A comparison of nitrogen fertilizer additives In recent years, many products have been introduced for the purpose
of reducing nitrogen loss from soils. This paper summarizes our studies
at NDSU, since the early 1980's, on the topic of nitrogen fertilizer additives.
For the inhibition of urease or reduction of ammonia loss, we have tested
ammonium thiosulfate (ATS), Agrotain, calcium thiosulfate (CaTS), Nutrisphere-N,
NZone, StayN, and NStay. Agrotain is the only product that we have tested
that could be considered a general-purpose urease inhibitor for use with
urea-ammonium nitrate (UAN) or granular urea. The thiosulfates, ATS and
CaTS, have mild urease-inhibition properties when used with UAN, especially
if the soil is relatively dry and if the fertilizer droplet size is large.
Nutrisphere-N failed to inhibit urease in all of our studies, but can
have small effects on reducing ammonia loss, especially with UAN. The
products NZone, StayN, and NStay had no effect on ammonia volatilization
in our studies with granular urea. Regarding nitrification inhibitors,
we have evaluated ATS, N-Serve, dicyandiamide (DCD), urea granule size,
Nutrisphere-N, NZone, NStay, StayN, SuperU, and Instinct. In our studies,
ATS demonstrated mild nitrification inhibition properties when applied
in a concentrated band. Increasing urea granule size in combination with
addition of DCD can lead to a very slow rate of nitrification. N-Serve
was generally superior to DCD or ATS at inhibiting nitrification in fertilizer
bands. With granular urea, Instinct and SuperU (DCD) had slower nitrification
rates than unamended urea. Nutrisphere-N, NZone, StayN, and NStay did
not inhibit nitrification in our studies. Farmers interested in fertilizer
additives for the purpose of inhibiting urease, ammonia volatilization,
or nitrification are advised to select the most effective inhibitor appropriate
for the form of N being applied.
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