PRE-Tassel Nitrogen Rates Applied Across Multiple Corn Cultivars.

Other the last few years research emphasis has been placed on managing corn production with pre-tassel nitrogen (PTN) applications.  Research at the Delta Research and Extension Center (DREC) has shown a significant increase in grain yields when urea (46-0-0) applications are 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.   When related trials were evaluated in producer fields, cultivar differences were observed with limited significance in only a few cultivars.  With this in mind, new studies were established at DREC with the objective of evaluating PTN rates across a selected group of corn cultivars ranging from 109 days to 121 days in relative maturity (RM).  Both studies had 120 lb N/acre (134 kg N/ha) applied prior to planting with either 60 or 120 lb N/acre (67 or 134 kg N/ha) applied as a sidedress at the V5-V6 growth stage.  Urea (46-0-0) was then pre-weighed and hand-applied in a simulated aerial application at rates of 0, 20, 40, and 60 lb N/acre (0, 22, 45, and 67 kg N/ha).  The center two rows of each 4-row plot (40-in rows, 100 ft in length, [102-cm rows, 30.5 m in length]) was harvested with samples taken at harvest to determine harvest moisture, bushel test weight and Seed Index.  There was a greater response to PTN at the lower standard N rate as expected with some variation across cultivars.  To date, two years of the study have been completed.  The corn follows irrigated soybean in a 1:1 soybean/corn rotation.