Soil Water and Temperature Under Bioenergy Cropping Systems At the COBS Site.

The COBS (Comparison Of Biofuel Systems) site was established in central Iowa in 2008.  Treatments were a conventional corn-soybean rotation harvested for grain, continuous corn with stover removed, both with and without winter cover crop, and reconstructed prairies both with and without N fertilization.  Soil wetness and temperature have been continuously monitored.  Each plot was instrumented with Decagon ECH2O sensors at 5 depths.  Prairie plots were generally cooler than row crop plots in the summer, and warmer and wetter during the winter.  This can be largely attributed to the presence of a dense thatch layer, which insulates the soil surface, aids infiltration, and holds snow.  The corn portion of the corn-soybean rotation also trapped snow in the standing stubble, and was warmer and wetter during the winter than the rows crops which had less standing stubble.  We also report on our experiences with the sensors in a long-term research setting.  Other presentations in this symposium, also based on the COBS site, report on quantity and quality of tile drainage water.