Do Hybrids Respond Differently to Row Spacing?

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  • Farmers that have adopted narrower row spacing in corn emphasize that hybrids respond differently to narrower row spacing.
  • In this research, Pioneer screened 11 hybrids with known differences in plant height, leaf uprightness, drought tolerance, disease susceptibility and stalk strength.
  • The goal of this research was to help farmers in narrower row spacing systems select the best genetics for their operations.

Study Description

Years:    2011-2013
Location:     1 in Missouri
Replications:   5
   Row Spacing:   15 and 30 inch
   Plant Population:   30,000 and 36,000 plants/acre  
   Hybrids:   11 Pioneer® brand corn hybrids selected to
  represent a range in leaf uprightness, plant health,
  disease and drought tolerance.
Pioneer® Brand Corn Hybrids
 Hybrid Characteristics  Hybrid/Brand¹
Expected to respond to narrow
row spacing. Erect leaves and
relatively higher ear placement.
33T57 (HX1, LL, RR2)
P0636AM™ (AM, LL, RR2)
P1498AM™ (AM, LL, RR2)
Not expected to respond to
narrow row spacing. Horizontal
leaves and lower ear
P0621HR (HX1, LL, RR2)
P1151AM™(AM, LL, RR2)
P1324HR (HX1, LL, RR2)
Horizontal leaves and relatively
high ear placement.
P0461HR (HX1, LL, RR2)
P1018AM™ (AM, LL, RR2)
P1420HR (HX1, LL, RR2)
Erect leaves and lower ear
P1360HR (HX1, LL, RR2)
P1395AM™ (AM, LL, RR2)


  • When averaged across years and hybrids, there was a small but statistically significant advantage to 15-inch vs 30-inch row spacing (Figure 1).
  • Corn yield was not significantly affected by plant population in this study (data not shown).
  • In 2 of 3 years, drought stress significantly limited yield potential. Narrow row management decisions should not be based solely on the results of this study.

Figure 1. Effect of row width on corn yield

Chart: Effect of row width on corn yield
  • In this study, hybrids responded differently to narrower row spacing (Figure 2). The narrow row advantage for Pioneer® hybrids P1324HR, 33T57 and P1018HR was positive ranging from 7 to 17 bushels (significant at p<0.15).
  • Based on plant structure, P1324HR was not expected to respond to narrower row spacing. In field experience with this hybrid, it is known to tolerate higher plant density and early season moisture stress. This tolerance to early season moisture stress could explain the observed yield response to narrow rows with this hybrid.
  • The hybrid with the most erect leaves in this study, Pioneer® hybrid P1360HR, did not respond to narrow row spacing. Having poorer drought tolerance and lower ear placement could explain this lack of response.
  • A key observation in this study was that some hybrids tended to change their leaf angle in response to narrower rows. For example, leaves in Pioneer® P1395AM™ and P1018AM™ brand corn tended to be more upright in 15-inch rows (Figure 3).

Figure 2. Yield advantage of various hybrids in 15- vs 30-inch row spacings.

Chart: Yield advantage

Figure 3. Some genetics changed their leaf angle in response to narrower row spacing.
Left: P1018AM™ in 15-inch rows. Right: P1018AM™ in 30-inch rows.


Hybrid Suggestions for Narrow Row Corn

  1. Start with hybrids most adapted to your area. Hybrids that do well in 30-inch rows will likely perform equally well in narrower rows.
  2. Consider hybrids with tolerance to higher plant density. In the example of P1324HR, there seemed to be a relationship in tolerance to high plant density in 30-inch rows with performance in narrow rows.
  3. Consider hybrids with better foliar health and stalk strength. While not observed in this study, disease pressure can be greater with narrower rows due to the more humid canopy. 
  4. Test several hybrids to optimize genetics in your system. The observation that some genetics change their leaf angle in response to narrow row spacing makes it difficult to predict hybrid responses.

Research conducted by Kelly Nelson, University of Missouri, as a part of the Pioneer Crop Management Research Awards (CMRA) Program. This program provides funds for agronomic and precision farming studies by university and USDA cooperators throughout North America. The awards extend for up to 4 years and address crop management information needs of Pioneer agronomists, Pioneer sales professionals and customers.

¹All Pioneer products are hybrids unless designated with AM1, AM, AMRW, AMX and AMXT, in which case they are brands. 2013 data are based on average of all comparisons made in one location through November 21, 2013. Multi-year and multi-location is a better predictor of future performance. Do not use these or any other data from a limited number of trials as a significant factor in product selection. Product responses are variable and subject to a variety of environmental, disease, and pest pressures. Individual results may vary.

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 refuge must be planted with Optimum AcreMax products.


HX1 - Contains the Herculex® I Insect Protection gene which provides protection against European corn borer, southwestern corn borer, black cutworm, fall armyworm, lesser corn stalk borer, southern corn stalk borer, and sugarcane borer; and suppresses corn earworm.
Herculex® I Insect Protection technology by Dow AgroSciences and Pioneer Hi-Bred. Herculex® and the HX logo are registered trademarks of Dow AgroSciences LLC.
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®Roundup Ready is a registered trademark used under license from Monsanto Company.

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.
YieldGard®, the YieldGard Corn Borer design and Roundup Ready® are registered trademarks used under license from Monsanto Company.