What to Expect from Prevent Plant Fields

10:57AM Mar 02, 2020
2019 Prevent Plant Acreage Totals
Fertility, weed control and cover crop management should be top of mind.
( Source: USDA–FSA, Farm Bureau Calculations; Photo: Sonja Begemann )

The nightmare of 2019 is over — or is it? The long-tail implications of 20 million prevent plant (PP) acres have yet to play out. As spring nears, be mindful of these three challenges ahead for PP fields.

Manage Fallow Field Syndrome

As the name implies, when a field has no plant growth for an extended period of time it can affect the crop that follows.

When soils are cold, are saturated or lack active roots, which was the case for PP fields, it reduces biological activity, according to Ken Ferrie, Farm Journal Field Agronomist.

To improve soil biology on PP acres that did not get planted to a cover crop, Glen Newcomer applied 1,300 tons of chicken liter. The Bryan, Ohio, farmer hopes the litter will stimulate soil microbial activity.

“When dealing with fallow field syndrome, plants, especially corn and small grains, have trouble extracting nutrients [primarily phosphate and zinc] from the soil. The crop is stunted, and corn typically turns purple,” Ferrie explains.

To address phosphorus needs for corn to be planted in a fallow field, consider in-furrow starter.

”If you don’t have starter attachments, you can broadcast an extra 15 lb. to 20 lb. of phosphorus,” explains Antonio Mallarino, Iowa State University Extension.

Because leeching or other nitrogen loss was possible this past fall, Mallarino says spring and in-season nitrogen will be critical.

“If you didn’t get nitrogen down preplant, consider 2x2 placement. Apply 20 lb. to 50 lb. with the planter and sidedress the rest,” he says.

Get Ahead of Weeds

It was so wet in 2019, DuWayne Bosse, Britton, S.D., only got across PP fields once. “We had to spray for weeds, but we never got to do tillage. Even now it’s saturated,” he says.

With each growing weed comes hundreds — if not hundreds of thousands — of seeds that can emerge over the next five or more years.

“The big concern [in PP fields] is the summer annual population and how high that weed density could be,” says Aaron Hager, University of Illinois Extension weed scientist.

High weed population means farmers should take a whole-season approach to weed management. Don’t solely rely on a post herbicide application, Hager warns. “It’s a recipe for disaster.”

Here are a few tips from Hager and other experts to manage weeds in PP fields:

  • Consider planting PP fields last. You can kill the seedling weed and the viable seed at the same time.
  • Use a multifaceted weed control approach. Consider tillage, use pre-emergent residual herbicides and overlap residuals when you make your post application.
  • Don’t hold back on herbicide application rates.
  • Remember, you’re fighting more than just waterhemp. Don’t forget about velvetleaf or cocklebur  — those populations likely increased in 2019.
  • Scout for escapes and check for weeds you don’t recognize. Fields near rivers could have weed seed that came in from miles away with the floodwater.

Terminate Cover Crops

If you planted cover crops that don’t winterkill, be mindful of weather conditions to determine the best time to terminate. Here are a few tips from Iowa State University:

  • If using herbicides, consider cover crop type and growth stage. Winter wheat, annual ryegrass and red clover can be more difficult to control with herbicides.
  • Tillage can kill the cover crop and integrate the biomass into soils while prepping the seedbed. It could also lead to compaction if it’s wet.
  • Cereal rye (after pollen shed), hairy vetch (at full bloom), barley and triticale are good for crimping/rolling. Cover crop mixes aren’t the best candidates because the species are at various growth stages.

In addition to agronomic implications, the market is dealing with the long tail of prevent plant acres. Learn more at AgWeb.com/PP-market-effect