Fig. 4

Temporal change in matric potential head at each depth. Control: no biochar; A: surface application; B: plow layer application; C: subsurface application. The matric potential head was converted from the volumetric water content (measured using TEROS12 soil moisture sensors) using soil water retention curves. The curves were obtained using the van Genuchten equation and the measured curve. The red and blue areas indicate the dry and wet stress ranges, respectively.