Wednesday, March 23, 2011
Corn Population: Does It Pay To Increase It?
What will your corn planting population be this year? Has that changed from the past several years? Assuming your population trend is up, how does it compare to population rates planted by your neighbors? And how does your population compare to what the seed company recommends? So many questions, and we have answers.
USDA’s National Agricultural Statistics Service not only measures yields, but also makes a record of plant population. In his weekly newsletter Ohio State University agronomist Peter Thomison says farmers in his state are increasing population about 280 plants per acre per year. They have risen 16% in the past 10 years in Ohio and 56% from the 1970’s. The agronomist says Ohio farmers are ratcheting up the seeding rate, “Final stands on nearly 40% of the state’s corn acreage was 30,000 plants/A or higher in 2010. Four years ago, final stands were 30,000 plants/A or higher on only 14% of the corn acreage.”
Across the Cornbelt NASS says 2010 populations were: Minnesota, 29,900 plants/A; Iowa – 29,950 plants/A; Illinois – 29,650plants/A; Indiana- 28,350 plants/A, and 28,200 plants/A in Ohio. How do yours compare to your state average? Thomison says his colleagues have found that modern corn hybrids perform best at higher plant populations. They test hybrids from various farming eras, including the 1930’s through 2001 by planting them in a low stress population environment of 4,000 per acre. There was very little difference in yield.
When those same hybrids were planted at a 32,000 population, hybrids yielded at higher rates for each era of genetic improvement. Thomison said those improvements included, “increased yield stability across a range of environmental conditions, greater tolerance to drought (and higher plant populations), enhanced stalk and root strength, and resistance to diseases and insects.”
Thomison and other corn specialist typically advise that population should be matched with the potential of the field, compared to the rates recommended by seed companies, which generally range from 35,000 to 36,000. Other population trials Thomison has tested ranged from 24,000 to 42,000 with varied results. Yields have averaged from 191 to 228 bushels per acre. However, in further analysis, Thomison reports, “In 2006, 2009, and 2010, results suggested that final stands of 36,000/A or higher were required for optimal yields. In 2007 and 2008, there was no yield response to plant populations above 30,000 plants/A.”
At the higher populations, more lodging was noticed with stalks breaking just below the ear. The situation was aggravated with the remnants of Hurricane Ike in 2008 resulting with severe lodging in higher population plots. The lodging data indicated that the 42,000 population had 52% lodging and the stalk damage was blamed on the lack of yield increases for the higher population fields. There was negligible lodging in 2007 when populations above 30,000 did not show any yield advantage. Thomison also reports that when high population fields are under stress from drought, disease, insects, or have other similar issues, then the yield potential is reduced.
He is recommending a seeding rate of 31,000 to 33,000 per acre for most fields planted in late April or early May, if the field has a moderate potential for yield. Fields with low yield potential may do better with a 24,000 to 25,000 rate. Thomison says if the field has very productive soil and a yield potential of 180 bushels or better, then the population should be 36,000 to 37,000. He says if a hybrid has a particular trait for an issue such as stalk quality, then the recommendations of the seed company should be followed.
Summary:
The higher the plant population for corn the better the yield, to a degree. Over time, corn hybrids have been yielding better if their population is increased, and many farmers have been taking advantage of that with increases in population. At upper ends of planting rate, there is an increased tendency toward lodging, some stalk barrenness, and other problems that diminishes yield.
Posted by Stu Ellis on 03/23 at 12:00 AM | Permalink