With recent temperatures exceeding 30degC across much of the UK and soil moisture deficits as high as 120mm, the yield potential of many cereal crops is under threat.
Dr Helen Holmes, crop physiologist at ADAS, says the relentless high temperatures are likely to impact on grain set.
“Recent studies on heat stress in UK field-grown wheat crops have estimated that 15 hours of temperatures above 31degC during the period of 15 days before anthesis, during anthesis and five days after anthesis could result in about a 15 per cent reduction in grain yield, mainly through reduction in grains set per ear.
“Cereals, especially wheats, may compensate for any reduction in grain numbers per ear by increasing grain size, but this depends on getting favourable, cool weather for grain fill and on varietal differences in maturity times. Perhaps later maturing varieties, which stand more of a chance of cooler temperatures for some of grain fill, will get the best chance of compensating.”
Drought conditions may also be stressing cereal crops, which could further reduce grains set per ear, she adds.
At Southesk Farms near Montrose, Scotland, a lack of rainfall is of great concern to farm manager Neil MacLeod.
He says: “We have experienced no rainfall in eight weeks and understandably the word suffering is an understatement. Our spring barley should have awns at paintbrush, and the panicles on the spring oats should be about to emerge. Neither of these key growth stages look likely to happen any time soon, with some crops on lighter land no more than ankle height.
“What is even more concerning is that some of our winter cereals on lighter, shallower soils are burning up, and for them the money is all spent. Every day that goes by, our yields are suffering.”
The rare early harvest which was experienced by many last year is likely to make a reappearance this season as a result of the dry weather, with reports of progress being made on lighter soil types in Suffolk, Staffordshire and Cambridgeshire.
Potato crops have also been quick to develop. Andrew Francis, senior farms manager at Elveden Farms, Norfolk, says: “The crop we have in sandy soils has moved through the growth stages very quickly. We are now probably one or two weeks ahead of normal, despite the late start.
“Some canopies are looking wilted, even by lunchtime after a morning irrigation. At the moment we are working on a four-day irrigation cycle and applying 15-18mm.
“While tuber numbers look like they might be around average, we cannot be sure what is happening to the tubers themselves. The worry is that their growth rates are outstripping their nutrition uptake, and there may be some concern over potential problems appearing in store.”
According to the Met Office, the heatwave conditions are unlikely to waver, with temperatures of 30degC plus still possible across southern and central England over the coming days.