The University of Missouri, like most who make N recommendations, says the BMP of timing for N fertilizer applications is to apply fertilizer as close as possible to the period of rapid crop uptake. Fall N application is considered relatively high risk and is not a BMP. For those who are willing to take the risk in order to apply N at a lower cost and without interfering with spring field work, the University of Missouri Extension recommends:

  • Use only anhydrous ammonia—it converts to nitrate more slowly than any other form.
  • Use a stabilizer.
  • Apply N on no more than half—preferably only one-quarter—of planned corn acres to limit your risk.
  • Delay application of anhydrous ammonia until the soil temperature at a 6-inch depth reaches 50 degrees
  • The risk of N loss increases the farther south you farm in Missouri
  • High-pH soils are more likely to lose fall-applied N, don’t fall-apply N on them.