So I have already had the call this spring. “My yield of corn last year was low, and I think I had a problem with my population.” Turns out I was in the field late last June, saw the issue of missing plants and said it was too late to determine the problem. Now they want to know how to avoid the problem again, but they changed planters. So I suggest basically the same things I did last year. You must go the field and look!
There are a number of things we look for when we have missing plants, delayed emergence and the possibility of low yield. Here is what we looked at to determine his problem and assess the situation.
I thought from some comments this spring that this was the problem. But when I looked over the Kinze planter the expected problems did not seem to be there. It is interesting that the problem last year started after a rain delay. I still think something changed then, I just cannot put my finger on it — perhaps mud or dirt build up?
Cool conditions and/or variable soil temperatures
This can be frustrating. I have seen it be very spotty. It usually occurs at or just after planting and leads to extended emergence. We often see some of this early impact from cool, wet soils just after planting. Check your records for this. The second period that cooling injury can occur is when the growing point is just emerging above the soil surface — after V5, so about a month into the growing season. We looked through some temperature records and saw a couple of places a month to six weeks after planting when there were a string of warm days followed by cool nights of 41-, 43-, 45-degree F temperatures. This can cause blanking of ears, disrupt the dominant ear formation. Often this V5-V6 cooling affect occurs on one hybrid and not another, in one field and not another as well. And this could help explain the low yield and misshaped and delayed ears.
My report from this field in June of 2016 said I was pleased with the minor compaction issue. I did not look at every field, but generally I think this farmer does a good job of managing this concern. I still consider this the No. 1 root disease of corn. Let’s try to always minimize this.
Pathogens (damping off diseases)
These would be soil-borne diseases. This farmer does use a fungicide on the seed, which covers many of the concerns. But an extended cool, wet period could cause damage to germinating seed that would not be adequately protected. Fungicides have a life of maybe 10 days to two weeks.
These can certainly cause the reduced stands we saw. A seed applied insecticide can control these. We generally see these after we convert from a hay or pasture situation. I don’t think that is the case on this farm.
Cutworms, seedcorn maggots and other insects
Early season insect feeding may be caused by uncontrolled weeds being attractive to migrating insects. Often some tillage is done after the insect eggs are laid and when they hatch they go after corn plants as the next best target. This spring driving around I saw a number of fields where fields on this farm has volunteer grasses and some broadleaf weeds still growing, and you hope to plant soon.
From last month’s OCJ column on managing cover crops and insects, the story is the same for insect management:
- Do be committed to scouting
- Don’t treat unnecessarily
- Don’t plant immediately after killing a cover crop
- Do wait 10 to14 days after a cover crop has died
For black cutworm issues (Agrotis ipsilon) see: https://extension.entm.purdue.edu/fieldcropsipm/insects/black-cutworms.php
For seedcorn maggots (Delia platura) see: https://extension.entm.purdue.edu/fieldcropsipm/insects/corn-seedcorn-maggot.php
Injury from excessive rates of seed-placed fertilizer
I do not think salting injury was the problem on this farm. However, sometimes a loose or bent fertilizer applicator may move into and deposit fertilizer in the seed row. I think the operator would notice this. And, with the low rate of fertilizer we generally apply at planting, I generally don’t think it is enough to cause a problem when next to the row. But do check it anyway.
Many of these items are discussed further in this 2014 article from Vermont: https://agronomator.wordpress.com/2014/06/19/the-case-of-the-missing-corn-plants/. But you can also find remarks from Peter Thomison at OSU, from Bob Nielsen at Purdue and from Joe Lauer at the University of Wisconsin on the web.
So I cannot at this late date say what exactly the problem was. Looking over the above remarks and doing a little more checking on may show some answers. But stick to the basics — all the planter monitors and digital analysis cannot tell you how some small thing which happens in the field may have a major affect on your crop.
Scouting and immediate diagnosis by you, your agronomist or consultant should take place early in the season. We start scouting crop fields as soon as emergence, and then check regularly throughout the season. Our final check is usually in August, when we can get an estimate of yield. A good thorough check of the field can often get a yield estimate within 5% of final yield. I have talked with many agronomists who understand this late-season yield check method, but you must be thorough in scouting and conduct the checks across the field.