The lack of stand uniformity in corn is costly, particularly when seeding depth, spacing and soil-to-seed contact are at the root of the problem.
North Dakota State University (NDSU) researchers and Extension agents in 2015 studied stand variability in farmers' fields over a wide range of conditions and locations. Their findings showed, even within a planter width, the most variable row yielded up to 9 bushels per acre less than the least variable row.
"The most common cause of variability in this study was emergence date and not skips and doubles," explained NDSU Extension Agronomist Joel Ransom. "Skips, when they did occur, of course, were the most impactful on yields, but they were followed closely by plants emerging 11 to 17 days after the earliest emerging seedlings.
"Plants next to skips could add 10% greater yield when compared with normal spacing, but this was much less than the 50% needed to totally compensate for the lost plant," he said. "Plants next to late emergers were able to add 5% greater yield, but again, they could not completely compensate for the loss of production by the plants emerging late."
Ransom said most often, stand variability stems from differences in seed access to moisture, differences in soil temperature and seeding depth. All can often be traced back to less-than-optimum planter condition, adjustment and planting speed.
LITTLE DIFFERENCES ADD UP
"Small differences in temperatures encountered by newly planted seeds can be caused by different depths of seeding, along with the amount of residue retained directly above the seed row," Ransom said. "If you have been disappointed in the uniformity of emergence, you may want to spend some quality time with your planter adjusting, leveling and replacing worn parts before you use it to plant another crop."
In 2000, a study of 96 farms across the U.S. and Canada concluded yield losses because of nonuniform plant spacing could amount to 4 bushels per acre per inch of standard deviation improvement (spacing). Oft-quoted USDA studies indicate a planter delay in seed drop of 1/25 of a second can cause seed to be 3 1/2 inches off proper spacing, and that can often be traced to excessive planting speed, worn drive chains and idlers, and poorly maintained seed meters.
John Long, an agricultural engineer at Oklahoma State University, said gambling with expensive seed and the potential of significant yield losses because you haven't spent the time making sure your planter is in top shape is a good way to lose money.
TIME TO MAKE IT RIGHT
"Proper adjustment of planting equipment, whether you are a conventional grower or a no-tiller, is far more important than adding attachments," he explained to his Southern Plains cooperators. "That means checking wearable parts, adjusting for and maintaining a level ride for your planter, taking pains to ensure proper planting depth in a variety of conditions and applying adequate downforce for good seed-to-soil contact.
"Growers need to focus more on the correct seeding rates for their fields and getting a good, uniform stand from that rate," he explained.
Phil Needham, a longtime farm consultant and planter specialist with Needham Ag Specialties LLC, in Calhoun, Kentucky, said winter or preseason planter maintenance must be a systematic, "front-of-the-machine-to-the-back" maintenance exercise. Below are Needham's recommendations.
"This list will cover 90% of what you need before planting, and you can use it right after harvest or during downtime in winter months," he explained. "The important thing is to make the effort and do the maintenance. You'll be money and bushels ahead come harvest if you do," he added.
1. Level. Make certain the planter is level from front to back and side to side. "You need to take the planter to the field, not just a farm lane, and make sure everything is level. The drawbar and tongue should be level to slightly higher at the front than the back," he explained. "This configuration does many things. It allows the parallel linkage to work properly and the closers to do their job gathering. If the closing wheel arm droops downward toward the back, you won't get adequate closing because you'll lose gathering action. Most growers are unaware of this," he said. Also, Needham said the leveling procedure is a good time to make certain tire pressure is correct and that side-to-side leveling is "bubble on," assuming you're working in a level field.
2. Cleaners. Most growers benefit from well-maintained floating row cleaners, which turn freely and travel up and down to efficiently clear the way for the disc openers. Check the row cleaners before you check the parallel arm linkages.
3. Play. Parallel arms are designed to maintain the row units in proper relation to the soil under varying field topography and soil conditions. The best way to check their operating efficiency is to jack them up with a floor jack to a horizontal position and wiggle them side to side. "If there is significant play in the pins and bushings, you'll have erratic seed placement as the row unit pitches forward to rear and side to side," Needham said.
4. Openers. Check the disc openers. Generally, double-disc openers require replacement when they lose a half an inch of their original diameter or if they've become dull -- whichever comes first. "When you replace disc openers, be sure the tension is set to manufacturer's recommendations. Most need 2 to 3 inches of contact, but the owner's manual will provide the exact specification," he said. "Usually, the thicker the blade, the less contact is required, but as thickness and diameter change, so do the contact distances."
5. Tube. Check the seed tube protector, the steel insert that holds the double-disc openers apart. "Most have a wear detector, and different planters have different setup widths. Compare the seed guard with a new one for guidance on how much wear is showing. If the seed tube protector is worn, chances are good the seed tube is getting thin in spots. Pull it out and inspect it for wear or abrasion from double-disc openers.
6. Bearings. Check disc blade bearings by wiggling the disc openers to make sure hubs are firmly attached to the disc and there is no lateral wear or play.
7. Wheels. Move on to gauge wheels and gauge wheel arms. If you can move gauge wheel arms from side to side, they need to be tightened or replaced, Needham said. "Check for wear or cracking of rubber on the gauge wheels, and be certain bearings are good and that the wheel fits tightly into its socket."
8. Meters. Check the seed meters for mechanical wear. "I recommend growers using finger pickup meters have them tested and adjusted by professionals on a factory-approved test stand. Take the seed you plan to use so the pros can calibrate the meters for what you will be planting," Needham said. "It's confusing with all of the different hybrid seed sizes and shapes, but it's a consideration you should make before planting."
9. Closing. Check the closing wheel arms to be sure they are centered directly over the row. "Ideally, there will be no side-to-side wear. Use what adjustments are available to ensure the closing wheels run accurately over the center of the row. All parts wear, and if there is play in the closing wheels or arms, replace them," Needham explained. Closing wheels need to be selected based on conditions in which they will be running. "I've never seen one that will work well in all conditions," he continued. "Growers need to be aware certain conditions may require one configuration, and others will require something else. Be flexible and attuned to differences in field moisture conditions and tillage practices. Be ready to change when changes are needed to ensure good closing and soil-to-seed contact."
10. Walk. Do a walk-around of the planter looking for hydraulic leaks, cylinders seeping off, worn or frayed electrical connections and wiring. Raise the planter to see if the hydraulics bleed down. Check chains for condition and free movement, and lube them thoroughly. "Remember, too, drive chains need to be lubed twice a day during planting to keep them clean and wear-free, and transferring power properly," he said.
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