Environmentally Smart Nitrogen Performance in Northern Great Plains’ Spring Wheat Production Systems

Table 6

Effect of at N source, preplant and topdress N rate on spring wheat grain uptake Conrad, Corvallis and Kalispell, 2011–2013 growing seasons.

Effect	Conrad			Corvallis			Kalispell
	2011	2012	2013	2011	2012	2013	2011	2012
N source	kg ha^−1
Urea	51.6	117.7	106.5	96.4	106.5	72.9	99.8	106.5
ESN	54.9	114.3	107.6	78.5	107.6	71.7	104.3	105.4
Blend	54.9	116.6	109.9	81.8	102.0	67.3	107.6	107.6
Prob >	0.620	0.328	0.401	<0.001	0.664	0.853	0.011	0.782
At-seeding N rate
0	44.8	86.3	68.4	65.0	86.3	46.0	53.8	85.2
Low^†	43.7	98.7	104.3	77.4	94.2	71.7	96.4	104.3
Medium	53.8	118.8	111.0	88.6	116.6	77.4	106.5	104.3
High	62.8	131.2	108.7	91.9	105.4	62.8	108.7	109.9
Prob >	<0.001^‡	<0.001^‡	0.047^‡	0.001^‡	0.008	0.395	<0.001^‡	0.051^‡
Topdress N rate
0	50.5	112.1	106.5	79.6	99.8	70.62	98.7	107.6
45	57.2	120.0	108.7	91.9	111.0	70.6	109.9	105.4
Prob >	0.049	<0.001	0.321	<0.001	<0.001	0.932	0.001	0.204

Down a column for each site-year source means followed by different letter are significant at .
^†At-seeding N rates: low, medium, and high were 56, 112, and 168 kg ha⁻¹ for Conrad and 112, 224, and 336 kg ha⁻¹ for Corvallis and Kalispell.
  &   represent significant linear and quadratic trends, for at-seeding N rate for each site-year.
Down a column for topdress N rates, LS means followed by different letters are significant at for each source.