K Fertilization Following Corn Stover Removal

250 lbs K₂O/acre were broadcasted on May 30,2014 (417 lbs Potash 0-0-60) prior to planting soybeans across one 90-foot strip in Edmunds County.  This was accomplished in a part of the field that had corn stover removed the previous fall.  The average K soil test level for the strip was 382 ppm. The treated part of the field is under a center pivot irrigation system. The yield was collected with a combine mounted yield monitor.

Looking at the whole strip, the check (untreated control) received a 42.275 bushel/acre yield while the K-fertilization strip yielded 42.17 bushels/acre, equating to a 0.19 bushel/acre loss to the K fertilization. However, site specific analysis resulted in a different conclusion.  Viewing the map above, the K strip advantages occurred on the shoulder and the depressional areas of the field.  In these areas, there where yield increases of 10-20 bushels occurred. This may be due to more K+ being available for the plant in the transpirational stream at these elevations. In other parts of the field, there was no difference or a yield reduction due to the K.  Our speculation is that this may be salinity related, but more work needs to be done.  Overall, at the rate applied, there was not a whole field positive yield response that economically justified K+ application.  In areas that resulted in a yield increase, optimum economic K rates need to be determined.