FARMERS through South Australia and Victoria, two of the states with the best yield potential for this year's winter crop, are anxiously awaiting the fall-out of a string of heavy frosts through September.
The Longerenong weather station, near Horsham recorded eight subzero nights for September with a further nine nights under 3 degrees.
In South Australia, temperatures at Jamestown in the Mid North plummeted as low as -5.5 degrees on September 18.
Combined with the prospects of a drier than average October, the frost has growers nervous about the potential for serious crop loss.
This will have severe implications for the national grain supply and demand balance sheet, with big grain users in Queensland and northern NSW banking on supplies from both Victoria and SA to help meet their needs given the lack of grain in their region due to the drought.
A true indication of the frost damage in the south is hard to gauge, with a combination of stem and head frost reported.
Along with that there have also been farmers who have said they have suffered a rare 'wet frost', where a light shower the evening before a frost has been frozen.
Moisture on the plant canopy exacerbates frost damage.
In the Victorian Mallee, Birchip Cropping Group research projects leader Claire Browne said there were wildly different scenarios emerging.
"It is very difficult to get a real handle on it, in the northern Mallee we have heard of damage ranging between 0 and 60pc within the same paddock of cereals, with the heavier, lower country more impacted," Ms Browne said.
"In parts of the Wimmera, such as Rupanyup, farmers have spoken to us about losses of 20-80pc in cereals, but it all depends on how cold it was and for how long, which can vary a lot in a short distance."
However, she said the temperatures had been very cold, which led to the risk of severe damage.
"At Longerenong there were 17.6 hours below zero in September."
"At Birchip on 17 September the temperature was below zero for six hours and then on the 18th it was below freezing for a further five hours."
Ms Browne said croppers, especially those with dwindling moisture reserves, were also worried about heat.
"There are really hot temperatures forecast in the northern Mallee this weekend but Wimmera farmers are hoping it does not get too hot there."
So far she said there had been a solid hay making program, primarily those scheduled for baling but also some crops that had been frosted.
"A lot was dedicated hay, now people are cutting unplanned area.
"I would just caution, though, that people get out and really check their paddocks and don't cut prematurely without knowing the extent of the damage."
Nandaly farmer Terry Kiley said he had cut one paddock of frosted wheat, but was generally not too heavily impacted by frost.
"There is good money in hay so we decided to cut it along with the scheduled oaten and vetch hay, but overall I think frost damage in this area would only be about 5 per cent, so a lot of people are leaving the crop to go through to grain."
Wimmera-based agronomist Simon Mock, Clovercrest Consulting, said more advanced crops were at a higher risk of yield loss.
"In general the crops east of Horsham, where there was an earlier break are more advanced and probably more susceptible to damage," Mr Mock said.
However he said due to the extremely cold conditions there were reports of later sown crops being damaged, via stem frost.
"We saw some pockets of crop around Kaniva severely hit by stem frost but this is isolated rather than the rule."
South Australia hard hit
Grain Producers South Australia (GPSA) director and Hamley Bridge farmer Adrian McCabe said his local area in the lower Mid North had been hit relatively hard by frost.
"I'd estimate it could be 15pc all up in this area, but there will be individual crops that are a wipe-out, especially in the valleys and across to Pinery," Mr McCabe said.
"Over through the Mallee I have heard there are some bad patches and up into the Upper Mid North it also got very cold."
Mr McCabe said wheat appeared to be the worst hit in his local area.
"Wheat has been hit right at flowering, so even the light frosts have damaged it but with the legumes the damage is only apparent in areas that have had the really cold conditions."
Light rain, then frost
Natimuk, Victoria, farmer Brian Klowss said he was generally not too concerned by frost damage but said the wet frost event had smashed a narrow strip across his farm.
"You can see where the light shower went through before a frost around a week ago, it absolutely touched up some wheat and a clover crop.
"The paddocks were visually frost damaged within 24 hours, the plants went white and even though the heads were not even out it is just like it has been cooked, I've never seen the damage present so quickly."
"Obviously the moisture on the plant has made the damage worse."
Luckily, however, he said the rest of his crops do not seem to be significantly hit by the cold.