What is in this article?:
- Sample this Spring for Soil Nitrogen, Adjust Rates When Needed
- Adjusting N rates based on spring sampling
The priority for spring sampling should be fields where corn in 2013 will follow corn (from which fall samples were taken) in 2012. We suggested last fall that any spring sampling done in order to adjust rates for the 2013 corn crop should best be done close to corn planting time, or at sidedress time. However, it would be useful if at least some of those sites where fall soil nitrogen (N) levels were high could be sampled within the next few weeks so that we could better guess how much additional sampling would be useful.
I suggest that sites with fall nitrate-N above 25 ppm in the top foot (that is about 25% of Illinois sites) be sampled first, but any and all sites can be re-sampled if volunteers are willing to do this. (All those who coordinated sampling last fall and who requested forms and shipping materials through me will get an email in the next few days with brief instructions. The process will be the same as it was last fall, with samples sent to A&L for analysis, and funding provided through C-BMP. Those who sampled under GROWMARK’s direction last fall will continue in that program this spring. Those who did not sample fields last fall but would like to do so this spring are also invited to participate. Instead of sending requests through me, however, we ask that those sampling this spring for the first time send requests to Jean Payne firstname.lastname@example.org at the Illinois Fertilizer & Chemical Association, who will pass along the request for sampling materials and instructions.)
It might be difficult to get the deep (1-2 ft.) samples in fields where soils remain wet. We think the 1-ft. sample will show us how much N rate adjustment might be appropriate. Those willing and able to take samples from the second foot are encouraged to do so, however.
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It is best to take samples before any N has been applied in the spring, though we can avoid the band if, for example, some starter was used at planting and sampling is done after that. Combine in a bucket enough samples to represent the area you want to represent, and take a subsample of this to send to the lab for analysis. Soils should be sent for analysis as soon as possible, and kept refrigerated if needed, to minimize N transformations before analysis.