Cover crops have quickly become a well-established practice over the last decade. The latest USDA Census of Agriculture done in 2017 reported cover crop acres at 15.4 million, a 50% increase from 2012. 8 states doubled cover crop acres over that same timeframe. Use of cover crops is growing in part due to their ability to build soil organic matter, improve soil structure, reduce erosion and help suppress weeds. Cereal rye is one of the most popular cover crop species being used. However, it may negatively impact corn production if not managed correctly. There are factors to consider when using cereal rye cover crops prior to planting corn.
Cereal Rye Considerations
Reduced soil moisture: Drought-prone soils could be dried out further by rye moisture uptake.
Increased pest pressure: Delaying termination of rye until after planting can result in a “green bridge” for disease and insects to relocate from cover crop to newly seeded crop after die-back begins. Pythium, wheat stem maggot, black cutworm and armyworm have been observed to cause worse crop damage after cover crop termination.
Reduced nitrogen (N) availability: Corn planted directly into green rye can often have a yellow, sickly appearance when emerging. It is believed that previously applied N may be tied up in the rye cover crop and not available until the rye dies and begins to be mineralized back into the soil.
Allelopathy: Allelopathic chemicals are released by rye and are known to inhibit germination and early growth of many smaller-seeded plants. Terminated rye begins to degrade and release allelopathic chemicals into the upper soil surface. Field effects of allelopathic chemicals on large-seeded crops like corn and the impact on germination and early growth are not well understood. Lab studies have indicated a possibility of reduced early growth or germination; therefore, it is often recommended to terminate rye at least 2 weeks before planting.
Hybrid sensitivity: There is not a great understanding as to why corn planted into rye will sometimes have a negative yield impact. The effect of rye mulch on soil warming and drying, in combination with other factors such as N tie-up and soil pathogens, likely all interact to potentially create a negative response. Due to this, understanding the reason for hybrid differences is even more challenging.
2021 Hybrid and Cover Crop Interaction Trial
The Golden Harvest® Agronomy in Action team established an exploratory trial in Seward, NE, in 2021 to better understand differences in hybrid sensitivity to planting following a cereal rye cover crop. N was applied pre-plant in spring of 2021 at a rate of 180 lbs./A. 20 hybrids ranging from 106- to 115-day relative maturity (RM) were planted on April 16 within randomized strips with no cover crop and strips with cereal rye that were established in October 2020. Corn was planted into green cereal rye 2-3 in. in height with stems beginning to elongate. Termination of the cereal rye was attempted immediately following planting with a burndown and preemergence herbicide program. However, due to cool and wet weather following application, a second herbicide application 2 weeks after planting was necessary to achieve complete termination of the cereal rye.
Trial Results
Areas planted into cereal rye and areas without cover crops both established similar final plant stands, although early growth and development in cover crop strips was delayed by roughly 1 leaf stage early in the trial. On average, hybrids planted into cereal cover crops in Seward yielded 7% less than if planted into no cover crop. Yield losses were higher than anticipated considering the robust N rate applied in spring and the relatively small amount of mulch that was present at time of planting. Individual hybrid yield loss associated with cereal rye ranged from 1-15%. Hybrids indicated with asterisks were more severely affected (Table 1). Interestingly, hybrids in the 106-109 RM range were impacted more negatively (9.6%) than fuller season 113-115 RM hybrids, which averaged a 4% yield loss. Hybrid management decisions based on this single trial should be limited, although results are pronounced enough that future trials will be conducted to understand if hybrid differences are repeatable.
Table 1. Hybrid yields from trial with no cover crop and cereal rye cover crop Tips for Planting into Green Cover Crops
Terminating cereal rye at least 14 days before the anticipated planting date greatly reduces many of the risks associated with rye cover crops. When this is not an option, consider the following for green planting:
Figure 1. Established cereal rye cover crop strips prior to planting
Figure 2. Corn emerging from cereal rye and strips without cover crops Allow corn or soybeans to germinate prior to terminating cover crop.
Total N should not need to change, but timing 30-60 lbs./A of highly available N at or around planting, close to the seed, may reduce tie-up in rye.
Apply in-furrow N containing starter or higher rates of N in 2x2, 2x2x2 or dribbled to the side of row at planting, and consider additional early sidedress, if needed.
Scout for insects and be prepared to manage pests that could become an issue in the emerging crop, such as armyworm and black cutworm.
Pay extra attention at time of planting to:
Adjust down pressure and depth adjustment. Seed depth changes due to cover crop residue.
Use opening wheels, coulters, trash whippers or other planter attachments to clear cover crop debris.
Consider planting rye cover crop into wider, 30-in. rows to allow for clean corn/soybean planting strips the following spring.
Always make sure soil conditions are optimum for good seed germination and growth.
Larger maturing cover crops can be hard to control with herbicides. Ensure adequate application rates are used while plants are actively growing.
Consider the planting restrictions of herbicides that could be used to terminate a cover crop.
Maximize spray volume and ensure application weather conditions are good to get the best control of cover crops.
Tillage can be an option for certain species, but multiple passes may be needed which negate the benefits the cover crop is providing.
To learn more about cereal rye as a cover crop prior to planting corn, watch this video.
All photos are either the property of Syngenta or used with permission.
Syngenta hereby disclaims any liability for Third Party websites referenced herein.
Performance assessments are based upon results or analysis of public information, field observations and/or internal Syngenta evaluations.
Product performance assumes disease presence.
© 2022 Syngenta. Important: Always read and follow label instructions. Some products may not be registered for sale or use in all states or counties. Please check with your local extension service to ensure registration status. AAtrex 4L, AAtrex Nine-O, Acuron, Agri-Flex, Agri-Mek 0.15EC, Agri-Mek SC, Avicta 500FS, Avicta Complete Beans 500, Avicta Complete Corn 250, Avicta Duo Corn, Avicta Duo 250 Corn, Avicta Duo COT202, Avicta Duo Cotton, Besiege, Bicep II Magnum, Bicep II Magnum FC, Bicep Lite II Magnum, Callisto Xtra, Cyclone SL 2.0, Denim, Endigo ZC, Endigo ZCX, Epi-Mek 0.15EC, Expert, Force, Force 3G, Force CS, Force 6.5G, Force Evo, Gramoxone SL, Gramoxone SL 2.0, Gramoxone SL 3.0, Karate, Karate with Zeon Technology, Lamcap, Lamcap II, Lamdec, Lexar EZ, Lumax EZ, Medal II ATZ, Minecto Pro, Proclaim, Tavium Plus VaporGrip Technology, Voliam Xpress and Warrior II with Zeon Technology are Restricted Use Pesticides.
Some seed treatment offers are separately registered products applied to the seed as a combined slurry. Always read individual product labels and treater instructions before combining and applying component products.
Orondis Gold may be sold as a formulated premix or as a combination of separately registered products: Orondis Gold 200 and Orondis Gold.
Important: Always read and follow label and bag tag instructions; only those labeled as tolerant to glufosinate may be sprayed with glufosinate ammonium-based herbicides. LibertyLink®, Liberty® and the Water Droplet logo are registered trademarks of BASF. HERCULEX® and the HERCULEX Shield are trademarks of Corteva Agriscience LLC. HERCULEX Insect Protection technology by Corteva Agriscience LLC. Under federal and local laws, only dicamba-containing herbicides registered for use on dicamba-tolerant varieties may be applied. See product labels for details and tank mix partners. Golden Harvest® and NK® soybean varieties are protected under granted or pending U.S. variety patents and other intellectual property rights, regardless of the trait(s) within the seed. The Enlist E3® soybean, LibertyLink®, LibertyLink® GT27®, Roundup Ready 2 Xtend®, Roundup Ready 2 Yield® and XtendFlex® soybean traits may be protected under numerous United States patents. It is unlawful to save soybeans containing these traits for planting or transfer to others for use as a planting seed. Only dicamba formulations that employ VaporGrip® Technology are approved for use with Roundup Ready 2 Xtend® and XtendFlex® soybeans. Only 2,4-D choline formulations with Colex-D® Technology are approved for use with Enlist E3® soybeans. The trademarks or service marks displayed or otherwise used herein are the property of a Syngenta Group Company. ENLIST E3® soybean technology is jointly developed with Corteva Agriscience LLC and M.S. Technologies, L.L.C. The ENLIST trait and ENLIST Weed Control System are technologies owned and developed by Corteva Agriscience LLC. ENLIST® and ENLIST E3® are trademarks of Corteva Agriscience LLC. GT27® is a trademark of M.S. Technologies, L.L.C. and BASF. Roundup Ready 2 Xtend®, Roundup Ready 2 Yield®, XtendFlex®, VaporGrip® and YieldGard VT Pro® are registered trademarks used under license from the Bayer Group. All other trademarks are the property of their respective owners. More information about Agrisure Duracade® is available at http://www.biotradestatus.com/.