Harrington Seed Destructor shows dramatic impact on weed control

An Australian innovation, the integrated Harrington Seed Destructor (iHSD), successfully intercepts and destroys weed seeds by crushing them during grain crop harvest and could help reduce herbicide use in the future.

As grain harvesters capture and sort weed seeds the grain harvesting process presents an excellent opportunity to intercept and destroy weed seeds by damaging them as they exit the grain harvester in the chaff fraction.

The iHSD works on any seed which has not been shed at harvest, helping to reduce the seed-bank, explains agronomist Peter Newman, who is a member of the Australian Herbicide Resistance Initiative communication team.

This results in a reduction in the weed load the next season, which in turn reduces the pressure on chemical means of control and herbicides at-risk because of increasing weed resistance, he says. Most crop weeds are annuals that rely on annual seed production for long-term persistence, he explains. Crop and weed seed maturation in many species is synchronised and, therefore, at grain harvest both weed and crop seed are collected by the harvester.

Modern grain harvesters are efficient at sorting weed seed from crop grain, with the weed seeds returned to the field, primarily in the chaff fraction.

For example, annual ryegrass which is a globally important weed of grain crops, retains most seed heads intact and attached to the plant at the same height as the crop seed heads at grain harvest. Some 95 per cent of ryegrass seeds pass intact through the grain harvester to be returned to the crop field in the chaff fraction, therefore perpetuating an ongoing weed problem.

There are few mechanical options for growers to take action on weeds at harvest, with many of those in Australia choosing to collect the chaff and undertake narrow windrow burning.

“Often we spend a fortune controlling the weeds during the growing season, only to return them to the field at harvest so we have something to spray next year,” says Mr Newman.

Research has shown that using a cage mill- based chaff processing unit consistently destroyed weed seed infesting grain crop chaff fractions. The construction of the iHSD incorporating this unit had more than 95 per cent weed seed destruction efficacy when used during commercial harvest of three major grain crops, wheat, barley and lupin. One of the further benefits of the iHSD is that by removing need for autumn burning, and by returning the chaff to the ground, nutrients remain in the paddock for the next year’s cash crop.

Originally the HSD was trailed, but the updated model is mounted on the back of the harvester. Although most of the work has been done to date using the largest classes of combines known in North America and Australia as the Claas 8, 9 and 10, as long as the harvest has a large enough engine it can be retro-fitted to any make, he notes.

Looking back at the evolution of the iHSD, early models of the iHSD were plagued with reliability issues. However, says Mr Newman, these have mostly now been resolved and he is hoping for a good harvest this year. There are, of course, some slight drawbacks involved with using this method to keep weeds down, he notes. For example, using the new machinery also increases fuel use of the harvester, reduces capacity and can also slow harvesting down, he says, adding that his could be a problem in countries with short harvesting windows because of climate and weather. Moreover, as with all investments of this kind, there is also a capital cost of purchasing the device, points out Mr Newman. Moreover, as a machine, it needs to be properly maintained to work efficiently.

Nevertheless, the iHSD has the potential of making a dramatic impact on global grain production by providing the unique combination of effective weed control with complete retention of grain crop harvest residues, he says.

“It is well suited to high production farms, particularly where wild radish and annual ryegrass are the most prevalent.

Only herbicides offer this same combination of highly effective
weed control and complete residue retention in large scale grain crop
production systems, the iHSD company claims.

A short online survey conducted by Australian Herbicide Resistance Initiative (AHRI) and WeedSmart on Twitter showed that many grain growers are planning to adopt chaff lining, chaff tramlining or using one of the seed destroying mills. This illustrates that they are moving away from doing nothing and windrow burning. While AHRI notes that results may have a little bias as it was completed by growers who were already following WeedSmart, it says the results were still extremely encouraging.

It has yet to be trialled with the black-grass, which is plaguing many cereal growers in northern Europe. This weed flowers in April-May and mainly sheds its seeds before harvest.

Mr Newman stresses that although the iHSD is not a silver bullet, by providing another tool to manage weeds and resistance, it can make a big difference to growers across the different continents.