We conducted a 3-year field experiment on an Anthrosol paddy soil to investigate changes in crop yield, P uptake and soil organic phosphorus (P) fractions after 3 years of conventional tillage (CT) conversion to no-tillage (NT) under a rape -rice rotation in central China. Treatments were established following a split-plot design of a randomized complete block with tillage practice as the main plot and fertilizer as the sub-plot treatment. The yields of rape and rice ranged from 1378 to 2264 kg ha -1 and from 5895 to 9453 kg ha -1 across 3 years, respectively. Moreover, P uptake for rape and rice (aboveground) varied from 3.9 to 10.4 kg ha -1 and from 9.5 to 32.0 kg ha -1 , respectively. Fertilization significantly enhanced crop yields and P uptake, but tillage did not affect the yields and P uptake. Fertilization significantly increased total P concentrations, acid phosphatase activity, Bray-1 P and labile organic P in the 0-5 cm soil layer. Compared to the CT treatments, the NT treatments had significantly higher acid phosphatase activity, total P, Bray-1 P, total organic P and organic P fractions in the 0-5 cm soil layer but lower organic P fractions in the 5-20 cm soil layer. Therefore, our results suggest that short-term NT does not enhance organic P concentrations in the 0-20 cm soil layer, and only improve P availability on the soil surface.

Differences in soil CO 2 emissions between no-tillage (NT) and conventional intensive tillage have been well assessed in paddy fields, but few studies evaluate the effects of different NT modes on soil CO 2 emissions. Therefore, a field experiment was conducted to assess paddy soil CO 2 flux as affected by different NT modes [ridge cultivation with NT (RNT) and conventional flat cultivation with NT (FNT)] and its influencing factors during the 2012-2014 rice growing seasons in central China. Soil CO 2 fluxes were determined by a LI-8100A soil CO 2 flux system. The mean soil CO 2 fluxes on the ridges in the RNT treatment increased by 49%, 52% and 35% compared with those on the flat land in the FNT treatment in 2012, 2013 and 2014, respectively. Cumulative CO 2 emissions ranged from 1042 g m -2 to 1489 g m -2 from the RNT treatment, and from 724 g m -2 to 1016 g m -2 for the FNT treatment. Moreover, soil CO 2 its emissions were significantly correlated with dissolved organic C, aboveground biomass and root biomass. Therefore, our results suggesting that annual rice-fallowoilseed rape rotation should be considered to assess the effects of tillage systems on soil CO 2 emission.