After 90 days of cultivation, soil samples were taken for
analysis at depths of 0–2.5, 2.5–5.0, and 5.0–7.5 cm.
Soluble soil organic C and N contents were determined
after extraction with a 0.5 M K2SO4 solution (soil:solution
1:5 w/v) using a TOC meter (model TOC 5000; Shimadzu)
for C and the persulfate oxidation-hydrazine reduction
method (Sakamoto and Hayashi 1999) for N. Soil pH was
measured using a soil:water or 1 M KCl ratio of 1:2.5 (w/w).
Electrical conductivity was measured using a soil:water ratio
of 1:5 (w/w). The number of soil microorganisms (fungi and
bacteria) was measured by the dilution plate method (Soil
Microbiological Society of Japan 1992)