Dryland soil chemical properties and crop yields affected by long-term tillage and cropping sequence

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Table 6 Effect of tillage and cropping sequence combination on soil Ca, Mg, and Na concentrations at the 0–120 cm depth in 2013

Tillage and cropping sequence^a	Soil depth
Tillage and cropping sequence^a	0–7.5 cm	7.5–15 cm	15–30 cm	30–60 cm	60–90 cm	90–120 cm
Ca concentration (g Ca kg⁻¹)
NTCW	0.99b^bC^c	1.60C	3.55B	5.32A	4.67A	3.98B
STCW	0.89bC	1.61C	2.97B	4.65A	4.72A	4.31A
FSTCW	0.99bC	1.78C	4.09B	5.34A	4.51AB	4.05B
FSTW-B/P	1.26aB	2.06B	3.76A	4.66A	4.32A	4.30A
STW-F	1.29aB	2.36B	3.89A	4.67A	4.68A	4.25A
Contrast
NT vs. T	0.04	−0.09	0.02	0.32	0.05	−0.20
CW vs. W-F	−0.40**	−0.75	−0.92	−0.02	0.04	0.06
CW vs. W-B/P	−0.27*	−0.28	0.33	0.68	0.19	−0.25
Mg concentration (g Mg kg⁻¹)
NTCW	0.21E	0.34bDE	0.48D	0.70C	1.23B	1.52A
STCW	0.19E	0.35bDE	0.47CD	0.65C	1.19B	1.36A
FSTCW	0.21D	0.40bCD	0.50C	0.83B	1.34A	1.53A
FSTW-B/P	0.25D	0.38abD	0.50CD	0.75C	1.18B	1.40A
STW-F	0.25D	0.43aCD	0.54BC	0.73B	1.13A	1.40A
Contrast
NT vs. T	0.01	−0.04	0.01	−0.04	−0.04	0.08
CW vs. W-F	−0.06*	−0.08*	0.07	−0.08	0.06	−0.04
CW vs. W-B/P	−0.04	0.02	0.00	0.08	0.16	0.13
Na concentration (mg Na kg⁻¹)
NTCW	14.5ab^bB	15.5B	16.0B	19.0B	30.3bB	58.8bA
STCW	14.8bB	14.3B	15.3B	19.0B	36.8bB	65.5bA
FSTCW	15.8abC	15.3C	18.5C	24.8C	66.8aB	119.3aA
FSTW-B/P	16.6aC	21.0C	30.4C	37.4C	64.5aB	102.6aA
STW-F	12.4bB	14.4B	16.9B	19.5B	27.0bB	57.4bA
Contrast
NT vs. T	−0.8	−0.7	−0.9	−9	−21.5*	−33.6*
CW vs. W-F	2.4	−0.1	−1.6	−0.5	9.8	8.1
CW vs. W–B/P	−0.8	−5.7	−11.9	−12.6	2.3	16.7

NTCW no-till continuous spring wheat, STCW spring till continuous spring wheat and STW-F spring till spring wheat-fallow. CW represents continuous wheat, NT no-till, T till, W–B/P spring wheat–barley/pea and W-F spring wheat-fallow.
* and ** Significant at P = 0.05 and 0.01, respectively.
^aTillage and cropping sequence are FSTCW fall and spring till continuous spring wheat, FSTW–B/P fall and spring till spring wheat–barley (1994–1999) followed by spring wheat–pea (2000–2013).
^bNumbers followed by different lowercase letters within a column among treatments in a set are significantly different at P ≤ 0.05 by the least square means test.
^cNumbers followed by different uppercase letters within a row among soil depths in a set are significantly different at P ≤ 0.05 by the least square means test.