Seasonal and interannual variability of ecosystem respiration in maize-soybean cropping systems

Fluxes of CO₂, water vapor and energy are being measured year-round in maize-soybean agroecosystems in eastern Nebraska employing tower eddy covariance instrumentation. CO₂ flux data are used to calculate ecosystem respiration at two study sites: rainfed maize-soybean rotation and irrigated maize-soybean rotation. Ecosystem respiration from the maize and soybean crops varied from about 800 to 1200 g C m^-2 annually. A detailed discussion of the magnitudes of ecosystem respiration in these cropping systems during the growing season and “non-growing season” periods will be presented. Results will be compared with data from other ecosystems. An examination of key biophysical controlling factors will also be presented.