Corn Planting Depth, Down Force, Singulation and Soil Contact Studies in AGCO Crop Tour

Three years of on-farm trial data confirms best practices when planting.

By Marilyn Cummins | Photos By Jamie Cole

Yield numbers are in from the third year of the AGCO® U.S. Crop Tour™ program. The data confirms best planting practices and shines even more light on what corn growers can expect to gain from adopting new methods and new technology.

From South Dakota to Ohio during the growing season, several hundred growers attended events at the on-farm plots to see differences in emergence, root strength, kernel counts and more. What follows is a summary of the story the harvest numbers tell, along with observations about different ways to approach planting based on the needs in a particular region or individual field.

Down-force needs vary 

Figure 1. Average yield results from three years of trials at 19 Crop Tour locations comparing levels of down force. Click to enlarge.

The study of automatic row-unit down-force control versus two common, fixed, spring-operated pressure settings across 19 plot locations over the three years (2016–2018) again showed the yield improvements achieved with DeltaForce® from Precision Planting.® The gain was 16 bushels per acre in average yield with DeltaForce when compared side-by-side to a setting of constant, too-light down force that failed to keep the row unit in the ground enough for even emergence.

The advantage over corn planted with too-heavy, static down force was 2 bushels an acre over the three years of trials. The per-acre bushel advantage of using DeltaForce—which monitors row-unit weight and ground contact at the gauge wheels and continually adjusts down force with hydraulic cylinders, row by row—comes to a potential 9 bushels an acre if the two yield differences are averaged (16 bushels and 2 bushels).

“With that 9-bushel advantage at $3.50-a-bushel corn, a grower could hit payback for adding DeltaForce to a White Planters™ 9812VE planter within the first 330 acres of corn planted,” says Darren Goebel, AGCO director, Global Agronomy and Farm Solutions. In addition, he notes several insights from observing results across varied planting situations during the study period.

Operators using planters with spring-operated down-force systems, or even air-bag systems manually adjusted from the cab, miss out on being able to automatically adjust down force on the go in the following situations, Goebel says:

  1. When additional down force is needed as seeding depth increases to reach uniform moisture
  2. When different amounts of row-unit down force are needed to handle seedbeds prepared with different tillage systems
  3. When soil types, and therefore down-force requirements, change within a field
  4. When using central-fill planters, since more down force is needed on the wings when the planter is fully loaded to keep those rows at the right depth
  5. When more down force is needed to plant at higher speeds.

Seed singulation problems reduce yield 

Figure 2. Average yield results from three years of trials at 17 Crop Tour locations comparing good seed-spacing uniformity (99.6% singulation) with poor uniformity (93.3% singulation). Click to enlarge.

AGCO now has three years of data over 17 sites showing the difference in yield when poor singulation creates skips and doubles. Using seed discs modified with plugged holes (skips) and extra holes (doubles), the “problem” rows were planted at an average of 93.3% singulation versus the control of 99.6% singulation achieved using White Planters VE Series planters factory-equipped with vSet® meters and vDrive.® 

The control rows with nearly perfect singulation produced an average of 5 bushels more per acre, based on more than 6,000 acres of side-by-side Crop Tour corn trials from 2016 through 2018. Looked at another way, that’s a .8-bushel-per-acre gain for every percentage point difference in singulation achieved.

Some of the trials were run with the controls being planted at high speeds with SpeedTube.® Yield results show that the 99.6% singulation accuracy was maintained, with no real difference in yield, when planting at 10 mph versus 5 mph, cutting the time it takes to plant in half. Being able to get more acres planted in a day can make a positive yield difference, especially if it means hitting the optimum planting window for the region to maximize growing degree days for as much of the crop as possible, says Larry Kuster, AGCO senior marketing product specialist.

Best depth? No less than 1.5 inches 

Figure 3. Average yield results from three years of trials at 16 Crop Tour locations comparing a range of planting depths. Click to enlarge.

The conventional agronomic wisdom of planting corn at a depth of at least 1.5 inches holds true, based on three years of Crop Tour depth-of-planting studies. Corn planted just ½ inch shallower (at 1 inch) resulted in a 14-bushel-per-acre yield loss on average across 16 sites. 

At the other end of the spectrum, the 3.5-inch planting depth cut 10 bushels off the yield compared to a depth of 3 inches. The takeaway from the study three years in a row, says Goebel, is that planting into uniform moisture at depths from 1.5 to 3 inches allowed uniform emergence and adequate nodal root formation, resulting in optimized corn yields.

Seed needs good soil contact 

Figure 4. Average yield results from two years of trials at seven Crop Tour locations comparing closing-wheel aggressiveness from light to heavy.

In the last set of studies conducted in 2017 and 2018, AGCO looked at the effect on uniform emergence of closing-wheel aggressiveness as well as the use of Keeton® Seed Firmers versus no seed firmer. Goebel says that while closing-wheel aggressiveness always will need to be adjusted to soil type, tillage practices and planting conditions, “the key is using just enough pressure to close the seed trench adequately without overdoing it, especially in conventional soils.” In the plots, the two lightest settings of the four tested had yield advantages of 5 and 6 bushels, respectively, over the heaviest closing pressure setting. 

The yield results for using Keeton seed firmers versus using no firmers ended up being equal on average over the two years of trials. However, a deeper look at the data showed that locations with lighter soils benefited from extra firming compared with heavier soils where no seed-firming may be needed. There was a 4-bushel-per-acre difference when results were sorted by soil type (light versus heavy).

Looking ahead 

With three years of data captured for planting practices and technology in hand, AGCO is starting a three-year, on-farm agronomic study of the effect of tillage systems and practices on seedbed quality, planting success and yields, Goebel says. The plots will compare seedbed preparation outcomes such as residue management, compaction, seed-to-soil contact, planter ride and more. 

Editor’s Note: The number of plots varies between study topics, because not all trials were run in all plots each of the three years. The summary data reported here is from all plots that produced statistically sound data in a specific trial protocol.