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EC Nebraska | I farm a long ways south of you, so take this with a grain of salt. These are my "off the cuff" thoughts after reading your post.
Here, I have been growing 220-240 bpa corn under the pivots for several years now. Last year was the first year I fertigated, and that appears to have added 10 bushel to my yields. Under the pivot I harvested 245 bpa. Fertigated Nitrogen after V10 is much more efficient than pre-plant N. I apply about .6-.8 lbs of N per bushel of final yield.
You're planning to apply about 1 lb N per bushel, correct? I would drop that first fertigation pass from your program. There is no way V4 corn is going to have used up the 240 lbs of Urea and 100 lbs of AMS. (unless you get so much spring rain that the N and S leach away. If that's very likely to happen, then I would cut 80 lbs of Urea from the preplant application instead of cutting the fertigation pass.)
Others will disagree, but I suspect over-nitrating the ground is just as bad as over-tilling it. You stimulate microbe blooms that burn up organic matter. That releases any micronutrients stored in that organic matter, so you may get a nice short-term yield boost from doing that but it's not a great idea, IMO.
Bottomline on N rates, I think you could cut around 30 lbs of N from your planned applications and not worry about running out of N.
100 lbs of 28% should be fine. The chemigation class I took for certification suggested that 100 lbs of 32% per application pass was the highest rate that should be used. They also said each application pass should be less than 1/2 inch of water (to reduce chances of run-off)
You can put micros through the pivot, but be careful. It might not be worth it. From the crop's perspective it will be just fine but some things such as copper sulfate can be very corrosive to your pivot.
Use tissue tests to determine micronutrient needs.
Those are my thoughts, hope some of is useful. | |
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Help w/ Corn nutrition program and fertigation
