Impact Of Tillage On The Spatial Distribution Of Ch4 And N2o In The Soil Profile Of Late Rice Fields

To better understand the effects of tillage on the spatial heterogeneity of CH4 and N2O in the soil profile of late rice fields, we conducted a field experiment to investigate the impacts of tillage methods (rotary tillage (RT) and no-tillage (NT)) on the spatial patterns and influential factors of CH4 and N2O in the soil pore water under different fertilization treatments (inorganic fertilizer with straw (FS) and no fertilizer (CK)). The results showed that great spatial variation was observed in the concentrations of CH4 and N2O in the soil profile. The content of CH4 in the soil pore water was significantly higher in the deep layer (-17.5 cm - -22.5 cm) than the upper layer (-2.5 cm - -7.5 cm) for NT-CK; but it was opposite for NT-FS. RT significantly increased the content of CH4 in the soil pore water at depths of -7.5 cm, -12.5 cm, and -17.5 cm as compared with NT irrespective fertilization. High values of N2O were observed in the deep layer (-17.5 cm - -22.5 cm) for NT-CK, middle layer (-7.5 cm - -15 cm) for RT-CK, upper layer (-2.5 cm - -10.0 cm) for NT-FS, and across the whole profile for RT-FS. The horizontal distribution of CH4 did not show a significant difference at different distances from the rice plant, whereas the horizontal distribution of N2O showed a general pattern where high values of N2O occurred at a distance from the rice plants. The results of classification and regression tree (CART) analysis showed that K+ and PO43- presented relatively higher importance to the spatial heterogeneity of CH4 and N2O in the soil profile of late rice fields, in contrast to the contents of carbon and nitrogen. These results provide detailed insight into the spatial distribution and influential factors of CH4 and N2O in the soil profile of rice fields.