Changing climate offers opportunities for early maize

• Ultra early varieties increasingly popular

• Optimum resilience in variable conditions

• Rotational benefits for farm enterprises

A warmer UK climate is creating opportunities for farmers to grow earlier maize varieties, say plant breeders.

Maize requires a minimum of 1200 Maize Heat Units (MHU) between May and September for the earliest varieties to reach full maturity without film – and this has largely been achieved over the past decade.

“You would think a warming climate means we can start using more productive, later maturing maize types and benefit from the resulting higher yields,” says Emily Pick of forage specialists Grainseed. “But that is certainly not the case.

“You only have to look at the last 30 years of weather data to see what the general UK climate trends are – but that’s not really giving the full picture of what is happening in individual years,”

“In fact, the average for East Anglia over the last 30 years has been 1390 MHU and even in the East and north-east region of the UK it has been 1136 MHU, with this increasing by approx. 10-15 MHU each year over the last ten years.

“Three years out of the last ten have actually exceeded 1400 MHU on average.”

Heat units

Looking specifically at 2024, the average for the UK still exceeded 1300 MHU, but this is somewhat misleading in terms of the year’s potential to drive the all-important maize yields and quality for dairy farmers, she says.

“Last year – 2024 – was actually a very wet cold year with one of the coldest summers since 2015  and some of the wettest months recorded, especially in the key maize growing period.

“Rainfall persisted throughout the summer and if it wasn’t actually raining then there was almost complete cloud cover. In the critical May to September period, overall sunshine hours were actually down 3.4% against the 30-year average.

“This excessive rainfall also led to the leaching of nutrients which affected crop development with many growers needing to use bagged fertiliser or foliar feeding to optimise yields.

“While overnight temperatures in May helped increase early season MHU accumulation, in reality only July experienced more MHU’s than the long term average with the key months for accumulating yield and starch being below average.

“So, within the year there were many extremes of weather and it is precisely these conditions and the swings between them that are increasingly becoming more important than traditional temperature accumulation.

“Earlier varieties, those typically in maturity groups 8 and above or with FAOs less than 200, require less heat units to reach maturity, so if you are growing maize in seasons with significant weather changes, they are really the best option.”

Rotational fit

Neil Groom of Grainseed says that fit into the rotation is another key reason why early varieties will continue their dominance in the UK.

“Early and ultra early varieties have come a long way in recent years with names like Faith and Myrdal more than capable of matching the yields of established, later maturing high yielders, but with higher starch yields and energy.

“As well as providing more reliable crops generally, they have also opened up a greater area of the UK where maize can realistically be grown and producers can access the best quality forage for their dairy cows.

“In a purely livestock or dairy situation an early maturing variety will also give you a greater number of options regarding reseeding for grassland in the autumn or getting a cover crop drilled in time to work to its best advantage.

“But maize is increasingly seen as an attractive break crop in arable and mixed farming situations so the earlier it matures, the greater the options for what follows next in the rotation and the less the risk there is of potential soil damage.

“Earlier varieties also give a wider part of the country the opportunity to take maize through to full maturity for grain production and that is definitely an area we saw grow in in 2024.

“While on the face of it our warming climate should favour later maturing varieties in the future, there are many compelling reasons why early varieties will continue to be the mainstay of UK maize production and it’s little wonder they remain the key focus of breeders.”