Corn plant population plot results from the Leon Yoder farm now available
The plot was planted May 20, 2010, with a three-row Pequa (30-inch row) planter and an older model two-row (36-inch row) planter. The plot was conventionally tilled into an alfalfa-grass meadow. Fertility was determined by soil testing. Manure, broadcast, and starter fertilizer was applied for a 160-bushel yield goal. Pre-side dress nitrate soil testing at the V-6 stage of corn growth revealed the soil nitrate level to be below the desired level. Twenty gallons of 28 percent UAN was “dribble applied” June 17 at the V8-V10 stage of plant growth, to raise soil nitrate. The plot was cultivated after the nitrogen application June 17.
The plot was small and not replicated, but instructive observations are still possible, if not conclusive. There is considerable variability of soils in the field (as is true of nearly every Holmes County field).
Results
The Pequa planter gave plant populations that were 8.9 percent below the book-value planter setting. The older model planter gave plant populations that were 31.5 percent below the “best guess” settings for the desired plant population. No planter will produce perfect “picket fence stands,” but many of the older planters are unable to be adjusted to approximate ideal seed placement and plant stands.
The single corn hybrid planted across the plot was one known to adjust ear size with plant population changes--large ears at low populations, smaller ears at high populations. Ear size ranged from 0.41 pounds per ear to 0.84 pounds. But ear size adjustment did not offset the yield reduction that comes with low populations. The ear size at less than 18,000 population was 28.5 percent larger than at 28,000 plants; but the yield was 39 percent greater at the higher populations.
It was interesting that the proportion of grain to cob was constant across all plant populations and ear sizes. Eighty percent grain to 20 percent cob was the constant ear makeup (range 79/21-83/17).
While the hybrid was challenged at very high plant populations, higher plant populations significantly out-yielded lower populations.
• Under 21,000 ppa - averaged 138 bu./acre
• 21,000-24,000 ppa - averaged 183.3 bu/acre. That is plus 45.3 bushels
• 24,000-27,000 ppa - averaged 202.8 bu/acre. That is another 19.5 bushels/acre.
• Above 27,000 ppa - averaged 185 bu/acre. That is down 17.8 bushels/acre.
The “dribble” side dress nitrogen application at the V8-V10 stage of corn growth resulted in an additional 30.5 bushels of corn per acre, compared to the field areas not receiving the nitrogen. That $36 worth of 28 percent UAN resulted in about $183 more corn grain. The pre-side dress nitrate soil test revealed a nitrogen shortage and the UAN application was indicated to be very profitable.
Take home messages
• Low corn plant populations, whether planned or accidental, are not profitable.
• Make certain that your corn planter is at optimum function and able to place the seeds at the desired soil location and at the rate needed for optimum corn yields.
• No planter will perform exactly as the “book setting” says. Adjust the planter, check its performance in a check strip, readjust, and recheck until it is right, before you head to the field to plant.
• Choose a corn hybrid, and a plant population goal that allows that hybrid to optimize its performance in your fields.
• Keep in mind that seed drop recommendations are 15 percent higher than the desired plant population for populations under 30,000 and 10 percent higher for population goals above 30,000.
• Develop a nutrient management plan (including manure nutrients) for your crops, and follow it. Holmes SWCD can assist you with a nutrient management plan--simply call the office in Millersburg at 330-674-2811.
Published: February 16, 2011
