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Fall Ammonia Damage to Soybean (06/21/18)

I have had two calls within the past few days on a rare phenomenon. An ag-consultant and a farmer from the central part of ND have seen soybean damage over last fall’s anhydrous ammonia bands.

Fall Ammonia Damage to Soybean

I have had two calls within the past few days on a rare phenomenon. An ag-consultant and a farmer from the central part of ND have seen soybean damage over last fall’s anhydrous ammonia bands. The last time I have seen damage from a fall ammonia application was in 1997 outside of St. Thomas, ND. The farmer had applied ammonia in late October 1996, seeded spring wheat in spring 1997, and the wheat did not emerge over every ammonia band track in the field. People think that nitrification happens immediately following ammonia application, but this is not what happens.

Ammonia remains ammonia for at least a week following application regardless of when it is applied. North Dakota farmers can successfully apply fall ammonia on most soils close to freeze up because we have real winter; not the namby-pamby post-fall season commonly referred to as ‘winter’ in Indiana. Ammonia application is essentially ‘in the freezer’ until this year almost May (hard to remember it was that cold in April, but check out the NDAWN archives). As soon as it was fit to plant, everything went into the ground, including soybean. When there is concentrated ammonia in a band, a portion of it will partition (my physical chemistry class experiences recalled) into free ammonia. Any free ammonia is toxic to seeds and harmful to seedlings. If we had experienced some earlier spring weather and a little moisture than actually occurred, the ammonia toxicity to seedlings would not be apparent. With the evidence that ammonia is still active after 6 months, it serves as an object lesson that ‘there is no safe time after ammonia application to seed’, at least in a practical sense. Fortunately, these fields so far have been solid-seeded soybean, so the natural ability of soybean to fill in gaps and yield similarly at lower populations will make these observations informative, but not economically important.

Dave Franzen

Extension Soil Specialist

701-799-2565

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