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Cereal Rye Cover Crop Considerations

Categories: PLANTING, CORN
  • Timely establishment and termination of cover crops is key to realizing benefits without yield reduction.

  • Hybrids may respond differently to cover crops.

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
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:

close-up of cereal rye cover crop strips before planting corn hybrids
Figure 1. Established cereal rye cover crop strips prior to planting
Corn growing from cereal rye and strips without cover crops
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.

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