Residual activity important when choosing herbicides for sandy soil

For any farmer, controlling stubborn weeds is a nuisance. But for many Southern Ontario farmers who have sandy soil, it's an all-out battle.

The porous particles that make up sandy soil can allow herbicide treatments to move below the root zone before they have a chance to take effect on the target weeds.

So what's a sandy soil farmer to do?

According to BASF technical specialist Trevor Kraus, residual activity is an important factor when choosing which herbicide to use for sandy soil. "Applying a herbicide that has residual characteristics is one of the best ways to protect yield. Plus it provides flexibility for an in-crop application of glyphosate," he says.

Because most weeds germinate within the top two inches of soil, residual activity insures the herbicide application stays where it is most effective: on the surface. Herbicides that adhere to more dense compositions, such as a loam or clay soil, often move too quickly in sandy soil rendering them less effective It can also cause crop injury and rob yield, especially if the herbicide comes into contact with developing crop roots.

"The soil surface is where that herbicide needs to be in order to control active weeds," says Kraus. "A product that will adhere to the surface of the soil will give longer lasting control against shallow germinating weeds."

Cambridge-based grower Brian Domm understands the unique needs of sandy soil first-hand. Early season grass control is a top concern for his corn and soybean crops. During the 2011 crop year, Domm used new Prowl H2O on 1500 acres of corn and 1500 acres of soybeans because it touted residual activity. "We have a lot of sandy soil mix on the farm and Prowl H2O did a very good job on controlling grasses in that type of condition. The multiple modes of action are really working well for us."

Registered in 2010, Prowl H2O contains an improved formulation offering less odour and reduced staining than the original Prowl EC. The product works by binding itself to coarse soil particles offering effective, early season grass control.

In side-by-side trials, Kraus and his team identified that the residual activity in Prowl H2O made it a good option for sandy soil.

"When we applied other herbicides to sandy soil trials, the leaching movement was quite obvious and allowed grass weeds to escape the herbicide treatment," says Kraus. "On the Prowl H2O treatment though, the product remained on the surface where it was most effective in controlling weeds."

Kraus advises growers to identify which soil types are recommended for any herbicide as part of an effective weed management program.