3.1 Effect of amendments on soil physicochemical properties
Amended treatments and incubation time had significant effects on physicochemical properties, and with significant interactions between the two factors (P <0.001). During the entire incubation period, soil pH was significantly lower after addition of N fertilizer than CK treatment; a significant increase in SOC, TN, AN, AP, AK contents in all amended treatments than CK treatment (Table 2).
Specifically, pH decreased more in N3 level, ordered by C-M2-N3, C-M1-N3 and C-N3. SOC with higher contents in M2 level, in which C-M2-N0 treatment supported the highest value, followed by C-M2-N2, C-M2-N1, C-M2-N3. TN and AN contents had higher contents in N3 level, ordered by C-N3, C-M2-N3, C-M1-N3 and C-M2-N3, C-M1-N3 C-N3, respectively. N2 level had higher AP and AK contents, in which both C-M2-N2 treatment supported the highest value, followed by C-M1-N2 (Fig. 2). With the increasing incubation time (Fig.2), pH increased up to day 12 and then decreased during the remaining incubation time (day 12 to 90) in all amended treatments. AN, AP and AK increased significantly in all amended treatments up to day 45, and then decreased during the remaining incubation time (day 45 to 90). In addition, there was an increase in SOC and TN contents over the entire incubation time in all amended treatments.