kg -1 ) Nitrates (mg NO 3 20000 15000 10000 5000 0 Broiler Litter Ammonium Nitrate y = 1012.55 + 15.85x + .1328x 2 r 2 = 0.8159 p = < 0.0001 0 20 40 60 80 100 120 140 N Rate (kg N ha -1 ) Shenandoah Valley Interactions between N source and rates were not significant for the first, second, and fourth harvests at the Shenandoah Valley location, therefore results are presented by N rate (Figure 3-16-A, 3-17-A; 3-19-A) and N source (Figure 3-16-B; 3-17-B; 3-19-B). No source effect was observed for any one of the harvests in 2010. Nitrate levels for harvest one increased with increasing N rates quadratically (Figure 3-16). Nitrate levels peaked at the 90 kg N ha -1 rate with nitrate accumulation reaching toxic levels. Nitrate levels were in the dangerous category for all four rates (Figure 3-16). Overall, high N rates from the first harvest led to dangerous levels of nitrates in the teff (5000 mg kg -1 NO3 -1 +) (Table 3-8, Figure 3-16). The second harvest showed a linear response to N rate, with lower levels of nitrates overall. Generally, the dangerous level of nitrate was associated with the higher N rates, however, some high levels of nitrates were observed for the 55 y = 1190.09 + 13.37x r 2 = 0.5540 p = 0.0009 Figure 3-15. The effect of N rates and sources on nitrate accumulation for the second harvest at the Southern Piedmont, 2010.
lower N rates (Figure 3-17-A). Nitrogen rate x N source interactions were significant at harvest three at Steeles Tavern in 2010, therefore interaction means are plotted (Figure 3- 18). Ammonium Nitrate showed quadratic response to increasing N rate (Figure 3-18). Broiler Litter showed no response to the increasing N rate (Figure 3-18). Response to N rate in the fourth harvest was only different at the highest N rate (135 kg N ha -1 ). Nitrate accumulation levels in teff for the third and fourth harvest were safe for livestock consumption (Table 3-8, Figures 3-18 and 3-19). 56