The Mallee lesson: farm the rain

Image of a man in a paddock

South Australian Mallee grower Dean Wormald is keen to awaken policymakers to farming’s cost structures.

PHOTO: Rebecca Jennings

Mallee grower Dean Wormald shows just how much cropping in this region has changed over the past decade as growers have learned to “farm the rain”.

Dean Wormald’s father Ken used to tell him about Mallee dust storms in the 1940s, when it was too dark to see inside at 9am without hurricane lamps.

“Things have certainly changed since then,” the South Australian grower says. “Adoption of no-till farming, research into the Mallee environment, the role of vegetation in looking after our fragile soils – these have all made dust storms virtually a thing of the past.”

Dean’s family has farmed around Caliph (40 kilometres south-west of Loxton) since 1913 when his grandfather won 1200 hectares in a land ballot.

Today, Dean crops 2832ha. As a sole operator with one seasonal worker efficiency is a priority.

The enterprise has undergone many changes. In the late 1990s, the Wormalds moved from a one-year crop/two-year pasture rotation with self-replacing Merinos to straight cropping.

Ten years ago, Dean started pulling down fencelines and now crops paddocks of about 400ha, some with 4km runs for the cropping machinery, lifting efficiency considerably. The number of seed and chemical changes is reduced and the longer runs are ideal for autosteer, saving time, fuel, seed and fertiliser.

Summer weed control is a top priority to conserve moisture in variable seasons, and removing fencelines has reduced in-paddock weeds.

The Mallee has a highly variable climate for grain growing, requiring astute management of resources and costs: “We have years when we don’t get seed back, then years such as 2010 when the yield monitor hit five tonnes/ha. Sure it only showed that for a few seconds in one spot, but when your average is 1.2t/ha for wheat, it’s a good year,” Dean says.

Based on rainfall records from 1920 to the present day, the farm’s annual average is 270 millimetres – 175mm during the growing season. This year, Dean had already received 256mm by June, raising hopes that the averages – 1.2t/ha for wheat, 1.4t/ha for barley and 0.4t/ha for canola – could easily be doubled in 2014.

Research outcomes


Owner: Dean Wormald

Location: Caliph, South Australia

Area: 2832 hectares arable 

Crops: 900ha canola, 600ha barley, 900ha wheat and 500ha chemical fallow in 2014

Soil: sandy loam, sandy rises, some heavier flats and limestone areas

Annual average rainfall: 270 millimetres

Soil pH: 7.5 to 8.5

“The main thing we have seen from research outcomes in the Mallee is how important it is to farm the rainfall,” Dean says. “Summer weed control is vital to store moisture from any rain that falls between October and April.

“Top-dressing and summer weed control give us the potential for a $3 to $5/ha return on investment for each $1 of applied chemical through extra yield as result of moisture and nutrient conservation and nitrogen turnover.”

When it comes to converting stored moisture to grain, Dean estimates that he achieves 50 per cent of his goal of 20kg/mm of in-crop rain. He is targeting 70 per cent in the next five years by increasing the legumes grown to benefit the cereal phase through less root disease and grass weeds.

The local cropping landscape has changed in the past five years as more growers include canola and legumes in their rotations for disease breaks and to provide extra nitrogen for cereals.

“When we predominantly grew cereal on cereal we hit a wall with root diseases, and brome and barley grass were out of control. We targeted barley grass before sowing but it evolved to the point where it wouldn’t germinate until after sowing – we had knocked out early germinating varieties so it became difficult to control.

“I brought canola into the rotation and it has made a big difference. My rotation at the moment is canola/wheat/barley/legume/wheat/barley. Increasing the amount of legumes such as vetch, field peas and lupins ensures a lot more nitrogen for the following cereals.”

Frost and hot winds at flowering are also barriers to productivity, so Dean uses a mixture of varieties and maturities to spread out flowering.

His annual seeding program begins in early to mid-April with canola. Vetch is sown dry if going into brown manure (the vetch is chemically fallowed at mid-flowering, when the crop has reached its maximum nitrogen-fixing capacity). Cereals are sown from mid-April. This year, Dean’s main varieties are Pioneer® 43C80 (CL) and Telfer canola, Mace and Kord CL Plus wheat, and Scope barley. A chemical fallow has been used to control ryegrass and brome grass on 500ha.

In 2013, Dean direct-headed canola for the first time and was pleased with the result; he picked up less sand and avoided the issue of windrows blowing around. His canola fertiliser program includes 15 to 20kg/ha of monoammonium phosphate and 30kg/ha sulfate of ammonia (SOA) at sowing, followed by topdressing 45kg/ha SOA and 45kg/ha urea.

Dean incorporates findings from local research into his enterprise, such as planting shelter belts to reduce erosion.

“Growers need scientists who understand how we think and operate,” Dean says. “The Australian research community should not underestimate the value of locally relevant information so we can identify results from operating environments that are similar to our own. We also need economic data to back up trials – the rigour of economic analysis shows us if research is viable on-farm.”

Looking ahead, Dean is interested in the New Horizon trial site, hosted by Mallee Sustainable Farming at nearby Karoonda, South Australia, which looks at the potential of deep sands.

“Mallee growers have to contend with deeper sands, which are not as productive. Even in a year like this with good rain, the sandy rises are slower to get away compared with our flats. This research will hopefully shed light on what we can do with these areas and if strategies such as clay spreading, delving or growing particular crops are economically viable and can produce more grain. This could be untapped potential for Mallee growers.”

He would also like to see more legumes bred to suit the Mallee environment, coupled with information on how to make these crops profitable and sustainable.

On-farm, Dean’s sights are set on “the little pieces of the jigsaw”: stricter timing for management, ensuring rotations are adequate for disease control and incorporating variable-rate (VR) technology. He used VR in 2013 but has put it on the back burner until he can sort out software glitches that were delaying VR inputs “a few laps” of the paddock.

More information:

Dean Wormald
08 8587 4153,


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