Six-row strips boost yield success
Corn harvest conjures up visions of combines pouring golden kernels into an awaiting truck for delivery to the bin.
In reality, there's another harvest occurring from the time corn plants break the soil surface. The plants harvest sunlight that fuels photosynthesis, a process that converts sunlight into vital plant nutrients like sugars.
The more photosynthesis plants generate, the more they thrive. Ultimately, this boosts yields. Finding a way to deliver more sunlight to your plants could increase corn yields.
There is a way
Due to their position in the cornfield, outer rows garner more sunlight. That's what caused Marc Burggraff's yield monitor to jump as the Flandreau, South Dakota, farmer harvested corn on the rows bordering a soybean field four years ago.
“On the six rows on each side of the field, the yield monitor read 20 bushels per acre higher than the rest of the field,” says Burggraff.
This confirmed what Burggraff had read about outside rows yielding more corn due to increased sunlight exposure.
In 2009, he evaluated this on a larger scale by planting intermittent 12-row and 24-row corn strips between matching soybean strips on 90 acres.
Positive results did occur, but not across the entire strip.
“When we weighed the corn row by row, there was only a yield advantage two rows in,” he says. “After that, the yields began plateauing. Yields for the center rows went back to what corn rows normally would be.”
Having more outer rows gave 12-row strips the edge in field-wide tests. In 2009, 12-row strips averaged 195 bushels per acre; 24-row strips averaged 188 bushels per acre.
“We found we gained some yield from 24-row strips. But 12-row strips were a better way to go,” says Burggraff.
In 2010 and 2011, he narrowed strips further to six rows in order to compare them to 12-row strips.
This worked well. In 2010, the average of a six-row strip dwarfed yields of the 12-row strip by over 40 bushels per acre. That was due to the doubling of outside rows in the six-row setup.
In one six-row analysis, outer rows averaged 277 and 291 bushels per acre, respectively. Moving inward, row yields decreased. The innermost two rows garnered 203 and 244 bushels per acre. Another perk was outer rows were 1% drier at harvest. (See chart at right.)
Overall, Burggraff says strips boost corn yields an average 10 to 20 bushels higher than they'd normally be.
Bob Recker, Waterloo, Iowa, noticed the same corn yield bump as he's experimented with strip intercropping. “The edge of the strips is where high productivity lies,” he says.
Ditto for several academic studies' findings. A 1986-1990 Purdue University study showed corn strips with extra population and nitrogen yielded 20 bushels per acre more on average than nonstripped corn (with regular management of that time).
The knock against strip intercropping is the same one that's plagued the practice since it surfaced over two decades ago. Soybean yields take a big hit. The taller corn shadows soybean plants, thus, decreasing the amount of sunlight they garner.