Soil bulk density of different tillage treatments in 2008 (A for the early rice season and B for the late rice season).

<p>Data are means of three replications; means followed by different letters are significantly different at <i>P<0.05.</i> Sampling was done during the harvest of the early and late rice in 2008.</p

Cumulative N₂O emissions of each farm operation phase during the rice growing period.

<p>Values are means of three replications for each treatment; means followed by different letters are significantly different at <i>P<0.05</i>.</p

Soil porosity of different tillage treatments in 2008 (A for the early rice season and B for the late rice season).

<p>Data are means of three replications; means followed by different letters are significantly different at <i>P<0.05</i>.</p

N₂O flux under different tillage during the rice growing seasons (A, B for the early rice season and the late rice season in 2007; C, D for the early rice season and the late rice season in 2008, respectively).

<p>Vertical bars represent standard errors of the mean (n = 3).The arrows in the figures indicate the time of field operations.</p

Principal soil properties of the test soil.

<p>Principal soil properties of the test soil.</p

CH₄ flux under different tillage during the rice growing seasons (A, B for the early rice season and the late rice season in 2007; C, D for the early rice season and the late rice season in 2008, respectively).

<p>Vertical bars represent standard errors of the mean (n = 3).The arrows in the figures indicate the time of field operation.</p

Effects of winter cover crops on CH₄ and N₂O emission from rice fields during whole growing season of early and late rice (g m⁻²).

<p>Ry-R-R: rice–rice–ryegrass cropping system; Mv-R-R: rice–rice–Chinese milk vetch cropping system; Fa-R-R: rice–rice cropping system with winter fallow.</p><p>Values are presented as mean ± SE (n  =  3). Means in each column with different letters are significantly different at the <i>P</i> <0.05 level.</p><p>Effects of winter cover crops on CH₄ and N₂O emission from rice fields during whole growing season of early and late rice (g m⁻²).</p

Effects of winter cover crops on N₂O flux in early and late rice fields in 2012 and 2013.

<p>Ry-R-R: rice–rice–ryegrass cropping system; Mv-R-R: rice–rice–Chinese milk vetch cropping system; Fa-R-R: rice–rice cropping system with winter fallow. ERT: early rice transplanting; LRT: late rice transplanting. N₂O emission rate is the mean of values measured within each treatment (n = 3).</p

Management practices of different cropping systems.

<p>Management practices of different cropping systems.</p

Effects of winter cover crops on CH₄ flux in early and late rice fields in 2012 and 2013.

<p>Ry-R-R: rice–rice–ryegrass cropping system; Mv-R-R: rice–rice–Chinese milk vetch cropping system; Fa-R-R: rice–rice cropping system with winter fallow. ERT: early rice transplanting; LRT: late rice transplanting. CH₄ emission rate is the mean of values measured within each treatment (n = 3).</p