How To Stop The Spread Of Weed Seeds

How To Stop The Spread Of Weed Seeds CROPS Miscellaneous 22-1-40 The threat of herbicide resistance to weeds has prompted University of Manitoba weed scientist Steve Shirtliffe to investigate how much effect combines have in spreading weed seeds. Last year in a research plot near Carman, Manitoba, he counted wild-oat seeds after a combine had gone through. The seeds were carried and spread a surprising distance, he says. He had planted the plot to spring wheat, and near one end of it he had also planted a patch of wild oats so that the combine would pass through it. "At 100 meters away from the patch, we found that the combine was dropping 25 to 75 wild-oat seeds per square meter," says Shirtliffe. "We were still finding wild-oat seeds up to 150 meters away." He had a computer programmed to project how far the wild oats might be spread in following years. It showed that after four years, seed from the original patch of about 1,000 sq. meters would have grown to cover an area of at least 9,000 sq. meters, or 2.2 acres. On another test plot, Shirtliffe equipped the combine with a chaff collector. He found that the collector didn't eliminate the spread of wild-oat seed, but it did lessen it significantly. The computer model showed that the weed patch would have grown by 30 percent over 4 years with use of a chaff collector; 700 percent with no chaff collector. Foxtail and ryegrass, which have also shown herbicide resistance, are also spread mostly by mechanical means, he says. In Australia, some farmers are resorting to chaff collectors to help clean up fields invaded by herbicide-resistant ryegrass. How-ever, they've found that the devices are more useful as a means of collecting livestock feed or bedding than weed seeds. Also, the high volume of residues collected presents a disposal problem. That's what prompted development of a combine attachment designed to collect as many weed seeds as possible with a mini-mum of chaff. Called the Rytec Weed Seed Collection System, the Australian-made unit consists of an extended sieve section an ex-tended seive section at the rear of the top sieve. It separates weed seeds from the flow of chaff. Seeds collect in a hopper under the sieve and are augered to a hydraulically-dumped 1 1/2 cu. yd. bin mounted on the back of the combine. Seeds are dumped in small piles throughout the field. They can later be collected or simply burned where they lay. A control box in the cab turns augers off and on and a bin-full light tells when it's time to dump the bin. Available for Case-IH 1600 series combines (including long sieve), Deere 8820 Titan and 9600, and New Holland TR97. Sells for $9,500 to $9,750 (Australian). Contact: FARM SHOW Followup, Harvestaire Pty. Ltd., 18 Mumford Place, Balcatta, Western Australia 6021 (ph 61 9 3447433; fax 3453506). Glenn Reicheld, Jarvis, Ontario, built his own weed-collection unit for his 1982 White 8600 combine (Vol. 20, No. 2). A bolt-on steel plate diverts material that falls off the sieves into a high-speed 6-in. dia. auger that's connected to a blower unit mounted alongside the combine. The blower sends the material into a self-unloading forage wagon that he pulls behind the combine. Reicheld says the unit doesn't collect much chaff but the material has a high concentration of seeds. He can adjust the angle of the steel catch plate to allow more or less material to fall into the auger.

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