Volatilization of Surface Applied Urea/UAN

Surface broadcasting of N fertilizers has become popular to increase operational efficiency – increasing the speed of seeding and reducing risk of seed injury. Growers must consider the risks of volatilization loss and take precautions when risk is high.

Volatilization of ammonia from urea or the urea portion of UAN (28-0-0) is affected by several factors:

Volatilization Risk

Often we experience such conditions in Manitoba. Research has shown losses to be:

Table 2. Loss of applied urea in 7 days as influenced by temperature and N source (Grant et al, AAFC, Brandon)

Table 2 Loss of applied N

Ways to minimize losses:

  • Treat urea with a urease inhibitor NBPT like Agrotain Ultra. Several Agrotain formulations are available and some other NBPT products are now available. NDSU staff indicates to expect similar performance as long as the active ingredient NBPT rate per tonne urea is the same.
  • Wait for rain.
  • Banded UAN is less subject to volatilization than broadcast sprayed.
  • The addition of other fertilizers has been inconsistent in their impact on volatilization (ie Ammonium thiosulphate).

Submitted by:  John Heard, Crop Nutrition Specialist, MAFRD

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