2.3 Determination of soil physicochemical properties
The fresh soil sample was divided into two parts. One fresh soil sample
was used for the determination of
soil
ammonium nitrogen content (NH4+-N) and
nitrate nitrogen content
(NO3--N),
and the other was naturally air-dried and screened for the determination
of other indices. Soil weight
water content (SWW) and soil bulk
density (SBD) were measured by the drying method. Soil pH was determined
by a glass electrode pH meter (STARTER 300, Shanghai) (soil‒water ratio
1:5). The soil total carbon
content (TC) was determined by a total organic carbon analyser (Vario,
German). The soil total nitrogen
content (TN) was measured by the Kjeldahl method.
NH4+-N and
NO3--N in soil were extracted by 1
mol/L KCl (soil‒water ratio 1:10), and the extract was determined by a
continuous flow analyser (SEAL Analytical AA3, German). The content of
available phosphorus
(AP) in soil was determined by
the molybdenum-antimony resistance colorimetric method after leaching
with sodium bicarbonate.