Cornell study - sawdust as eco-friendly weed control

By Blake Jackson

Cornell researchers are exploring a new weapon in the fight against weeds: sawdust. A recent study published in Weed Science investigated the effectiveness of adding carbon to soil, in the form of sawdust and rye hay, to control weeds in corn and soybean fields.

Traditional methods like tilling and herbicides often come with drawbacks. Tilling disrupts soil structure and promotes erosion, while weeds can develop resistance to herbicides.

“But there are other ways to manage weeds that are based on general principles of soil biology,” Kao-Kniffin study author and professor at Cornell. “Adding carbon to soil triggers a cascade of microbial processes that can work in favor of weed management, if it’s applied at the right time.”

The research team conducted field experiments in 2020 and 2021. They compared plots with sawdust or rye hay additions to control plots that were hand-weeded or left untouched.

The study found that sawdust significantly reduced weed growth in soybean fields, with minimal impact on soybean growth itself. Soybeans fix their own nitrogen, so they may not compete with microbes for the nitrogen immobilized by the decomposing sawdust.

In contrast, rye hay, containing its own nitrogen source, led to more weed growth in soybean fields. Corn, which requires external nitrogen, showed a similar pattern.

While sawdust somewhat inhibited weeds in cornfields, rye hay addition led to the most weed growth but also the highest corn yield in the first year, likely due to the available nitrogen in the rye hay.

Microbial activity, measured by respiration levels, increased in plots with both sawdust and rye hay amendments in both corn and soybeans.

The study suggests that farmers could time carbon applications to coincide with weed germination for maximum weed suppression. This research offers a promising eco-friendly approach to weed control, warranting further investigation.

The study was supported by the U.S. Department of Agriculture and the Foundation for Food and Agriculture Research.

Photo Credit: cornell-university