The Annual Carbon and Water Balance of a Mid-Western No-Till Corn/Soybean Ecosystem

Since 1997, measurements of CO2 and water fluxes have been measured over a no-till agricultural ecosystem in the central Mid-western United States. The crop is rotated annually between corn and soybeans.Gap filling of data when flux observations were not available was accomplished using the Atmosphere Land Exchange (ALEX) model. Although the growing season is relatively short, the large CO2 uptake observed during this period for corn more than offsets the loss of carbon during the period when the field lies fallow. Annual NEE rates for corn exceed 500 g C per year. Annual NEE rates for soybeans are much less, and at times constitute a net source of carbon for the year. During the summer months, the evapotranspiration tracked the carbon fluxes very closely, with nearly 50% of the total water occurring during the June, July and August. The year to year variability of carbon, water fluxes, air temperature and precipitation will also be presented