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Northern Illinois Agriculture

University of Illinois Extension
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Fall soil tests


This past week we pulled soil samples from a nitrogen stabilizer study with an encapsulated nitrapyrin. One of the challenges of a fertilizer and fertilizer additives is collecting data that measures available soil nutrients at varying times of the growing season. It can and often is a labor intensive project. In the harvested field we are in today we have 10 treatments that have each been replicated 4 times. Two of the treatments had their urea ammonium nitrate (UAN) nitrogen surface applied. The remainder of the treatments had the UAN solution soil injected at 170 or 200 pounds of actual nitrogen, with and without the stabilizer. To evaluate the nitrogen assimilated by the corn we also need to know the residual nitrogen remaining in the soil. We are pulling post- harvest soil samples from 0 – 12 inch depth and the 12 - 24 inch depth. We expect any residual nitrates will likely be found within those depths. There is another wrinkle, we want to know if and how far the injected UAN dispersed from the concentrated injection band. For those treatments a soil sample is collected directly over the strip made by the application knife, and a sample is collected nearer the actual corn row. For each soil sample we collect a composite of three probes. Getting dizzy with all the numbers?

Let me help you with the math, for each set of 10 treatments we need to collect 36 soil samples, x 4 treatments equaling 144 samples. 144 samples x 3 probes per composite sample equals 432 probes, all collected in an area less than ½ acre. If those numbers seem daunting, realize this is the third time this trial has had samples collected. A pre-plant sample was collected to determine base line levels; samples were collected when the corn was at V7 in June, (when I was considerable warmer). The samples are collected and were delivered to the University of Illinois soil laboratory of Dr. Fabian Fernandez for evaluation. We have one more large study to pull soil samples from and then we can put the probes away until next year!

I'll look forward to sharing the results from this and other studies at a future date.


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