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Because of heavy rains this spring, there has been substantial concern among farmers about the fate of nitrogen fertilizers applied last fall. In order to meet this concern, soil samples were collected from 19 fields in south-central, southwestern, and west-central Minnesota during the week of June 11. In each field soil was collected from depths of 0 to 12 inches and 12 to 24 inches.

Interpretation of the analysis for nitrate-nitrogen leads to major conclusions. The information collected shows that there has been no substantial loss of nitrogen. This conclusion applies to fields that were fertilized with either urea or anhydrous ammonia. Thinking back to last fall, the soil profile was empty and could absorb a substantial amount of rainfall before becoming saturated. The potential for loss of nitrogen remains low until the soil profile does become saturated. Therefore, it should not be surprising that there was very little if any loss of fertilizer nitrogen.

The measurement of nitrate-nitrogen of these samples also show that there are relatively high amounts of nitrate-nitrogen at a depth of 12 to 25 inches. Nitrogen at this depth can easily be used by an actively growing corn crop.

Some crop producers may choose to measure nitrate-nitrogen in their individual fields. If so, collection of soil from depths of 0 to 12 and 12 to 24 inches is highly recommended. Collection of soil from 0 to 12 inches only may lead to a conclusion that soil nitrogen is low and additional nitrogen fertilizer is needed. Collection of soil from the additional depth of 12 to 24 inches may reveal that adequate nitrogen is present thereby saving dollars that would have been spent on nitrogen fertilizer.

The soil nitrogen information collected in this survey is thought to be very reliable. The fields sampled were representative of production fields in southern Minnesota. Two samples were collected from each field and the measured amounts of nitrate-nitrogen were in close agreement.

At this time, it’s impossible to predict what will happen to nitrogen losses during the remainder of the growing season. For now, however, nitrogen loss, if any has been minimal.