Check out this article, “Testing Soil Nitrate In Corn Fields Following 2012 Drought”
It is interesting to look at all the data collected in this study and see the affects of the drought. I looked at points in Northwest Iowa and compared these points to locations in Southeast Iowa. In some cases the amount of nitrate was almost double in locations in the southeast where more precipitation fell last year.
Check out this table, and see the results for yourself.
I would invite you to spend some time reading this article and see if you can find trends in the data collected. I also like how the article summarizes all of its findings and offers advice for 2013.
Spring 2013 preplant soil sampling for nitrate—follow these guidelines
Soil profile nitrate-N amounts will likely vary across fields, due to many factors such as variable corn yields, soils and 2012 crop fertilizer or manure band placement. Therefore, sampling should include several sites within each field and collection of many cores per sample. Suggestions from various state universities for preplant profile sampling, and ISU Extension publication PM-1714 for late spring soil nitrate sampling, indicate the following should be considered:
* Sample by one-foot increments with a minimum two foot depth, each sample representing no more than 10 to 20 acres
* Collect 15 to 30 cores per sample depth (use the higher number in fields where N had been banded), thoroughly mix each sample depth, subsample/label the samples, and keep separate samples per foot.
* Since these samples are to represent soil nitrate-N, do not store for any period of time unless dried or frozen. Otherwise, send samples immediately (within one day) to the lab for testing.
Reference “Testing Soil Nitrate In Corn Fields Following 2012 Drought” – Rod Swoboda, Nebraska Famer, February 27, 2013