Shifting rainfall patterns, shifting sheep


Growers: Susan, Ben and Ben Carn
Region: Quorn, Flinders Ranges, South Australia
Commodities: wheat, barley, Merino sheep, feedlot for lambs
Farming area: 11,000 ha (2000 arable) Annual average rainfall: 220 to 300 mm

Susan Carn, her husband Ben and son Ben grow wheat and barley, produce Merino sheep and run a feedlot at Quorn in South Australia’s Flinders Ranges. In this article, Susan considers the lessons of the past three years for their cropping and sheep operation. Due to changing rain patterns in the Flinders Ranges region, the Carns’ gamble on using stored subsoil moisture to sow did not work out well. However, using a combination of seasonal forecasts, being more conservative with cropping, and shifting grazing and lambing times, Susan feels confident about the future.

Susan and Ben Carn enjoyed a successful crop in 2010, which was marked by a wet harvest.

“All the forecasts agreed we would have a dry winter, wet spring and a wet harvest,” Susan says, “so we didn’t go for broke. Our decision was to sow conservatively and be ready to harvest as quickly as possible.”

Photo of couple with their sheep

Growers Susan and Dan Carn, Quorn, South Australia.

PHOTO: John Kruger

The decision paid off when the Carns quickly reaped the 2.03 tonnes per hectare of wheat and barley they had sown, and had no grain downgraded.

“By sowing less, we made more,” Susan says. Quorn, South Australia, is a marginal cropping area and the historic average yield is 1.4 t/ha.

However, 2011 and 2012’s seasons taught many northern SA growers a hard lesson: “Even though the year’s predictions were average at best, we had so much subsoil moisture that we felt we couldn’t not sow some crop.”

But through autumn, winter and spring the Carns saw little rain. “In 2011, anything coming from the south, we missed, and we only got rain in July,” Susan says.

“The timing of the rain in those years ended up being dismal. The lesson we learnt was that we can’t sow just on subsoil moisture.”

Winter rain limits

Susan is a keen watcher of Australia’s climate drivers, and says that one in particular seemed to steer away the rain they needed for a top harvest – the subtropical ridge (STR).

The STR, an extensive area of high pressure, is a major feature of the general circulation of our atmosphere. It is one of the major influences on the climate and weather of southern Australia.

The position of the ridge varies with the seasons, allowing cold fronts to pass over SA in the winter and pushing them to the south in summer. “In the end, the STR went where it should, but the rain was too late for the crop. We reaped only a couple of paddocks,” Susan says.

Susan says their property is in a danger zone for rain if the highs are too far south and they find they can no longer rely on winter rain due to the STR.

So how have the Carns’ cropping practices changed? “Not much, as we always like to sow some barley for the feedlot, and a crop can provide extra feed for our sheep,” Susan says. “We are just more cautious about how much we crop.”

Grazing ground cover

Climate Champions

The GRDC’s Climate Champions program provides early access to research assessing the impact of climate variability in different agricultural regions and helps growers adapt their production systems. Participants have been selected for their willingness to learn more about the influences of climate variability and to provide leadership to other farmers by sharing their experiences and what they have learnt.

The Carns also carefully plan their livestock movements according to paddock feed. They move their 6000 Merinos according to the amount of ground cover. “The soil is prone to drift, so because we have lots of country we’d rather keep the ground cover and move the sheep around.”

The Carns take advantage of paddocks with more feed – usually due to erratic thunderstorms – and lighten the load on other paddocks with less feed.

This erratic rainfall combined with a trend towards less autumn, winter and spring rain and more summer rain has prompted Susan and Ben to change their lambing management to match the summer rain. For the past three years, they have been putting their rams in earlier.

“2011 and 2012 were wet summers, so it was likely we’d have more feed on the ground in autumn than winter. We put the rams in earlier and the ewes ended up lambing on better feed,” Susan says. “We had amazing lambing percentages those years.”

Seasonal forecasts helped with that decision, guiding Susan on when the most useful rain might fall. This year, the couple have timed lambing to take advantage of a forecast for a dry summer, but wetter March. “We’ll see how we go,” Susan says.

Climate information online

Over the past five years, grower Susan Carn has collected a list of her favourite weather websites. Although she says there are many of them, she has worked out which ones to look at daily, weekly and monthly. Some are included below.

You can find Susan’s weather list with links included on Climate Kelpie.

Useful resources on the Bureau of Meteorology website include:

Estimated rainfall for the coming week is available from the National Oceanic and Atmospheric Administration’s Air Resources Lab (

Planning with forecasts

Susan fears that changes in Quorn’s climate may be permanent, and she has seen a change in the region’s climate predictability.

“Maybe the STR is going to be in the wrong place for us in winter more often than not,” she says.

However, if seasonal forecasting is the tool to plan for future cropping opportunities, the Carns are relatively comfortable. “Three-month outlooks are pretty darn good. Longer than that – six months – is harder. We use seasonal forecasts as a broad guide for that block of months,” Susan says.

Helping researchers

In late 2012 in Melbourne, Susan was asked to present to researchers about how she uses POAMA (the Predictive Ocean Atmosphere Model for Australia), the Bureau of Meteorology’s global climate model.

“I think my presentation helped the researchers to understand how growers use forecasts and outlooks, and how the models are contributing to our operations,” Susan says. “I really felt that growers are appreciated and our opinions are valued by scientists and researchers.”

Susan believes that now is the time to throw everything into seasonal predictions. “We can’t cut down on research or staff. People need to know about these forecasts.”

And Susan is doing her bit: shortly afterwards, she spoke to five groups of grain and sheep producers on the Eyre Peninsula, SA, about the benefits of using POAMA in their management decisions.

“I don’t have all the answers,” she says, “but I can show people where to look for some guidance.”

More information:

Susan Carn
08 8648 6438

Climate Kelpie

GRDC project Climate Champion program

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GRDC Project Code MCV00033, ECO00005

Region South