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Soil by the numbers

The growing season can be considered over, and harvest almost so. The Nov. 5 USDA National Agricultural Statistics Service report for Illinois has corn harvest reported at 98 percent complete compared to a five-year average of 77 percent. Soybean harvest is reported at 96 percent complete compared to a five-year average of 87 percent. I see fewer and fewer fields with standing crops in my travels across northern Illinois, even the double crop soybeans planted after wheat harvest in late June or early July appear to have been harvested within the last week. We are getting closer to the end of harvest at the Northern Illinois Agronomy Research Center but are still taking advantage of dry days to collect useful data from the 2012 growing season.

Why does it take so long to harvest and collect data from research plots? While our plots are smaller scale than a traditional field, accuracy in measurements of weights used to determine yields is crucial, and we take time to insure the accuracy. Sample collection is a time consuming process that also slows down the process but can yield valuable information. We have learned that it is better to be slow and careful; the chance for a do-over rarely exists. This is also the reason we replicate our research, to adjust for any unforeseen complications.

Today we are pulling 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 four 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- to 12-inch depth and the 12- to 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, times four treatments equaling 144 samples. Of those 144 samples times three probes per composite sample equals 432 probes, all collected in an area less than one-half 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 will be delivered to the University of Illinois soil laboratory of Dr. Fabian Fernandez for evaluation. I’ll look forward to sharing the results from this and other studies at a future date.

Upcoming Extension events include “The Keys to Profitability and Sustainability in a Changing Beef Industry,” from 5 to 8:30 p.m. Dec. 11, to be held at Celebrations 150 in Utica.

Russ Higgins is from the University of Illinois Extension, Northern Illinois Agronomy Research Center.

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