Have you finished applying anhydrous ammonia or an alternative form of nitrogen this fall?  And by the way, how did you determine how much to apply? It may have been based on your typical rate of application, or it may have been driven by the cost of anhydrous, or it may have been from either a recommendation from your supplier or from the Iowa State web-based decision maker on nitrogen application. Nevertheless, this is the fall fertility season and there are some significant trends occurring.

USDA says that despite environmental and conservation regulatory directives, a large share of cropland does not receive nitrogen according to best management practices. In 2006, that included 65% of cropland, and 86% of cropland in the Upper Mississippi River Basin needed improvements in at least application rate, application timing, or the method of application for nitrogen.

  • Rate. Applying no more nitrogen (commercial and manure) than 40 percent more than that removed with the crop at harvest, based on the stated yield goal, including any carryover from the previous crop. This agronomic rate accounts for unavoidable environmental losses that prevent some of the nitrogen that is applied from actually reaching crops.
  • Timing. Not applying nitrogen in the fall for a crop planted in the spring.
  • Method. Injecting (placing fertilizer directly into the soil) or incorporating (applying to the surface and then discing the fertilizer into the soil) nitrogen rather than broadcasting on the surface without incorporation.

In that 2005 to 2010 period when nitrogen rates were declining somewhat, the share of corn acres not meeting the rate-timing-method guidelines declined from 65% to 60%. That trend was for commercial sources of nitrogen, but the trend was not the same for corn acres receiving manure as a nitrogen source. Consequently, ERS suggests that when commercial nitrogen prices rise and farmers with access to manure shift to that nutrient, the rate-timing-method practices may fade somewhat. And ERS says, “As a result, improved nitrogen management on cropland continues to be a major conservation policy goal.”


Only 65% of US cropland receives nitrogen using best management practices, and 86% of cropland in the upper Midwest receives nitrogen outside of the recommended rates of application, timing of application or method of application. Some improvement occurred when commercial fertilizer costs increased, but those have faded as prices have decreased. While manure remains a replacement for commercial sources of nitrogen, its application rate, timing, and method is not as compliant with best management practices, compared to commercial sources of nitrogen.

Source: FarmGate blog