Grassweeds are difficult and costly to control, and are an increasing problem on Irish tillage farms. Increasing levels of resistance to grassweed herbicides, increasing non-inversion tillage, a move to earlier autumn sowing and the introduction of potentially devastating weeds from other regions all combine to make this a very real threat to future crop production. Variable knowledge within the industry regarding grassweed identification and control measures is compounding the threat.

Conservation tillage

The enable conservation tillage (ECT) research and dissemination project aims to address many of these issues. But it is obvious that we need to up our game considerably with regard to grassweed control and transfer. For anyone who does not already have these problems, it is very important to be aware of where infestation of weeds actually comes from. While there are many possibilities for infestation and spread, transfer by machinery is one that is very important.

All guards need to be opened up and swept or blown and then run idle to encourage material to fall out.

Farmers and contractors have little choice but to act to prevent this transfer of grassweed seeds between regions, farms, and fields. This means ensuring that machinery is cleaned and not a cause of transfer. We need to be aware that the introduction of blackgrass threatens the viability of crop production on an individual farm.

In the case of blackgrass, a zero-tolerance approach must be pursued which will involve many actions on different fronts to help prevent or reduce infestation. The prevention of weed seed transfer by machinery is a critical one as grassweeds can be introduced in to farms and fields by machinery.

This article outlines measures to help reduce the risk of grassweed introduction via machinery at harvest.

There are very many places in a combine where seeds can be carried from place to place.

Know your fields

Whether a grower is to use an owned or a contractor’s combine, the operator must know if there is an issue with difficult-to-control weeds (bromes, wild oats, blackgrass etc) and where these problems are located. This should influence the approach to harvesting within the farm, and within the field, to minimise the spread of seed within and between fields and across farms.

If you discover a blackgrass problem, the first decision hinges on whether to harvest it at all. If it is to be cut, it is best to leave this field until the end of the harvest after which the combine can be cleaned thoroughly. The cleaning of combines and other machines which follow them, such as balers and other machines, should ideally be done in a grass field or an area that will not be cultivated. Failing that, clean in a confined corner of an already infested field.

Combines provide lots of places where seeds can sit and be carried between fields.

Cleaning the combine

Pre-season or following a second-hand purchase

  • It is essential to start the season with a thoroughly clean combine that has no crop residues anywhere on it.
  • To facilitate cleaning during the season, ensure all cleaning access points and appropriate guards are easily opened, that the full cleaning fan speed range is available, and that all adjustable sieves are easily changed.
  • Have cleaning equipment such as sweeping brushes and/or a leaf blower for external surfaces. Consider having access to a high-output air compressor and long wand for areas difficult to access.
  • Be familiar with specific cleaning advice from manufacturers for the machine.

    • Moving field or site

  • Before leaving the field, use any opportunity to drive across a rough headland with the threshing drive engaged but not harvesting to loosen crop residue.
  • Follow a strict safety protocol in all aspects of the cleaning process. Ensure that the operator or bystanders are not at risk. Use a dust mask and PPE for protection.
  • When the combine engine is stopped, remove all external chaff, awns and crop material from header, ‘neck’/front elevator, or any area where it gathers using a long-handled brush and/or leaf blower.
  • Then run all working sections of the combine (header, threshing, straw chopper, and grain auger) up to speed in a stationary position. Some modern combines have a cleaning programme setting which varies fan speed and sieve openings. Otherwise change combine fan and sieve opening positions to vary, volume, pressure, and direction of air.
  • With combine turned off, thoroughly clean all external surfaces and areas under guards using the leaf blower or brush. Pay particular attention to areas that are difficult to access, such as the header, crop conveyor/elevator, combine axles etc.
  • Open and clean the stone trap and all conveyor, elevator, threshing and cleaning section access points, which will allow material to fall out, or allow air from blower or compressor in to dislodge crop residue.
  • Blow down the grain tank.
  • If it is safe to do so, run the combine with access points open to allow more material to exit, but ensure it is safe before doing this.
  • Following this thorough clean down, refit all guards, and run the combine again to allow loosened material to be ejected.
  • After travelling to and reaching a new field or farm, give a quick external clean with the blower again and run the combine in a stationary position for a minute or two to allow dislodged material be ejected before starting (preferably in a non-cultivated area).
  • Record the field in which the combine begins working and follow a known or recorded path at the start. Turn off the chaff spreader in this area, if possible. This area should then be closely monitored in the subsequent crop for any new grassweeds introduced.
  • Where some grassweeds already exist in a field or farm, try and limit spread during harvesting. For example, if there is brome on the turning headlands, ensure this is all cut on the headland runs to avoid pulling it into the main body of the field.

    • Blackgrass risk

    If a secondhand combine has come from the UK, or if a combine has worked in a field in Ireland where blackgrass was present, then a much deeper clean is essential. Follow the full cleaning process outlined elsewhere in this article but much more meticulously. In this instance all areas of the threshing, separation and cleaning areas of the combine must be thoroughly cleaned, which may require more dismantling and much more time.

    Baler and others

  • Clean thoroughly, as with a combine, before the season starts – this makes it easier to clean during harvest.
  • Never carry a part bale from farm to farm – eject it where it was baled.
  • Always run the baler in a stationary position before leaving the field to allow crop residue to fall off.
  • Use a leaf blower or brushes to remove any chaff from all areas, opening all guards in the process and cleaning inside the chamber as well as the pick-up and undercarriage.
  • Use the blower on the tractor too, particularly around the rear linkage, axle and under cab areas.
  • Give a quick clean again to all areas following road transport and run the baler while stationary.
  • Keep a record of the first field baled and direction/position of the first bale. After ejecting the first bale, open and close the door of a round baler a number of times while stationary before proceeding to bale the field.
  • Follow safe practice for all cleaning procedures. Never dismount the tractor or attempt to manually clean when it is running with the safety guards open.

    • Others

  • Trailers: Clean body, undercarriage, and axles thoroughly.
  • Tractors: Clean all areas thoroughly, particularly axles, underneath the cab and around fuel tanks etc.
  • Do not forget loaders, straw rakes, bale trailers etc.

    • It is worth doing

    Proper cleaning of a combine (or any other machine) takes time and will add to operating costs. But in the case of blackgrass, for example, the cost of not doing it could effectively put a grower out of business. The cost of controlling weeds like sterile brome is also significant. The basic cleaning routine outlined here is a must for combines, or other machines moving between fields. Where a known problem or blackgrass is suspected, a different harvesting scheduling and more radical cleaning is essential. This may affect the harvest and grain quality. Where blackgrass is suspected, straw should not be baled for use off the farm.