Published Apr 18, 2019

Terminating Cereal Rye Cover Crop Before Corn

By Sierra Becker

corn with a terminated rye cover crop controlling weedsIt’s time to plant corn, but the first step is to handle the over-wintered cereal rye cover crop, which is greening and growing during corn planting season. Because of potential competition between rye and corn – and concerns about plant diseases potentially transferring from the rye via what’s termed the “green bridge” – the steps leading to corn planting must be handled adeptly.

We have reached out to farmers across the state to provide you with a “recipe for success” — a set of guidelines to help you effectively kill your cover crops in preparation for corn planting!PFI2021 CC CostShare Ad 1024x224px

When to Spray:

If your plan is to terminate your cover crop 10-14 days before planting, follow these guidelines:

  • Spray when the rye is actively growing
  • Factor in temperature when spraying
  • To get the best results spray when temperatures are above 40 F at night and above 60 F during the day
  • When possible, spray during the middle of the day
  • Recommended to spray cover crop when it is less than 6 to 8 inches tall
  • Field conditions could deteriorate if rye is killed at height taller than a foot and rain is present (making the field wet)
  • Use trash whippers to move dead, brown cover crop out of the path of the planter
  • Ensure proper seed placement and slot closure by regularly getting off the tractor and checking during planting

If your plan is to terminate at or right before planting, follow these guidelines:

  • Scout for shared pests between rye and corn such as armyworm and terminate cover crop 10-14 days ahead of corn planting if present. If it’s not possible to terminate early and pests are likely to move from the living rye to the living corn, spray a control treatment for the pest.
  • Spray herbicide right at planting or immediately after planting corn to burn down the cover crop.
  • Spray when the rye is actively growing.
  • Ensure adequate nitrogen is applied at or around corn planting (30 to 60 pounds)
  • Create skip zones

How to Spray:

  • Use the full recommended rate
  • Fully read and follow the herbicide label especially regarding spray volume, nozzle type, recommended adjuvants and herbicide rate
  • Avoid tank mix partners or carriers that may reduce glyphosate translocation if possible

What PFI Members are Recommending:

Apply acid equivalent (a.e.) of one pound per acre (28 ounces per acre of WeatherMax or 43 ounces per acre of generic; I normally use less)

32-40 ounces of Roundup mixed with normal corn herbicide. Atrazine + pre-emerge (usually Harness), 2,4-D, 5 gallons per acre UAN.

1.5 quart per acre of glyphosate; 1 pint per acre 2,4-D

After You Spray:


  • Total nitrogen amount should stay the same, but type and timing of application might change
  • Apply 30 to 60 pounds of highly available nitrogen at or around planting time, close to the corn seed
  • Especially if there is excess growth of rye because termination has been delayed

What PFI Members are Recommending:

Knife UAN at an angle to the rows, 4 inches deep which is 2 inches deeper than the seed

Nitrogen placement: 2×2, 2x0x2, or 2x dribble

Add AMS (ammonium sulfate)

Pre’s are applied at planting. ~50% of nitrogen applied pre, then sidedress balance of nitrogen at ~V4-V6

Spring NH3

When You Plant:

  • Pay attention to seed depth when cover crop residue is present
  • Provide sufficient down pressure and depth adjustment to place seed in soil
  • Equip planter with opening wheels, coulters, trash whippers or other planter attachments to clear the cover crop debris
  • Make sure seed trench is closed

What PFI Members are Recommending:

Planter has Yetter shark tooth row cleaners, Keaton seed firmer, one stock and one Copperhead closing wheel

One spike Martin closing wheel and one stock rubber closing wheel followed by drag chain,

Planter has residue managers without coulter.

Additional Member Testimonies

We try to terminate rye at 6 inches or less before corn. Ten to fourteen days before planting, but I wouldn’t delay planting. Terminate with 32-40 oz/ac Roundup mixed with normal corn herbicide. Atrazine + pre-emerge (usually Harness), 2,4-D, 5 gal/ac UAN. Spring NH3, Planter has residue managers without coulter.

Spray in the middle/warmer part of the day. Plan to terminate 10-14 days prior to planting plus include 30-50 units of nitrogen per acre with the burndown. Pre’s applied at planting. ~50% of nitrogen is applied pre, then sidedress balance of nitrogen at ~V4-V6.

Graze 30 days and spray regrowth at 6-8 inches with 1.5 quart per acre glyphosate and 1 pint per acre 2,4-D. Apply 5 gallons per acre 3-18-18 on furrow and 10 gallons per acre UAN (32%) in front of drag chains. Side dress balance of nitrogen with high boy.

These lists are not all-inclusive. Inclusion in this list is not an endorsement of a product nor is exclusion non-approval. Always read herbicide labels prior to purchasing or using the product.

For alternative herbicides that you may be able to use, contact a local university extension specialist or ag service provider. Remember to check fertilizer labels too, as some mixtures of fertilizers and herbicides are detrimental to the performance of one or both of the products.