Paul Hicks uses a normalised difference vegetation index, which identifies the amount of infrared and other wavelengths of light reflected from vegetation, to assess plant health.
PHOTO: Evan Collis
Like all Western Australian growers, Paul and Siobhan Hicks are finding they are constantly having to push out the technical boundaries to cope with declining rainfall that is compounded by non-wetting soils and increasing frost events. With the effects of a drying, warming climate never far from his mind, Paul is even developing his own tools and technology to manage their 3750-hectare mixed-cropping enterprise at Pingrup.
Paul has developed a sensor-driven, moisture-seeking seeding solution and is customising off-the-shelf products for frost management. The main frost period at Pingrup is between mid-September and early October. The Hicks family expanded into export hay production in 1999 as an alternative market for frosted crop, but there is still the challenge of assessing the extent of frost damage.
“We have a two-week window after a frost to decide if we will mow for hay or wait to harvest,” Paul says. “Our preference is to harvest, but if we misjudge frost damage it can cost us.” Paul distributes sensors around the farm to record temperatures every half hour. During a severe frost in September 2012, he recorded minus 6°C in one paddock, with temperatures then soaring to 30°C the next day. “This 36°C difference really knocked the crop around, and we knew we had to make a decision to mow or harvest. The problem was working out which area of the paddock was frosted.”
Paul used all the resources he had at his disposal including a set of digital, multispectral image maps with two-metre pixel resolution. He also used EM38 and gamma radiometrics maps (including thorium to identify sand and gravel areas) combined with a digital elevation model (DEM) topographic overlay to identify the lower, frost-prone areas. He found the best correlation with actual frost damage was the DEM slope map. He overlaid the maps to create a ‘frost-prescription’ map, loaded it as a background layer in his John Deere 2630 screen on the SP mower, then selectively mowed the frosted crop.
It was a decision that paid off. Paul mowed 60 per cent of the worst-frosted paddock of barley and harvested the rest. The hay yielded 3.5 tonnes/ha and netted $416/ha, while closely adjoining areas of crop that were frosted but harvested only yielded 0.6t/ha, netting $109.75/t.
“The break-even point for barley grain in our business is 1.2t/ha, so the decision to mow frosted crop gained us $305.75/t compared with if we had left it all to harvest.”
Paul plans to start planting earlier, from 25 April. Previously, he has not seeded barley before 10 May or wheat before 20 May to avoid the frost window, but the ability to assess the timing and severity of frost is an opportunity to turn risk into reward.
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