Agronomy Content

Is continuous corn production possible?

May 10, 2021

The short answer is yes. But if you’re thinking about continuous corn, you definitely need to know what you’re getting into first.

This kind of cropping system requires intense management, potentially higher input costs and realistic yield goals in order to compensate for the gains that usually come from growing corn in rotation – such as pest control and replenishing soil nutrients.

To wit: in a six-year study conducted by the University of Illinois, researchers found that the yield penalty in a continuous corn system was 9 to 42 bushels per acre compared to corn grown on soybean stubble. They also tracked a steady year over year decline in corn yields over the course of the study – something they attributed to nitrogen availability, accumulation of residue and, as with any crop system, weather.¹

Still, with the right management and attention to detail, continuous corn is possible. Here are some tips.

Field selection and residue management

Findings of University of Illinois study into continuous corn indicate that fields best suited to this practice have good drainage plus high water-holding capacity, optimum fertility, no compaction and low pest pressure – specifically insects and disease.

Key to growing corn-on-corn on the same field is residue management because a great corn crop the year before leaves behind a lot of stubble and trash that can lower soil temperatures in spring, harbour disease pathogens, protect overwintering insects and reduce available nitrogen. All of this can lead to a host of challenges, like delayed emergence and crop damage from pests.

You want residue to decompose quickly, and this depends on a number of factors, like soil moisture and temperature, microbial activity and enough nitrogen to support those microbes. Post-harvest shredding can help break up and more evenly spread residue, while intensive tillage or strip-tillage can help bury it.

You’re aiming for good seed-to-soil contact in warm soils come spring, so what ever you can do to get rid of, break up and even out residue should be done.

Hybrid selection

Choose hybrids that have the strength for this task. That means high vigor and germination ratings, an excellent disease resistance package, insect resistance and excellent root and stalk strength.

The rationale is clear enough: Corn that can get out of the ground fast and strong has a better chance of getting through the previous year’s residue, especially if conditions are cool. As well, the corn residue it’s pushing through can be an excellent reservoir of overwintering disease pathogens, such as Northern corn leaf blight, Goss’s wilt, grey leaf spot and Diplodia stalk rot, so which is where the disease package comes in.


Figure 1: Northern corn leaf blight.



Figure 2: Gray leaf spot.



Figure 3: Goss’s wilt.



Figure 4: Diplodia ear and stalk rot.

The potential for insect damage is also increased with continuous cropping, so look for hybrids with good resistance to some of the key pests, like corn rootworm and European corn borer.

However – be very aware that populations of corn rootworm resistant to Bt traits have been found in Ontario, so use an insecticidal seed treatment, hone your scouting techniques, and seriously consider rotating out of corn after no more than three years.

Seed treatment

Seed treatments are an absolute must in continuously cropped corn. You need one with an excellent fungicide package to protect against the seedling disease complex, as well as an excellent insecticidal component for protection against early season pests like wireworm, seed corn maggot, grubs and more. Don’t plant without one.

Fertility

Nitrogen is your biggest concern. Soil-applied N isn’t necessarily plant-available N, plus soil microbes busy breaking down residues can immobilize nitrogen just when you need it most.

Use a higher rate of nitrogen when planting corn after corn. Compared to corn after soybeans, corn on corn may require an additional 34 to 56 kg per hectare (30 to 50 pounds per acre).²

Nitrogen uptake in corn is greatest during its late vegetative stages, from about V6 to R1, so consider a split application of N – once at pre-plant and again around V5-V6 – for greatest nutrient efficiency. Remember that nitrogen needs to be right in the root zone to be plant-useable.

Maintain optimum levels of phosphorous and potassium as this supports strong stand establishment while minimizing any problems with stalk rots and stalk strength. Corn uses more of these two nutrients than soybeans do, so balance your fertility program accordingly.

Planting considerations

Emergence losses are generally higher in continuous corn, but with proper residue management, hybrid selection, fertility and seed treatments, this is not likely to be a huge problem.

It means that increasing your seeding rate to offset such losses might not be necessary. But talk to your seed partner to determine the optimum seeding rate for the hybrid or hybrids you’ve chosen.

Lastly, plant your corn-on-corn acres last to give maximum time for soil under all that corn residue to warm up and dry out a bit.

Weed control

Weed control can be a challenge in continuous corn. You really need to be proactive with early weed control because options are limited once the crop is established.

Again, residue can be a problem because it can reduce the efficacy of any soil-applied herbicides and it can also protect young weed seedlings from post-emergent contact herbicide applications.

Early season weed control in corn is absolutely key to crop success, so start with a pre-plant, or pre-emergent, soil-applied herbicide that has some residual activity to keep early weeds, including any resistant ones, at bay.

Make post-emergence herbicide applications when the weeds are still quite small. Make sure to use multiple modes of action between your pre- and post-emergence herbicide applications. For more information about this, please visit MixItUp.ca. Pay special attention to volunteer corn, which carries herbicide resistance traits and can be harder to manage.

Indeed, pay attention at harvest to minimize volunteer corn the following season. Lodged plants, ear drop, incorrect combine adjustments and harvesting during less than ideal conditions can all contribute to a volunteer corn problem next spring.

Disease control

Continuous corn cropping means you are not breaking disease cycles, so scout vigilantly and take action immediately if necessary.

If disease pressure looks fairly normal, scout at tasselling (VT) and decide if a fungicide is warranted. In fields with heavy disease pressure, start scouting earlier – you may need to do a sequential fungicide application, spraying at pre-tassel then again in the VT to R2 window. Talk to your agronomist or advisor about fungicide timing and what product options will give you the best control. It’s all about protecting yield!


Footnotes:
¹ Gentry, L.F., Ruffo, M.L., and Below, F.E. 2013. Identifying factors controlling the continuous corn yield penalty. Agronomy Journal. 105: 295-303
https://acsess.onlinelibrary.wiley.com/doi/full/10.2134/agronj2012.0246
² Nielsen, R.L., Johnson, B., Krupke, C., and Shaner, G. 2007. Mitigate the downside risks of corn following corn. Corny News Network. Purdue University. https://www.agry.purdue.edu/ext/corn/news/timeless/CornCorn.html.