Carbon budget for a plastic-film mulched and drip-irrigated cotton field in an oasis of Northwest China

Abstract Plastic-film mulched drip irrigation (PFMDI), a new crop management technique which combines plastic film mulching (PFM) and drip irrigation (DI), has been widely practiced in arid areas to save water. While this management enhances crop yield and respiration, the consequences for the net ecosystem carbon (C) budget (NECB) of PFMDI fields remain poorly unknown. Here, an investigation of the NECB over five years was conducted in a PFMDI cotton field in an arid oasis in Northwest China. The NECB was calculated by subtracting the C output associated with harvest from the Net Ecosystem Productivity (NEP). NEP was obtained as the reverse CO2 flux measured with the eddy covariance (EC) method. C output associated with harvest was estimated with biomass collections. The PFMDI field lost C with the annual NECB of −67±37g C m−2 yr−1 on average. Considering CO2 emission associated with the use of PFM and DI, C loss of the production system reached −120 g C m−2 yr−1. PFMDI enhanced both assimilation (i.e., GPP) and respiration (i.e., Reco), but Reco increased more than GPP, and the ratio of Reco to GPP reached 0.93, resulting in a reduction of NEP and NECB comparing with non-PFMDI fields. Tillage increased C loss through increasing respiration while straw return decreased C loss through decreasing C output. In addition to straw return, organic fertilizer and less tillage, PFM and DI recovery should be applied in the management practices to counteract C loss in the system.