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eturn to table of contents Table 1. Average yield of 19 Pioneer ® brand hybrids with a low rate and full rate of applied N and calculated RTN across 4 locations in 2012 and 5 locations in 2013. Hybrid/Brand 1 Low N Yield Full N Yield — bu/acre — RTN P0621HR (HX1,LL,RR2) 122 221 0.45 P0832HR (HX1,LL,RR2) 134 230 0.42 P0876HR (HX1,LL,RR2) 124 217 0.43 P0902HR (HX1,LL,RR2) 122 229 0.47 P0912HR (HX1,LL,RR2) 134 239 0.44 P0987HR (HX1,LL,RR2) 131 221 0.41 P1018YHR (YGCB, HX1,LL,RR2) 128 243 0.47 P1151HR (HX1,LL,RR2) 132 231 0.43 P1173HR (HX1,LL,RR2) 126 233 0.46 33T57 (HX1,LL,RR2) 129 233 0.45 P1319HR (HX1,LL,RR2) 133 245 0.46 P1324HR (HX1,LL,RR2) 133 237 0.44 P1395HR (HX1,LL,RR2) 133 237 0.44 33K44 (HX1,LL,RR2) 117 225 0.48 P1498HR (HX1,LL,RR2) 134 239 0.44 32T84 (HX1,LL,RR2) 132 232 0.43 33D49 (HX1,LL,RR2) 133 241 0.45 P1564HR (HX1,LL,RR2) 132 235 0.44 P1567XR (HXX,LL,RR2) 121 231 0.48 Differences in hybrid yield with full N appeared to be partially attributable to hybrid CRM – yield increased with fullerseason hybrids to a greater extent with full N than under limited-N conditions (Figure 7). Grain Yield (bu/acre) 260 240 220 200 180 160 140 Full N y = 1.4318x + 73.169 120 y = 0.4667x + 76.317 100 104 106 108 110 112 114 116 Hybrid CRM Low N Figure 7. Average grain yield by hybrid CRM with a low rate and full rate of applied N (2012-2013). A similar study was conducted in 2014 using a different set of 19 Pioneer brand corn products. Corn products included in this study covered a similar range in CRM – from 105 to 114. Trials were conducted at five locations in Illinois, Iowa, Nebraska, and California. Results of the 2014 study were very similar to those of the 2012 to 2013 study. Average RTN values for hybrids ranged from 0.32 to 0.45 (Table 2). Average yield varied by 14 bu/acre among hybrids at low N compared to 59 bu/acre at full N, meaning that differences in RTN among products tended to be driven more by differences in top-end yield rather than differences in yield stability under low N. For example, Pioneer ® hybrid P0636HR and Pioneer P1339AM1 brand corn had the same average yield under low N, but P1339AM1 yielded 21 bu/acre more with full N, making the difference in RTN between the 2 products entirely attributable to a difference in top-end yield. Table 2. Average yield of 19 Pioneer brand corn products with a low rate and full rate of applied N and calculated RTN across 5 locations in 2014. Hybrid/Brand 1 Low N Yield Full N Yield — bu/acre — RTN P0506AM (AM,LL,RR2) 137 210 0.35 P0636HR (HX1,LL,RR2) 145 227 0.36 P0912HR (HX1,LL,RR2) 147 216 0.32 P0969AM (AM,LL,RR2) 135 220 0.39 P1018HR (HX1,LL,RR2) 135 229 0.41 P1105YHR (YGCB, HX1,LL,RR2) 146 236 0.38 P1173HR (HX1,LL,RR2) 136 225 0.40 P1197AM (AM,LL,RR2) 149 257 0.42 P1241AMXT (AMXT,LL,RR2) 142 242 0.41 P1257AM (AM,LL,RR2) 139 247 0.44 P1266AM (AM,LL,RR2) 145 233 0.38 P1311CHR (RW,HX1,LL,RR2) 149 269 0.45 P1319HR (HX1,LL,RR2) 146 243 0.40 P1339AM1 (AM1,LL,RR2) 145 248 0.42 P1352AMXT (AMXT,LL,RR2) 138 238 0.42 P1395HR (HX1,LL,RR2) 148 237 0.38 P1417AMX (AMX,LL,RR2) 149 251 0.41 P1479AM (AM,LL,RR2) 147 237 0.38 P1498HR (HX1,LL,RR2) 145 240 0.40 As with the 2012 to 2013 study, yields under low N fell within a relatively narrow range for the majority of hybrids, from 145 to 149 bu/acre. Hybrids yielding below this range under low N also tended not to be the highest performers with full N. Hybrids that were top yielders with full N also tended to be at the upper end of the yield range under low N. Differences in hybrid yield with full N again appeared to be partially attributable to hybrid CRM, showing an even stronger yield response than in the 2012 to 2013 study (Figure 8). 66

eturn to table of contents Grain Yield (bu/acre) Of the corn products evaluated in the 2012 to 2014 DuPont Pioneer research studies, five were tested over all three years. Comparing performance of these hybrids among siteyears illustrates the effects of location and year on hybrid response to N. Results show that hybrid response to N varied by location and year (Figure 9), which aligns with similar findings from university studies. Differences among hybrids in Response to N (0-1) 260 240 220 200 180 160 140 120 100 104 106 108 110 112 114 116 P0912HR P1173HR P1319HR P1395HR P1498HR 1 0.8 0.6 0.4 0.2 0 1 0.8 0.6 0.4 0.2 0 1 0.8 0.6 0.4 0.2 0 1 0.8 0.6 0.4 0.2 0 Johnston, IA Macomb, IL Marion, IA Woodland, CA Full N Hybrid CRM Low N y = 3.5602x - 159.91 y = 0.6287x + 72.826 Figure 8. Average grain yield by hybrid CRM with a low rate and full rate of applied N (2014). 2012 2013 2014 RTN observed at a single location were not repeated across other locations and years, and very little consistency was observed in the relative ranking of RTN among hybrids from site-year to site-year. Much more variability in RTN was associated with site-year than with hybrid. Recent Pioneer research comparing hybrid RTN by evaluating hybrid yield under full and low N application rates suggest that this method likely has little to no value for improving grower N management efficiency and profitability. To the extent that differences in hybrid response to N were observed in DuPont Pioneer research, they were primarily attributable to differences in yield performance under full N. Since testing at only two N rates does not allow any determination of the optimum N rate for a given hybrid, the most noteworthy management implication to be taken from this research appears to be that the yield advantage of fuller-season hybrids tends to be greater when supplied with adequate N. CONCLUSIONS Numerous research studies have been conducted over the past few decades to evaluate possible corn hybrid by N rate interactions. Most of these studies have either found no interactions or the interactions were inconsistent across locations and years due to variability in growing conditions. Several Pioneer studies conducted over this time period produced similar findings. The accumulated body of research has not provided a sufficient basis to drive hybrid-specific N management into common practice for most growers. The frequent variability in results, with N response of hybrids differing greatly depending on the conditions experienced in a particular location and year, calls into question the general practicality of using field experiments as a basis for hybrid-specific N management recommendations. Future Directions Differences in N requirements among hybrids appear to be relatively small and are likely masked by other, larger sources of in-field variability. In order to be successful, future efforts to optimize N management based on hybrid genetics will likely require a more sophisticated and prescriptive approach, rather than simply assigning a static hybrid rating based on a limited number of field trials. Dynamically accounting for other factors unique to a given field and year may provide an opportunity to better zero in on the hybrid signal by filtering out some of the environmental noise. The Encirca℠ Yield Nitrogen Management Service incorporates N analytics that simulate the major processes that affect soil N, including crop growth, N mineralization, leaching, denitrification, and volatilization. DuPont Pioneer researchers are currently developing expanded analytical capabilities that will also incorporate genetic coefficients into N management recommendations. Nitrogen management continues to be one of the most complex and challenging aspects of modern corn production. With an extensive history and ongoing engagement in N management research, as well as the advanced analytics of the Encirca Yield Nitrogen Management Service, Pioneer is better-equipped than anyone in the industry to help growers better manage their N. Figure 9. Average RTN of five Pioneer ® brand hybrids at four locations in 2012, 2013, and 2014. 67

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