Evaluation of Residual Herbicides for Interseeding in Corn

Trials conducted over three years show that several shorter-lived residual corn herbicides can be used successfully with interseeded cover crops.
Evaluation of Residual Herbicides for Interseeding in Corn - News


The trials also showed that the use of longer-lived residual herbicides will likely preclude successful interseeding practices in corn.

We have examined interseeding cover crops in corn for the last several years. The results have shown that annual ryegrass and red clover cover crops can successfully establish when interseeded at the V5 corn growth stage. However, this strategy may be limited by carryover injury to cover crops from residual herbicide programs.

We conducted field experiments from 2013 to 2015 in Pennsylvania, Maryland and New York (10 total site-years) to evaluate the effect of common residual corn herbicides on interseeded red clover and annual ryegrass. We tested 22 herbicide treatments in at least two-site years and collected cover crop biomass in late-fall to evaluate herbicide carryover injury. Cover crop establishment and response to herbicide treatments was variable across study locations.

High levels of red clover and annual ryegrass biomass reduction were observed across herbicide treatments at the MD location, whereas negligible to moderate levels of biomass reduction were observed at other locations. Among herbicides used for annual grass control, s-metolachlor (Dual Magnum), pyroxasulfone (Zidua), pendimethalin (Prowl) and dimethenamid-P (Outlook) resulted in significant annual ryegrass biomass reduction relative to the untreated check, whereas annual ryegrass biomass in acetochlor (Harness) treatments did not differ from the untreated check.

The relative order of observed annual ryegrass biomass reduction among chloroacetamide herbicides was Dual Magnum > Zidua > Outlook > Harness. Among herbicides used for broadleaf weed control, mesotrione (Callisto) resulted in significant red clover biomass reduction compared to the untreated check. Red clover biomass in saflufenacil (Sharpen), rimsulfuron (Resolve/Basis) and atrazine treatments did not differ from the untreated check. This research provides preliminary evidence that annual ryegrass and red clover can be interseeded following use of several shorter-lived residual corn herbicides and also demonstrates that use of longer-lived residual herbicides likely preclude interseeding practices in corn production systems. Finally, our research demonstrates that the potential for carryover injury to interseeded cover crops can vary significantly across different soil and environmental conditions.

The table below provides some guidelines for herbicide use in the mid-Atlantic region with interseeded cover crops.

Residual Corn Herbicides For Interseeding

Potential for Cover Crop Injury (% Fall Biomass Reduction)

<15% = LOW (L) 15-30% = MODERATE (M) >30% = HIGH (H)

Herbicide TreatmentsProduct RateLabel RateApp TimingAnnual RyegrassRed CloverGrass-Legume Mix
SUs (2)
Resolve 25 DF0.5 oz½XPRELLL
Resolve 25 DF1 oz1XPRELLL
Triazines (5)
Atrazine (4L)1 pt½XPRELMM
Atrazine (4L)2 pt1XPREMMM
Atrazine (4L)3 pt1 ½XPREHHH
Metribuzin 75 WG4 oz1XPREHLM
Chloroacetamides (15)
Dual II Mag 7.64 EC1.67 pt1XPREHMH
Zidua 85 WG2.5 oz1XPREHMH
Harness 7 EC1 pt½XPREMLM
Harness 7 EC2 pt1XPREMLM
Outlook 6 EC½ pt½XPRELLL
Outlook 6 EC1 pt1XPREMLM
Dinitroanilines (3)
Prowl H2O 3.8 CS1.5½XPRELLL
Prowl H2O 3.8 CS3 pt1XPREHMH
PPOs (14)
Sharpen 2.85 SC1.5 fl oz½XPRELLL
Sharpen 2.85 SC3 fl oz1XPREMMM
HPPDs (27)
Balance Flex 2 SC5.3 fl oz1XPREMMM
Callisto 4 SC5.4 fl oz1XPRELHH
Impact 2.8 SC0.75 fl oz1XPOSTMHH
Keystone LA NXT2 pt½XPRELLL
Prowl + Atrazine1.5 pt+1 pt½XPREMMM
Harness + Resolve1 pt+0.5 oz½XPRELLL
Verdict 5.57 EC8 oz½XPRELLL
Lumax EZ 3.67 SE1.35 qt½XPREHHH
Acuron 3.44SC1.25 qt½XPREHHH

Potential for interseeded cover crop injury from residual corn herbicides (Pennsylvania Guidelines).