Table 2. Changes of the soil chemical properties of the wheat-based cropping systems in 0-30 cm soil depthCROPPNG
SYSTEMSSOC g kg-^1 pH (KCl) Al-P 2 O 5 (mg 100g -^1 ) Al-K 2 O (mg 100g -^1 ) CaCO 3 (%)
1970/80 2000/10 1970/80 2000/10 1970/80 2000/10 1970/80 2000/10 1970/80 2000/10
WSMF 16 .9ab 15 .4b 7 .19ab 7. 47 120a 63 a 49a 39a 2 .8b 4 .3b
WMF 16 .3ab 14 .9b 7 .17b 7. 32 74b 32 b 40a 33b 2 .3b 2 .6b
WWF 17 .7a 16 .3a 7 .24ab 7. 40 41c 24bc 43a 37ab 2 .2b 3 .4b
WMS 15 .2b 13 .2c 7 .20ab 7.52 7d 5c 16b 14c 1 .8b 4 .7b
WM 13 .7b 12 .1d 7.31a 7. 54 8d 4c 15b 15c 6 .8a 11 .5a
aData followed by the same letter within a column do not differ significantly at the P ≤ 0.05 level; WSMF - Fertilized 3-year crop
rotation; WMF - Fertilized 2-year crop rotation; WWF - wheat monoculture; WSM - Unfertilized 3-year crop rotation; WM -
Unfertilized 2-year crop rotation.