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Have your agronomic questions answered by a Farm Journal agronomist. E-mail us directly at TestPlots@FarmJournal.com, and we’ll respond on this blog to provide an interactive dialogue.

How do I maximize populations for maximum corn yields?

Mar 24, 2014

Question: It seems to me that the high population talk is a trap by the seed companies.  If they would breed a good flex-eared hybrid so we could plant at 25,000 to 28,000 population, we would be much better off in a year like 2012. Also I am not aiming for 250 bushels when my maximum yield potential is only 200 to 220 bushels. A 45,000 to 60,000 population may be fine for test plots but not for whole farms. How can we afford seed at the high populations?

Answer: You’re right in your thinking.  But you have to intermingle ear type with leaf structure.  So, if we’re trying to conserve water any year in any soil type, we want to reduce populations because they consume less water.  But as soon as you reduce populations, as you’ve noted, you need a good flex ear.  You need a hybrid that will flex and get you back to where you want to be in yield.  You also need to look at leaf structure.  In genetics, there’s what we call three leaf types: upright, pendulum and semi-upright.  You also need to capture at least 96% of the sunlight out there to maximize yield.  So, if you lower the population fewer plants means you need bigger leaves and in a pendulum format. Those leaves need to flop out in the row to capture that sunlight. Then, you need an ear style, a flex ear, that can make up that difference.  When we talk about a 45,000 to 60,000 population we’re talking about a very upright leaf structure that allows the sunlight down inside the canopy so plants capture that sunlight to produce food. And we’re also talking about a very determinate hybrid. So you need to push populations to make yield, because the ears won’t flex as much; they have an upright architecture to let sunlight deep inside the canopy.  If you lower populations with an upright hybrid you could burn up and lose all your water if too much sunlight gets in. If you lower populations with a determinate ear you can give up too much yield because the ear won’t flex to make up that difference.  So, in this format, you’re correct. What if you chose a flexed ear in 25,000 or 28,000 and did it on less population? You’ll need a pendulum leaf structure versus an upright structure so you can capture the sunlight to produce the yield you’re looking for.  You’re going to need to get between 7 bu. and 10 bu. per 1,000 population and not the 5 bu. or 6 bu. that we usually look for. So we’re talking about high populations, determinate ears and upright leaf architecture. We’re also talking about low populations to manage water and flex ears and a very pendulum leaf architecture.  You have to marry both of these two up.  It’s amazing how much yield today we have given up by pushing populations too high for the leaf structure we’ve got.  The problem with flex-eared hybrids is if you push them too hard, they flex both ways. They can flex yields off.  Determinate hybirds, if you don’t push them they won’t yield.  But if you push them they’re more resilient and won’t back up. If you’re going to lower the population you need full flex and you need pendulum leaves—you’re looking for both of these characteristics in the hybrid.

Seed to Success

The first step in variable-rate populations is working with a seed representative to select the right hybrid.

 

Zero In On Population

Improvements in seed corn genetics have resulted in hybrids that perform best when planted in higher populations.

 

Calculate Your Soybean Seeding-Rate Needs

Soybean seed costs have risen, farmers don’t want to plant more seeds than they need for top yields.

 

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