With more and more of the Prairies going underwater, some farmers are wondering what the effects of all this water will be on the fertilizer they applied on their fields. I did some looking around and found a couple of good articles on estimating nitrogen losses on flooded fields.
The MAFRI article, Impact Of Flooding On Soil Fertility In The Red River Valley Of Manitoba, emphasizes the variety of factors that can play a role in nitrogen losses. The focus seems to be spring flooding on fall-applied fields.
The Mississippi article, How does nitrogen loss occur during wet, saturated conditions?, provides a formula for developing a rule of thumb estimate. One key point is that as the soil temperatures come up to about 18 degrees you can expect nitrogen losses to double from what they would be in a 5 degree soil.
If you’re really worried about whether a field has enough nitrogen left on it to support the crop, the best way to know is to soil sample it. In most cases, this wouldn’t be economically viable, but if you’re reseeding a field or willing to float some nitrogen on, it might be worth it.
Wet field June 1, 2010 - it hasn't gotten any drier.
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