Soil temperature is the best indicator we have to reduce the risk of nitrogen loss when fall application of anhydrous ammonia, or manure with high ammonia content, is deemed expedient. Experience has taught us that the conversion to nitrate is greatly reduced at soil temperatures below 50 F, though not totally avoided.
Iowa State University
Taylor, S. Elwynn and Sawyer, John E., "Watch the Soil Temperature" (2008). Integrated Crop Management News. 742.
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