But not too soon!

I was asked several times over the weekend if we could start to apply fall NH3 at 60* soil temps if a nitrification inhibitor was used. Absolutely not, too risky! Campus experts, fertilizer dealers, and agronomists agree, starting before 50*- and falling- soil temperatures is begging for nitrogen losses. Nitrification inhibitors can be very effective, but their breakdown is temperature driven, so applying on warmer soils will lessen the effective time that they will inhibit the conversion of ammonium (the more soil stable N form). Great article explaining this here.

50*- all of our Ag retailers agree, and their Agribusiness Association of Iowa even has an educational campaign/policy statement promoting best management practices for fall NH3-

1. Soil Factors
A- Mid-day soil temps at a 4″ depth not greater than 50* and trending lower.
B- Soil moisture conditions conducive to proper application and sealing.
C- Soil drainage classification from the Iowa Soil Survey should be consulted to confirm soil ability to retain nutrients.
2. Application Rate Factors
A- Reference ISU PM-1268 “Establishing Realistic Yields” and ISU PM-1714 “N Fertilizer Recommendations for Iowa Corn” for N rate guidance.
B- Proper N credits for previous crop history.
C- Proper N credits for manure and other N sources.
D- Use properly calibrated equipment in good repair.
3. Other management factors
A- Consideration given to the use of a nitrification inhibitor.
B- Consideration given to the flooding potential of the field.
C- Consideration given to the use of a managed, multiple N application system. These systems could include spring pre-plant, pre-emerge, and/or
side-dress applications.

Iowa fertilizer dealers post these in their offices, share with their customers, and implement to get the most efficient, cost effective, and environmentally sound application of fall NH3.

Watch soil temps here.

Soil temps have been in the upper 40’s, so we maybe will be able to get started soon, but please watch the trend. Our 10 day forecast looks promising, but then 10 day forecasts sometimes are even less accurate than Kansas City Chiefs quarterbacks passes. (Sorry, couldn’t resist, although Thigpen looked pretty good yesterday…)

Having sold tens of thousands of tons of nitrogen as a retailer, I still agree with the old retailer motto- “Don’t go until it’s 50* or below”. We all agree it’s still the best policy.

SOURCE: ISU’s Clarke McGrath

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