Managing Corn for Greater Yield Potential

Crop Insights by Mark Jeschke, Ph.D., Agronomy Manager

Summary

  • Improved hybrids and production practices are helping corn growers increase yields. Over the past 20 years, U.S. yields have increased by an average of 2.1 bu/acre/year.
  • The NCGA National Corn Yield Contest provides a benchmark for yields that are attainable when conditions and management are optimized.
  • The 2019 contest had 130 entries that exceeded 300 bu/acre; down from the record high of 224 entries set in 2017.
  • Selecting the right hybrid can affect yield by over 30 bu/acre, making this decision among the most critical of all controllable factors.
  • Establishing sufficient population density is important to allow a hybrid to maximize its yield potential.
  • High-yielding contest plots are usually planted as early as practical for their geography. Early planting lengthens the growing season and moves pollination earlier.
  • Maintaining adequate nitrogen fertility levels throughout key corn development stages is critical in achieving highest yields. In-season applications can help supply nitrogen when plant uptake is high.

Introduction

Improvements in corn productivity that began with the introduction of hybrid corn nearly a century ago have continued through the present day. Over the last 20 years, U.S. corn yield has increased by an average of 1.9 bu/acre per year. These gains have resulted from breeding for increased yield potential, introducing transgenic traits to help protect yield, and agronomic management that has allowed yield potential to be more fully realized.

As growers strive for greater corn yields, the National Corn Growers Association (NCGA) National Corn Yield Contest provides a benchmark for yields that are attainable when environmental conditions and agronomic management are optimized. The average yields of NCGA winners are about double the average U.S. yields. This difference can be attributed to favorable environmental conditions, highly productive contest fields, and high-yield management practices used by contest winners.

Arial photo - harvesting in field

2019 NCGA National Corn Yield Contest

The 2019 growing season was extremely challenging for corn production in many areas, a fact that was reflected to some extent in the results of the 2019 NCGA National Corn Yield Contest. The number of high-yield entries in the contest – defined for the purposes of this discussion as all entries yielding over 300 bu/acre – was down for the second year in a row from the all-time high set in 2017 (Figure 1). The biggest change was in the central Corn Belt states of Nebraska, Iowa, Illinois, and Indiana, all of which saw a sharp drop in the number of high-yield entries compared to the past two years (Table 1). The geography that posted the best results relative to previous years was the Mid-Atlantic region, with an uptick in high yield entries in Pennsylvania, Delaware, New Jersey, and Virginia.

Figure 1. Total entries in the NCGA National Corn Yield Contest exceeding 300 bu/acre by year from 2013 to 2019.

The top yield overall in the 2019 contest was 616.2 bu/acre bu/acre achieved with Pioneer® hybrid P1197YHR (YGCB, HX1, LL, RR2). This marks the third time that the highest overall yield in the contest was produced with a product in the Pioneer® brand P1197 family of products.

Table 1. Number of NCGA National Corn Yield Contest entries over 300 bu/acre by state, 2015-2019.

The average yields among national winners tend to be skewed by a small number of very high yields, particularly in the irrigated classes. Therefore, as a yield performance benchmark, it can be useful to look at a larger set of contest entries. Table 2 shows the median yield of the top 100 yielding entries in the irrigated and non-irrigated classes. Median yields of top entries in both the irrigated and non-irrigated classes exceeded 300 bu/acre for the third year in a row, which is about 75% greater than the current U.S. average. Median yields of the top 100 non-irrigated entries and irrigated entries in 2019 were both down from the highs achieved in 2017.

Table 2. Median yields of the top 100 irrigated and non-irrigated NCGA National Corn Yield Contest entries, and the USDA average U.S. corn yields from 2013 to 2019.

Table - Median yields of the top 100 irrigated and non-irrigated NCGA National Corn Yield Contest entries, and the USDA average U.S. corn yields from 2013 to 2019.

Hybrid Selection

Hybrids tested against each other in a single environment (e.g., a university or seed company test plot) routinely vary in yield by at least 30 bu/acre. At contest yield levels, hybrid differences can be even higher. That is why selecting the right hybrid is likely the most important management decision of all those made by contest winners.

The yield potential of many hybrids now exceeds 300 bu/acre. Realizing this yield potential requires matching hybrid characteristics with field attributes, such as moisture supplying capacity; insect and disease spectrum and intensity; maturity zone, residue cover; and even seedbed temperature. To achieve highest possible yields, growers should select a hybrid with:

  • Top-end yield potential. Examine yield data from multiple, diverse environments to identify hybrids with highest yield potential.
  • Full maturity for the field. Using all of the available growing season is a good strategy for maximizing yield.
  • Good emergence under stress. This helps ensure uniform stand establishment and allows earlier planting, which moves pollination earlier to minimize stress during this critical period.
  • Above-average drought tolerance. This will provide insurance against periods of drought that most non-irrigated fields experience.
  • Resistance to local diseases. Leaf, stalk, and ear diseases disrupt normal plant function, divert plant energy, and reduce standability and yield.
  • Traits that provide resistance to major insects, such as corn borer, corn rootworm, black cutworm, and western bean cutworm. Insect pests reduce yield by decreasing stands, disrupting plant functions, feeding on kernels, and increasing lodging and dropped ears.
  • Good standability to minimize harvest losses.

Pioneer brand products were used in 10 national winning entries (Table 3), as well as 245 state-level winning entries – more than any other seed brand. State-level winners included a total of 79 different Pioneer® brand products from 51 different hybrid families ranging from 82 to 120 CRM (Appendix).

The brands of seed corn used in the highest yielding contest entries in 2015 through 2019 are shown in Figure 2. In all years, Pioneer brand products were used in more entries exceeding 300 bu/acre than any other individual seed brand.

Table 3. 2019 National Corn Yield Contest national winning entries using Pioneer brand products.

Table - 2019 NCGA National Corn Yield Contest national winning entries using Pioneer brand products.

Table - 2019 NCGA National Corn Yield Contest national winning entries using Pioneer brand products.

The brands of seed corn used in the highest yielding contest entries in 2015 through 2019 are shown in Figure 2. In all years, Pioneer brand products were used in more entries exceeding 300 bu/acre than any other individual seed brand.

 

Bar Chart - Seed brand planted in National Corn Yield Contest entries exceeding 300 bu/acre from 2015 to 2019.

Figure 2. Seed brand planted in National Corn Yield Contest entries exceeding 300 bu/acre from 2015 to 2019.

Yields exceeding 300 bu/acre have been achieved using Pioneer brand products from 65 different hybrid families over the past five years, ranging from 91 to 121 CRM. The top-performing Pioneer hybrid families in the National Corn Yield contest are shown in Table 4. The Pioneer brand P1197 family of products has had the best performance in the contest by far, topping 300 bu/acre 78 times since it’s debut in the contest in 2014.

Table 4. Pioneer hybrid families with the most high-yield entries in the NCGA National Corn Yield Contest over the past five years.

Table - Pioneer hybrid families with the most high-yield entries in the NCGA National Corn Yield Contest, 2015-2019.

Table - Pioneer hybrid families with the most high-yield entries in the NCGA National Corn Yield Contest, 2015-2019.

High-Yield Management Practices

Top performers in the NCGA yield contest not only have produced yields much higher than the current U.S. average, they have also achieved a higher rate of yield gain over time. Over the past 20 years, U.S. corn yields have increased at a rate of 1.9 bu/acre per year while winning yields in the non-irrigated yield contest classes have increased by 5.2 bu/acre per year. Contest fields are planted with the same corn hybrids available to everyone and are subject to the same growing conditions, which suggests that management practices are playing a key role in capturing more yield potential. The following sections will discuss management practices employed in contest entries yielding above 300 bu/acre.

Graph - Average yields of NCGA National Corn Yield contest non-irrigated class national winners and U.S. average corn yields, 2002-2019.

Figure 3. Average yields of NCGA National Corn Yield contest non-irrigated class national winners and U.S. average corn yields, 2002-2019.

Planting Practices

Plant Population

One of the most critical factors in achieving high corn yields is establishing a sufficient population density to allow a hybrid to maximize its yield potential. Historically, population density has been the main driver of yield gain in corn - improvement of corn hybrid genetics for superior stress tolerance has allowed hybrids to be planted at higher plant populations and produce greater yields.

Harvest populations in irrigated and non-irrigated national corn yield contest entries over 300 bu/acre from 2015 through 2019 are shown in Figure 4. The average harvest population of irrigated entries (37,300 plants/acre) was slightly greater than that of non-irrigated entries (36,700 plants/acre) over five years. However, yields over 300 bu/acre were achieved over a wide range of populations, from 28,000 to 56,000 plants/acre, demonstrating that exceptionally high populations are not necessarily a prerequisite for high yields. Although population density is important in establishing the yield potential of a corn crop, it is just one of many factors that determine yield.

 

Scatter Plot - Harvest populations and corn yield of irrigated and non-irrigated NCGA National Corn Yield Contest entries exceeding 300 bu/acre, 2015-2019.

Figure 4. Harvest populations and corn yield of irrigated and non-irrigated NCGA National Corn Yield Contest entries exceeding 300 bu/acre, 2015-2019.

Planting Date

High-yielding contest plots are usually planted as early as practical for their geography. Early planting lengthens the growing season and more importantly, moves pollination earlier. When silking, pollination and early ear fill are accomplished in June or early July, heat and moisture stress effects can be reduced.

Planting delays were a major challenge for corn production in many areas in 2019 and a lot of corn was planted in June. Planting dates for entries exceeding 300 bu/acre ranged from March 21 to June 4 in 2019. Mid-April to early-May planting dates have typically been the most common for high-yields in the central Corn Belt. The 2019 contest had numerous high-yield entries planted in mid- to late-May (26 entries over 300 bu/acre were planted after May 15), demonstrating that high yields can still be achieved under favorable conditions if planting is not delayed for too long.

Row Width

The vast majority of corn acres in the U.S. are currently planted in 30-inch rows, accounting for over 85% of corn production. A majority of 300 bu/acre contest entries over the past five years have been planted in 30-inch rows (Figure 5). This proportion has increased slightly in recent years as wider row configurations (most commonly 36-inch or 38-inch) have declined and narrower row configurations (15-inch, 20-inch, 22-inch or 30-inch twin) have largely remained steady.

Row spacings narrower than the current standard of 30 inches have been a source of continuing interest as a way to achieve greater yields, particularly with continually increasing seeding rates. However, research has generally not shown a consistent yield benefit to narrower rows outside of the Northern Corn Belt (Jeschke, 2018).

 

Graph - Row width used in NCGA National Corn Yield Contest entries exceeding 300 bu/acre, 2015-2019.

Figure 5. Row width used in NCGA National Corn Yield Contest entries exceeding 300 bu/acre, 2015-2019.

Crop Rotation

Rotating crops is one of the practices most often recommended to keep yields consistently high. Rotation can break damaging insect and disease cycles that lower crop yields. Including crops like soybean or alfalfa in the rotation can reduce the amount of nitrogen required in the following corn crop. A majority of the fields in the 300 bu/acre entries were planted to a crop other than corn the previous growing season (Figure 6).

Figure 6. Previous crop in NCGA National Corn Yield Contest entries exceeding 300 bu/acre in 2019 and 5-year averages.

The so-called “rotation effect” is a yield increase associated with crop rotation compared to continuous corn even when all limiting factors appear to have been controlled or adequately supplied in the continuous corn. This yield increase has averaged about 5 to 15 percent in research studies but has generally been less under high-yield conditions (Butzen, 2012). Rotated corn is generally better able to tolerate yield-limiting stresses than continuous corn; however, yield contest results clearly show that high yields can be achieved in continuous-corn production.

Tillage

Over the past five years, close to half of the high yield entries in the NCGA contest have used conventional tillage, with the other half using no-tillage or some form of reduced tillage (Figure 7). The 2019 contest had a notable increase in the proportion of high yield entries using no-till, offset by declines in conventional tillage and strip tillage. The proportion of high-yield entries using no-till (32%) was greater than the proportion of no-till entries in the contest overall (26%).

 

Bar Chart - Tillage practices in NCGA National Corn Yield Contest entries exceeding 300 bu/acre in 2019 and 5-year averages.

Figure 7. Tillage practices in NCGA National Corn Yield Contest entries exceeding 300 bu/acre in 2019 and 5-year averages.

Soil Fertility

Achieving highest corn yields requires an excellent soil fertility program, beginning with timely application of nitrogen (N) and soil testing to determine existing levels of phosphorous (P), potassium (K), and soil pH.

Nitrogen

Corn grain removes approximately 0.67 lbs of nitrogen per bushel harvested, and stover production requires about 0.45 lbs of nitrogen for each bushel of grain produced (IPNI, 2014). This means that the total N needed for a 300 bu/acre corn crop is around 336 lbs/acre. Only a portion of this amount needs to be supplied by N fertilizer; N is also supplied by the soil through mineralization of soil organic matter. On highly productive soils, N mineralization will often supply the majority of N needed by the crop. Credits can be taken for previous legume crop, manure application, and N in irrigation water. Nitrogen application rates of entries exceeding 300 bu/acre are shown in Figure 8.

The N application rates of 300 bu/acre entries varied greatly, but around half were in the range of 250 to 350 lbs/acre. Some entries with lower N rates were supplemented with N from manure application. As corn yield increases, more N is removed from the soil; however, N application rates do not necessarily need to increase to support high yields. Climatic conditions that favor high yield will also tend to increase the amount of N a corn crop obtains from the soil through increased mineralization of organic N and improved root growth.

Timing of N fertilizer applications can be just as important as application rate. The less time there is between N application and crop uptake, the less likely N loss from the soil will occur and limit crop yield. Nitrogen uptake by the corn plant peaks during the rapid growth phase of vegetative development between V12 and VT (tasseling). However, the N requirement is high beginning at V6 and extending to the R5 (early dent) stage of grain development.

Figure 8. Nitrogen rates (total lbs/acre N applied) of NCGA National Corn Yield Contest entries exceeding 300 bu/acre in 2019 and 5-year averages.

Timing of N fertilizer applications in 300 bu/acre entries is shown in Figure 9. Very few included fall-applied N. Many applied N before or at planting. Around 90% of 300 bu/acre entries included some form of in-season nitrogen, either side-dressed or applied with irrigation. Multiple nitrogen applications were also used in around 90% of high-yield entries.

Figure 9. Nitrogen fertilizer application timing of NCGA National Corn Yield Contest entries exceeding 300 bu/acre in 2019 and 5-year averages.

Micronutrients

Micronutrients were applied on approximately half of the 300 bu/acre entries (Figure 10). The nutrients most commonly applied were sulfur (S) and zinc (Zn), with some entries including boron (B), magnesium (Mg), manganese (Mn), or copper (Cu). Micronutrients are sufficient in many soils to meet crop needs. However, some sandy soils and other low organic matter soils are naturally deficient in micronutrients, and high pH soils may make some micronutrients less available (Butzen, 2010). Additionally, as yields increase, micronutrient removal increases as well, potentially causing deficiencies.

Figure 10. Micronutrients applied in NCGA National Corn Yield Contest entries exceeding 300 bu/acre in 2019 and 5-year averages.

2019 NCGA State Pioneer Winners

2019 NCGA National Corn Yield Contest state-level winners using Pioneer® brand products.

Alabama - Georgia


Idaho - Iowa


Kansas - Louisiana


Massachusetts - Montana


Nebraska - North Dakota


Ohio - Pennsylvania


South Carolina - Utah


Virginia - Wyoming


References


January 2020

           

             

AM - Optimum® AcreMax® Insect Protection system with YGCB, HX1, LL, RR2. Contains a single-bag integrated refuge solution for above-ground insects. In EPA-designated cotton growing counties, a 20% separate corn borer refuge must be planted with Optimum AcreMax products. AMXT (Optimum® AcreMax® XTreme) - Contains a single-bag integrated refuge solution for above- and below-ground insects. The major component contains the Agrisure® RW trait, the YieldGard® Corn Borer gene, and the Herculex® XTRA genes. In EPA-designated cotton growing counties, a 20% separate corn borer refuge must be planted with Optimum AcreMax XTreme products. YGCB,HX1,LL,RR2 (Optimum® Intrasect®) - Contains the YieldGard® Corn Borer gene and Herculex® I gene for resistance to corn borer. AMT - Optimum® AcreMax® TRIsect® Insect Protection System with RW,YGCB,HX1,LL,RR2. Contains a single-bag refuge solution for above and below ground insects. The major component contains the Agrisure® RW trait, the YieldGard® Corn Borer gene, and the Herculex® I genes. In EPA-designated cotton growing counties, a 20% separate corn borer refuge must be planted with Optimum AcreMax TRIsect products.

AVBL,YGCB,HX1,LL,RR2 (Optimum® Leptra®) - Contains the Agrisure Viptera® trait, the YieldGard Corn Borer gene, the Herculex® I gene, the LibertyLink® gene, and the Roundup Ready® Corn 2 trait. HX1 - Contains the Herculex® I Insect Protection gene which provides protection against European corn borer, southwestern corn borer, black cutworm, fall armyworm, western bean cutworm, lesser corn stalk borer, southern corn stalk borer, and sugarcane borer; and suppresses corn earworm. HXX - Herculex® XTRA contains the Herculex I and Herculex RW genes. YGCB - The YieldGard® Corn Borer gene offers a high level of resistance to European corn borer, southwestern corn borer and southern cornstalk borer; moderate resistance to corn earworm and common stalk borer; and above average resistance to fall armyworm. LL - Contains the LibertyLink® gene for resistance to Liberty® herbicide. RR2 - Contains the Roundup Ready® Corn 2 trait that provides crop safety for over-the-top applications of labeled glyphosate herbicides when applied according to label directions. Q (Qrome®) - Contains a single-bag integrated refuge solution for above- and below-ground insects. The major component contains the Agrisure® RW trait, the YieldGard® Corn Borer gene, and the Herculex® XTRA genes. In EPA-designated cotton growing counties, a 20% separate corn borer refuge must be planted with Qrome products. Qrome® products are approved for cultivation in the U.S. and Canada. For additional information about the status of regulatory authorizations, visit www.biotradestatus.com

Herculex® Insect Protection technology by Dow AgroSciences and Pioneer Hi-Bred. Herculex® and the HX logo are registered trademarks of Dow AgroSciences LLC. YieldGard®, the YieldGard Corn Borer design and Roundup Ready® are registered trademarks used under license from Monsanto Company. Liberty®, LibertyLink® and the Water Droplet Design are registered trademarks of BASF. Agrisure® and Agrisure Viptera® are registered trademarks of, and used under license from, a Syngenta Group Company. Agrisure® technology incorporated into these seeds is commercialized under a license from Syngenta Crop Protection AG.

¹All Pioneer products are hybrids unless designated with AM1, AM, AMT, AMRW, AMX, AMXT, AML, and Q in which case they are brands.

PIONEER® brand products are provided subject to the terms and conditions of purchase which are part of the labeling and purchase documents.

The foregoing is provided for informational use only. Please contact your Pioneer sales professional for information and suggestions specific to your operation. Product performance is variable and depends on many factors such as moisture and heat stress, soil type, management practices and environmental stress as well as disease and pest pressures. Individual results may vary.