Evaluation of ESN Vs Urea for Irrigated Field Corn Production in Montana.

Field corn (Zea mays L.) is grown in the more temperate regions of Montana, more specifically, the Yellowstone River Valley of south-central and eastern Montana where irrigation is readily available.  Environmentally Safe Nitrogen (ESN) is a relatively new time-released form of polymer-coated urea developed and marketed by Agrium Advanced Technologies.  In 2012 and 2013, field experiments were conducted near Huntley to compare the performance of field corn harvested for grain using either conventional urea, ESN, or blends of the two products.  Urea and ESN were applied at rates of 56 to 336 kg N/ha in 56 kg increments as mixed ratios of 100:0, 67:33, 33:67 and 0:100 of percent urea:percent ESN.  Treatments included an un-fertilized check plot, with all 25 treatments arranged in a randomized complete block design replicated 4 times.  All treatments were applied and incorporated amidst fall tillage operations to level land for flood irrigation and final seed bed preparation.  Fall soil tests indicated approximately 130 and 58 kg of residual NO3-N/ha in a 1.25 m profile for Garst 89A33-3000GT hybrid corn (85 RM) planted in the spring of 2012 and 2013, respectively. In 2012, corn yields increased from 11.5 metric tons/ha for the unfertilized check to 12.8 metric tons/ha with the application of 112 kg N/ha.  In 2013, corn yields increased from 8.4 metric tons/ha for the unfertilized check to 13.1 metric tons/ha with the application of 224 kg N/ha.  The amount of nitrogen, including residual NO3-N, required to maximize yields in this environment was estimated at 18.9 and 21.5 kg N/metric ton of grain (1.1 and 1.2 lb N/bu) in 2012 and 2013, respectively.  No interaction between applied nitrogen rates and the nitrogen products, including blends, was observed in either year.  Post-harvest residual NO3-N correlated with applied nitrogen rates, but was not associated with the form of pre-plant nitrogen applied.