Should Pre-Tassel Nitrogen Applications Become Standard Practice for Mid-South Corn Production?.

In recent years much emphasis has been placed on managing corn production with pre-tassel nitrogen (PTN) applications.  Research at the Delta Research and Extension Center has shown a significant increase in grain yields with urea (46-0-0) applications made into standing corn prior to pollen shed.  Pre-tassel can refer to any time from V6-V8 up and through tassel emergence.  Pre-tassel N applications have ranged from 20 to 60 lb N/acre (22.4 to 67.2 kg N/ha) but significance has only been observed with the 20 lb N/acre (22.4 kg N/ha) application.  However, in many cases in the Mid-south, the minimum application from the air is 100 lb material/acre (112 kg/ha).   The greatest benefits have occurred where insufficient N was applied as a standard split application (Preplant [PPN] + Sidedress [SDN] or where environmental conditions have led to denitrification, runoff, or in some cases leaching of the applied N.  Nitrogen uptake by growing corn is slow from seedling emergence through about V5-V6 then increases rapidly as the corn advances to reproductive growth.  Initial thoughts were that later N applications were not utilized by the plants and converted to yield increases.  Research data has shown that the plants are able to take up the later N as long as sufficient moisture (rainfall or irrigation) is available to carry the N to the root system.  Some producers are investigating a possible three-way split and planning for a PTN application while others are wanting to by-pass any N early in the growing season.  While these practices may reduce the potential for early N losses, they also subject the plants to early N deficiency at a keep growth stage.