AMS Boosts Late Weed Control

With planting delays pushing back glyphosate applications, many growers will be treating bigger weeds, which are tougher to control. Water conditioners are a type of herbicide adjuvant that can boost performance, but how do you choose the best one?

Researchers say the ammonium sulfate (AMS) content is key.

Glyphosate and other herbicide labels recommend at least 8.5 pounds (lbs.) of actual ammonium sulfate for every 100 gallons of spray solution. Harder water or more difficult-to-control weeds may require up to 17 lbs. But many premixed water-conditioning adjuvants on the market today deliver less than half the minimum recommended rate.

According to Mark Bernards, weed specialist with University of Nebraska, these adjuvants just don’t have enough AMS to consistently improve weed control. In many cases, performance is no better than glyphosate alone.

In a recent University of Nebraska trial, two out of seven AMS alternatives were as effective as AMS when added to glyphosate for velvetleaf control. The other five resulted in weed control that was equal to — or lower than — weed control from glyphosate alone.

Likewise, the best velvetleaf control in a 2005 Kansas State University study came from glyphosate plus liquid AMS, followed closely by three adjuvants with high AMS content. The remaining six adjuvants had low or no AMS content and resulted in control roughly equal to or less than glyphosate alone.

Bernards says glufosinate has responded similarly to the addition of AMS and low-AMS substitutes.

The take-home seems simple enough: Make sure your herbicide adjuvant contains the minimum recommended rate of AMS. But according to Bernards, few aspects of glyphosate-based weed control systems have generated as much confusion as the role of AMS.

“Shortly after glyphosate was commercialized as Roundup herbicide, farmers and scientists recognized that its ability to kill weeds was reduced when it was mixed with hard water, which was typical for many of the areas where it was being used,” Bernards says.

The problem was antagonism. Negatively charged glyphosate ions bind to positively charged calcium, iron, and magnesium ions — three minerals commonly found in hard water.

“After many years of testing with many different materials, most researchers concluded that AMS was the most consistently effective and economical approach to overcoming hard water antagonism,” says Bernards. If you add enough ammonium sulfate to the spray tank, then the hard water ions (calcium, iron, and magnesium) precipitate from the solution as sulfate salts, and the glyphosate ions bind to the ammonium ions instead of the hard water minerals.

“It’s more commonly used as a nitrogen fertilizer, but all of a sudden ammonium sulfate got a lot of attention for improving weed control,” says Dean Collamer, agronomist with Honeywell. “The hitch was that many granular grades were designed for large-volume fertilizer application — not for dissolving in herbicide spray tanks.”

To alleviate handling problems, suppliers came out with a profusion of AMS pre-mixes made with less AMS and more alternative ingredients, like defoaming agents and surfactants.

“To make sure that you’re using the best adjuvant with your glyphosate spray, ask your supplier for formulations that deliver the minimum required dose of AMS,” advises Bernards. “Alternatively, you can apply a dry sprayable grade of ammonium sulfate directly to your tank.”

Collamer says adjuvant formulators now have access to grades of ammonium sulfate that are free of impurities, easier to dissolve, and more stable in solution. Honeywell, for example, produces Sulf-N PRO soluble ammonium sulfate specifically for liquid applications.

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

Top 100 Articles

CropLife 100CHS: Driving Momentum To Help Farmer-Owners Grow
December 11, 2014
CHS Inc., the nation’s leading farmer-owned cooperative and a global energy, grains and foods company, must capture new opportunities to Read More
CropLife 100BRANDT, Verdesian Ink Distribution Agreement
December 9, 2014
The agreement grants BRANDT the exclusive right to sell and market Verdesian’s patented Steric chemistry in the Turf and Ornamental and eastern U.S. ag markets under the BRANDT Reaction product line name. Read More
CropLife 100CropLife 100: The Colors Of Custom Application
December 5, 2014
Although many color spray rigs are in the yards of the nation’s top ag retailers, the majority of them still come in only a few shades. Read More
CropLife 100Pinnacle Invests In Meridian Agriculture Distribution
December 4, 2014
Meridian will provide retailers with supplier-branded products and numerous opportunities to differentiate themselves from their competitors. Read More
CropLife 100CropLife 100: Entering A New Seed Era
December 4, 2014
The seed category has been re-vitalized during the past few years, and more good news (and varieties) are headed the industry’s way in 2015. Read More
CropLife 100CropLife 100: The Depressed State Of Fertilizer
December 3, 2014
Following downright giddy growth earlier this decade, fertilizer sales have fallen back down to earth the past two years. Read More

Latest News

Seed/BiotechKaren Arthur Joins AgriThority As Seed Treatment Produc…
December 19, 2014
Prior to joining AgriThority, Arthur directed research and development programs, overseeing laboratory and field research, to build the Valent U.S.A. seed treatment portfolio. Read More
EquipmentJohn Deere To Sell Crop Insurance Business
December 19, 2014
Deere & Co. has reached a definitive agreement to sell its crop insurance business, subject to regulatory approval, to Farmers Mutual Hail Insurance Co. of Iowa. Read More
Crop InputsNufarm Fills Regulatory VP Position
December 18, 2014
Nufarm announced today that Rob Schwehr has been promoted to the position of Vice President of Innovation & Regulatory Affairs for Nufarm Americas. Read More
Seed/BiotechReport: China Approves Viptera Corn, U.S. Officials Awa…
December 17, 2014
Chinese authorities have informed some agriculture industry officials the government has approved U.S. imports of a type of genetically modified corn developed by Syngenta. Read More
FertilizerMonty’s Plant Food Brings In New Sales Rep
December 16, 2014
Monty's Plant Food Company has hired Warren Kearns as its newest Sales Representative for the South Carolina area. Read More
EquipmentHagie Wins 2014 CropLife IRON Product Of The Year Award
December 15, 2014
The self-propelled sprayer maker has a hit on its hands with the new STS Series model. Read More
Syngenta
Seed/BiotechSyngenta Sees China Approving Contentious GMO Corn Soon
December 15, 2014
Syngenta will make an announcement when it receives official documentation from China that Agrisure Viptera corn, known as MIR 162, has been cleared for import. Read More
Crop InputsVerdesian Life Sciences Names Vice President Of Communi…
December 15, 2014
Amy Bugg will oversee the execution of all promotional strategies for the corporate brand and the complete product portfolio. Read More
StewardshipFarmers, Retailers Attend 4R Certification 4U Workshop
December 15, 2014
More than 160 farmers and ag retailer attended the “4R Certification 4U” workshop December 12 to learn more about the 4Rs of nutrient stewardship, water quality research in the area and cost-sharing opportunities. Read More
Matt Hopkins10 Best New Agriculture Apps For 2015
December 15, 2014
These new agriculture apps are certain to help ag professionals do their jobs more efficiently in 2015 and beyond. Read More
ManagementARA Learnings, Retail Buying Intentions: Welcome To Cro…
December 12, 2014
This informal video program puts news and events effecting retailers into context, and features Editors Paul Schrimpf and Eric Sfiligoj. Read More
Seed/BiotechMonsanto Herbicide-Tolerant Technology Closer To Commer…
December 12, 2014
The final EIS moves Monsanto one step closer to the introduction of Bollgard II XtendFlex cotton and Roundup Ready 2 Xtend soybeans, paving the way to provide access to dicamba-tolerant soybeans and cotton. Read More
Seed/BiotechUSDA Issues Final Environmental Impact Statement On Her…
December 12, 2014
The USDA Animal and Plant Health Inspection Service (APHIS) is issuing a final environmental impact statement on varieties of cotton and soybeans that have been genetically engineered for resistance to several herbicides, including the one known as dicamba. Read More
CropLife 100CHS: Driving Momentum To Help Farmer-Owners Grow
December 11, 2014
CHS Inc., the nation’s leading farmer-owned cooperative and a global energy, grains and foods company, must capture new opportunities to Read More
LegislationARA Applauds CFATS Passage Prior To Holiday Adjournment
December 11, 2014
The streamlined bill provides a four-year authorization of the CFATS program and guidance to DHS on key issues of chemical facility security Read More
Seed/BiotechBayer CropScience’s ILeVO Approved By EPA
December 11, 2014
EPA has approved ILeVO, the only seed treatment that protects the root system against infections caused by the Sudden Death Syndrome fungus and has activity against dangerous nematodes. Read More
Biologicals in Emerging Markets Map.
Crop InputsBiocontrols Could Quadruple By 2025; Will Regulators Pl…
December 11, 2014
The European experience with GMOs offers caution — and a promise — for biologicals. Read More
Crop InputsBASF Donates $75,000 To Feeding America
December 10, 2014
The donation will support Feeding America’s National Produce Program, an initiative that helps with planning, transportation and logistics to ensure fresh produce deliveries to the 200 member food banks around the country. Read More