How can we translate “farming smarter” and technology into an extra 40 bu.? Fasten your seatbelts for a tour of what may be the future of corn and bean farming.

Strip intercropping leverages sunlight, guidance technology and sometimes variable-rate planting to average roughly 290-bu./acre corn, according to several years’ research by curious growers in Iowa, South Dakota and Minnesota. Their alternating swaths range from four to 12 rows wide, with various row widths.

In Flandreau, SD, strip-intercropper Marc Burggraff has seen up to a 100-bu./acre difference between the outside corn row (of six-row corn strips) and the middle corn row of his strips. A few of his outside corn rows exceeded 290 bu./acre in 2010. He tested both 12-row and six-row strips of corn/soybeans in 2010.

“My six-row corn strips averaged 235 bu./acre, with two of them going over 250 bu./acre. This is amazing since our county average is in the 160s,” Burggraffsays. “A whole field of my mono-crop corn would average around 200 bu./acre in that field.” 

He does not vary corn-row populations by location, and rotates between Roundup Ready and Liberty Link genetics.

“My 12-row strips right beside the six’s yielded 215 bu./acre,” he says, compared to the whole field of 2010 (mono-crop) corn yield of 200 bu./acre. “It was amazing to see those numbers,” Burggraff says.

He’s experimented with strip intercropping for six years, expanding to 45 and then 90 acres. He first tried strip intercropping in 2006 after reading online ag forum strip-intercropping results from Clay Mitchell, Buckingham, Iowa, and Iowa’s Bob Recker.

Burggraff is the buzz at the local coffee shop because he plants two crops on the same pass with variable-rate electronic controls on a White 12-row planter. “I plant three rows of beans on the outside rows, and six rows of corn in the middle, effectively making six-row strips,” he says.

In southern Minnesota, “strips are the most profitable ground I farm, says southern Minnesota grower and engineer Sheldon Stevermer from Wells. “My (2010) strip intercrop had a net return of $120/acre over all soybeans. This is based on a strip-intercrop corn yield average of 231 bu./acre,” he says. “I have never combined corn with stalks that thick, like trees,” Stevermer says.

 “This fall’s corn yield was about 5 bu. better than the three-year corn average (of continuous corn),” he says. “I think it’s possible to get 30-40-bu./acre better corn yields if the right hybrid’s planted. Some hybrids respond significantly better than others in this environment. The hybrid we planted this year just didn’t have the large ears on the outside rows.

 “The beans were a few bushels better than our 2011 farm average. Given that the field’s been in continuous corn, I’d have expected the bean yields to be better. However, we did plant a group 2.3 bean there, and the mid-September frost did nail them rather hard, especially the green ones. I think hybrid and variety selection is key in optimizing yield with strip intercrop.”

This year, he devoted 80 acres to strip intercropping.

So why the bump in yields? When corn grows along the edge of a field, the outside rows respond disproportionately well to extra sunlight (see sidebar). By boosting the corn plant populations of these sunniest outside rows to leverage the extra light reaching them, Bob Recker sees corn yields of 348 bu. in that outside row, gradually tapering off in relation to distance from the edge. Recker is a retired John Deere engineer and owns Cedar Valley Innovation, Waterloo, IA.

He’s tested strip intercropping across nine sites in east-central Iowa over five years. Not all strip intercroppers vary corn populations by row, but they still realize worthwhile gains.

Either way, Recker likens strip intercropping to “a roadster that performs extremely well on a good road, but not rough ground or muddy lanes. It’s not a panacea unless you’re paying attention. But it is a consistent way, especially with the variable-rate planting, of taking some giant strides in corn yields.”

He scrutinizes inter-plant spacing, grain yield per plant and other agronomic variables of strip intercropping to tailor the microclimate that teases out every last kernel from each plant.

Creating artificial field edges and outside rows is also a fascination for Roger Knutson, Hubbard, IA, and his son-in-law, ag engineer Jacob Bolson. Collaborating with Recker, they’ve concluded that “you need eight or fewer rows per strip to maximize the outside-row effect,” Knutson says.

In 2010, he evaluated a set of four-row strips, with the outer two corn rows planted at 56,000/acre and inner two rows planted at 28,000. For 2011, he plans to evaluate strips at an even higher population.

 “Once you take strip intercropping to a production scale, RTK guidance is key to optimize nutrient placement and residue management from year to year,” Bolson says.

“Strip intercropping also offers a huge opportunity to introduce controlled traffic to reduce compaction,” he adds. Controlled traffic was the focus of his graduate research.

Recker’s brother Herb and nephew Mike have tested strips for three years on their home farm near Dyersville, IA, where they operate a seed dealership. Alternating six-row strips of corn/beans, they gained an average of 40 bu./acre on their corn, with “edge-row” corn yields as high as 325 bu./acre on ground “that has to stretch to reach 200 in monocrop,” Bob says. The Reckers bumped plant populations on the outside corn row to 62,000/acre. The second row in from the edge is planted at 52,000, and the third row is at 36,000.

“Equipment-wise, the biggest challenge was coming up with a six-row bean (combine) head, but if I make an extra $160/acre, I’m pretty motivated,” Herb admits.

Variable-rate planting generally increases the outside-row sunlight effect, but is not a requirement to capture its benefit.

The Reckers note that they did not lodge during the July high-wind event in east-central Iowa. “Of course hybrid selection is key, but we dispelled the conventional wisdom of higher populations lodging from those 65-mph winds,” Mike says.

 “It makes sense that it didn’t lodge because the outer plants are not resource-limited due to neighbor competition since they are instead dominating over the soybean,” says Iowa State University’s Lori Abendroth, project manager, climate and sustainable corn-based systems. “Lodging and high populations only go together, typically, when plants are resource-limited in some way.”

Strip intercropping today “reminds me of GPS when I first evaluated it in 1992,” says ECI Co-op Agronomy Manager Gene Mitchell, Hudson, IA. “It was pretty Star Wars. But the software has evolved, and the data we now get from it is really useful. If we’re going to double our crop production by 2030, this might be a concept to consider.It probably doesn’t lend itself well to a 20,000-acre grower with a 48-row planter right now; it’s going to be an early adopter who thinks out of the box,” Mitchell says.