To estimate the
risks and benefits that the biochar types may have as a soil
amendment, moderately high to high concentrations of biochar
were used in the experiment corresponding to an application rate
of 20 or 80 t/ha at a tillage depth of 10 cm. The experimental design
consisted of two simultaneously conducted identical pot “experiments”
on 4 greenhouse tables each with 28 pots, altogether 112
pots (Fig. 1). The treatments were assigned to 28 pots on each table,
according to a row-column experimental design: each column
consisted of one control pot, one BC300 pot, one BC375 pot and one
BC475 pot. The row-column design is efficient in greenhouse experiments
because it takes into account two-dimensional gradients,
while a randomized complete block design considers only one
dimension (Williams et al., 2002). Biocharwas properly mixed with
the soil separately for each pot. After filling, the soils were fertilized
with 25 ml of a 1.8% solution of Yara Combi 1 (NePeK: 14-5-21) and
soil moisture content was set to 30% of fresh soil mass. The pots
were randomly placed on a moist filter bed to ensure constant soil
and air moisture during the experiments. An exclusion area - extra
pots growing ryegrass e was established around the primary pots
to reduce the edge effect (Fig. 1). The 7.5-month (9/2012-3/2013)
experiment constituted of five phases: 1) stabilization period (5
weeks), 2) radish growth period (5 weeks), 3) barley growth period
(6 weeks), 4) winter rest (4 weeks) and 5) ryegrass period (10
weeks).