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

Table 2

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

Effect	Conrad			Corvallis			Kalispell
	2011	2012	2013	2011	2012	2013	2011	2012
N source	kg ha^−1
Urea	2488	5111	4506	3161	4640	2623	3699	4506
ESN	2556	5515	4439	2690	4842	2488	3901	4304
Blend	—	5447	4708	2757	4640	2152	4035	4371
Prob >	0.969	0.051	0.117	<0.001	0.699	0.452	0.003	0.517
At-seeding N rate, kg ha^−1
0	2488	4035	3699	2623	3833	1816	2898	3833
Low	2556	5178	4640	2757	4304	2556	4237	4371
Medium	2892	5447	4573	2959	5044	2556	4237	4371
High	3161	5582	4439	3026	4640	2152	4102	4371
Prob > (trend)	0.006^‡	0.003^‡	0.055	0.048^‡	0.050	0.051	0.114	0.945
Topdress N rate, kg ha^−1
0	2389	5380	4573	2690	4506	2354	3699	4371
45	2741	5447	4506	3026	4977	2488	4035	4439
Prob >	<0.001	0.749	0.410	<0.001	<0.001	0.813	0.003	0.175

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.
represents significant linear trend, 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.