Carbon balance and controlling factors in a summer maize agroecosystem in the Guanzhong Plain, China

BACKGROUND Quantifying the carbon balance of agroecosystems and clarifying the factors controlling it are essential for estimating the regional carbon cycle and global carbon balance. RESULTS Based on the eddy covariance (EC) technique and soil respiration observations during the 2017 and 2019 summer maize growing seasons, this study analyzed the carbon balance and revealed the factors controlling carbon fluxes in the summer maize agroecosystem. Green leaf area index was the most important factor affecting net ecosystem exchange (NEE), total primary productivity, and total ecosystem respiration (TER) in the rapid development stage during the growing season, followed by soil water content. However, precipitation, air temperature, relative humidity, saturated vapor pressure difference, and photosynthetically active radiation were the main factors that influenced carbon balance at the middle stage. The cumulative TER in 2019 was 40% (320.9 g C m−2) higher than that in 2017. The NEE estimates of summer maize agroecosystems in 2017 and 2019 were −71.7 and 160.4 g C m−2, respectively. Accounting for the carbon input at sowing (10 g C m−2) and the similar carbon output at harvest owing to grain removal, the net biome productivity in 2019 was 1.75 times that in 2017, at −636 and −363 g C m−2, respectively. CONCLUSION The carbon balance of the summer maize agroecosystem in the Guanzhong Plain was determined to be a net carbon source that could export carbon at an average rate of 499.5 g C m−2 yr−1. © 2022 Society of Chemical Industry.