3. Results
3.1. Effects of treatments on physicochemical characteristics of soil
After 7 weeks of microcosm treatment the water holding capacity
(WHC) and the available phosphorous and potassium were influenced
beneficially by the A1 (grain husk and paper fibre sludge biochar) and
B1 (wood screening biochar) application, while amendment with A2
(grain husk and paper fibre sludge biochar treated with nitrogen, compost
and rockstone powder) had no significant effect on these soil parameters,
except for phosphorous (Table 4).
Treatment with 1% A1 biochar increased the water holding capacity
to the highest extent. Accordingly we found a significant increase (33%)
in the WHC of the acidic sandy soil after addition of A1. The WHC values
of B1 amended soils with or without compost (31–32%) were also significantly
higher than of the untreated sandy soil (25%).
The highest values of soil available phosphorous (P) content
were measured in the 0.5% A1+ compost and 1% A2 amended soils,
206 mg/kg and 240 mg/kg, respectively, compared to the control
(89 mg/kg). Similarly the available potassium (K) was approximately
two times higher in the 1% A1 and 1% B1 amended soil compared to
the control.
The pH values significantly increased with incremental biochar
application rates to soil (Fig. 1). After 2 and 7 weeks of biochar additions
significant differences were observed in soil pH between the control and
the 0.5% and 1% biochar (A1, B1) amended soil. Compared with the
control the 1% A1 and 1% B1 treatment increased the pH of the acidic
sandy soil by 0.9 and 1.3 units after 7 weeks, respectively. Simultaneously,
compost addition increased the pH of the acidic sand only by
0.4 units by the end of the incubation. A slight increase (0.2–0.6 units)
in pH was measured by application of the A2 biochar in 0.1–1% after
7 weeks compared to control soil.
There are also notable differences in the electrical conductivity
values between the control and the various biochar amended soils
(Fig. 2). Addition of A1 and B1 biochars (without compost and fertilizer)