Picket-fence corn requires planter parts to work in sync
The basic design of every planter is the same, whether it’s a shiny new GPS-guided, vacuum-metered 36-row megaplanter or an acre-worn eight-row planter with finger-pickup units and bent marker arms. Planters are designed to meter and place seed.
Equipment manufacturers and farmers have the metering side down to an exact science. Well-maintained seed units, whether vacuum or finger- pickup style, can drop seeds with
robotic accuracy and set the stage for picket-fence stands.
But many farmers still don’t achieve those fabled stands. Skips and doubles mar their final population and reduce yield. Even more insidious are yield reductions from stands of corn that initially appear perfect. Even though there’s a stalk every 6.5" during the growing season, random stalks at harvest can be barren.
One is not like the other. "A seed meter can singulate a picket-fence stand to the top of the seed tube, but poor seed placement in the furrow can lead to erratic germination and emergence," explains Dustin Blunier, marketing communications manager for Precision Planting. "We like to see all plants in a field germinate and emerge within 36 hours of each other. Plants that emerge a day or two behind become weeds that absorb nutrients and moisture. They often end up barren or producing nubbin ears."
Blunier cites research by Robert Nielsen at Purdue University that indicates erratic germination and emergence can reduce final yields in corn by as much as 10%.
"It may take $400 per row to go through an older 12-row planter and replace worn disk openers, gauge wheel arms and components other than the seed meter," Blunier says. "That’s $4,800 in parts. If you plant 500 acres of corn that maintenance costs $9.60 per acre. At today’s prices, that’s less than 2 bu. of corn spent to maintain the planter to potentially gain 20 bu. at harvest, if the corn yields 200 bu. per acre."
Doug Toepper, a product specialist with John Deere Seeding Group, says the interactions between disk openers, gauge wheels, seed tubes and closing wheel assemblies are critical to accurate seed placement.
"A planter is a system," he says. "All the pieces have to be matched and working properly to get optimum planting results."
Disk openers start the placement process by creating a precisely engineered seed furrow. If the contact area where the leading edges of disk openers touch is too small because the disks are worn or out of adjustment, or if there’s a gap between the disk openers, loose soil falls into the bottom of the seed furrow and positions some seeds shallower than others. Uneven depth of seed placement is a major factor in erratic seedling emergence.
"Even ‘good’ disk openers that aren’t worn smaller than 14½" can be out of adjustment and affect seed placement," Toepper says. "If the farmer shimmed them to get the proper 2" to 2½" of contact at the front of the disks but put more shims on one side of the row unit than the other, it can off-center the disks and one of them can rub on the side of the seed tube. That will eventually wear a hole in the seed tube, and anything that causes a seed to tumble or bounce as it leaves the tube can affect spacing in the furrow."
A special relationship. Tom Evans, vice president of sales for Great Plains Manufacturing, says the relationship between disk openers and gauge wheel tires deserves attention.
"If the soil is damp and there’s a gap between disk openers and gauge wheel tires, wet soil will stick to the disk opener, peel off inside the gauge wheel rim and eventually plug the gauge wheel so it can’t turn," Evans says. "If the soil is dry, it’s even worse because it affects seed placement and potential yield. Any gap between the gauge wheel tire and the disk opener allows the gauge wheel tire to kick dry soil into the bottom of the furrow."
In that situation, some seeds germinate quickly in damp soil, while other seeds sit higher and dryer on soil allowed into the furrow by the gap between the gauge wheel tire and disk opener. Even if a rain germinates them all at the same time, shallower seeds will emerge first and potentially dominate the plants on either side.
- Mid-February 2012