Lessons of 20-Inch Rows

The Skinny on 20s

Pamela Smith
By  Pamela Smith , Crops Technology Editor
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A narrow-row corn crop gets hungry, and Wallis Farms uses sidedressing to meet the yield goals of each field. (Mary Ann Carter)

Scott Wallis didn't get narrow-minded overnight. The Princeton, Indiana, farmer studied the idea of moving to 20-inch rows for three years before making the switch in both corn and soybeans.

Narrow-row beans were a no-brainer. It was corn that required the numbers crunching. While Wallis was convinced reducing row width would result in a more efficient corn factory, the need for both a specialized planter and a 20-inch corn head made the decision more than an impulse buy.

The question of how to supply additional groceries to a hungry corn crop without tearing it up was another piece of the puzzle.

"It's difficult to dip your toe in and just try 20-inch rows without making a financial commitment," Wallis says. It's not like you can easily hire or rent everything it takes to try the practice on for size.

"The planter and fertilizer rig could be changed back to 30-inch rows, but we faced a financial hit on a 20-inch corn head if things didn't work out," he adds.

That was 20 years ago. This spring, Wallis Farms, which includes Scott's father, Bob; his son, J.R.; and son-in-law, Brad Winter, will plant 1,850 acres of corn and 1,550 acres of soybeans on 20-inch spacings. In 2019, they bought into the system further with the addition of a second 20-inch-row planter (John Deere 1795 24Row20) to allow simultaneous planting of both crops.

And, they've learned a lot along the way analyzing and tweaking the agronomics, while weighing how each change influences timeliness and labor requirements.


Indiana-based Advanced Agrilytics, an agronomic consulting firm that helps link precision with production in eight Midwestern states, notes that Wallis Farms is on track with the thinking of many of its customers.

Narrow rows first became popular in northerly climates, as farmers reached to capture more sunlight and gain an edge on weed control as rows canopy more quickly, observes Aaron Gault, Advanced Agrilytics lead agronomist.

"Early on, farmers in areas with shorter day lengths tended to see a bigger yield response to the practice," Gault explains. "Over the past decade, we've seen the practice move south as growers seek ways to build a bigger plant, harvest more sunlight and more intensely manage their crop."

Advanced Analytics research confirms anecdotal reports that better plant-to-plant spacing in 20-inch rows makes a difference. "Several years ago, we took plants back to the lab and dried them down, and found that we were producing 25% more biomass in 20-inch rows compared to 30s," Gault reports.


Row spacing and seeding rate both change the spatial arrangement of plants in the field, which further enhances the ability of the plant to capture sunlight, nutrients and water. Wallis has found the population sweet spot for 20-inch corn to be 36,000 to 38,000 plants per acre. "We probably plant 10 to 15% more than the 30-inch-row guys in this area," he says.

"In 2020, we had a big 80-acre test plot split between 38,000, 40,000 and 42,000 population with different foliar feeding programs. It was the first time we've seen those higher populations be economic. We're continuing to test population rates and look at hybrid differences and how they respond to both seeding rate and narrow rows," Wallis continues.

Hybrids with good agronomic characteristics, such as stalk strength, standability and disease tolerances, are another must, he notes. Beyond doing a better job of collecting sunlight to convert to energy, the thick canopy in 20-inch rows is the equivalent of lowering the shades in your house when the sun is beating down.

"It will be about 3 to 5° cooler inside a 20-inch row compared to 30s. When you get to really hot days when the crop starts hurting, maybe you can withstand just a little bit more before the straw breaks the camel's back," he says.

At the same time, air movement changes in narrower spacings. Field interiors don't dry as quickly in higher rainfall periods, and the humid conditions are perfect for disease development.

"Fungicides aren't even a question for us anymore, especially since Southern rust is a frequent problem," Wallis says. A generic azoxystrobin [Gold Rush] goes out at V5, followed by an aerial application of Trivapro or Veltyma at brown silk.

Gault sees the benefit of two fungicide passes, because narrow rows often experience an earlier onset of gray leafspot. "Two passes have been huge as we try to keep photosynthesis working with all this extra biomass and also take advantage of extended grain fill," he says.


For Wallis Farms, the most tinkering in 20s has come with the need to feed a demanding crop. "I wasn't sure we'd ever be able to sidedress our whole crop in a timely manner," Wallis confesses.

They had been weaning themselves from preplant anhydrous applications when a late planting situation in 2015 forced the issue. Wallis sold the anhydrous applicator and never looked back.

Moving to a 60-foot corn planter also opened up the opportunity to widen two rows to 24 inches to accommodate a tractor and sidedress rig outfitted with tracks. That leaves the two rows outside the track rows on 18-inch centers. Real-Time Kinematic (RTK) guidance helps thread the narrower widths.

"We tear out approximately 30% less corn with tracks than we did using a single-wheel system," Wallis says. "I was always fighting to keep the wheel machine on row, especially in hilly situations. Plus, we have 50% more coulters in the ground to help keep us anchored."

This year, Wallis Farms is installing Precision Planting Conceal planter fertility attachments on its John Deere DB60 36row20 corn planter. A knife running beside the seed in the groove of the gauge wheel places liquid fertilizer in a 2 x 2 x 2 band. The plan is to run 42 units of nitrogen (N) and 8 units of sulfur (S) in this banded treatment. Another 3 units of N, 8 units of phosphorus (P) and 1 unit of potassium (K) will be applied in-furrow at planting.

The remaining nitrogen, between 190 to 220 units, and 26 to 31 units of S are applied at V3 to V5 -- a critical stage for ear shoot formation. "We adjust sidedress amounts for the yield goal of each individual field," Wallis says.

Putting all the N out early doesn't leave enough in the right form when the corn plant needs it most, he believes. "We like 32% for ease of handling and besides, anhydrous tank wheel spacings don't fit 20-inch rows," he says.

The guts of their FAST brand liquid fertilizer sidedress applicator is mostly standard issue, with the exception of the additional 20-inch coulters and some plumbing adjustments to adapt to 20-inch-row configuration.

The tank has a 2,600-gallon capacity, and tractor side tanks each carry 500 gallons. "We're putting on 60 to 80 gallons of product per acre. That's around 45 to 60 acres per complete fill. The fewer times we go into that standing crop, the less we tear up," he says.


Spread out over 30 miles and four counties, and the states of Illinois and Indiana, Wallis Farms embraces different growing environments. One thing Wallis has noticed is a consistency to his crop since adopting the 20-inch configuration.

"I'll be the first to admit that we've not seen huge yield jumps that I can attribute specifically to the row spacings," Wallis says. "What we see is extreme consistency across the different classes of ground we're farming."

Since the farm moved to 20-inch rows two decades ago, whole field averages have risen from 200 bushels per acre (bpa) to 280 bpa. "Last year, our most-productive ground was 10 to 15 bushels under record yields, and our least-productive ground had record yields by 10 to 20 bushels," he explains. "We've been able to raise yields on all ground, but the biggest improvement has been in the medium and poorer soil types."


Cheap weed control doesn't enter into discussions very often these days, but early canopy closure is paying off for Wallis. A burndown application of glyphosate and atrazine, followed by a post application tank mix that includes mesotrione, brings the corn weed-control program in under $20 per acre.

Advanced Agrilytics lead soybean agronomist AJ Woodyard also likes the way narrow-row beans close the row to preserve moisture and crowd out soybean weeds.

"The 20-inch row may canopy a day or two slower than a 15-inch, but significantly ahead of 30-inch rows. The benefits to yield and weed control are real," Woodyard says. "Our data shows a 3- to 5-bushel increase in soybeans from switching to a narrow soybean row configuration such as 15- or 20-inch."

The desire to plant early soybeans as fast as possible in recent years has caused some farmers to shy away from narrow rows as a matter of convenience. Going back to larger 30-inch-row planters has allowed for more planting progress in the spring.

"However, a challenge in 30-inch soybeans is the increased duration of weed control required, which has resulted in the need to add a residual product to the postemergence tank mix. Faster canopy closure from narrow rows is another tool farmers have to increase success in those situations," Woodyard says.

Thoughts on Tight Rows:

Like any practice, moving to 20-inch rows has trade-offs. Here are some thoughts from farmer Scott Wallis:

-- Weigh the investment. A 20-inch-row planter can cost 50% more than a comparable 30-inch-row planter. Corn heads may cost the same, but you're covering less physical area. If you trade equipment frequently, the benefits may not offset the equipment cost.

-- Figure fertility logistics. How will you negotiate that narrow row without tearing up crop?

-- Count weed control in the savings column. But, don't count on canopy closure to do all the work. A strong herbicide program is still a must.


-- Follow Pamela Smith on Twitter @PamSmithDTN


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