Specialist: Residual Herbicides No Match For Wet Soil

Soil-applied herbicides can knock out a grower’s toughest weeds but the chemical products are no match against soggy fields, says Bill Johnson, Purdue University Extension weed specialist.

A wet early spring has made it difficult for crop producers to apply soil-applied, or residual, herbicides to their fields ahead of planting. Producers should not push the envelope on herbicide treatments while fields are holding too much water, Johnson says.

“If it’s dry enough to plant, it’s dry enough to spray,” Johnson says. “We don’t plant our crops when soil conditions are such that we’re dropping the seed into mud, so we don’t want to apply our herbicides onto muddy ground, either.

“We run into challenges when we apply to fields that are too wet. One, we’re going to leave ruts in the field. Two, all herbicides are labeled such that they cannot be applied to standing water anyway. If we want to get the most out of our soil-applied herbicides, we need to put them on in conditions similar to those in which we would plant the crops.”

As their name suggests, soil-applied herbicides are sprayed on the soil before, during or just after crops are planted. While too much water nullifies their effectiveness, most residual herbicides need some soil moisture in order to work properly.

The herbicides are activated by moisture within the soil and are then absorbed by weed seedlings. Weed growth stops or is stunted, leading to plant death shortly after it emerges.

“A residual herbicide will have activity in the soil anywhere from about one to six weeks after application, depending on the product that you use,” Johnson says. “So what you essentially get, then, is herbicide activity that you don’t really see, because you have fewer weeds coming up. The weeds that do emerge from that residual system are going to be a little bit easier to control with your post-emerge herbicides.”

Excessive wetness isn’t the only challenge to using soil-applied herbicides. Johnson say growers should be careful to:

  • Choose the right residual product. “You have to know which weeds you’re going after,” Johnson says. “The most effective residual herbicides are going to be matched to the weed species that are in that field. For instance, if you have a giant foxtail weed problem, using a broadleaf herbicide is not going to be of much value in that field. You want to use a herbicide that’s active against grass weeds.”
  • Apply at the proper carrier volume. Johnson says glyphosate is one of the few foliar herbicides that works well at carrier volumes of 15 gallons per acre or less, which is why it is often tank mixed with residual herbicides. Contact herbicides, such as paraquat or Gramoxone, require 15-20 gallons per acre, he said.
  • Avoid applying in windy conditions, to prevent spray drift.
  • Rotate between products and weed control practices, to minimize the development of herbicide resistance.

“More than 90 percent of our soybeans and 70 percent of our corn are glyphosate- or Roundup-tolerant crops, so it’s going to be important for us to treat that technology as an investment,” Johnson said. “We want to keep that technology around for as long as possible, and the way we do that is to minimize selection pressure for glyphosate-resistant weeds.

“Using the appropriate residual herbicide on your worst weed problems and then saving glyphosate for the post-emerge cleanup treatment, is going to be the best way to protect crop yields and slow the development of glyphosate-resistant weeds.”

For more information on weed control in agricultural crops, visit the Purdue Weed Science Web page.

(Source: Purdue University)

Leave a Reply

Herbicides Stories
HerbicidesScouting Key To Next Season’s Soybean Herbicide Program
August 12, 2014
When growing soybeans, growers need to think ahead to stay one step ahead of weeds. That means examining weed threats and evaluating which herbicides work best. Read More
Winter Wheat
HerbicidesArysta Touts Burndown Herbicide For Brome Management In Wheat
June 4, 2014
Arysta LifeScience North America recommends PRE-PARE Burndown Herbicide for effective brome management in winter wheat. Read More
HerbicidesFall Herbicide Applications More Effectively Manage Resistant Italian Ryegrass
May 14, 2014
Field studies show that a fall application of certain herbicides before weed emergence, leads to more successful crop planting and weed control in spring. Read More
Waterhemp in soybean stubble
HerbicidesThe Weed Resistance Problem: A Matter Of Billions
April 1, 2014
Not only is the amount of money being spent to control these yield robbers high, but the toll it has taken on the human population is growing lager by the day. Read More
Top 100 Articles
CropLife 100BRANDT Commemorates National Ag Day
March 20, 2015
The Illinois agriculture community gathered at BRANDT global headquarters on March 18 to celebrate National Ag Day behind this year's theme Sustaining Future Generations. Read More
Wheat Growers, North Central Farmers Elevator Pursue Merger
CropLife 100Wheat Growers, North Central Farmers Elevator Pursue Merger
March 3, 2015
Two CropLife 100 retailers — South Dakota Wheat Growers (ranked No. 11) and North Central Farmers Elevator (No. 19) — have entered into a Letter of Intent to unify the two companies into a newly named cooperative. Read More
Growmark Group
CropLife 100GROWMARK In 2015: Back, To The Future
March 2, 2015
The nation’s third largest ag retail organization is simultaneously moving forward while remembering its past. Read More
CropLife 100Pinnacle Expands Sanders Brand In The South
February 27, 2015
Pinnacle has acquired Hopkins Seed and Chemical in Qulin, MO, which expands the company's Sanders brand to nine Southern states. Read More
CropLife 100Pinnacle Launches New Providence Agriculture Location In Indiana
February 27, 2015
Pinnacle Agriculture Holdings — ranked No. 6 on the CropLife 100 — has established a new retail location in New Castle, IN, which will operate as part of Pinnacle's Providence Agriculture brand. Read More
Carl Casale of CHS
CropLife 100Cooperative CHS Returns $518 Million To Owners
February 23, 2015
The 2015 cash return to owners is based on CHS net income of $1.1 billion, the company's second highest on record. Read More
Latest News
Industry NewsH.J. Baker Creates, Fills New Pacific Northwest Sales P…
March 30, 2015
H.J. Baker announced today that Gary Bingham has joined the company’s Crop Performance Division to further deepen its sales portfolio Read More
Algal blooms
StewardshipStudy: Algae From Clogged Waterways Could Be Used As Bi…
March 30, 2015
Water-borne algal blooms from farm fertilizer runoff can destroy aquatic life and clog rivers and lakes, but scientists are reporting Read More
Young corn plants
Stewardship4R Nutrient Stewardship Summit Coming To DC
March 30, 2015
The annual 4R Nutrient Stewardship Summit will be held on May 12 in Washington DC. The summit will include a full Read More
FungicidesSyngenta Suing Willowood Over Azoxystrobin Fungicide
March 27, 2015
Syngenta announced today that it has sued agrochemical maker Willowood, LLC., for patent and copyright infringement, as well as unfair Read More
ManagementRetail Week: The Future Of Mycogen Seeds; The 4Rs At Na…
March 27, 2015
Editors Eric Sfiligoj and Matt Hopkins discuss recent trips, including a look at the future of Mycogen Seeds at Dow Read More
Eric SfiligojMonsanto Hears The WHO
March 27, 2015
Another challenge to the safety of glyphosate, and the responses from supporters and opponents, calls to mind a classic Dr. Seuss story. Read More
Industry NewsMonty’s Plant Food Expands Sales Team
March 27, 2015
Monty’s Plant Food Company, a leader in natural soil enhancement and  plant fertility products, has hired Andrew Bullock as a Read More
Crop InputsSyngenta Louisiana Plant Poised For 2015 Production
March 26, 2015
As the 2015 planting season gets underway, growers across the country will need crop protection products to combat pests and Read More
Lake Erie Nutrient Stewardship
LegislationOhio Lawmakers Finalize Phosphorus Restrictions
March 25, 2015
State lawmakers on Wednesday finalized new rules designed to curb toxic algal blooms on Lake Erie, calling the regulations a major step forward in addressing the problem. Read More
Spreaders17 Fertilizer Spreaders For 2015
March 25, 2015
Manufacturers shoot for versatility and accuracy in this year's crop of fertilizer spreaders. Read More
Industry NewsMonty’s Hires Mid-South Product Consultant
March 25, 2015
Monty's Plant Food Co. has hired Matt Woodring as a Product Consultant for portions of Central Kentucky and Tennessee.    Read More
StewardshipMapShots Integrates With DriftWatch
March 23, 2015
Growers and agricultural providers using AgStudio FARM and AgStudio PRO can now view vital information about specialty crops and apiaries through a recent integration with the DriftWatch Specialty Crop Site Registry from FieldWatch, Inc. Read More
Crop InputsWorld Health Organization Report Contradicts Scientific…
March 23, 2015
A new report from the World Health Organization has classified glyphosate with a “2A” rating as a probable carcinogen, a Read More
Eric SfiligojSeed Treatment Stays Necessary
March 20, 2015
Grower-customers looking to scale back spending in 2015 won’t consider seed treatment, say experts. Read More
HerbicidesMARCH MADNESS: Industry Rallies Around Glyphosate Safet…
March 20, 2015
A newly published report from the International Agency for Research on Cancer (IARC) classifies the herbicide glyphosate as a "2A-rated possible carcinogen" and the ag industry responds by circling the wagons. Read More
ManagementRetail Week: Precision survey, a technology acquisition…
March 20, 2015
Editors Paul Schrimpf and Eric Sflilgoj discuss recent travel, the upcoming precision adoption survey, and an unusual sighting at a Read More
CropLife 100BRANDT Commemorates National Ag Day
March 20, 2015
The Illinois agriculture community gathered at BRANDT global headquarters on March 18 to celebrate National Ag Day behind this year's theme Sustaining Future Generations. Read More
Crop InputsBioSafe Launching TerraGrow Soil Inoculant
March 20, 2015
TerraGrow is a blend of beneficial bacterial and fungal spores and nutrients carefully designed to promote healthier soil and crops. Read More