Frederick Below, Martín Uribelarrea, Stephen P. Moose, and Allen W. Becker. University of Illinois-Urbana-Champaign, Univ. of Illinois-322A ERML, 1201 W. Gregory, Urbana, IL 61801
Genetic improvement in N use efficiency (NUE) is a clear strategy for enhancing yield and fertilizer N management of corn (Zea mays L.), and has been the subject of our ongoing research. Calculation of the N requirement (N fertilizer usage/grain yield) based on statewide average grain yields and fertilizer sales shows a steady decrease since the mid 1980’s, suggestive of a genetic improvement in N use. Direct comparison of the response to N for a 1980’s hybrid with its modern counterpart confirmed a 1 Mg improvement in maximum yield with 30 kg/ha less N, for a 30% decrease in the N requirement. When calculated at the N rate that just optimizes yield, 55 modern commercial hybrids had an average overall NUE of 21.6 kg grain/kg N (range of 6-42), with an average uptake efficiency of 0.58 kg plant N/kg N (range 0.26-0.82) and an average utilization efficiency of 38 kg grain/kg plant N (range 18-56). No hybrid was optimized for both N uptake and N utilization suggesting room for improvement in overall NUE. A substantial increase in yield was observed in hybrid isolines containing the rootworm bt trait, which was accompanied by better performance at low N and a higher maximal yield at high N. Based on this research, three difference response models were developed to show the potential ways that yield response to N could be improved in a commercial corn hybrid.
