In each soil management type orchard, three randomly
replicated experimental plots were chosen, and in each of these,
five uniform citrus trees with similar growing potential were
sampled in March, July, and November 2013 during the vigorous
growth period of citrus trees. Soils and
fine roots from each citrus
tree were collected from east, south, west, and north sides from soil
layer depths of 0 to 30 cm after removing the upper vegetation
within the dripping line (the outermost circumference of the tree
canopy) by using a small digging shovel. Rhizospheric soil was
collected according to the method described by Scott and Condron(2003). The roots were gently shaken, soil still adhering to the roots
was considered rhizospheric soil, and it was separated from the
roots and stored in sealed sterile plastic bags. Roots (diameter
1 mm) were carefully washed with tap water, chopped into 1-cmlong
pieces, and
fixed in a formalin/acetic acid/ethanol (FAA,
13:5:200, v/v/v) solution for 24 h, and stored for subsequent
analysis. Soil samples were air-dried for 2 weeks, ground by hand,
passed through a 2-mm mesh screen, and then stored at 4 C before
analysis.