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Increasing Herbicide Volume To Sustain Control


Crop progress and conditions may call for higher carrier volumes if time permits.

A large percentage of the 2019 corn and soybean crop wasn’t planted on time. Spring planting delays and poor early-season growing conditions have many farmers entering mid-summer with concerns their crops have a lot of catching up to do. The problem is compounded in fields where weed pressures are rising.


The makeup of an effective post-emergence herbicide application changes considerably in a year like 2019. Weeds got a head-start on row crop progress where excess moisture and cooler-than-normal temperatures slowed or stalled early-season progress. As the crops reach toward the middle of summer, many farmers are examining ways they can adjust weed management strategies to maximize control before incurring crop damage.

Keeping herbicide effective

Increasing post-emergence herbicide application carrier volume is one way to manage weeds when they have had more time to grow than many late-planted crops. Higher carrier volume means applying herbicide will be more likely to provide adequate weed control.

“It’s all about timing and coverage. You want to spray when weeds are still very small but the taller your weeds are, the more coverage you need to hit all the growing points in the plants to effectively kill them,” said FAST AG Solutions Marketing Director Cody Fast, who’s also a Mountain Lake, Minnesota, farmer. “Coverage is becoming more and more important as farmers are battling resilient weeds  that need to be sprayed early with higher carrier rates.”

While it is true that with more spray volume comes more coverage, there is no single universal strategy for bumping herbicide volume, according to Purdue University Weed Science Professor Bill Johnson.

“Many post-emergence herbicides will have recommendations for droplet size, nozzle placement and ground speed,” he said. “On every herbicide label, there are specific instructions for all of these things to maximize the activity of the herbicide. You just need to read the label closely to maximize herbicide activity.”

Variables influencing higher carrier volume

The amount of carrier volume increase required to sustain control depends on a few factors. In addition to the size of the weeds in your fields, applicators should take into account previous applications.

“Producers who have been applying 10 or 12 gallons per acre will see a considerable difference if they go up to 15 gallons per acre,” Johnson said. “For the producer already applying 15 to 20 gallons per acre, the advantage of going to 25 gallons per acre may be less than the producer applying on the lower fringe of what’s labeled and effective. There’s not a one-size-fits-all answer.”

Time and equipment are major variables that determine the overall cost benefit and efficacy of increasing herbicide carrier volume. Many producers have been working against the calendar since the 2019 growing season started, and the time required to manage a higher-volume herbicide program should be considered in deciding if it will work in your fields.

“On the other end of the spectrum, if you’re cutting back on carrier volume, it’s done to help better manage time. If you have to bring fewer loads of water to the field, you will save time that way. The opposite is true when increasing volume,” Johnson said. “This year, the growing season has gotten so late and compressed, almost everyone is pressed for time. It often becomes an issue of time costs.”

Time and efficiency

Having more water readily available in the field can help ease the time crunch of increasing carrier volume. Operating a sprayer with a larger tank capacity is a way to ensure fewer interruptions to both application progress and transporting water to the field. FAST Ag Solutions pull-type sprayers — namely 9500T/TF and 9600N/TF models — offer tanks ranging from 1,050 to 2,400 gallons, enabling operators to work longer in the field between stops. That tank capacity translates to efficiency, which is at a premium this year, according to Fast.

“Everyone is so pressured by the conditions we saw early in the growing season and the resilient weeds we’re seeing now. We need to take advantage of every efficiency we can as we hit midsummer,” he said. “We can tie these sprayers’ larger tank capacities directly to our ability to make timely, efficient herbicide applications since you can cover more acres between fills with larger tank capacities. There is a lot of lost time spent mixing chemical and filling the sprayer so going from a 1,200- to a 2,400-gallon tank for example may give growers the opportunity to take better advantage of a tight application window. The 2019 crop is posing farmers a lot of challenges, and this is one way to overcome some of them.”

See more of the key specifications of FAST Ag Solutions pull-type sprayers and find out how they can help you spray your fields this summer.