John Rubin
M.S. Thesis Defense
Advisor: John Lamb
Committee: John Lamb, Jeff Coulter, Daniel Kaiser
Defense Date: September 20th at 9 am, 375 Borh.
Title: Influence of Nitrogen Rate on Corn Grain Yield, Nitrogen Use Efficiency, and Nitrate
Leaching on Coarse-Textured Minnesota Soils
Abstract:
Nitrogen (N) in its nitrate form poses a threat to water quality in agriculture because it is easily
leached following rain and irrigation events. Leaching is enhanced in sandy soil conditions
because sandy soils are particularly well-drained. In this study, N was broadcast applied as urea
on fields planted with corn (Zea Mays L.). The study was conducted at four locations, each
containing four replications in a randomized complete block. Nitrogen uptake, leaf chlorophyll,
normalized difference vegetation index (NDVI), grain yield, grain N, nitrogen use efficiency
(NUE), basal stalk nitrate (BSN), and residual soil nitrate (RSN) were evaluated with respect to
N rate. Nitrate leaching was monitored with suction tube lysimeters at three of the four locations.
Results showed an increase in leaf chlorophyll, N uptake, grain yield, grain N, and basal stalk
nitrate-N with increased N rate. Normalized difference vegetation index was not significantly
affected by N rate for most locations and sampling times. Residual soil nitrate-N and nitrate-N in
the leachate were often least for the control, but did not have a significant relationship with N
rate. Nitrate-N concentration in the leachate was affected by the day of the year at three of three
locations.