Production

I wanted to revisit the narrow row corn issue, not because we haven’t had enough written or said about it in the last ten years, but because a recently published study from Michigan State University emphasizes some important points. This particular study is attractive since it comes from nearby Michigan; it also 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 plants per acre. The study, conducted by William Widdicombe and Kurt Thelen, points to a consistent increase of 2% in yield for 22-inch rows over 30-inch rows, and a 4% increase for 15-inch rows compared to 30-inch rows (see Table 1). This yield increase resulting from 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 discussed through the early nineties and served as incentive for some of the early adopters to switch to narrow rows.

Of note in this research is the wide range of plant populations that were used within each row width and the fact that 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, Table 2 illustrates that yield increases resulting from increasing plant density were similar in nature to the increases resulting from narrowing row widths.

Hybrids used in this study were selected based on maturity and on particular characteristics in ear type (flex, determinate, indeterminate), in leaf orientation (erect, semi-upright, wide) and in plant height (short, medium, tall). As in most studies, the hybrid selected had a significant impact on the 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. There were differences in the way hybrids responded to the various populations, however. The researchers could not explain hybrid response to population by examining the aforementioned characteristics (ear type, height, leaf angle).

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 per cent 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.

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 with confidence from the tractor cab for a range of conditions. The following conditions may require more seeding rate adjustment than you have traditionally done:
• yield potential (most notably water availability)
• hybrid response to population (rely little on ‘hybrid characteristics’ such as flex ear and more on actual population results)
• time of planting (early season vs. late season)
• planting conditions (boosting seeding rates under tough soil conditions even if it is only on half the field)
• 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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