Corn Yield Response to Row Spacing in Southwestern Iowa


  • Evaluate corn yield response to row spacing in the Missouri Valley of western Iowa.
  • Determine if performance in narrow rows differs among hybrids and plant populations. 

Study Description

Locations: 9 farms in the Missouri Valley of western Iowa 
Years: 2010-2013
Plot Layout:    8-row field-length strips 
Factors:          Row Spacing:     20-inch and 30-inch
  Population:  36,000 and 42,000 plants/acre
                         Pioneer® Hybrids/Brands1:  
    33M16 (HX1, LL, RR2)
    33W88AM1™ (AM1, LL, RR2)
    P1162AMX™ (AMX, LL, RR2)
    P1480HR (HX1, LL, RR2)
  • Hybrids/brands were selected to represent a range in leaf architecture, foliar health and drought tolerance. 
  • All plots were planted using commercially available 20- and 30-inch row planters.  


  • Across all locations and years, average corn yield was 11 bu/acre greater in 20-inch rows than 30-inch rows (Figure 1).
  • Yield response to narrow rows varied greatly among years, with the greatest response observed in 2011.
  • The 4 hybrids/brands included in this study responded similarly to row spacing (Figure 2).
  • Yield response to row spacing was similar between plant populations (Figure 3).   

Figure 1. Average yield advantage of 20-inch rows vs. 30-inch rows over 4 years.

Figure 2. Average yield response of hybrids/brands to 20-inch rows.

Figure 3. Effect of row spacing and plant population on corn yield.


  • The average yield advantage observed in this study with 20-inch rows was greater than has been generally reported in Iowa.
  • The unusually large yield response to narrow rows could be associated with higher solar radiation in southwest Iowa relative to the rest of the state.
  • This research indicates that adopting narrower row spacing could potentially increase corn yields on some farms.
  • Narrow row spacing involves many management aspects that should be considered before adopting.

1All Pioneer products are hybrids unless designated with AM1, AM, AMRW, AMX and AMXT, 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. 2013 data are based on average of all comparisons made in nine locations through November 15, 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.

   AM1 - Optimum® AcreMax® 1 Insect Protection System with an integrated corn rootworm refuge solution includes HXX, LL, RR2. Optimum AcreMax 1 products contain the LibertyLink® gene and can be sprayed with Liberty® herbicide. The required corn borer refuge can be planted up to half a mile away.
  AMX - Optimum® AcreMax® Xtra Insect Protection system with YGCB, HXX, LL, RR2. Contains a single-bag integrated refuge solution for above- and below-ground insects. In EPA-designated cotton growing counties, a 20% separate corn borer refuge must be planted with Optimum AcreMax Xtra 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.
Liberty®, LibertyLink® and the Water Droplet Design are trademarks of Bayer.
® Roundup Ready is a registered trademark used under license from Monsanto Company.

  HXX - Herculex® XTRA contains both the Herculex I and Herculex RW genes.
Herculex® XTRA Insect Protection technology by Dow AgroSciences and Pioneer Hi-Bred. Herculex® and the HX logo are registered trademarks of Dow AgroSciences LLC.
  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.