OMAFRA Field Crop Report – September 3, 2020

Figure 1. Rye seeded after corn silage

Is It Bad to Plant Corn After Cereal Rye?

There has been interest in rye for cover crops or maximizing yields in silage systems (Figure 1) where rye can be harvested for silage by mid- to late May which still allows time for planting a corn silage crop. Benefits of rye include good winter hardiness, early maturity and high yield relative to other winter cereal forages. Benefits of this system include potentially higher yields than a single corn silage crop and ground cover nearly all year long. Rye gets a bad rap when followed by corn, however – how true is this, and what options reduce risks?

Figure 1. Rye seeded after corn silage
Figure 1. Rye seeded after corn silage

What Does the Yield Data Say?

Yield responses are variable, and likely dependent on environment and management practices. Some work in the Great Lakes and northern corn belt regions have shown yield loss for planting corn after rye, averaging 11-17% in past Ontario research (Raimbault, 1990) while others show minimal loss. In a silage system, the question would be whether the yield loss due to planting corn later after rye can be more than offset with the yield of the rye forage crop. Some research suggests this is possible (Raimbault, 1990) while others do not.

What Causes Yield Loss?

The mechanisms of yield loss, when it does occur, are not well understood. A few things that receive attention as possible causes for corn yield loss following rye include:

Allelopathy or toxicity from decaying rye from compounds released or formed following decomposition is one factor suggested for poor corn performance following rye. Impact of allelopathy is suggested to be highly variable depending on amount of rye residue, soil type, temperatures and moisture at termination. Some suggest that while rye can produce allelopathic compounds, impacts on corn growth may be over emphasized, and that due to corn’s large seed size and relatively deep planting depth away from the soil surface, allelopathic impacts may be minimal (Hartzler, 2014).

Plant root diseases bridging from decaying rye roots to developing corn seedlings has recently been noted as a potential cause for poor corn performance following rye, particularly if conditions are favourable for pathogen development (cold, wet) and populations or inoculum are already high (Kaspar et al, 2013). Authors have shown that root diseases that proliferate on decaying rye roots can also infect corn, and that corn root diseases, growth and plant stand issues can be more pronounced with rye cover crops terminated shortly before corn planting compared to a couple weeks prior (Bakker et al, 2016). Authors also noted that even under elevated disease levels, corn yield losses following rye do not always occur and may be highly dependent on environmental conditions.

Seedbed environment is noted as another challenge of establishing corn after rye. Early in season, rye biomass may limit soil warming and drying, creating challenges for planting and seedlings particularly in cooler and wetter springs. In silage scenarios, dry weather during rye’s later vegetative growth stages when evapotranspiration is high may result in significant soil moisture loss, creating planting, germination and crop uniformity challenges. Under no-till, dry conditions and rye root structure may cause opener, seed depth and slot closure issues, exacerbating seedbed dryness and introducing other challenges for developing seedlings (lack of moisture, temperature variability/extremes, desiccation, root establishment).

Nitrogen supply has been hypothesized to be another issue facing corn after rye given significant nitrogen uptake, and immobilization as rye biomass decomposes. Nitrogen responses have been variable. Some research has found rye to tie up nitrogen and for corn following rye to require more nitrogen while other research has not. Past Ontario research has shown increasing nitrogen rates could sometimes yield more corn but could not close the yield gap for planting corn after rye (Tollenaar et al, 1993).

How Do You Limit Risks?

Clearly there is no single silver bullet solution for removing risks of planting corn after rye, but some comments from past research:

  • Avoid planting rye in close vicinity to next year’s corn rows (e.g. “bio-stripping”) has been suggested to reduce allelopathy and disease risks (Kurtz et al, 2020) though may fit better in cover crop scenarios where rye yield is less important.
  • Terminate/harvest rye early or leave time (i.e. 1-2 weeks) between termination and corn planting as this improves corn performance relative to planting corn immediately after rye termination/harvest. Advantages of this could be greater probability of planting under better conditions (warmer, drier), time for allelopathic compounds to dissipate or conserving soil moisture with earlier rye termination/harvest. This approach may not always be feasible, particularly in silage scenarios where yield potential of both rye and corn are of concern, and corn planting is already delayed. Deeper planting (2.5” or deeper) has also been suggested to potentially reduce germination issues (Jasa, 2016).
  • Earlier rye harvest (before boot stage) during springs with low rainfall is cited as one method of limiting seedbed moisture losses and improving corn establishment, though at the expense of rye yields (Krueger et al, 2011). Quality of ryelage will be higher if harvested early.
  • Past research in Ontario has not shown rye residue removal (silage harvest versus clipping top growth on surface) to have a strong impact on reducing yield loss when corn follows rye (Raimbault et al, 1990; Tollenaar et al, 1993), but markedly improved corn performance has been observed when rye residue and top 1cm of soil are removed with planter mounted disc furrowers (Raimbault et al, 1991).
  • Ontario research demonstrated a strong yield response for tillage compared to no-tilling corn directly into silage harvested or clipped rye, and the yield advantage of including rye in a corn silage system hinged on this tillage yield (Raimbault, 1990). If reduced tillage is preferred, a delay between rye termination/harvest is more important, and a planter capable of handling seedbed conditions is critical – sufficient down pressure, opening and depth control, and being able to properly close the trench.
  • Nitrogen management was never a panacea, but it’s important to have a program that will reduce risks under high residue conditions. This likely includes starter nitrogen, a reasonable amount of nitrogen at planting or ensuring any delayed applications are made on a very timely basis and avoiding surface broadcasting nitrogen on high residue ground.


Bakker, M., J. Acharya, T. Moorman, A. Robertson and T. Kaspar. 2016. The potential for cereal rye cover crops to host corn seedling pathogens. Phytopathology. 106:591-601.

Hartzler, B. 2014. Cereal rye cover crops, allelopathy and corn. Iowa State University. (accessed 1 Sept. 2020).

Jasa, P. 2016. Planting corn into a cereal rye cover crop. University of Nebraska, Lincoln. (accessed 1 Sept. 2020).

Kaspar, T, T. Moorman, A. Robertson and A. Lenssen. 2013. Investigating Causes of Corn Yield Decreases Following Cereal Rye Winter Cover Crop. Iowa State University. (accessed 1 Sept. 2020).

Krueger, E., T. Ochsner, P. Porter and J. Baker. 2011. Winter rye cover crop management influences on soil water, soil nitrate and corn development. Agron. J. 103:316-323.

Kurtz, S., J. Archarya, T. Kaspar and A. Robertson. 2020. Seedling disease of corn caused by Pythium increases with proximity of rye. Plant Dis. In press.

Raimbault, B., T. Vyn and M. Tollenaar. 1990. Corn response to rye cover crop management and spring tillage systems. Agron. J. 82:1088-1093.

Raimbault, B., T. Vyn and M. Tollenaar. 1991. Corn response to rye cover crop, tillage methods, and planter options. Agron. J. 83:287-290.

Tollenaar, M., M. Mihajlovic and T. Vyn. 1993. Corn growth following cover crops: influence of cereal cultivar, cereal removal, and nitrogen rate. Agron. J. 85:251-255.