Australian Broadcasting Corporation: Extreme weather back in November has cut the expected crop yields of some South Australian farms by half. A record heatwave for the month wiped off between 40 and 60 per cent of yields in areas including the state’s south-east and mid-north. Farmers who were fortunate enough to begin harvesting earlier have had one of the best seasons in a long time. President of the South Australian Farmers Federation Peter White says crops that were still green when the heatwave struck …