Influence of No-Tillage on Soil Organic Carbon, Total Soil Nitrogen, and Winter Wheat (Triticum aestivum L.) Grain Yield

Table 4

Summary of relationships between wheat grain yield, TSN, and SOC under NT at E222 (Stillwater) and E502 (Lahoma), Oklahoma, USA, 2007–2014.

Treatment	N rate (kg·ha^−1)	TSN vs. grain yield			SOC vs. grain yield
		value	R^2	Equation	value	R^2	Equation
E222
1	0	0.0036	0.59	y = 1777.8x − 727	0.0076	0.53	y = 412.15x − 2946
2	45	0.0058	0.55	y = 2183.2x − 931	<0.0001	0.95	y = 615.2x − 5020
3	90	0.2087	0.15	y = 1139.8x + 376	0.0029	0.6	y = 418.36x − 2900
4	135	0.0951	0.25	y = 1544.1x − 223	0.0206	0.43	y = 402.05x − 2840
E502
2	0	0.0154	0.35	y = −2732.5x + 4280	0.2003	0.11	y = −477.8x + 6094
3	22.5	0.0008	0.56	y = −3659.2x + 5745	0.0491	0.25	y = −741.33x + 8983
4	45	0.004	0.46	y = −3571.1x + 6273	0.0015	0.53	y = −1455.9x + 16290
5	67	0.0053	0.42	y = −5196.7x + 7919	0.1457	0.14	y = −734.62x + 10194
6	90	0.0041	0.54	y = −5344.8x + 8852	0.3068	0.09	y = −1059.8x + 13849
7	112	0.0133	0.44	y = −4621.5x + 9196	0.0285	0.37	y = −1265x + 16803

E502 = experiment 502; E222 = experiment 222; n = 16 for each treatment; NT = no-tillage; TSN = total soil nitrogen; SOC = soil organic carbon.