Ground Cover South : Ground Cover 056 June-July 2005 - South
Frost 10 GROUND COVER JUNE/JULY 2005 STRATEGIES TO REDUCE LOSSES By HELEN OLSEN n The use of local topography is one of the most powerful tools to manage frost risk, say the authors of a recent report, 'Frost -- an applied climate perspective'. The report, by Peter Hayman, principal scientist in climate applications at the Waite Precinct, Adelaide, and colleague Josh Gordon, details potential strategies against frost. The authors endorse the recommendations of an earlier GRDC advice sheet, 'Reducing economic losses from frost', produced in 2000. Research has shown that sunken and wind-sheltered land and south-facing, sloping land are all more frost-prone. Also, the direction of sowing has an influence, with east-to-west furrows causing shading from the first dawn light. On undulating land, the researchers say, it is common to measure differences of four degrees Celsius, compared to one or two degrees on flatter country. The latest research report also says that El Niño years are expected to produce more frosts than La Niña years, since El Niño is associated with less cloud cover and dryer conditions. However, this pattern is stronger for the total number of frosts than the date of the last frost, and Dr Hayman stresses that the last frost is the one that often does the most damage. He says growers need to manage this risk by not having "wall-to-wall" wheat flowering in the same week. "The ability to sow large areas of wheat in a few days has increased our vulnerability to frost," he says. He also emphasises that a mix of enterprises can reduce the overall impact on a farm business -- a mix of crop types and flowering times, and even sheep, which handle frost well. The major new finding of researchers in South Australia is the effectiveness of soil that is dark, moist, bare and firm in elevating wheat head temperature above frosting temperature. The leader of a major GRDC frost project based in the Climate Risk Management Unit at the South Australian Research and Development Institute (SARDI), Melissa Rebbeck, says that while trials need to be repeated to gain more statistical significance, preliminary results are interesting. Ms Rebbeck says the drought year of 2002 knocked out the trials, and the dryer conditions of 2004 made it difficult to discern some data, but in 2003, the researchers found that clayed soil can raise the temperature of the wheat canopy by 2ºC compared to wheat canopies on adjacent unclayed sites. "It was a revelation that the measure can make such a difference," says Ms Rebbeck. However, the real test will come when the trial is repeated. This discovery might make clay spreading an option, but only if the mined- Blending varieties can reduce exposure to a frost event: this crop is sown with a mix of WyalkatchemA wheat and YitpiA wheat. Frost research seeks the cold hard facts Helen Olsen reports on the latest research into the causes and management of frost, estimated to be costing the grains industry more than $100 million a year n Losses to the Australian cropping industry caused by frost can be difficult to calculate or predict because of the random nature of frost strikes. However, as many growers well know, a severe frost can wipe out a crop as surely as disease or drought. This is why frost research remains high on the agenda, with funding of more than $693,000 this financial year, says GRDC's manager of the Agronomy, Soils and Environment group, Dr Martin Blumenthal. "Devastating frost episodes are random in time and in region affected," says Dr Blumenthal. "However the decreased yields incurred by growers sowing late to avoid frost damage cause significant financial losses to the industry every year." High-risk areas include the Eyre Peninsula, the Murray-Mallee and mid-north of South Australia, the Wimmera-Mallee region of Victoria, WA's southern wheatbelt, the central tablelands of NSW and south- central Queensland. Growers in these areas face the difficult choice of either sowing at times of increased frost risk or delaying sowing and risking excessive heat during the temperature-sensitive grain filling stage. GRDC-funded research throughout Australia is looking at the different aspects of the frost problem, from the use of topography and paddock management strategies to developing cereals with higher frost resistance. The strategies being developed, along with more frost-tolerant varieties, are designed to give growers more options to deal with frost.
Ground Cover 057 August-September 2005 - South
Ground Cover 055 April-May 2005 - South