Stalk nitrate testing

The end-of-season lower corn stalk nitrate test can be useful for determination of excess plant available N from the soil (i.e. concentrations above 2,000 ppm nitrate-N). However, that interpretation is for normal weather and production conditions. In 2012, test results could be abnormally high due to the dry conditions and severe impact on plant growth and grain production. Therefore, it is suggested to not use the stalk nitrate test this year, or to use it as a measure of potential nitrate carryover.

Timing of fall N application

With the potential for early fall harvest this year, carefully consider the risks of early N fertilizer or manure application. With typical warm soils in the late summer and early fall, conversion of fertilizer and manure ammonium to nitrate will be rapid. This places the applied N at risk for loss if wet conditions develop. For many years now the ag industry in Iowa has followed the “wait until 50° F and cooling” before anhydrous ammonia application. That would also be a good practice for manure with high ammonium-N content.

Dry periods

Corn yield response to N rate and needed fertilization rate decreases in years with below normal rainfall. This effect can persist across periods (years) of dry conditions, and even for year(s) after rainfall returns to normal (but not excessively wet). If below normal rainfall conditions continue, then consider using the low end of the Corn N Rate Calculator profitable range for corn N rate recommendations.