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

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Table 4 Effects of tillage and cropping sequence combination on P and K balance at 0–120 cm depth after 30 year (1983–2013)

Treatment^a	Initial total content in the soil in 2013 (A)	Total amount applied from fertilizers from 1984 to 2013 (B)	Total removed in crop grains from 1984 to 2013 (C)	Final total content in the soil in 2013 (D)	Balance^b
P content (kg P ha⁻¹)
NTCW	2,322	1,053	120a^c	2,257a	−988ab
STCW	2,322	1,053	121a	2,105b	−1,149b
FSTCW	2,322	1,053	131a	2,184ab	−1,060ab
FSTW-B/P	2,322	1,053	121a	2,109b	−1,145b
STW-F	2,322	527	80b	2,041c	−728a
Contrast
NT vs. T	–	–	−6	113**	107
CW vs. W-F	–	–	41*	64*	−421**
CW vs. W-B/P	–	–	10	75*	175*
K content (kg K ha⁻¹)
NTCW	4,490	816	137a	4,363a	−806a
STCW	4,490	816	137a	4,070b	−1,099b
FSTCW	4,490	816	149a	4,223ab	−934ab
FSTW-B/P	4,490	816	138a	4,077b	−1091b
STW-F	4,490	408	91b	3,947b	−860a
Contrast
NT vs. T	–	–	−6	217*	211*
CW vs. W-F	–	–	46*	93	−239*
CW vs. W-B/P	–	–	11	146	−157

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).
^bP or K balance = Column (C) + column (D) − column (A) − column (B).
^cNumbers 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.