Growing up on a farm in eastern England, I was always told by my grandfather that "well sown equals half grown." What he meant became more apparent when I moved to the U.S. in 1989 and began working with wheat producers using a European wheat management system introduced by Opti-Crop Consulting.
I observed that some producers were doing a much better job establishing their wheat than others, and that the result at harvest was often higher yields and profits.
Based on replicated research trials over the years, we were able to identify some of the elements associated with establishing a uniform wheat stand, and what impact they had on yield. The major contributors were forward speed, down pressure and ballast (especially in no-till), and row spacing. I think most farmers are aware of the impact forward speed has on yields, and it’s very much dependent on drill/air seeder condition and residue levels. I have found that most farmers are doing a better job ballasting their drills and air seeders, according to field conditions and forward speeds, but that row spacing is still an opportunity for many producers.
Tight spacing. In 2010, I worked with Great Plains Manufacturing on a replicated wheat row spacing trial, using disk openers. The company provided two identical air seeders, one set up with 7.5" rows and the other with 10" rows. The seed population per square yard and fertilizer rates were set equally across both air seeders by a Great Plains specialist, and nitrogen was split-applied in the spring. Four replications were created for fungicide treatment and four replications were left without a fungicide treatment.
The results showed that a farmer who plants 1,000 acres of wheat per year could capture another $10,000 to $15,000 by selecting 7.5" rows. If the drill is kept for five to 10 years, the farmer could pay for the drill with the difference in yield between 7.5" and 10" spacing.
In 2000, another replicated research trial in southern Kentucky compared 12" rows to 6" rows using disk openers. Across three different spring nitrogen rates, the average yield response to 6" rows was 6 bu. per acre, within a 75 bu. to 84 bu. per acre yield range. What was more interesting was that the lowest spring nitrogen rate on 6" row spacing outyielded the highest nitrogen rate on 12" spacing, at the same seed population per acre.
Across the pond in England, France and Germany, where winter wheat yields average 130 bu. per acre or more, almost all the wheat is planted in 4" or 5" rows. Research from Western Europe suggests that the narrower the rows, the higher the yields. The only 4" row spacing research I’m aware of within the U.S. was conducted by Virginia Tech, comparing soft red winter wheat planted in 4" and 8" rows in replicated trials. The researchers found that grain yields were 8.9 bu. to 11.9 bu. per acre higher when they were spaced 4" apart. Results were averaged across three locations using intensive wheat management systems, where yields ranged between 75 bu. and 121 bu. per acre.
To capture higher yields, some farmers are now modifying their drills or air seeders to plant narrower rows. The image at left shows how a 5" spacing air seeder was created from a three-rank John Deere 1895. Seed openers were positioned 15" apart on each of the three 4" rockshafts to create 5" rows. This configuration is designed for no-till and offers the same residue flow characteristics as a 7.5" spacing seeder with two ranks.