In conclusion, deficit irrigation during late vegetative and
reproductive growth stages increased grain yield, NUE, and
WUE. With three of the four rain-fed site-years reporting
increases in grain yield and NUE, we would recommend that
a pure ammoniacal N fertilizer source be applied if a preplant
only N fertilizer application is to be utilized. If irrigation
water is available, the N source is not as critical. However,
the producer should be cognizant of the potential N loss
mechanisms (leaching, volatilization, and denitrification)
of N fertilizer sources like UAN. Lastly, if producers are
going to utilize a preplant only fertilizer N application for
maize cultivated on the Southern Great Plains, they should
accordingly adjust N fertilizer rates based on a reasonable
irrigated or rain-fed yield goal or regional N response trials.