What Are the Variations of Carbon Fluxes and Evapotranspiration over Cotton Field under Drip Irrigation with Plastic Mulch?

Xinjiang is a typical irrigated agricultural area in arid and semi-arid regions of China. Drip irrigation with mulch film technology, as an effective water-saving measure, is widely used in Xinjiang. Recent years, the improvement of crop yield and water use efficiency under drip irrigation with mulch film has been widely studied. However, systematic researches of the carbon and water fluxes as well as their controlling factors over cotton field under drip irrigation with mulch film were not well documented.

Based on the experimental data from Wulanwusu Agrometeorological Experiment Station, Xinjiang, Dr. BAI Jie et al. analyzed the carbon and water fluxes and investigated their diurnal, seasonal and inter-annual variations in a cotton field under drip irrigation with mulch film. The experiment was conducted in the cotton growing seasons of 2009, 2010, 2012 and 2013. Drip irrigation was applied 7 to 8 times at an interval of 10 days in each year. The carbon flux was measured by an eddy covariance (EC) system. Further, 3D coordinate rotation and density fluctuation correction were applied to obtain the half-hourly mean heat, water vapor and CO₂ fluxes. Then, the flux data processes (including gap filling and net ecosystem exchange (NEE) partitioning) were conducted by the EC gap-filling and flux-partitioning tool.

The mean diurnal gross primary production (GPP), NEE and evapotranspiration (ET) in each month showed an obvious sinusoidal dynamic, whereas the mean diurnal ecosystem respiration (Res) kept a horizontal level during the whole growing season. The seasonal and inter-annual variations of GPP, NEE and ET showed significant dynamics and were closely related with the development of leaf area index. The seasonal pattern of water use efficiency (WUE) in the growing season was similar to that of GPP and ET. The daytime hourly GPP and ET displayed significant asymptotic relationships with net solar radiation and concave patterns with vapor pressure deficit and air temperature.

Cotton field under drip irrigation with mulch film acted as a strong carbon sink during the main growing season (from squaring to harvest stage) and functioned as a carbon source before the squaring time as well as after the harvest time.

The result was published in Journal of Arid Land in April 2015.

Contact

Dr. BAI Jie

State Key Laboratory of Desert and Oasis Ecology, Xinjiang Institute of Ecology and Geography, Chinese Academy of Sciences

E-mail: baijie@ms.xjb.ac.cn