A TEAM of British agricultural engineers has brought an ancient Roman bullock-powered machine for harvesting grain into the modern age. The combine attachment they developed promises to revolutionize the way wheat, barley, and other small grains, including grass seeds, are harvested. It makes reaping possible under wet conditions, and twice as fast under dry, using less energy in the process. In the longer term it will enable modified, less expensive combines to come onto the market. It also presents farmers with several environmentally positive options.
Records show that about AD 70 Roman farmers hitched a bullock behind a cart and had it push a comblike implement through the ripening wheat so that the seed heads were trapped above the comb. The forward motion of the cart would then strip the grain from the ears as the stem was pulled down through the comb.
Twentieth-century inventors have pursued this grain-stripping idea, as it is called, with increasing frequency because of the advantages the system has over harvesting the entire plant. But until this decade all attempts foundered, for the same reason the Roman device fell out of favor in the first place: Too much grain was spilled and lost.
Now engineers at the Agriculture and Food Research Council near Silsoe, in Bedfordshire, along with others at the Shelburne Reynolds Engineering company in this Suffolk farming town, have developed an attachment that overcomes the shortcomings of the ancient design. They produced a reaping device that harvests 99 percent of the grain on combines traveling up to twice the usual speed.
In brief, an eight-bladed rotor, fitted with plastic combs or stripping fingers, spins counter to the forward movement of the harvester. Turning between 300 and 1,000 r.p.m., these combs catch and strip the grain from the plant, throwing it onto a conveyor belt that takes it into the combine.
Since World War II, nearly all improvements to combine harvesters have involved ``the threshing and separating equipment inside the combine,'' according to Tom Woollard, spokesman for Shelbourne Reynolds Engineering. In contrast, cutter-bar technology remained virtually static until the arrival of the stripper.
Removing only the grain heads, or in many cases only the grain itself, means that far less material has to be processed inside the combine.
The result is much faster harvesting: ``twice as fast with barley, with a 60 to 80 percent improvement in wheat,'' according to Michael Rowe, one of 16 English farmers who invested in strippers when they came on the market last summer. Shelbourne Reynolds's tests put improved speeds for wheat harvesting at between 40 and 60 percent.
Mark Schrock, a professor of engineering at Kansas State University, saw the stripper in action when the Massey company brought one to the United States for trials on wheat.
Professor Schrock, currently on sabbatical leave in China, described his reaction in the Minnesota agricultural equipment magazine Farm Show: ``It's potentially a great idea that could totally change the way we harvest grain.''
Schrock said grain losses at the front of the machine appeared somewhat higher than with conventional grain heads but that loss at the back was less, ``because there's much less crop material going through'' the combine.
``What I was most impressed with,'' he told editor Mark Newhall, ``was the way it threshed the grain at the head as it stripped it off the stalks.'' Schrock stressed, however, that these were his observations and that he had yet to test the machine scientifically.
While faster harvesting was the principal aim behind the new development, several other advantages soon became apparent:
Improved traction. In Scotland, heavy fall rains in 1987 resulted in such wet conditions that several fields of oats were abandoned until the stripper was brought in. Because only the grain was removed from the oats, the standing straw provided enough traction to the otherwise conventional combine to allow it to traverse the muddy fields.
Lodging overcome. Because the adjustable stripper combs counterrotate, they are able to pick up seed heads from lodged (fallen) crops where conventional cutter bars pass right over them. One drawback: On stony soils, the combs occasionally pick up pebbles when the rotor is set very low.
Green straw option. Some grains are at their harvesting peak when the straw is still green. The increased moisture in green straw gums up the internal mechanism of combines, but this is avoided by a stripper removing only the grain and leaving the straw. Dew or even rain-drenched crops become less of a problem for the same reason.
Easier weed control. After harvest, most grain farmers apply a herbicide to control weeds growing in the fields. Heavy applications are needed, because conventional harvesting cuts down weeds along with the straw, leaving only a small leaf area to accept the chemical. With grain stripping, however, weed leaves remain intact, providing a much larger target area, and farmers have found they can control weeds with lighter applications.
Grain-stripped straw is readily turned into the soil with conventional plows, because it remains anchored to the soil. Left standing, it provides a highly protective cover against wind erosion and holds winter snow.
But what about the farmer who wants to harvest the straw? ``We are looking at an American-made augur that can be attached immediately behind the stripper [which will cut and leave the fallen straw in the field] and a cutter bar-baler from India that can be attached to the back of the combine,'' says Mr. Woollard.