Three improvements in methodology varying from indirect estimates
using water balance method were explored in the current
study to directly obtain the amount of water export: (1) two electromagnetic
flowmeters (Fig. 2) were installed to precisely measure
the water volume of individual irrigation and runoff events on the
field scale; (2) a slightly modified rapid-response percolation meter
(International Rice Research Institute, 1987; Fig. 3b) was designed
to actually observe the volume of water transferred via leaching
during rice season; (3) field undisturbed tension-free monolith
lysimeters with a special design (Fig. 3c; Wang et al., 2011) were
used to proximately obtain the volume of water transferred via
leaching in wheat season.