.grdc.com.au/grdc-nfi-frost-rankings which give some handy insights. Another one is info like the table in the DPIRD Crop Sowing Guide (Table 1).

Figure 1. Estimating flowering dates based on sowing dates for selected varieties on “Flower Power”.

Figure 2. Comparing frost ranking for selected varieties on “GRDC NFI”

Table 1. Duration of days from sowing to flowering (relative to Scepter) at selected NVT and DPIRD Trials in 2021.

What else can we do to reduce frost risk this season?

Nutrition:
Potassium – make sure crops are getting sufficient K, if crops are deficient then this will increase frost risk, tissue test to confirm in season.

Copper (Cu) – make sure crops aren’t Cu deficient either as this will increase frost risk too, again tissue test, this can be amended by a foliar spray up to booting stage of cereals which will also give a yield bonus.

Use conservative fertilizer rates – if you have a high-risk paddock that always gets frosted it would be worth putting on conservative fertilizer rates (particularly N and P) this will certainly give some economic insurance for frost risk but also reduce frost risk impact as lower yielding crops typically yield less than their bulkier counterparts. This, however, does not include K and Cu.

Cut seeding rate – less dense canopy and plants tillering more with more spread-out flowering will reduce frost impact.

Important to note, cutting fertilizer and seeding rates will have yield and weed control implications.

Stubble management – reducing stubble will reduce the severity and duration of frost. A few approaches can be taken here like cutting low, chaff carts, windows, stubble crunching, grazing and burning. For this year
burning might be the only option left, and could be an option to justify an earlier sowing? Remember retaining stubble as a long-term strategy will improve yield, thus I do prefer to avoid it where possible.

Grazing – if you want to sow earlier with more confidence or have gone early and worried about frost, another option is grazing. 2 weeks of grazing will move back flowering 1 week, additionally it will reduce
biomass and compact the soil which will also help with frost.

What can we do next year?
Soil amelioration like mouldboarding, spading, clay delving / spreading can provide a number of agronomic benefits and are commonly used in the wheatbelt. These practices can also improve the capacity for soil to absorb and release heat and, therefore, are a frost mitigation strategy. Whilst these practices are very expensive you may not use them specifically to help with frost but may be an added benefit when considering paddocks to treat.

Key Points:

• Identify high frost risk areas – plan your seeding order around them.
• Slow down!
• Long season wheat and barley would be a great fit this year.
• Don’t allow K and Cu deficiency, tissue test in season to be sure.
• Burning stubble may give you some more confidence going in earlier if your engines are revving.
• Grazing available if you’ve got seeding regrets