Monitoring Nitrogen Status of Corn

The strong relationship between nitrogen (N) availability in soil and crop yields makes N management a primary concern of producers. Over the past several decades, a majority of corn producers have come to regard fertilizer N as the primary source of N nutrition. Most producers acknowledge other sources of N such as manure, legumes, nitrate in water used for irrigation and mineralization of organic matter (microbial conversion of organic N to inorganic N as ammonium and nitrate). Giving credit for non-fertilizer sources of N is a common practice, but the amount of credit is usually conservative because producers are uncertain about when it will become available and how much can be used by the crop. Another reason for only giving minimal N credits is to reduce the risk yield reduction associated with an N deficiency and the general inability to easily correct a deficiency after sidedressing. The exception is where irrigation is available or where producers have access to high clearance vehicles