Be Aware Of Potential For Herbicide Carryover

The effectiveness of soil-residual herbicides at controlling weeds has been reduced due to the dry soil conditions in most of Illinois during the 2012 growing season. Associate professor of weed science Aaron Hager warned that these conditions also slow the rate of herbicide degradation, increasing the likelihood that herbicide carryover could damage rotational crops.

“Once a herbicide is applied, there is little that can be done to shorten the time it remains active in the soil environment,” Hager said. “Herbicide persistence depends on the interaction of the herbicide’s characteristics, the soil, and climatic conditions.”

Characteristics of the herbicide molecules affect its persistence in the soil. Some herbicides, such as thifensulfuron, have very little soil persistence whereas others, such as picloram, can persist for several months.

“Soil persistence can also vary among herbicides within a particular chemical family,” Hager noted. “For example, within the imidazolinone herbicide family, soil persistence of imazamox is much shorter than that of imazethapyr.”

Chemical, physical, and microbial soil properties also influence herbicide persistence. For some herbicides, soil pH is important because it impacts how much herbicide is available for plant uptake and how quickly it is degraded by hydrolysis.

“For example, atrazine is more available for plant uptake when the soil pH is approximately 7.0 or higher,” Hager explained. “It also persists longer because the rate of hydrolysis slows at higher soil pH values. The degradation rate of many sulfonylurea herbicides slows with high soil pH values. Imidazolinone herbicides persist longer in soils with low pH values.”

Physical properties of soils, such as sand, silt, clay, and organic matter content, affect herbicide persistence. Soils with high clay and organic matter content adsorb more herbicide onto soil colloids than coarse-textured soils or soils with less organic matter.

“Herbicide bound to soil colloids cannot be taken up by plants, move downward through the soil profile, or be degraded by microbes,” said Hager. “Rotational crops can be injured when water molecules displace these bound residues late in the season or in the following spring.”

Soil microorganisms degrade many herbicides; the speed of degradation depends on the levels, species and activity of microorganisms. They work most efficiently when there is adequate soil moisture. Under extremely dry conditions, microbial degradation can slow enough to allow the herbicide to persist into the next growing season.

What can be done to minimize the risk of injury to rotational crops from herbicides applied this season?

“Apart from a return to normal or above normal precipitation amounts, there is little that can be done to accelerate herbicide degradation at this point,” said Hager. “Degradation requires time and moisture.”

Shallow tillage can help distribute herbicide more evenly across a field, but it will do little to accelerate herbicide degradation in extremely dry soil. If planting is early next season, the likelihood of crop injury from herbicide carryover could increase.

Planting the same crop that was planted in 2012 in the following season would eliminate the potential for crop injury from herbicide residues. This option may not be feasible for every situation where herbicide carryover is possible, but it warrants some consideration. If crop rotation must occur where there is a risk of herbicide carryover, delaying planting as long as possible could allow time for additional herbicide degradation.

“Several producers have asked about the feasibility of planting a cover crop, fall forage crop, or small-grain crop after the 2012 corn crop is harvested or destroyed,” Hager said. Most herbicide labels indicate the amount of time that must elapse between application and planting the rotational crop. Labels of most corn herbicides also indicate an interval that must elapse between application and harvest for grain, silage, or grazing.

“In many instances, the interval between application and winter wheat planting will not be long enough this year,” Hager warned. “Small-grain crops can be sensitive to even small amounts of residue herbicides, such as atrazine, that remain in the soil.”

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
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

Trending Articles

Crop InputsPlatform Specialty Products To Acquire Arysta LifeScience
October 20, 2014
Once the acquisition is complete, Platform Specialty Products will combine Arysta LifeScience with previously acquired companies Agriphar and Chemtura Crop Solutions. Read More
Seed/BiotechMonsanto Offers New Support For Ferguson, Area Communities
October 8, 2014
Monsanto Co. has committed $1 million in new support for several collaborative efforts in Ferguson, MO, and surrounding communities in North St. Louis County. Read More
Seed/BiotechUnapproved Genetically Modified Wheat Found In Montana
October 3, 2014
USDA reports that one year after discovery of Monsanto's unapproved wheat in a single Oregon field disrupted U.S. wheat export sales, the GMO wheat has again been found in Montana. Read More
Equipment2014 Product Of The Year Voting
September 19, 2014
The deadline to vote for the 2014 CropLife IRON Product of the Year is October 31. Please cast your vote today to help us determine the winner. Read More
FertilizerFall Fertility 2014: Forecasting Fertilizer Use
September 7, 2014
Great crops this year have tapped the soil, and fall work is definitely called for, but how challenging will that get? Read More
CropLife 100CHS To Build $3 Billion Fertilizer Plant In North Dakota
September 5, 2014
The fertilizer plant in Spiritwood will be the single largest investment in CHS history, as well as the single largest private investment project ever undertaken in North Dakota. Read More

Latest News

CropLife 100GROWMARK Announces Appointments In Plant Food Division
October 22, 2014
GROWMARK, Inc. has announced the three key staff changes in its Plant Food Division. Read More
CropLife 100GROWMARK Appoints New VP Of Finance And Risk Management
October 22, 2014
Wade Mittelstadt has been named GROWMARK Vice President, Financial and Risk Mangement, effective December 1, 2014. Read More
FungicidesEPA Approves BASF In-Furrow Corn Fungicide
October 22, 2014
Field trials show Xanthion In-furrow fungicide provides more rapid emergence, extended residual control and improved seedling health than untreated crops. Read More
EquipmentAgraScout App Available At No Cost To Universities
October 21, 2014
AgraScout, a fast and easy to use mobile crop scouting app, is now available at no cost to University students, Read More
LegislationNew Farm Bill Program To Provide Relief To Farmers Affe…
October 21, 2014
The USDA has implemented a new Farm Bill initiative that will provide relief to farmers affected by severe weather, including drought. Read More
ManagementGreenfield Scholars Program Aims To Sustain Agronomy Wo…
October 21, 2014
The program encourages talented students to study agronomy, crop and soil sciences while cultivating networks to develop the necessary workforce to sustain the profession. Read More
Paul SchrimpfPrecision Ag: Taking It To The Hill
October 21, 2014
A new coalition took the good news message of precision agriculture to Washington, DC, last month. Read More
ManagementUSDA Awards $18 Million In Small Business Research Gran…
October 21, 2014
The grants will provide high quality, advanced research and development that will lead to technological innovations and solutions for American agriculture. Read More
FertilizerCF Industries Terminates Merger Discussions With Yara I…
October 21, 2014
CF Industries Holdings and Yara International have terminated their discussions regarding a potential merger of equals transaction. Read More
Seed/BiotechSyngenta Ranked A Top 10 Biotech Employer For Third tim…
October 20, 2014
Syngenta ranked in the top 10 among the world’s top biotech employers, according to an annual survey conducted by Science magazine. Read More
CropLife 100Wheat Growers Break Ground For New Facility At Kennebec
October 20, 2014
Wheat Growers has broke ground for a state-of-the-art shuttle loader grain handling, fertilizer and agronomy facility in Kennebec, SD. Read More
FertilizerVerdesian Life Sciences Signs Agreement With Los Alamos…
October 20, 2014
Verdesian Life Sciences has signed a licensing agreement with Los Alamos National Laboratory to develop and market LANL’s latest nitrogen enhancement technology for plants. Read More
MicronutrientsStoller Group Announces Groundbreaking At New Office Bu…
October 20, 2014
Jerry Stoller, founder and president of Stoller Group, announced the groundbreaking at the site of the company’s future headquarters in Read More
Crop InputsBioSafe Systems Opens New Production Facility In Nevada
October 20, 2014
BioSafe Systems has completed construction of a state-of-art production facility in Sparks, NV, for its line of activated peroxygen products. Read More
Crop InputsPlatform Specialty Products To Acquire Arysta LifeScien…
October 20, 2014
Once the acquisition is complete, Platform Specialty Products will combine Arysta LifeScience with previously acquired companies Agriphar and Chemtura Crop Solutions. Read More
Seed/BiotechEPA Approves Dow’s Enlist Duo Herbicide
October 15, 2014
The Enlist Weed Control System, breakthrough technology to fight resistant and tough weeds, has received the long-awaited green light from federal regulatory authorities. Read More
MicronutrientsGypsum On Farms Could Help Keep Water Clean, Not Green
October 14, 2014
Gypsum, which has roots in the past as a farm soil treatment, also may have a bright future, and not just as a booster of crops but also as a protector of water. Read More
Photo credit: The United Soybean Board/The Soybean Checkoff.
Crop InputsVerdesian Grows Sales Staff
October 14, 2014
The new account managers will drive sales growth and support relationships with key customers in the plant nutrition and seed treatment and inoculants product categories. Read More