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Some varieties thrive in heat How drought tolerant maize delivers dividends

Maize varieties which adapt better to summer drought are helping to make livestock businesses more resilient.

Last season proved to be another challenging year for UK maize production – with clear evidence that some varieties are better adapted to summer droughts than others.

Maize deals better with extreme heat than traditional British grassland. But not all varieties thrive in hot conditions with low rainfall – and the UK’s main maize growing areas received just 75% of average expected precipitation last year.

The months of June, July and August saw very low levels of precipitation, says Wilson Hendry of plant breeders Grainseed. At the same time, it was extremely hot, with record-breaking temperatures.

Maize heat units (MHUs) exceeded the 30-year average every month from May to September. While hot dry conditions were a problem for many growers, they meant all regions comfortably exceeded the 1200 MHU threshold required for maize.

Southern England, south-east England and central southern England all experienced more than 1500 MHU, says Mr Hendry, with East Anglia achieving an extraordinary 1633 MHU during the critical summer period.


“Overall, considering the lack of water, it’s surprising how well maize performed generally, but without doubt, crops with good cobs delivered the best yields and quality, regardless of the state of the plant.”

What is also clear is that some varieties performed much better than others in the same region. The knowledge learned from this should inform varietal choices for future years, says Mr Hendry.

“As well as varieties with large cobs, larger, leafier plants have tended to cope with the drought conditions better than others and, in particular, some of the maturity group 6 and 7 varieties really stood out.

”For some growers, the key varietal decision is around choosing the maize variety that will finish properly when heat units are limited. Later maturing varieties can require significantly over 1200 MHUs to mature fully and produce high energy forage.

“In the face of more variable growing conditions, people have understandably been drawn to earlier varieties, particularly as the best of them produce yields comparable to later maturing varieties that require all the season’s heat units to mature.”

Variety selection

With availability of heat units seemingly no longer a problem, Mr Hendry says some growers would be better served by choosing varieties in a maturity group one or two notches below their choice a decade ago.

“Such varieties are characterised by bigger plant structure generally with deeper rooting systems and this gives them greater resilience than earlier varieties which are more likely to ‘burn-up’ in hot, dry conditions.”

There are three stand-out maturity group 7 varieties that combine all the characteristics required for optimum drought tolerance, says Mr Hendry. These varieties have performed particularly well in the UK over the last three years of low rainfall summers.

“The first is Emeleen. It’s a tall plant featuring particularly large cobs with large number of grain sites providing maximum starch production with good maturity for more favourable maize sites.

“Then there’s Crosbey – another very robust strong plant with large cobs.” This variety features early starch lay-down, resulting in good cob ripeness and high starch content for its maturity class.

“We’ve seen it deliver high yields in difficult droughts even on light soil.”

Crosbey is a dual purpose variety which can also be grown for grain. Some producers drill it and decide later whether to take a forage crop or to crimp the grain depending on their feedstock situation at that time.

Drought conditions

“Finally, Legolas is a tall plant with very erect, wide leaves providing plenty of bulk. It has excellent cob ripeness for the maturity group and a large bulky plant to produce huge yields.”

All are well-adapted to drought conditions with their in-built resilience allowing them to express their full genetic potential in far from optimum conditions, says Mr Hendry.

“Clearly maize grain drives yield, dry matter and energy and growers must do everything to ensure they can produce large cobs with high number of grain sites.

“Even when leaves die back, with strong cob performance you will always have a high energy feed that will form the basis of high performance rations. Cob is very definitely king.”