Effects of plastic mulching on soil CO efflux in a cotton field in northwestern China.

In Northwestern China, more and more traditional cultivation system (TC) with no mulching and flood irrigation have been replaced by modern cultivation technology (MC) combining plastic film mulching with drip irrigation. Does plastic film mulching increase or reduce soil CO emission in arid areas? In order to study the effects of plastic mulching on soil CO efflux, a field study was conducted to compare soil CO concentration, soil CO efflux, soil temperature and moisture between the TC treatment and the MC treatment during a cotton growing season in Northwestern China. The seasonal patterns of soil profile temperature and soil moisture in the TC treatment were similar to that in the MC treatment. The mean value of soil profile temperature in the MC treatment was higher than that in the TC treatment. Except for soil moisture at 15 cm depth, the mean value of soil moisture at 5 cm and 10 cm depths in the MC treatment was higher than that in the TC treatment. The variation patterns of soil CO concentration and soil CO efflux in MC treatment were different to that in the TC treatment. Although the peak of soil CO concentration in the TC treatment was earlier than that in the MC treatment, the duration of soil CO concentration with high values in TC treatment was shorter than that in the MC treatment. Based on the model of Fick's first diffusion law, soil surface CO efflux in the MC and TC treatments were determined. The surface CO efflux in the TC treatment calculated by Fick's first diffusion law model was in good agreement with the value measured by chamber method. The seasonal curve of soil surface CO efflux in the MC treatment indicate the similar pattern with that in the TC treatment, and the rate of CO efflux was lower in the MC system. In the MC treatment, the seasonal variation of soil surface efflux was explained more by soil moisture than by soil temperature. However, in the TC treatment, the seasonal variation of soil surface efflux was explained more by soil temperature than by soil moisture. Over the completely experimental period, accumulated rates of soil CO efflux were 361 g C m and 474 g C m for the MC and TC system, respectively. We concluded that converting agricultural practices from traditional cultivation to the plastic mulching cultivation could reduce soil CO efflux by approximately 110 g C m year in agricultural land in arid areas of Northwestern China.