Evapotranspiration Measurements in Reconstructed Prairie and Row Crop Systems With a Portable Canopy Chamber.

Transformation from continuous corn and corn-soybean rotation to native perennial plants in the Midwest is promoted for sustainable cellulosic biofuel production. This transformation may impact the field water balance. Therefore, it is important to understand how different cropping systems affect water use and water partitioning. Because evapotranspiration, ET, is a large part of a field water balance, accurate determination of ET is particularly important. The objective of this study is to quantify the ET of several cropping systems. Three cropping systems, including corn and soybean in a corn-soybean rotation, and reconstructed prairie, were studied at the Comparison of Biofuel Systems (COBS) research site near Ames, IA. Canopy chambers were used to measure ET in the different cropping systems during the 2013 growing season. Three different chamber sizes were used to match different crop growth periods. Chamber-measured ET data were collected on more than 20 days. The chamber ET rates of corn were generally largest, and the chamber ET rates of prairie were larger than those for soybean. The differences in cropping system ET rates were especially apparent during daily peak times. The field water balances of the three cropping systems are estimated with measurements of precipitation, ET from the chambers, soil water storage, and subsurface drainage volumes. Relationships between field water balance and cropping system performance are evaluated.