Abstract
Abstract. Plastic film mulching (PFM) has widely been used around the world to save water and improve crop yield. However, the effect of PFM on soil respiration (Rs) remains unclear and could be further confounded by irrigation and precipitation. To address these topics, controlled experiments were conducted in mulched and non-mulched fields under drip irrigation from 2014 to 2016 in an arid area of the Xinjiang Uygur Autonomous Region, northwest China. The spatio-temporal pattern of soil surface CO2 flux as an index of soil respiration under drip irrigation with PFM was investigated, and the confounded effects of PFM and irrigation/precipitation on soil respiration were explored. The main findings were as follows. (1) Furrows, planting holes, and plastic mulch are three important pathways of soil CO2 emissions in mulched fields, of which the planting hole efflux outweighs that from the furrow, with the largest values of 8.0 and 6.6 µmol m−2 s−1, respectively, and the plastic mulch itself can emit up to 3.6 µmol m−2 s−1 of CO2. (2) The frequent application of water (i.e. through irrigation and precipitation) elevates soil moisture and soil respiration and enhances their variation. The resultant higher variation of soil moisture further alleviates the sensitivity of soil respiration to soil temperature, leading to a weak correlation and lower Q10 values. (3) Soil CO2 effluxes from furrows and ridges in mulched fields outweigh the corresponding values in non-mulched fields in arid areas. However, this outweighing relation attenuates with increasing precipitation. Furthermore, by combining our results with those from the literature, we show that the difference in soil CO2 effluxes between non-mulched and mulched fields presents a linear relation with the amount of precipitation, which results in negative values in arid areas and positive values in humid areas. Therefore, whether PFM increases soil respiration or not depends on the amount of precipitation during the crop-growing season.
Highlights
Soil respiration (Rs), the flux of microbe- and plant-respired CO2 from the soil surface to the atmosphere, represents the second largest CO2 flux of the terrestrial biosphere following gross primary productivity and amounts to 10 times the current rate of fossil-fuel combustion (Bond-Lamberty and Thomson, 2010; Davidson et al, 2006; L. Liu et al, 2016; Reichstein and Beer, 2008)
Nishimura et al (2012) revealed in a laboratory experiment that N2O gradually permeates the plastic mulch. These findings indicate that the pathways for gas emissions in a mulched field may include furrows, planting holes, and plastic mulch, which have not been evaluated in terms of soil CO2 efflux in plastic film mulching (PFM) fields
From the comprehensive analysis and discussion of the effects of plastic mulch, irrigation, and precipitation on soil respiration based on the results of our controlled experiment, some new findings were discovered in this study
Summary
Soil respiration (Rs), the flux of microbe- and plant-respired CO2 from the soil surface to the atmosphere, represents the second largest CO2 flux of the terrestrial biosphere following gross primary productivity and amounts to 10 times the current rate of fossil-fuel combustion (Bond-Lamberty and Thomson, 2010; Davidson et al, 2006; L. Liu et al, 2016; Reichstein and Beer, 2008). Anthropogenic activities, agriculture expansion and changes in cultivation practices, have brought significant challenges to the control of CO2 emissions in association with climate change (Baker et al, 2007). The conversion of natural to agricultural ecosystems has been recognized to cause a depletion of the soil organic carbon pool by as much as 60 % (Lal, 2004), and soil respiration in agricultural ecosystems is relatively greater than that in natural ecosystems due to intensive cultivation (Buyanovsky et al, 1987; Raich and Tufekciogul, 2000). A particular example is plastic film mulching (PFM), which was invented as an advanced agriculture cultivation technology for saving water and improving crop yield in the 1950s and has since been widely applied around the world, e.g. in the tropical USA, Europe, South Korea, and China.
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