Corn product selection is likely the single most important management decision in cropping profitability.1 To take advantage of the increased yield potential offered in new products each year, growers should regularly introduce new corn products to their fields. Seed company representatives are a good resource, as they have data summaries to evaluate corn product performance over a wide range of conditions.
Yield Potential and Agronomics.
Generally, the first selection criteria when evaluating corn products is yield potential, followed by various agronomic characteristics. Product performance in plots across multiple locations and years can indicate the consistency and yield potential of a product, and in which environments it tends to excel or falter. A few variables about each location to consider are soil type, crop rotation, tillage, temperature, and rainfall.
Commercial products often have very good or excellent vigor and emergence ratings. Products with poor emergence or vigor are generally not advanced to commercial status. A strong emergence and vigor rating for a commercial product is especially beneficial if that product will be placed in no-till or reduced tillage fields, or will be planted early.
It is important to evaluate products for tolerance to diseases that are common in your geography. Keep in mind that fungicide applications may mitigate some of the negativity associated with the susceptibility of a product to fungal diseases such as gray leaf spot, and northern corn leaf blight, among others (Table 1 and Figure 1). Drydown, stalk quality, and root strength can influence harvest schedules. Several variables can affect these characteristics, such as stresses endured throughout the growing season, untimely frosts, and various pathogens.
Table 1. Example of a 1 to 9 disease rating scale showing the severity of foliar fungal diseases, like Northern corn leaf blight.
Slight Infection: Few lessons on lower leaves
Light Infection: Lesions on lower leaves
Moderate Infection: Lesions on lower and middle leaves
Heavy Infection: Lesions on lower leaves, extending to upper leaves
Very Heavy Infection: Lesions on all leaves. Plants may be prematurely killed
Figure 1. Corn infected with Northern corn leaf blight as a disease severity rating of 7 (Heavy Infection, see Table 1).
Different Relative Maturities.
A good management practice is to plant a package of products with a combination of early-, mid-, and full-season maturities to help spread out the harvest schedule and help minimize losses from drying costs and lodging. The early products can help with getting harvest equipment set properly and/or fulfilling early fall delivery commitments to elevators. The majority of acres in an operation should be planted to mid- and full-season products due to the tendency for them to have higher yield potential since they have more days to photosynthesize and fill grain. In addition to helping manage harvest schedules, having a spread of maturities can help mitigate risks associated with an early fall frost, such as low test weight, lower yield potential, and poor drydown.
An often overlooked characteristic when selecting a package of corn products is crop heat unit (CHU) requirements to flowering or mid-pollination. Spreading out CHU requirements to mid-pollination can help decrease risks of heat and drought stress during pollination.
A package of products with different maturities may or may not result in a package with differing CHU requirements to flowering. A difference of CHUs to mid-pollination might be a difference of one or two days for flowering. While this might not seem like much, it could be the difference of a cold front coming through or a much needed rain. It could also be compounded by different planting dates.
Agronomic Characteristics for Corn on Corn
Product selection is no easy task and selecting corn products that can handle the additional stress that can be associated with corn-on-corn environments can be even more challenging. Several product characteristics should be evaluated. Regardless of the environment, the first selection criteria should be yield potential. When evaluating product performance, there is a strong trend for the best products to perform well in most environments.
Data can often be pulled for yield performance on corn-on-corn acres, but the year effect can be quite large. Information from previous years could be misleading if the weather pattern is different in the current growing season. Since future weather cannot be predicted, multi-year corn-on-corn data from a large geography provides the best insight regarding yield performance.
While there is no substitute for actual yield data, there are many product characteristics that are generally believed to be more important when products are to be placed in corn-on-corn situations. In many cases there is more perception and personal opinion than hard evidence to support these beliefs. Some agronomic characteristics to consider include:
Figure 2. The two producs were planted at the same time; the product on the right has stronger early emergence that the hybrid on the left.
- Strong Emergence and Early Vigor. The effects of cooler and wetter soils due to heavy residue can be challenging in some corn-on-corn fields.3 Figure 2 shows how one product may have a stronger, earlier emergence compared to another.
- Insect Tolerance. To help minimize the acres that are at higher risk of insect damage, products with dual-mode protection of above and below ground pests, such as Genuity® SmartStax® RIB Complete® corn should be utilized. Corn rootworm (CRW) survival can be affected by soil structure.2 Recently hatched CRW larvae must travel through the soil to reach corn roots. Sandy soils may have less CRW pressure as sand can scratch the cuticle of the larvae and cause them to die due to desiccation.
- Disease Tolerance. Planting corn products that are tolerant or resistant to diseases that are problematic in an area is a good management strategy. Diseases such as gray leaf spot (GLS), Northern corn leaf blight (NCLB), many common stalk rots, ear rots, seedling blights, and in some areas Goss’s wilt are all potentially more severe for corn-on-corn. Many of the common foliar fungal diseases can be effectively managed with fungicide applications.
- Root and Stalk Strength. With the potential for increased traffic, more compaction and overall poorer soil structure, root growth and development can be more challenging. Heavier disease pressure and increased plant stress can negatively affect stalk quality.
1 OMAFRA Staff. 2009. Corn: hybrid selection. Pub 811: Agronomy Guide.
2 2009. Corn rootworms. Purdue University. http://extension.entm.purdue.edu (verified 10/09/2014).
3 Johnson, A. 2005. Producers have new management concerns with corn-on-corn. Farm & Ranch Guide. http://www.farmandranchguide.com (verified 10/13/2014).