A Q&A on chaff lining with Michael Flessner

What is chaff lining? 

Chaff lining is one of the easiest entry points to harvest weed seed control. A combine set up for chaff lining will condense the weed seeds that enter the combine header out through a narrow chute in the back, with the chaff fraction of the crop residue. 

That leaves a field’s worth of weed seeds lined up in narrow rows across the field, covering less than 10% of the field, as Michael Flessner, Virginia Tech Extension Weed Specialist explains in the video below.

What crops work best with chaff lining? 

Chaff lining was first developed in wheat, so it works well in that cropping system. But Flessner and other researchers are testing it in other crops, such as soybeans. Any crop harvested with a grain header could potentially work with chaff lining, Flessner notes.  

What equipment modifications does chaff lining require? 

First, in many combines, a baffle will have to be added to keep the chaff separate from the straw, Flessner explains. That way, straw can still be ejected evenly across the field, without the chaff and weed seeds. Second, a chute needs to be added to the back of a combine, to funnel the chaff and weed seeds out in narrow rows. See a visual of this process in the video below. 

Do chaff lines interfere with planting or crop growth? 

It depends on the size of the residue in the chaff lines, says Flessner. A residue-heavy crop like wheat can produce chaff lines that will reduce germination of any crop rows planted directly into them. In contrast, soybeans, which produce thinner chaff lines, have not caused this issue in his field work. 

What happens to the weeds? 

The weed seeds in those narrow chaff lining rows can still germinate, but at lower rates than they would when spread out across the field, says Flessner. Sitting in piles aboveground leaves those seeds vulnerable to changing weather, animal predation and other adverse germination conditions. They also compete against each other for resources. Normal broadcast herbicide applications work well to control those narrow bands of weeds that do emerge, Flessner adds. 

How can I build a chaff lining chute on my combine? 

Anyone with welding skills and materials such as sheet metal on hand should be able to create and install a chaff lining chute in a day’s time, to the tune of about $500 to $1,000, Flessner estimates. You can also buy chaff lining kits online from various manufacturers for about $5,000 to $6,000. You can find a guide to chaff lining chute creation from GROW here.

How does chaff lining perform in experiments? 

So far, Flessner’s field experiments show that chaff lining works well with both soybean and wheat rotations. Yields have been either the same or better in chaff lined fields compared to fields where conventional harvesting methods were used. Any reduced emergence within the narrow chaff lines seems to be offset by reduced weed pressure across the field, Flessner explains. 

Finally, chaff lining should lead to reduced herbicide use on a field, as the practice has lowered weed emergence by up to 60% in his experiments, which will shrink a field’s weed seed bank over time considerably. 

To hear further details on these questions and more, watch the full video of Flessner’s Q & A below. 

Find more details on chaff lining and other harvest weed seed control tactics at GROW’s webpage here: https://growiwm.org/how-harvest-weed-seed-control/ 

Video by Claudio Rubione, GROW

Article by Emily Unglesbee, GROW