CONTINUED warm dry conditions in the north and frosts in the south have dashed hopes of an average season, according to the latest Grain Industry Association of Western Australia (GIWA) crop report released on Monday.
It is unlikely WA's grain harvest will now exceed 12.5 million tonnes for all crops this season, GIWA said.
An "average" September could have pushed production past 15mt but predictions of a warmer and slightly drier September have so far proved right.
GIWA said growers away from southern regions had already factored in the risk of below average yields due to the late break and little subsoil moisture.
The disappointing aspect, the GIWA report pointed out, is that cereal crops generally looked like they could produce close to average yields as little as two weeks ago.
Crops in the southern regions were further advanced than the north as many had germinated before the season break in June.
Unfortunately, this contributed to wide scale damage from the frost events near the end of the first week in September, GIWA said.
Crops generally had more top and were running the moisure profile down when the very severe frosts occurred.
The frost events were then followed by a blast of heat - the worst possible combination at a susceptible growth stage.
While total grain production has been downgraded, the greatest impact will be on canola, lupins and pulses, GIWA said.
These crops in the north have not had enough time to yield near average and have also taken the greatest hit in the south from frost.
All crops have been badly affected in the worst frost areas, but canola and pulses particularly have had the top taken off their potential yield as they were in the middle of flowering.
Canola production in the State is expected to dip below one million tonnes for the first time in 10 years.
Over the 2018 growing season, the Esperance and Geraldton port zones produced about 6mt of total grain and this year the two zones will be battling to produce half this tonnage, GIWA said.
While crops are short and lack the biomass of last year, the head size is good so there was potential for the cereals to reach close to average grain yields.
This will not eventuate now as the heat has come on and with no rain in the past two weeks adding to very light falls at the end of August, crops are transpiring themselves to expiry.
The Midlands region is holding up a little better than further north as the rainfall events in late August were slightly higher.
In the eastern parts cereal crops are dropping tillers and the leaves curling up from lack of moisture.
In the central and western regions, the crops are better and particularly in the line north and south through Moora are sitting on at least average grain yield potential.
The southern part of the zone is still in good shape considering the warm temperatures and lack of rain recently.
The western areas of the zone are still looking good and the region seems to have escaped most of the frosts.
But in the south, cereals and canola have been hit hard from the frost events and the differences in eventual grain yield is going to be massive as some of the better looking earlier maturing crops have been the hardest hit.
Crops in the lakes region (east) are still going to have below average grain yield potential for most areas due to the late start and cold conditions at germination.
Widespread damage from frost events in the zone is estimated to have wiped between 700,000 tonnes and one million tonnes of grain production for the region.
Dry conditions leading up to three days of frost and then very hot conditions combined with most crops being at their most susceptible growth stages, resulted in some of the worst damage for many years with some paddocks wiped out.