Grain corn is a relatively new crop to the U. K. It was little more than a decade ago that several enterprising growers decided to have a go at harvesting corn with a combine.
The main stumbling block was the fact that corn doesn’t actually manage to ripen in U. K. conditions to the point that the grain is dry enough to store without a significant amount of physical drying. The growing season is not long enough, nor is it warm enough.
The best that can be hoped for, even with today’s modern, early-maturing varieties, is a harvesting date of mid-October and a grain moisture content of about 30 per cent.
So, if grain corn was to have any future, short of spending considerable amounts of money on drying costs, there needed to be a way of preserving the grain. And the solution was to crimp it and add a preservative.
With this technique mastered — we shall hear more of crimping later — interest in grain corn accelerated to the point that it is estimated that there are now over 10,000 acres harvested each year.
One of the pioneers of combining grain corn is Hampshire farmer and contractor Alan Cook, who started combining the crop over 10 years ago.
“There were only three of us doing it at that time, so it was something that the industry looked on with bemusement.”
He adds that it was clear from the start that grain corn offered him the opportunity to be able to use his combine for much longer each year.
Today, Cook runs a four-wheel-drive John Deere S690i combine to cut a total of over 3,750 acres each year, an acreage that he says he couldn’t hope to achieve with just cereals and oilseed rape alone.
“I reckon to change combines every two or three years, when they are still young machines and have all the current gadgets on board,” he explains. “But they will have done probably upwards of about 11,250 acres. The only bit we lose out on is the four-wheel drive, which we find useful for corn but few actually need during the cereal harvest.”
Based at Sherfield English, near Romsey, Cook now grows and harvests 500 acres of corn on his own farm and reckons to contract cut a further 1,000 acres.
This area could increase, however, as growers realize that their silage clamps are full and that there really is nowhere to store any additional forage corn. The option then is to have the crop combined, and either feed the processed grain or find a purchaser for it.
It’s one thing to decide to harvest corn for grain and quite another to have a combine available to do the job. While modern combine harvester threshing and separation systems are quite capable of producing clean grains, the conventional header to cut the crop is not suitable.
A dedicated header is required that can strip the cobs from the plants as they are cut, so that only the cobs make their way into the combine. The bulk of the corn plant should be left behind.
Cook uses an eight-row Olimac Drago header which, like several other designs, has contra-rotating chains and flights to pull the stems towards two rollers. These rollers grip the stem and drag it downwards through a narrow gap so that the cobs are stripped off.
The cobs then enter the elevator housing while the leaves and stems pass underneath the header. “It would be great to be able to use a Kemper-type header, which isn’t row dependent,” he says. “But it simply isn’t an option.”
He adds that it’s the drill man who makes the job difficult or easy. Straighter lines reduce the stress levels, and it also helps if the drill has the same number of rows as the header.
“At times we have to cut corn in rows that don’t match our header,” he explains. “This could be because a six-row drill has been used, or it’s a drill that has been set at different spacings.
“The only way to proceed is to harvest the crop at right angles — across the rows — which gets the crop into the combine, albeit at a much slower forward speed.”
According to Cook, the JD S690i has a rotary threshing system that handles the cobs well and threshes them cleanly with no problems.
Combine operators with con-
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ventional threshing drums and concaves need to open the concave gap to its widest point and insert a filler plate to prevent cobs getting into the drum. After all, a kilo of cobs flying ’round stuck to the inside of a rasp bar doesn’t help with the balance of the drum and could soon cause some expensive bearing damage.
Other settings for the combine require the crop accelerator speed to be reduced and, if only for the safety of others, the chaff spreaders and chopper should also be slowed down. Cook says the threshed cobs can come out like bullets if this set ting isn’t altered.
“You have to remember that there is no bulk of crop going through the combine. It’s just cobs, so there is no cushioning of the cobs as they travel along straw walkers,” he says.
The sieve setting is pretty straightforward, with the top one set wide open and the fan running at full blast. The weight of the corn grain ensures it is not going to be blown out of the combine. The bottom sieve can be removed, insists Cook, as it has no effect on the sample.
The ideal moisture content at harvest time is around 30 per cent or lower, and it would appear that grain moisture is not affected adversely by wet weather — the sheath tends to shelter the grain and the cob from the rain.
“Combining when the grain is at 35 per cent or more moisture can be done but only for about an hour before the top sieve bungs up and all of the grain is shovelled out the back of the combine,” he says. “You’ll then spend a good few hours trying to unblock the sieve.”
When grain is ready for combining it has a shiny orange look about it — not a milky yellow. The ripe grain also tastes more of chestnut and is certainly not sweet. The worst harvesting conditions can be when a stem produces two cobs — a good solid main one that ripens as it should and a weak unripe cob that just refuses to ripen to any degree. “The second cob never seems to ripen completely, and its inclusion in the sample tends to make the overall moisture content abnormally high,” he explains. “In an ideal world, one corn plant would always produce one cob.”
A combine harvester operating in fields during the autumn will always have the risk of getting stuck or leaving deep ruts, and, if it is not the combine, the grain trailers can make a mess. Having said that, Cook makes the point that the freshly deposited carpet of fluffy leaves and stems seems to aid traction for the combine and, as a result, reduces any ground damage. Four-wheel drive is also a help in these conditions. But when it comes to getting stuck, he says four-wheel drive is a mixed blessing in that the extra traction provided ensures the combine gets seriously stuck. “Four-wheel drive just means you can go deeper before you are forced to stop.”
A GOOD DAY’S HARVESTING
Cook says anything over 75 acres is more than acceptable: the hours of daylight at that time of the year are not long and the weather far from predictable. He drives the combine at a speed of about 10 km/h — any faster and the stems are not pulled vertically downwards to have their cobs removed. The combine’s output isn’t always the limiting factor, though. Wet grain corn, just like any other harvested grain, will not last very long without being dried or processed, and it is the capacity of these jobs that can govern daily outputs. There is no point harvesting more tonnes in a day than can be coped with. “Most of my grain corn is taken to the farm for crimping and treating with a preservative,” he explains. “It is then stored on farm under sheeting until it is sold to a dairy farm.”
CRIMPING AND STORING GRAIN CORN
Hand in hand with grain corn has been the upsurge in the demand for grain to be crimped/ treated so that it can be safely stored at what would normally be excessive moisture levels. One of the U. K.’s leading crimping firms is headed up by Frans de Boer. Based at Steyning, in West Sussex, each year sees de Boer crimp and treat about 20,000 tonnes of grain corn. “We have four crimping