Narrow Row Corn

Narrow Row Corn

I continue to get quite a few questions on narrow row corn so I thought I would review some of the results again. A study from Michigan State University (William Widdicombe and Kurt Thelen) emphasizes some important points.

Michigan Study

This study from nearby Michigan included 11 test sites over two years (1998 and 1999), with various hybrids, 3 row widths (30”, 22” and 15”) and five plant populations ranging from 22,400 to 36,000 plant per acre. The study points to a consistent increase of 2% in yield for 22 inch rows over 30 inch rows and a 4% increase for 15” rows to 30 inch rows (refer to Table 1). This yield increase due to row widths is more than others have reported, especially from the Northeast where it has been rare to see consistent narrow row response. However, it is a more modest yield advantage than the 8% increase that was talked about through the early nineties and which served as incentive for some of the early adopters to switch to narrow rows.

Source: W. D. Widdicombe and K. D. Thelen, Agronomy Journal 94:1020-1023 (2002)

 A wide range of plant populations were used within each row width. There was no population by row width interaction. That is, increased plant population boosted corn yields in a similar fashion in both the wide and narrow rows. Interestingly, the yield increases due to increasing plant density were of a similar nature as the increase due to narrowing row widths (refer to Table 2).

Source: W. D. Widdicombe and K. D. Thelen, Agronomy Journal 94:1020-1023 (2002)

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Hybrids used in this study were selected based on maturity, characteristics in ear type (flex, determinate, indeterminate), leaf orientation (erect, semi-upright, wide) and plant height (short, medium, tall). As in most studies, the hybrid selected had a significant impact on yield, but there were no particular hybrids that did better in narrow rows. In other words, hybrids that yielded better in wide rows also yielded better in narrow rows. However, there were differences in the way hybrids responded to the various populations. The researchers could not explain hybrid response to population by examining the aforementioned characteristics (ear type, height, leaf angle).

Switch To Narrow Rows?

So as you ponder this most recent report, you may be considering a switch to narrow rows. I generally have been of the opinion that it takes a system approach to pay for the narrow row conversion. If the twenty inch planter is also going to do soybeans and edible beans, and do them better with less seed cost, then perhaps you can pencil it out. However, if the planter, tire and header conversions all need to come out of a 2 – 4 % increase in corn yield, then I am not very excited about the idea. More to the point from this data set is the fact that you first should be optimizing your productivity based on plant population where the extra capital costs are zero and the yield responses are similar to narrowing rows.

Seeding Rate Adjustments

Perhaps the changes to your corn planter for this winter should be an accurate acreage meter and an accurate variable rate seed drive. I am not suggesting a GPS driven variable rate seeding system, just one that allows you the flexibility to adjust seeding rates from the tractor cab with confidence for a range of conditions. What conditions? Here are my suggestions for conditions that may require more seeding rate adjustment than you have traditionally done.

1. Yield potential
• most notably water availability
2. Hybrid response to population
   • rely little on “hybrid characteristics” such as flex ear and more on actual population results
3. Time of planting
• early season better than late season
4. Planting conditions
   • boost seeding rates under tough soil conditions even if it is only on half the field
5. Improved soil conditions
   • if you have done deep tillage or boosted fertility a higher seeding rate may be a good indicator if you really have made any difference in yield potential

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