Soil water deficit under switchgrass during 2017 growing season

Hussain, Mir Zaman, Hamilton S.K., Basso B., and Robertson G.P.
Michigan State University

Presented at the All Scientist Meeting and Investigators Field Tour (2017-10-06 to 2017-10-07 )

Water availability is an important constraint for bioenergy crop production. Southern Michigan has recently experienced two strong drought periods, one in 2012 and other one in 2017, with temperatures that were exceptionally warmer than average and precipitation that was about half of normal during the growing season. Since 2009, we have been making continuous measurements of soil water under switchgrass, a potential candidate for bioenergy production, using Time-Domain Reflectometry (TDR) probes at the Biofuel Cropping System Experiment at the WK Kellogg Biological Station, Michigan. TDR probes were installed at 7 different depths (up to 125 cm) in the soil profile based on our knowledge about crop rooting depth. For this study, we are presenting the soil moisture measurements of a normal year (2011) and compared with the two drought years (2012, 2017). Soil water deficit was calculated as difference between drained upper limit (DUL) and equivalent soil water depth in the profile. Compared to 2011, 2012 and 2017 had unusual soil dryness as a result of warmer temperatures and rainfall deficit. In 2011, the soil profile was repeatedly recharged by frequent and larger rainfall events compared with insignificant recharging in 2012 and 2017 due to less frequent and smaller rainfall events. As a result, deeper soil layers in 2012 and 2017 were consistently drier, with soil moisture content falling below 10 percent. Soil water deficit, representing the soil water that plants have withdrawn, leveled out at ~200 mm and was similar in both drought years (2012, 2017), indicating that the 2017 growing season has been nearly as drought stressed as 2012, although some early rain events in 2017 maintained the crop productivity higher than in 2012.