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Combine clean-out can help reduce weed seed spread

Combine clean-out can help reduce weed seed spread

  • Updated
Combine in corn

Editor’s note: The following was written by John Thomas, University of Nebraska crops Extension educator, and John A. Smith, emeritus professor, for the university’s CropWatch website Aug. 25.

With increasing pressure from herbicide-resistant weeds such as kochia and introduced herbicide-resistant weeds such as Palmer amaranth and waterhemp, it is more and more important to reduce spreading of weed seed.

Harvest equipment moving through the fields in the fall at the peak of weed seed production are very likely to move this seed around. Doing a limited cleaning between fields and choosing which fields to harvest first can be an important factor in minimizing weed seed spread.

Here are some steps for cleaning the combine, from the North Central Agricultural and Natural Resources Academy:

  • Run the unloading auger after it is empty for at least one minute.
  • Open the clean grain and tailings elevator doors, rock trap and unloading auger sump. Make sure all bystanders are at least 50 feet away. Start the combine and separator. Adjust the cleaning shoe fan to full speed for maximum airflow. Alternately, open and close cleaning shoe sieves electronically. Also adjust the rotor to full speed for maximum air suction or open and close the concaves. Operate the combine this way for at least two minutes and drive over end rows or rough terrain to dislodge more material for self-cleaning.
  • Clean out any material left in the rock trap.
  • Try to get the “top” of trapped material in sumps or areas that hold straw, chaff and grain. As you start the next field or crop, it is likely that new material from the next field will fill in these areas as opposed to the remaining material in the bottom of these areas being moved out.
  • Use a leaf blower or air compressor to remove material from the exterior of the combine, focusing on the head, feeder house, and axle and straw spreader at the rear of the machine.

The areas of the combine holding the most biological residue are the header, feeder house and grain tank. If time is limited, consider cleaning these areas first. From a practical perspective the grain tank under the augers is one of these areas and is very difficult to clean. Top material in this area can possibly be removed with a shop vacuum.

Beyond the process of cleaning out the combine between fields, some additional considerations are important. If there are some weeds in your field such as Palmer amaranth and if it is possible to rogue them out or remove them before harvest by hand, the effort would be well worthwhile.

Another consideration would be to combine weedy fields last and even to cut around a weedy spot in the field and save it until last to minimize spreading the seed.

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