One of the major elements in trying to beat a weed problem is to prevent seed return to the soil.

Most commercial farmers depend on herbicides to do this, but these chemicals are being put under increasing pressure from regulatory authorities and from the development of weed resistance.

So it is time to look at what others are doing in this area.

Combatting ryegrass in Australia

The Irish Tillage and Land Use Society meeting last week reminded me of something that we saw a lot of as we travelled through Australia earlier this year.

A lot of stubble fields seemed to have the chaff collected and tipped in windrows. Those that didn’t seemed to have a very high density of chaff in the tram tracks.

As we moved around, we learned that this was an effort to combat a ryegrass problem.

Basically, the chaff, which would include the seeds from weeds that travel with the crop, was being gathered during combining to be dealt with separately later.

The windrows might eventually be burned ahead of the next planting, once the sheep were removed from the stubbles.

Chaff deck

The newer system gathered the chaff and light material at the back of the combine and dropped it into the two tram tracks. As many farmers were using controlled traffic systems, they used the same tram tracks every year.

This means that seeds would find it difficult to grow there and, if they did, they would be trampled on during standard fields operations.

And if control was still necessary, it might be confined to the areas either side of the tram tracks, thus considerably reducing herbicide use and weed control cost over time.

The system can significantly reduce weed numbers over time

The device to do this is fitted to the rear of the combine and called a chaff deck. The system originated in Australia and was developed by farmers to help mechanically manage the problem of weed resistance.

Placing and concentrating all the chaff and weed seeds into the compacted wheel tracks meant that weed germination was reduced significantly.

And with an estimated 95% of the weed seeds coming into the combine exiting with the chaff, the system can significantly reduce weed numbers over time.

One such piece of equipment is the EMAR Chaff Deck. The manufacturers claim that the system significantly reduces weed seed germination and establishment because they are concentrated on compacted tracks, making them more likely to rot.

The system is not power hungry and has low running and maintenance costs. It can be easily removed for cleaning or maintenance or it can be disconnected where chaff spreading is needed. Units can be retrofitted to most combines.

Redekop Seed Control Unit

Another piece of technology attempting to do a similar job, but in different way, is Redekop’s Seed Control Unit.

This also channels the chaff and weed seeds through it and it effectively mills and destroys weed seeds before they come back out of the combine.

The Redekop seed control unit fitted to a combine mills all the seeds that travel in the chaff before they leave the machine.

This unit requires slightly more power to mill the chaff. On exit, the fine material is blown back into the straw and either windrowed or chopped and spread across the cutting width.

The manufacturer claims that the unit will destroy up to 98% of harvested weed seeds that enter the combine.

Again, this year-on-year reduction in the return of weed seeds (and volunteer crop seeds) will result in reduced herbicide requirement over time and reduce the pressure for resistance development.