Thursday, August 22, 2019

Breeders throw light on maximising maize efficiency

February 1, 2019 by  
Filed under Crops

A new focus on breeding maize varieties with greater light utilisation efficiency could make the crop even more productive.

New trials suggest maize with a strikingly different plant architecture than conventional varieties could be significantly better at converting sunlight into forage, says Grainseed technical director Neil Groom.

If the results seen in UK trials this year translate into practical gains on-farm, the benefits could be considerable, he believes.

“It’s very early days and 2018 was a far from normal year for drawing any definitive conclusions, but there seems to be a real benefit from looking at light radiation absorbed by plants as well as the heat units they are exposed to throughout the growing season.

“Current thinking is that maize requires a minimum of 1200 heat units – day degrees above 6ºC from 1 May to 30 September – to grow and reach full maturity. But very little attention is paid to the amount of light they receive in that period.”

This runs counter-intuitively to most current crop production thinking, where light is increasingly seen as the ultimate limit on plant growth in the UK, says Mr Groom.

Optimum growth

“We can provide a crop with all the nutrients and water it needs, but it is ultimately light that drives the reactions necessary to produce optimum growth and take the plant through the various growth stages.

“This is very clear in a large, bushy plant like oilseed rape, where we’re only achieving around 50% of the crop’s genetic potential and why so much research looking at Green Area Index and Canopy Management has taken place.”

It is exactly the same in maize, with the plant’s abundance of growth being in direct conflict with the ability of light to reach cobs and leaves alike to drive growth, explains Mr Groom.

“We all want bulk and growth in order to fill the clamps but this can sometimes be at odds with the final feeding quality of a maize crop which is why the ‘Bred for Britain’ type of earlier varieties have become increasingly popular in the UK.

“In most cases, these will deliver the ideal combination of yield and quality whereas a potentially higher yielding but later maturing variety can just produce a lot of green material with a lower intrinsic feed quality.”

Light absorption

Clearly, though, there is a balance to be struck between quantity and quality. Mr Groom says this is where better light absorption comes in.

“As long as we’ve got the plants needs addressed in terms of nutrients and water – not usually a problem in the UK but obviously a bit of an issue in some parts of the country during 2018 – then the more light we can get on a plant, the better.

“Furthermore, the parts of the UK which have the longest day length are in the north, so if we can improve light capture and increase the rate of photosynthesis, the greater the opportunities for high quality forage production in areas which are currently outside the main maize production regions.”

Five high so-called Light Utilisation Efficiency (LU) varieties have been trialled in 2018 at various UK locations. The results have proved interesting, says Mr Groom.

“They’re all slightly different and look noticeably at odds with the type of maize we usually grow in the UK,” he explains.. “Some have less leaf above the cob and others carry the cobs slightly higher so more light can get to them.

Higher production

“Generally the plants are less bulky than we’re used to, [but] we believe plant density can be increased significantly – by as much as 60-70% to 70,000 seeds/acre – and this will increase starch and energy production.

“With existing varieties at these sorts of densities, you would certainly be running the risk of smaller cobs and reduced overall energy production, but the trials we have carried out suggest this would not be the case with the new varieties.”

The trials also suggest quality analysis is comparable to the best ultra-early varieties with comparable dry matter levels at harvest too, says Mr Groom.

“We see three possible opportunities for UK growers with these varieties. Firstly, for areas where maize is grown successfully, enhanced light capture should simply produce more energy/ha through bigger, better cobs and more plants grown in any given area.

“Secondly, in marginal parts of the UK where growing under plastic is more or less essential, it could mean that this becomes unnecessary.

“Finally, it could become possible to grow maize in parts of the UK where it is currently not even thought of. We’ve got our own conventional ultra early varieties growing as far North as Dumfries, so the high LUE varieties may extend this even further even as far up as Aberdeen.”

Plant maturity

What is immediately clear is that the varieties are much earlier finishing than even the earliest of ultra earlies currently available, so there are real management opportunities too, Mr Groom adds.

“This looks to be coming from genuine plant maturity rather than the early senescence that we saw is some varieties this year as a result of high levels of fusarium stalk rot infection.

“This early maturity means you could get a winter crop or a reseed in behind the maize in a much more timely manner, particularly in more northerly locations, than with current varieties – even those grown under plastic.

“It also reduces potential damage to soils by being able to harvest in better conditions in some of the more marginal areas where cutting often extends into November. It is a great concept and we’ve seen enough to take it to the next stage and really find out what it can deliver.

“We’ll have 15-20 full scale farm trials growing the varieties alongside existing types in a range of locations and conditions next year, so we’ll really know whether this is something that can be on-farm in a few years or whether further breeding development is required.”