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Tuesday, February 19, 2013

Have you decided yet on a seeding rate for your 2013 corn crop?


Planters are being repaired, upgraded, and modified, as well as torn apart and reassembled in machine sheds throughout the Cornbelt.  New gizmos are being attached, electronics added, and soon planters will be pulled out into the sunlight with new paint, new grease, and scrubbed spic and span.  They will be ready for work, burying seed corn at whatever rate per acre you want.  And by the way, what rate will that be?


Purdue cornmeister Bob Nielsen says, “Of all the many agronomic management decisions a corn grower makes each year, one would think that choice of seeding rate would be among the simplest. Yet, this topic continues to garner a lot of attention in coffee shops, Internet chat rooms, the farm press, and in crop seminars. So, apparently this decision is not clear-cut.”


Hardly.  About every farmer has a different seeding rate, but every farm is different.  And for that matter every field is different, and in many fields there is a significant agronomic difference just from here to there. Interviewing a young farmer for my morning television program earlier this week, he planned to make a number of changes in hybrids as he moved across a field.  Another young farmer scheduled for the program later this week puts several different varieties in his planter at the same time.  But seeding rates have been staying the same.  Nielsen says, “Identifying the optimum seeding rate for corn is difficult because it involves a delicate balancing act among the various yield components that multiply together to determine grain yield:

Yield = [Plants per acre] x [Ears per plant] x [Kernels per ear] x [Weight per kernel].”


In a year like 2012, many farmers who had lower plant populations than their neighbors actually had higher yields because of the shortage of soil moisture.  With prospects for wet soils in the eastern Cornbelt and dry soils in the western Cornbelt, the National Agricultural Statistics Services field surveyors will have a challenging time coming up with an average plant population for 2013.  But your challenge is determining the plants per acre rate you want, because the 2013 planting season will hit when the baseball season starts, and the pitchers and catchers are already at training camp.


When reading the farm magazines that have been piling up, the winners of the National Corn Growers Yield Contest told you their populations were 40 thousand or more per acre or some very expensive number. 40 thousand would be $200 per acre, just for seed.  Nielsen says, “Crop input suppliers sometimes recommend to their customers that seeding rates should be in the neighborhood of 35,000 or higher to maximize yield and furthermore show yield response data that appear to support those recommendations. Results of some university research also tend to favor these higher seeding rates.”


To dispel the NCGA population tale, Nielsen says, “While it is true that a fair number of those winners use exceptionally high seeding rates, it is also true that there is not much of a relationship between grain yield and harvest population among those NCGA Contest winners.”


Nielsen suggests two alternatives:

  1. Yield increases to a maximum, then decreases at seeding rates beyond the maximum.  If you accepted (that) model, the optimum seeding rate mathematically predicted from the equation would be 39,000 plants per acre.
  2. Yields increase with increasing seeding rates to a point, then levels out at higher seeding rates.  If you accepted (that) model, the optimum seeding rate predicted from the equation would be 32,000 plants per acre or 7,000 fewer plants per acre than the optimum rate calculated from the (first) model.


 Nielsen feels that researchers such as himself have a responsibility to analyze and interpret yield response to various seeding rates, and says that the yield response of today’s hybrids to seeding rates are best described by the second scenario. Subsequently, he recommends to Indiana corn growers they should have a seeding rate around 33 thousand seeds per acre, with a final population about 31 thousand plants per acre, except for those farmers with soil or growing conditions that severely limit yield potential.  While your farm may not be like Indiana soils, they vary considerably throughout that state, just as much as soils vary from the eastern to the western Cornbelt.


In the western Cornbelt, corn specialist Roger Elmore at Iowa State University suggested last week that farmers concerned about the lack of soil moisture should consider a lower population than normal, because in field trials last year, the lesser populations performed better.


And as you are researching the optimum number, visit with your LG Seeds dealer for his or her thoughts.....


The corn seeding rate per acre and the resulting plant population may not be exactly the same for every farmer, farm, and field, and finding the optimum rate may take some experimentation.  Yield does not increase as plant population and seeding rate increase, but may level off at some point.  Other factors boosting the yield beyond the optimum seeding rate and plant population may be linked to fertility, lack of competition for moisture and nutrients, and plenty of optimum growing days.

Posted by Stu Ellis on 02/19 at 10:00 PM | Permalink

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