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Fluid Journal : Winter 2015
12 The Fluid Journal Winter 2015 0 20 40 60 80 100 120 140 160 180 200 1.0 1.5 2.0 2.5 3.0 Yield (bu/A) Ear-Leaf N (%) P33D53 - 2013 Nebraska Iowa Illinois to 279 bu/A) and yield was poorly correlated with Mg concentration (r2 = 0.19). The remainder of the 2013 study, following up on observations made in 2012 at York, NE, showed an apparent increase in micro-nutrient concentrations with an increase in ear-leaf N concentrations. Five fertilizer N rates at three locations were used in 2013 to create a range in soil N availability for two Pioneer brand hybrids (P33D53 and P1498). The Nebraska location was under sprinkler irrigation while the Iowa and Illinois locations were both rain fed. Yields increased with ear-leaf N concentration (N rate) as expected. The yields ranged from 39 to 196 bu/A across these three locations for P33D53 (Figure 2) and from 44 to 190 bu/A for P1498. Data in Figures 2 and 3 illustrate that not only did N rate affect yield, but so did the apparent availability of water. Seasonal rainfall amounts are not available for the Iowa and Illinois locations. It should be noted that the commonly accepted sufficiency- level for ear-leaf N concentration at silking is 2.75%. Water deficit had a strong influence on ear-leaf N concentration in Iowa and Illinois, even though the highest fertilizer N rate was 30 percent higher than recommended for maximum yield at these locations. Also note that the zero-N rate treatment under irrigation in Nebraska yielded 68 and 84 percent of the maximum yield for P33D53 and P1498, respectively. Hybrid P1498 is an AquaMax hybrid that typically performs quite well under limited water conditions. This characteristic is commonly attributed to a more extensive rooting system. Data indicate that the rooting system of P1498 was also more effective in extracting N from soil than P33D53 (Figure 2). The effect of ear-leaf N concentration on nutrient 0.00 0.02 0.04 0.06 0.08 0.10 0.12 0.14 0.16 0.18 0.20 P2088 AM P0987 HR 32T84 P1498 HR P0876 HR P1508 CHR 33D47 P1151 HR P0591 XR P0365 YHR P1768 AMX P1266 YHR P1168 YXR P1690 HR Ear Leaf Mg @ Silking (%) Shelton - 2013 Figure 1. Ear-leaf Mg concentrations for fourteen corn hybrids at Shelton, NE in 2013. Values between 0.9 and 0.13% ae considered "low". Figure 2. Effect of ear-leaf N concentration at silking on corn yield for P33D53 at three locations in 2013. 0 20 40 60 80 100 120 140 160 180 200 1.0 1.5 2.0 2.5 3.0 Yield (bu/A) Ear-Leaf N (%) P1498 - 2013 Nebraska Iowa Illinois Figure 3. Effect of ear-leaf N concentration at silking on corn yield for P1498 at three locations in 2013. "Make sure ear-leaf N concentrations are adequate."