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Research, over years, has shown that the potential to maximize corn (Zea mays) yield has challenges in continuous corn production systems compared to rotated acres.1 A 6-year University of Illinois study documented a continuous corn yield penalty (when compared to corn following soybeans) of 9 to 42 bu/acre and found that continuous corn systems can be at risk for up to 7 years due to decreasing net soil nitrogen (N), corn residue, water, and weather.1 This research also suggested that corn residue should be managed properly to help provide the best opportunity for maintaining continuous corn production.
Fields selected for continuous corn should have good drainage, high water holding capacity, good fertility, no compaction problems, and low insect and disease pressure.1
Healthy, high-yielding corn can result in increased levels of residue that can hinder emergence, seedling establishment, standability, and even yield potential of the next crop. Accumulated corn residues can reduce soil temperatures, reduce N availability, increase soil moisture, and favor the survival of specific insects and diseases. Appropriate residue management at harvest and at planting is a key to successful continuous corn production (Figure 1). To help overcome residue challenges, farmers may need to use intense tillage or strip-tillage to aid in the burial and destruction of residue. Combine attachments or post-harvest shredding can be used to help size and spread residue uniformly. The rate of residue decomposition is influenced by soil temperature, moisture, microbial populations, and N to support microbial degradation of residue. Using strip-tillage and row cleaners at planting can facilitate better seed-to-soil contact and allow soil to warm more quickly.
Figure 1. Corn seedlings emerging through heavy corn residue.
Another hurdle in continuous corn production is the immobilization of N (N is tied up by microbes to decompose residue from the previous corn crop) (Figure 2). To overcome this when planting corn following corn, a higher N application rate is often recommended. An additional 30 to 50 lb/acre of N may be required for continuous corn acres when compared to a corn-soybean rotation.2 The application of N at multiple times throughout the season, such as N applied preplant and sidedress, may help increase N use efficiency by corn plants in a continuous corn system.
Phosphorus (P) and potassium (K) should also be maintained at optimum levels on continuous corn ground to encourage stand establishment and help minimize problems with stalk strength and stalk rots. Corn plants use more P and less K than soybean plants. Using a balanced starter fertilizer is more likely to produce a positive response in continuous corn than in a corn-soybean rotation because of the stressful early growing conditions.
Figure 2. Leaf showing symptoms of nitrogen deficiency.
Another key for successful continuous corn production is selecting a well adapted corn product. Products should be selected with high characteristic ratings for emergence, seedling vigor, disease resistance, and root and stalk strength. Products with higher emergence ratings have a better chance of pushing through heavy residue, particularly when the residue is keeping soils cool and moist. Prior year residue can harbor pathogens for diseases such as northern corn leaf blight, gray leaf spot, Goss’s wilt, and Diplodia stalk rot; therefore, higher tolerance or resistance to these and other diseases is beneficial for continuous corn production (Figure 3). The likelihood of feeding by certain insect pests during the growing season, such as corn rootworms (Diabrotica virgifera) and European corn borer (Ostrinia nubilalis), is higher with continuous corn. To help protect against these insects, products with multiple modes of insect trait protection for above and below ground insects should be considered.
During seedling establishment, seed and seedling pathogens and soil insects, such as wireworms, seed corn maggots (Delia platura), and grubs can be a threat, particularly when heavy prior year residue is present. Appropriate seed treatments with fungicide and insecticide protection can help protect seeds and seedlings during emergence and early establishment.
Fungicides applied at VT to R2 growth stages may be beneficial if controllable leaf diseases have been observed during routine field scouting. Fields with heavier disease pressure may require a sequential fungicide program consisting of a pre-tassel application followed by a VT to R2 application. Fields should be scouted weekly to determine if a fungicide should be considered. Timely fungicide applications can be an important tool to help limit potential yield losses. Always read and follow fungicide labels.
The number of available herbicides is limited when planting corn after corn. Additionally, corn residue can reduce the efficacy of many soil-applied herbicides and/or shield young weed seedlings from contact type herbicides. A soil-applied residual herbicide should be applied either preplant or preemergence to decrease weed pressure and reduce potential selection of herbicide-tolerant weeds. Providing early-season weed control can widen the postemergence application window. For the most effective weed control, postemergence herbicide applications should be made when weeds are small. Additional information for weed control in continuous corn systems can be found at www.roundupreadyPLUS.com. Control of volunteer corn is especially problematic in continuous corn systems. A proactive management approach is necessary because control options are limited after the new corn crop is established. At harvest, lodged plants, ear drop, improper combine adjustments, and poor harvest conditions can cause grain loss and increase the potential for volunteer corn the next spring. Keeping harvest losses to a minimum and tilling fields in the fall are tools that can reduce volunteer corn in the following crop. Since herbicide options are limited, cultivation may be the best option for volunteer corn control in corn.
Unless all corn acres are continuous, consider planting corn on corn acres last because residue is likely to keep them wetter and cooler. Increasing seeding populations to help offset emergence losses associated with seedling diseases and insects is generally not necessary. The chance of seedling losses may be higher in continuous corn; however, other management decisions such as seed selection and quality seed treatments may help reduce seedling establishment issues. Your DEKALB® Brand Seedsman can help identify the recommended planting population for each product. Because corn residue from the previous year may impede seed-to-soil contact, manage the seedbed to reduce residue interference and improve seed-to-soil contact for improved stand establishment.
Sources: 1Gentry, L.F., Ruffo, M.L., and Below, F.E. 2013. Identifying factors controlling the continuous corn yield penalty. Agronomy Journal. 105: 295-303. https://dl.sciencesocieties.org/. 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/. Owen, M. 2007. Weed management in continuous corn. Iowa State University. IC-498. http://www.ipm.iastate.edu/. Wilson, R., Sandell, L., Klein, R., and Bernards, M. 2010. Volunteer corn control. 2010 Crop Production Clinics Proceedings. University of Nebraska-Lincoln Extension. http://nlc1.nlc.state.ne.us/. Erickson, B. and Alexander, C. 2008. How are producers managing their corn after corn acres? Purdue University. https://www.agecon.purdue.edu/. Sundermeier, A., Thomison, P., Reeder, R., Dick, W., and Mullen, R. 2007. Managing tillage and crop rotation in northwest Ohio. The Ohio State University Extension. AGF-506-07. http://ohioline.osu.edu/. Web sources verified 6/19/18. 130719070121