Destroying weed seed left

Harvest Weed Seed Control

At harvest time, weeds that have escaped season long management often have mature seed still attached to the parent plants. These weed seeds can enter the combine along with the cash crop, exit the back of the combine as chaff (small plant pieces and weed seeds), and be spread across the field, as well as from one field to another. It seems a waste to spend all year spraying weeds with expensive herbicides only to reward the survivors at harvest by spreading their weed seeds out for next year.

An excellent way to stop weeds in their tracks is to collect these weed seeds at harvest and either destroy them or deposit them in a known location where they can be monitored and controlled later. Soybean, wheat, and other crops harvested with a grain header are ideal choices for harvest weed seed control (HWSC). Other crops such as cotton and corn need further equipment development to make HWSC a viable option.

If you are considering adding harvest weed seed control (HWSC) to your weed control program there are excellent resources on the WeedSmart website to help guide you through the initial decisions and the implementation of this important weed control tool.

3 steps to get it working for you

1. Decide which system fits your farm best.

2. Get maximum weed seed into the header.

3. Know how to manage the collected weed seed.

What is Harvest Weed Seed Control?

Choose The Best System For You

Which system is best?

HWSC is being rapidly adopted in Australia and other countries around the world. There are six systems currently being used on Australian farms and they have been initially developed by farmers.

Research has demonstrated that all are very effective weed seedbank management tactics for a range of weed species, achieving over 80 percent control and for some nearly 100 percent.

See HWSC in Action

Over 80% weed control for species that retain seed at harvest

Crop residue management

There are six systems currently used to collect and manage weed seed at harvest. They can be grouped according to the way crop residue is managed: chaff only or chaff + straw.

CHAFF ONLY

Chaff carts are a tow-behind unit on the combine that collects the weed seed-laden chaff, which can then be placed into piles that are later either grazed by livestock, burnt, or both and sown through the following season. Chaff carts are often chosen for use on mixed cropping and livestock farms in Australia as the chaff is an excellent livestock feed; however, spreading manure back onto fields can allow for further seed spread.

Chaff lining funnels the chaff and weed seeds into narrow rows behind the combine, where the residue is left to overwinter. The weed seeds are exposed to natural elements that can lead to weed seed decay and predation. Typically a follow-up herbicide application is required. – Chaff lining is usually considered a good entry-level HWSC option.

Chaff decks (chaff tramlining) are similar to chaff lining, but place the chaff in one or both of the combine’s wheel tracks. The added compaction from the wheels can be beneficial in controlled traffic systems.

Impact mills run the chaff through a mill that pulverizes (destroys) the weed seed, which is then spread across the fields. This technology is usually considered the ultimate in HWSC.

CHAFF + STRAW

Bale direct collects all the crop residue directly from the combine and compacts it into large bales suitable for sale.

Narrow windrow burning collects all of the crop chaff and straw residue, and funnels it into narrow rows in the field. These rows are burnt to destroy the weed seed. This method is effective but removes all of the crop residue from the field.

Learn More About Each System in This Research Report

Calculate the cost

While each HWSC tactic is similarly effective in collecting weed seeds , they vary considerably in capital and ownership cost, nutrient removal costs, operational costs, and labor costs. Some HWSC tactics involve the purchase of substantial machinery – such as an impact mill, chaff cart, or chaff deck – but the operational and labor costs might be lower than methods such as narrow windrow burning, which involves low set-up costs but higher nutrient losses and labor costs associated with burning. Chaff lining is often chosen as the best entry-level tactic that requires minimal set-up cost, no additional labor and minimal nutrient loss or redistribution. To calculate the cost of each method for your farm you can use a calculator developed by WeedSmart’s Peter Newman. Download the calculator or learn more @ Calculating the cost of HWSC for your farm.

Keep Weed Seed Out of Your Harvest

Keeping your corn and soybean fields free of unwanted weed seed is an important task, as seeds in your harvest can lead to dockage at elevators. You’ve worked hard this season to keep your fields free of unwanted weeds, especially during a year where weed escapes might be more prevalent because of weather challenges. To get every possible bushel out of your acres, you’ll need to be extra vigilant about what goes into the combine this season.

If you do see weeds in your fields at harvest, consider some of these harvesting tips outlined by the United States Department of Agriculture:

  • Avoid harvesting crops that are located in areas that are densely populated with weeds – the risk of spreading weed seed is likely not worth the bushels you might get from that area of the field.
  • Adjust your combine’s cutting height settings to minimize the amount of weed seed that is harvested. Consulting your combine provider will help determine the right height for your field conditions.
  • Regularly clean your farm equipment between harvesting different fields to avoid contamination from weed seed.
  • Destroy all weed seed that is left in the field after harvest to prevent it from entering the soil seed bank. Burning weed seed is a common way to get rid of it.

Before taking your crops to the elevator, consider these additional precautions:

  • Examine corn and soybeans for weed seed upon arrival.
  • Separate weed seed from corn and soybeans through mechanical cleaning or other means.

Weed scientists are recommending a zero tolerance for weed escapes. Ridding fields of weed presence not only benefits your yield potential, but also lowers the chance of future seeds getting added to the seed bank. Incorporating a burndown harvest aid like Gramoxone ® SL 2.0 herbicide helps target difficult-to-control weeds and keeps the combine running smoothly.

Taking these preventive actions to minimize contamination from weed seed will help ensure the hard work you’ve put into this season pays off, and will help prevent weeds from growing on your farm in the future.

To learn more about managing weeds while preventing resistance development, visit ResistanceFighter.com.

Sign up for the Know More, Grow More Digest to receive twice-monthly agronomic e-mail updates pertinent to your area.

All photos are either the property of Syngenta or are used with permission.

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.

Table of Contents

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.

Solarization

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.

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.