Weed seed moves in dirt

Production Blog

When Palmer amaranth first fought back against glyphosate in the South a few years back, a bunch of midwestern farmers traveled that direction to see if the horror stories were real. Many shoes were left behind after that visit.

Joe Ikley recently proved why ditching that footwear was a smart move when he scraped the dirt off some muddy work boots and waited to see what would grow. Palmer amaranth (pigweed), grasses and hairy nightshade all emerged.

“We’d been flagging off a new research site in muddy conditions,” said Ikley, a North Dakota State University weed scientist. “We planted the mud from two pairs of boots in a greenhouse flat.

“It really wasn’t all that much mud. What it shows though is that it doesn’t take much to move weed seed,” Ikley said.

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Confinement livestock producers long ago took a hard look at biosecurity measures to protect against disease. Showering and wearing disposable boots and overalls were common requirements if you wanted to get inside a hog building. As my father used to delight in telling less-informed visitors: “Those boots aren’t to keep you clean, they are to protect my pigs.”

In another incident on the home farm, we noticed a new, gnarly weed that tried to gain a foothold in our pasture after buying some sheep from Oklahoma. Several years ago, I took a load a compost from a local cattleman and inherited a super aggressive spiny amaranth issue.

I can also attest that my Golden Retrievers are as accomplished at snagging weed seeds as they are tennis balls.

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None of this surprises Ikley. His idea to plant his muddy boot discard was to make a point to his own field staff about the need for more biosecurity. “We often talk about being careful about moving equipment, especially combines since they bring in a lot of seed that gets trapped in a lot of areas,” Ikley said.

Weed scientists often suggest harvesting your cleanest fields first and to save those where herbicide resistance is a known fact to the end. Find proper cleanout procedures between fields and instructions for deeper clean outs here: https://www.ag.ndsu.edu/…

“But, I think we need to start talking more about planters and cultivation equipment. Our little experiment highlights that anything that moves any soil will also move some weed seeds — and that includes our own boots,” he added.

That has implications for crop scouts, weed hoeing crews and even, curious ag journalists. Where your boots leave footprints, they could also spread weed seeds.

How to Kill Weed Seeds in Soil [5 Easy Methods]

To kill weed seeds in soil you will have to apply one or more of the following methods:

  • Heat soil to temperatures high enough to kill weeds seeds
  • Force seeds to sprout and destroy growing weeds
  • Apply chemical or natural weed killers that prevent weeds from sprouting
  • Use flame weeding to destroy weeds and seeds at once
  • Layer mulch in garden areas to suppress weed sprouting and attract insects that eat seeds

With this arsenal of tricks for killing weed seeds before they sprout, you can stop the spread of weeds in both your lawn and garden.

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5 Tips for Killing Weed Seeds

Rather than spending time and effort battling weeds as they sprout, attack weeds at the source by killing weed seeds. Each of these methods destroys weed seeds, which ensures you won’t have to battle recurring weed invasions. Try these ways to get rid of weed seeds yourself.


Soil solarization is a very powerful method for killing weed seeds. Weed seeds begin to die if soil temperatures surpass 108 degrees, with full seed death ensured by soil surface temperatures of 140 degrees or more. Solarization uses clear plastic tarps to trap heat at the soil surface, killing weed seeds within the tarped area. To solarize an area, follow these steps:

  • Clear the area of all vegetation through use of a hoe or other garden implement. Remove any woody stumps
  • Till the soil to further break up any weed root systems left behind.
  • Rake away all vegetation residue
  • Water the tilled and cleared soil with a garden hose until it is damp.
  • Lay a sheet of clear plastic over the area. Weigh it down tightly at the edges
  • Leave the plastic in place for at least two months.

Solarization is the best method to reclaim a weedy garden or other area. It is a “clean slate” for your soil, because seeds will be destroyed by the solar heat trapped beneath the plastic.

It is typically tough to implement solarization in large areas and is not usually suitable for use in lawns, where you may want to preserve grass or other plants. Pre-emergent weed killers and flame weeding are much better for use in lawns.

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Till and Kill

Weed seeds can lie dormant in soil for decades and are only “activated” when brought to within an inch of the surface. One method to rid soil of dormant weed seeds is to force these dormant seeds to sprout, then attack them with a powerful natural or chemical weed killer. To do this:

  • In spring, till the affected area. Tilling brings dormant seeds to the surface
  • Water the area for 1–2 weeks with a sprinkler or soaker hose
  • When weeds begin to sprout, apply the weed killer of your choice

This is another “clean slate” method, where you force weed seeds to show themselves and then kill young weeds before they mature and cast seeds. Because of the invasive tilling step, it is not best used in areas with desirable grasses and plants.

Use Pre-Emergent Weed Killer

Pre-emergent weed killer stops weeds in their tracks. It works by attacking weed seeds just as they begin to germinate, killing them before they even poke above the surface. It’s a weed killer so good, the only sign it’s working is that there will be no new weeds at all.