Soil CO2 Efflux and Concentration As Affected By Plastic Mulching in a Cotton Field.

Abstract In northwest China, plastic mulching is an effective method to increase crop production. Soil CO2 efflux and concentration in dry-land agriculture can be greatly affected by this cropping system. This study aims to examine whether covering fields with plastic film affects CO2 emission and concentration in cotton field. The experiment included mulched and non-mulched treatments. Soil CO2 efflux and CO2 concentration were measured in the ridges and furrows from July to October in 2013. In the ridges, mean soil CO2 effluxes were 0.069 and 0.076 g CO2-C?m-2?h-1 for mulched and non-mulched treatments, respectively. In the furrows, mean soil CO2 effluxes were 0.065 and 0.051 CO2-C?m-2?h-1 for mulched and non-mulched treatments, respectively. In summary, cumulative CO2 emissions were 546.09 and 548.72 g CO2-C?m-2 for mulched and non-mulched treatments. CO2 concentrations in the ridges were higher in the mulched treatment (ranged from 10.01 to 28.28 mg?L-1) than the non-mulched treatment (ranged from 4.91 to 24.28 mg?L-1). However, in the furrows, we only observed a significant increase in CO2 concentration of 4.33 mg?L-1 in the mulched treatment relative to the non-mulched treatment at 40 cm depth. In addition, soil CO2 efflux increased exponentially with soil temperature, and the temperature normalization of soil CO2 efflux to 10 ˇăC decreased once soil water content was below or above threshold value. Furthermore, plastic mulching also changed the temperature sensitivity of soil CO2 efflux and the optimal soil water content for CO2 emission, respectively. On the basis of these results, we found that plastic mulching significantly impacts on soil CO2 effluxes and CO2 concentrations in the furrows and ridges, respectively. However, the cumulative CO2 emissions were not significant reduced. Our results also suggest that the application of bivariate model combined with soil temperature and water content better predicts soil CO2 efflux both in mulched treatment and non-mulched treatment. Keywords: Soil CO2 efflux; Soil CO2 concentration; Plastic mulch film; Arid region; Cotton field