Managing Residual Nitrogen in Corn Production.

Previous research has shown that residual nitrogen levels in several key row crop production areas of Texas can be substantial. A 7-year study investigating nitrogen management in cotton showed residual nitrogen levels ranging from 34 to over 181 kg/ha to a depth of 1.22 m. Only 23% of study sites showed a yield response to supplemental N fertilizer. Corn is commonly used as a rotational crop with cotton. While it has a different root structure than cotton, corn also can benefit from residual soil nitrogen. However, limited information is available regarding how to properly credit residual nitrogen from different soil depths. Field studies were installed in the Blacklands and Coastal Bend regions of Texas to evaluate the response of corn to residual soil nitrogen. Deep profile sampling was used to identify study sites with a range of residual soil nitrogen levels. Supplemental N was applied to achieve soil test recommendations based on residual nitrogen at 0 to 15-, 0 to 30-, and 0 to 60-cm.