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

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Table 5 Effect of tillage and cropping sequence combination on soil pH, buffer pH, and electrical conductivity (EC) 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
pH
NTCW	5.33ab^bE^c	6.50abD	7.60C	8.35B	8.58A	8.75A
STCW	5.05bE	6.15bD	7.58C	8.25B	8.63A	8.70A
FSTCW	5.02bE	6.33bD	7.80C	8.30B	8.68AB	8.73A
FSTW-B/P	5.46aE	6.44bD	7.60C	8.15B	8.51A	8.59A
STW-F	5.73aE	7.03aD	7.65C	8.25B	8.50AB	8.66A
Contrast
NT vs. T	0.29	0.26	−0.09	0.08	−0.08	0.04
CW vs. W-F	−0.68***	−0.88**	−0.08	0.01	0.13	0.04
CW vs. W-B/P	−0.43*	−0.11	0.20	0.15	0.16	0.14
Buffer pH
NTCW	6.45bE	7.10abD	7.43C	7.60B	7.70AB	7.73A
STCW	6.38bE	7.00bD	7.43C	7.58B	7.68A	7.70A
FSTCW	6.43bE	7.05bD	7.45C	7.60B	7.70AB	7.73A
FSTW-B/P	6.66aD	7.13abC	7.44B	7.58B	7.69AB	7.70A
STW-F	6.80aE	7.24aD	7.44C	7.59B	7.66AB	7.72A
Contrast
NT vs. T	0.05	0.08	−0.01	0.01	0.01	0.01
CW vs. W-F	−0.43***	−0.24**	−0.01	−0.01	0.01	−0.01
CW vs. W-B/P	−0.24*	−0.08	−0.01	0.03	0.01	0.03
EC (dS m⁻¹)
NTCW	0.17B	0.10B	0.16B	0.25A	0.28A	0.30bA
STCW	0.18BC	0.16C	0.22AB	0.24AB	0.28A	0.28bA
FSTCW	0.19C	0.20C	0.28B	0.29B	0.38AB	0.47aA
FSTW-B/P	0.23B	0.21B	0.30AB	0.36AB	0.43A	0.45aA
STW-F	0.19B	0.20B	0.26AB	0.31A	0.34A	0.33bA
Contrast
NT vs. T	−0.02	−0.06	−0.09	−0.03	−0.05	−0.07*
CW vs. W-F	−0.01	−0.04	−0.04	−0.07	−0.06	−0.05
CW vs. W-B/P	−0.04	−0.01	−0.02	−0.07	−0.05	−0.02

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, 0.01, and 0.001, 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.