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The points of contact between Rutgers Cooperative Extension Service and the grower & business communities are the NJ County Agricultural Agents. The agents are a tremendous source of information for both new and experienced growers.
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Tuesday, August 21, 2012

Corn Population-Check Now for Next Spring

As we approach corn harvest, now is a good time to check each of your fields and hybrids to see how they look following the mid-summer drought many experienced. Because breeders have been breeding for increased yields by, among other things, increased population tolerance, many farmers have been increasing seeding rates over the years. I have seen several fields where ear size and fill suffered from too high a population. Here are some signs of stressed corn. Small ear length and girth(aka barrel size/circumference) is a sign of drought before tasseling; missing kernals randomly over the cob means stress at pollination; and barren tips( 1-2 inches or more) indicates stress at the end of pollination and shortly thereafter. All of these are likely a result of too high a population with insufficient rainfall. Another symptom this year is where some cob tips are poking through the husk which is a result of the recent rains following the earlier dry period. If you planted several hybrids in a field this will be a good check to see which might be the more tolerant of higher populations. If you saw only random spots of the above symptoms throughout your fields you can probably keep planting at the same seeding rate, but if you saw substantial amounts of the stress indicators you may want to reduce seeding rate next year by 2000 seeds/A. Such a small drop probably wont effect yields even in a good rainfall year and will save you a few dollars in seed costs. You also should check potash levels, because low levels can accentuate drought stress. Other factors such as planting date, compaction, etc. could have affected your corn’s tolerance to drought so think about your planting and management practices differences before concluding it was population alone.  
Zane R. Helsel