Sample Collection and Analyses of Physical-Chemical properties
Soils were sampled from each treatment plot. Nine soil cores (3.8 cm
diameter, 25 cm depth) were taken randomly from each plot, and mixed
thoroughly to form one composite sample. Each sample was placed in a
sterile plastic bag, sealed, and placed on ice when transported to the
laboratory. The fresh soil was used for microbial parameters
determination. Air-dried samples were used for physicochemical
properties determination. Soil moisture content was measured
gravimetrically, and the soil pH was measured in 1 M KCl (1:5, w/v).
NH4+-N, and
NO3−-N were extracted with 2 M KCl.
NH4+-N, and
NO3−-N concentrations were detected
using a flow injection analyzer (Tecator Inc., Hoganas, Sweden). Soil
organic carbon and total nitrogen concentrations were analyzed using the
CHNS-analyzer system (Elementar Analysensysteme GmbH, Hanau, Germany).
Soil microbial biomass was estimated using the chloroform
fumigation-extraction method (Vance et al. 1987).