main factor was tillage depth and the split factor was the
amount of rice straw incorporation. Soil puddling tillage was
performed by using a furrow plough and a rotary harrow driven
by tractors with 75 and 80 horsepower, respectively, resulting in
different depths of tillage (or plough layer), i.e. deep tillage (DT,
0.25–0.30 m deep) and shallow tillage (ST, 0.15–0.20 m). After the
plowing, the soil was puddled and smoothed by using a loaded
rake. Rice stubble (50–100 mm high) (C1) and total rice straw
(C2) from the previous season was incorporated into the plough
layer during the first plowing. An additional treatment without
organic C input (C0) was set up using a metal box (11m),
which was inserted in C1 plot and there was no cropping and no
fertilization.