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Abstract

Background and aims Biochar can be produced from a wide range of organic sources with varying nutrient and metal concentrations. Before making irreversible applications of biochar to soil, a preliminary ecotoxicological assessment is desirable. Methods First, we determined the effect of biochar type and rate on early growth of wheat in a soil-less Petri dish bioassay. Second, we investigated the effect of the same biochars on seed germination and early growth of wheat in ten soils with varying texture using a glasshouse bioassay. Finally, we investigated whether these biochars had similar effects on three plant species when grown in one soil. Results Biochar type and application rate influenced wheat seed germination and seedling growth in a similar manner in both the soil-less Petri dish and soil-based bioassay. Germination and early root growth of mung bean and subterranean clover differed from that of wheat in response to the five biochars. Conclusions We recommend use of the soil-less Petri dish bioassay as a rapid and simple preliminary test to identify potential toxicity of biochars on seed germination and early plant growth prior to biochar application to soil.
1 23
Plant and Soil
An International Journal on Plant-Soil
Relationships
ISSN 0032-079X
Volume 353
Combined 1-2
Plant Soil (2012) 353:273-287
DOI 10.1007/s11104-011-1031-4
Biochars influence seed germination and
early growth of seedlings
Zakaria M.Solaiman, Daniel V.Murphy
& Lynette K.Abbott
1 23
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REGULAR ARTICLE
Biochars influence seed germination and early growth
of seedlings
Zakaria M. Solaiman &Daniel V. Murphy &
Lynette K. Abbott
Received: 12 April 2011 / Accepted: 11 October 2011 / Published online: 5 November 2011
#Springer Science+Business Media B.V. 2011
Abstract
Background and aims Biochar can be produced from a
wide range of organic sources with varying nutrient and
metal concentrations. Before making irreversible appli-
cations of biochar to soil, a preliminary ecotoxicological
assessment is desirable.
Methods First, we determined the effect of biochar
type and rate on early growth of wheat in a soil-less
Petri dish bioassay. Second, we investigated the effect
of the same biochars on seed germination and early
growth of wheat in ten soils with varying texture
using a glasshouse bioassay. Finally, we investigated
whether these biochars had similar effects on three
plant species when grown in one soil.
Results Biochar type and application rate influenced
wheat seed germination and seedling growth in a
similar manner in both the soil-less Petri dish and
soil-based bioassay. Germination and early root
growth of mung bean and subterranean clover
differed from that of wheat in response to the five
biochars.
Conclusions We recommend use of the soil-less Petri
dish bioassay as a rapid and simple preliminary test to
identify potential toxicity of biochars on seed germi-
nation and early plant growth prior to biochar
application to soil.
Keywords Biochar .Germination .Stimulation .
Inhibition .Wheat .Mung bean .Subterranean clover
Introduction
Biochar is the product of pyrolysis, whereby organic
materials of either plant or animal origin are heated
(>250°C) in a low or no oxygen environment (Antal
and Grønli 2003). The quality (in particular surface
chemical characteristics and pore size) of biochars
produced depends on the production temperature,
while the carbon (C) and nutrient contents of biochars
also vary depending on the type of organic materials
used (Gaskin et al. 2008). Biochar is a highly stable
form of C which may remain in soil for hundreds to
thousands of years (Ascough et al. 2009; Gavin et al.
2003; Gouveia et al. 2002). It is used as a soil
amendment that can act as a C sink in agricultural
soils as well as improve soil fertility (Chan et al.
2007; Ogawa et al. 2006), and may adsorb herbicides
(Jones et al. 2011) and pesticides or neutralize natural
toxins in decomposing organic materials (Yelverton et
al. 1996). Application of biochar at high rates (t/ha)
can also increase soil water retention directly due to
its high surface area (Lehmann 2007) and indirectly
via subsequent increases in the soil organic C
Plant Soil (2012) 353:273287
DOI 10.1007/s11104-011-1031-4
Responsible Editor: Johannes Lehmann.
Z. M. Solaiman (*):D. V. Murphy :L. K. Abbott
Soil Biology Group, School of Earth and Environment
(M087), UWA Institute of Agriculture,
Faculty of Natural and Agricultural Sciences,
The University of Western Australia,
Crawley, WA 6009, Australia
e-mail: zakaria.solaiman@uwa.edu.au
Author's personal copy
(Blanco-Canqui and Lal 2004) if plant growth is
stimulated. However, biochars may contain undesir-
able compounds such as crystalline silica, dioxin,
polyaromatic hydrocarbons (PAHs), phenolic com-
pounds and heavy metals that are harmful to plants,
microbes and humans (Cao et al. 2009; Thies and
Rillig 2009) as well as essential nutrients (Gaskin et
al. 2008). Some compounds in biochars have the
potential to either inhibit or stimulate seed germina-
tion and seedling growth.
Biochar has been reported to both increase (Chan
et al. 2008; Yamato et al. 2006) and decrease (Deenik
et al. 2010) plant growth and yield but there have
been few studies reporting the influence of biochar on
early stages of plant growth such as on seed
germination and seedling growth. The stimulation or
inhibition of seed germination due to biochar appli-
cation has mostly been investigated for forest plants
(Choi et al. 2009; Pierce and Moll 1994; Reyes and
Casal 2006; Tian et al. 2007). For agricultural plants,
activated charcoal (steam treated) enhanced seed
germination of potato (Bamberg et al. 1986) while
Van Zwieten et al. (2010) showed that wheat seed
germination was increased with a single dose (10 t/ha)
of paper mill biochar. In contrast, Free et al. (2010)
reported that maize seed germination and early
growth were not significantly affected by biochars
made from a range of organic sources.
The application of biochar to soil can alter organic
matter mineralization (Steiner et al. 2008; Wardle et al.
1998) which is linked to the release of nutrients such
as nitrogen (Manzoni et al. 2008; Murphy et al.
2003). The resultant change in nutrient status of the soil
may affect both seed germination and seedling growth.
Application of biochar to acidic soils can increase soil
pH to alkaline levels, especially if higher rates of biochar
are applied and changes occur to soil cation exchange
capacity (CEC) (Ogawa 1994). The diversity in charac-
teristics of biochar indicate that biochar responses will
depend on the type and rate of biochar applied to soil as
well as on soil characteristics such as soil C, pH, CEC
and other components of soil fertility.
As there are very few comparative studies for
agricultural crops, we compared five biochars of
different origin on early growth of wheat. The wheat
assessments were made in a soil-less Petri dish
toxicity bioassay, as well as in a soil-based bioassay
using 10 soils. The objective was to identify a rapid
and simple preliminary test to detect potential toxic
effects of biochars before their use as soil amend-
ments. The Petri dish bioassay is a simple and rapid
ecotoxicological test for preliminary assessment of
biochars in soil-less conditions. It was expected that
biochars would differ in their effects on early seedling
growth, and that the Petri dish bioassay would be a
simpler preliminary screening method than a soil-
based bioassay using a standard soil (OECD 1984).
These two comparisons were complemented by a
glasshouse bioassay comparing wheat with two other
agricultural plants (mung bean and subterranean
clover) on one standard soil.
To evaluate the effect of biochars on early seedling
growth, we compared five biochars in the following
three ways: (i) using a soil-less Petri dish bioassay to
determine seed germination and seedling growth of
wheat in the presence of different types and rates of
biochar under laboratory conditions; (ii) using a
glasshouse bioassay to assess the variability in wheat
seed germination and seedling growth in response to
biochar type and soil; and (iii) using a glasshouse
bioassay to compare the effect of biochars on seed
germination and growth of three agricultural species
(wheat, mung bean and subterranean clover) in one
soil. Wheat was used because it is the main cereal
crop in Western Australia. Subterranean clover was
included as a common pasture legume, and mung
bean was included as an example of a food legume.
Materials and methods
(i) Biochar characteristics
Biochars made from Oil Mallee(OM; VERVE
Pty Ltd, Western Australia), Rice Husks(RH;
Philippines), New Jarrah(NJ; SIMCOA Pty Ltd,
Western Australia), Old Jarrah(OJ; 35 year old
stockpile of metallurgical charcoal) and Wheat
Chaff(WC; South Africa) were assessed for basic
characteristics (Table 1). The pH and EC of biochar
were measured in water at 1: 5 (w/v) ratios. Soil pH
was also measured in CaCl
2
at 1:5 (w/v) ratios. A
subsample of biochar was finely ground before total
carbon and nitrogen contents were determined by dry
combustion analysis using an elementar (vario MAC-
RO CNS; Elementar, Germany). All biochars were
sieved using a 4 mm sieve before use for both soil-
less Petri dish and soil-based glasshouse bioassays.
274 Plant Soil (2012) 353:273287
Author's personal copy
Particle size fractions (%) of all biochars were done
using a stack of sieves (Table 1).
(ii) Soil characteristics
Ten s o ils (010 cm surface layer) were collected
from different locations within the agricultural
region of Western Australia. The basic character-
istics and nutrient concentrations of these soils were
analysed using standard methods as presented in
Tab l e 2.
(iii) Soil-less Petri dish bioassay for wheat (Experiment 1)
Fifty wheat (Triticum aestivum L. var. Calingiri)
seeds were sown in Petri dishes (8.5 cm diameter) on
a layer of filter paper moistened with deionised water.
The amount of water (20 mL) added to the filter paper
was calculated based on the water holding capacity of
the biochar and the requirement of the highest biochar
rate (5 g). The same amount of water was added to the
Petri dish for each rate of biochar (Fig. 1). Each of the
five biochar types was added at the rates 0, 0.5, 1.0,
2.5, 5.0 g/Petri dish (equivalent to 0, 10, 20, 50, 100 t/
ha on a volume basis at 10 cm soil depth) with three
replicates following the design recommended by
Morrison and Morris (2000) where an individual Petri
dish was considered as a replicate and a control
treatment was used for each biochar. All Petri dishes
were covered with lids and incubated in the dark at
25°C for 72 h when germination percentage and root
length were assessed. Root length of germinated seeds
was measured in fresh roots using a ruler, and
summed for each Petri dish (m/Petri dish).
(iv) Soil-based glasshouse bioassay for wheat in ten
soils (Experiment 2)
Fifty wheat (var. Calingiri) seeds were sown in
500 mL soil in a plastic container (16 cm × 10 .5 cm
× 5 cm) for each of ten soils following the OECD
guidelines for terrestrial plant growth test (OECD
1984). Each biochar was mixed separately with each
soil at the rates 0, 10 (1%) and 100 (10%) t/ha
(calculated as soil volume to 10 cm soil depth). These
three rates of biochars were chosen based on the
results of the soil-less Petri dish bioassay. Pots were
placed randomly on a glasshouse bench, immersed
with water and allowed to drain for 24 h before
weighing to measure water holding capacity (WHC).
During the experiment, the pots were weighed and
water was added daily to maintain the soil at 80%
WHC as generally used for sandy soils of Western
Australia (Solaiman et al. 2010). Germination per-
centage was recorded daily from the 5th to 12th day
after sowing. Data are presented only for the 9th day
of sowing, the day of peak germination. On the 12th
day after sowing, roots were washed free of soil,
wiped with a paper towel and root lengths were
Table 1 Important characteristics of the five biochars used across Experiments 1, 2 and 3
Characteristics Oil Mallee (OM) Rich Husks (RH) New Jarrah (NJ*) Old Jarrah (OJ*) Wheat Chaff (WC)
Source of biomass Oil mallee waste Rice husks Jarrah trees Jarrah plus others woods Wheat straw
Production Temperature
(°C)
550600 600700 550650 550650 600700
pH (H
2
O) 9.39 9.83 9.52 4.80 10.26
pH (CaCl
2
) 8.40 8.43 8.41 3.72 9.31
EC (μS/cm) 1326 447 498 36 454
WHC (%) 75 247 162 97 137
Carbon (%) 29.7 29.3 78.4 50.5 77.6
Nitrogen (%) 0.53 0.32 0.40 0.49 0.77
C:N ratio 56 92 196 266 101
Particle size fractions (%)
24 mm 8.0 2.3 29.5 7.6 4.8
12 mm 39.0 13.4 29.5 28.5 13.4
0.51 mm 25.9 50.4 19.2 23.5 27.4
<0.5 mm 27.0 34.0 21.7 40.4 54.4
*NJ, New Jarrah biochar was obtained from SIMCOA Pty Ltd; OJ, Old Jarrah was obtained from old stockpile at Wundowie
Plant Soil (2012) 353:273287 275
Author's personal copy
measured using a gridline intercept method (Newman
1966), and estimated as m/pot. Shoot and root dry
weights (DW) were recorded after oven-drying at
60°C for at least 72 h at the end of the experiment.
t/ha 0 10 20 50 100
% 94 97 99 93 88
Fig. 1 Photograph of effect of biochar (new jarrah, NJ) at different rates 0, 0.5, 1.0, 2.5, 5.0 g/Petri dish (equivalent to 0, 10, 20, 50,
100 t/ha based on 10 cm field depth) on seed germination (%) of wheat conducted in the soil-less Petri dish bioassay (Experiment 1)
Table 2 Charateristics of 10 soils collected from Western Australia for comparison of the effect of five biochars on seed germination,
shoot and root growth of wheat (Experiment 2)
Characteristics Soil 1 Soil 2 Soil 3 Soil 4 Soil 5 Soil 6 Soil 7 Soil 8 Soil 9 Soil 10
Soil texture* LS LS C L LS LS LS L LS LS
Clay conent (%) 5 5 40 20 5 5 5 20 5 5
Organic carbon (%) 0.91 0.56 0.69 1.06 0.6 0.5 0.7 1.77 2.03 1.22
WHC (%) 10.6 11.2 20.5 14.3 12 12.3 11.8 14.5 12.2 11.9
pH (H
2
O) 5.7 5.9 7.2 6.6 7.0 6.5 5.8 5.7 5.9 7.5
pH (CaCl
2
) 5.0 5.3 6.7 6.1 6.6 6.1 5.4 5.2 5.4 7.0
EC (dS/m) 0.04 0.03 1.05 0.58 0.04 0.03 0.05 0.07 0.16 0.12
Exc. Cations (cmol
c
kg
1
) 2.4 1.6 14.9 17.6 3.2 2.0 2.1 3.9 7.7 6.8
Al (cmol
c
kg
1
) 0.17 0.2 0.001 0.001 0.001 0.001 0.15 0.11 0.03 0.001
Ca (cmol
c
kg
1
) 1.7 1.0 4.3 8.3 2.5 1.5 1.6 2.9 5.4 6.2
Mg (cmol
c
kg
1
) 0.3 0.3 4.6 6.0 0.4 0.3 0.2 0.6 0.9 0.4
K (cmol
c
kg
1
) 0.11 0.04 0.78 0.75 0.17 0.08 0.06 0.26 1.26 0.05
Na (cmol
c
kg
1
) 0.06 0.07 5.21 2.55 0.13 0.08 0.04 0.09 0.15 0.07
H (cmol
c
kg
1
) 0.03 0.01 0.01 0.01 0.01 0.01 0.03 0.04 0.05 0.01
Exc. Acidity (cmol
c
kg
1
) 0.11 0.05 0.01 0.02 0.01 0.01 0.14 0.06 0.05 0.01
CEC (cmol
c
kg
1
) 2.5 1.6 14.9 17.6 3.3 2.0 2.2 4.0 7.8 6.8
NH
4
(mg/kg) 1 1 5 5 1 1 1 2 10 3
NO
3
(mg/kg) 10 8 24 25 3 2 8 18 24 4
Colwell P (mg/kg) 41 14 61 84 36 21 8 52 59 3
Colwell K (mg/kg) 44 27 300 285 68 38 31 105 512 26
S (mg/kg) 9 8 191 273 5 7 25 15 23 7
B (mg/kg) 0.7 0.3 5.8 4.5 0.4 0.2 0.7 0.5 0.4 0.3
Cu (mg/kg) 0.5 0.3 1.4 0.9 0.5 0.5 0.2 0.8 0.8 0.2
Fe (mg/kg) 49.7 22.5 17.4 21.1 34.1 39 56.2 54.9 63.5 19.1
Mn (mg/kg) 0.6 0.8 4.3 7.2 0.8 1.8 0.4 5.1 30.4 1.2
Zn (mg/kg) 0.6 0.6 1.3 0.5 0.3 0.4 0.1 0.7 2.1 0.1
*CClay; LLoam; LS Loamy sand
276 Plant Soil (2012) 353:273287
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(v) Glasshouse bioassay for three plant species (one
standard soil) (Experiment 3)
Fifty seeds of wheat (Triticum aestivum L. var.
Calingiri), mung bean (Vigna radiata (L) R.
Wilczak) and subterranean clover (Trifolium subter-
raneum L. var. Seaton Park) were sown into soil in
germination trays together (2 L of soil with or without
biochar) with three replicates. The characteristics of
the soil were: brownish yellow sand, organic carbon
0.6 g/kg, soil pH 6.10 (H
2
O), 5.8 (CaCl
2
), conduc-
tivity 0.012 dS/m, nitrate nitrogen 1 mg/kg soil,
ammonium nitrogen 1 mg/kg soil, Colwell P 3 mg/kg
soil, potassium 12 mg/kg soil, sulphur 4 mg/kg soil,
aluminium 1 mg/kg soil and iron 119 mg/kg soil.
Each biochar was mixed separately with this soil at
rates equivalent to 0, 10 (1%) and 100 (10%) t/ha
(rate was calculated based on 10 cm soil depth). Trays
were filled with either soil or soil-biochar mixtures,
placed on glasshouse benches randomly, saturated and
drained prior to measuring WHC before sowing of
seeds. Trays were watered daily to 80% WHC by
spraying to a constant weight. Germination percentage
was recorded between days 5 and 10 after sowing. Data
are presented only for the 7th day of sowing
corresponding to peak germination. On the 10th day
after sowing, roots were sampled and assessed as for the
wheat bioassay conducted in the 10 soils.
(vi) Statistical analyses
Statistical analyses are summarised in Table 4. For
the Petri dish bioassay (Experiment 1), analysis of
variance (ANOVA) was performed using Genstat
(v.10) to separate the main effect of factors (biochar
types and rates of application) as well as their
interactions. In addition, ANOVA was performed to
find the effect of rates within each type of biochar.
The mean comparisons were made using Duncans
Multiple Range test (DMRT) at p<0.05 between
treatments (Fig. 2). For Experiment 2, mean values
with standard error are presented in Table 3where
analysis of variance (ANOVA) of 10 soils was
performed using Genstat and DMRT at p< 0.05 for
mean comparisons. Correlation matrix analysis was
performed among the seed germination, seedling
75
80
85
90
95
100
OM0
OM10
OM20
OM50
OM100
RH0
RH10
RH20
RH50
RH100
NJ0
NJ10
NJ20
NJ50
NJ100
OJ0
OJ10
OJ20
OJ50
OJ100
WC0
WC10
WC20
WC50
WC100
Germination (%)
b
a
ab ab
bb
ab
aa
b
ab
a
c
d
b
aaa
bb
a
b
b
c
0
1
2
3
4
5
6
7
8
OM0
OM10
OM20
OM50
OM100
RH0
RH10
RH20
RH50
RH100
NJ0
NJ10
NJ20
NJ50
NJ100
OJ0
OJ10
OJ20
OJ50
OJ100
WC0
WC10
WC20
WC50
WC100
Root length (m/50 seeds)
a
b
b
c
dc
bb
ab
a
b
a
aa
bb
aaa
bc
a
bb
d
bc
Fig. 2 Effect of biochar type and rate on seed germination (%)
and initial root length of wheat in a soil-less Petri dish bioassay.
Oil Mallee(OM), Rice Husks(RH), New Jarrah(NJ), Old
Jarrah(OJ) and Wheat Chaff(WC) biochars were tested at 0,
0.5, 1.0, 2.5, 5 g/Petri dish (equivalent to 0, 10, 20, 50, 100 t/ha
based on 10 cm field depth). Error bars show standard errors of
the mean. Mean data followed by a similar letter(s) are not
statistically significant within each biochar (Experiment 1)
Plant Soil (2012) 353:273287 277
Author's personal copy
growth and soil characteristics of the glasshouse
bioassay (Experiment 2) and correlation values are
presented in Table 5.
For the glasshouse bioassay (Experiment 3) com-
paring the three plant species, analysis of variance
(ANOVA) was performed using Genstat (v.10) to
separate the main effect of factors (biochar type, rate
of application and plant species) as well as their
interactions. In addition, ANOVA was performed to
find the effect of rates within each type of biochar.
The mean comparisons were made using DMRT at
p<0.05 between treatments.
Results
Characteristics of biochars
Most of the biochars used in these experiments were
alkaline (pH in water 9.32 to 10.26) except for OJ which
was acidic (pH in water 4.8) (Table 1). The C content of
biochars varied between types of biochar such as high
C in NJ (78.4%), WC (77.6%), OJ (50.5%) and low C
in OM (29.7% C) and RH (29.3% C). OM biochar
was saline compared to other biochars. The N content
was highest in WC (0.77%) and lowest in RH
(0.32%) biochars. The biochar C:N ratio was lowest
in OM (56:1) and highest in OJ (266:1).
Soil-less Petri dish bioassay for wheat (Experiment 1)
In the soil-less Petri dish bioassay, biochar type and rate
of application significantly affected wheat seed germi-
nation (p<0.001, Table 4). Biochar generally in-
creased wheat seed germination at the lower rates of
biochar application (1050 t/ha) and decreased or had
no effect at higher rates of application (Figs. 1and 2,
p<0.05, Table 4). For example, wheat seed germina-
tion increased from 93 to 98% with addition of 10 t/
ha OM biochar (p<0.05), but there were no statisti-
cally significant effects of higher application rates
(p>0.05; Fig. 2). RH biochar increased wheat seed
germination with addition of biochar up to 50 t/ha
(p<0.05), but application of 100 t/ha of this biochar
did not affect seed germination (p>0.05). In contrast,
NJ biochar application increased wheat seed germi-
nation with additions of 10 and 20 t/ha (p<0.05) and
decreased germination at applications of 50 and 100 t/ha
(p<0.05; Fig. 2). WC biochar applied at 10 t/ha
increased wheat seed germination and 100 t/ha of the
same biochar significantly (p< 0.05) decreased germi-
nation. Application of either 20 or 50 t/ha of WC
Table 3 Effect of biochar on seed germination, root length, shoot, root and total DW per pot of wheat grown in 10 different
agricultural soils from Western Australia (mean values n=10 soils, Experiment 2)
Biochar type Biochar rate Germination (%) Shoot DW (g) Root DW (g) Total DW (g) Root length (m)
Oil Mallee (OM) 0 87±2 b 0.71 ± 0.06 b 0.60 ± 0.07 b 1.33 ± 0.20 b 63± 7 a
10 96± 2 a 0.76± 0.06 a 0.61 ± 0.07 b 1.46±0.25 a 64±10 a
100 89± 3 b 0.76±0.05 a 0.65± 0.10 a 1.41± 0.24 a 64 ± 4 a
Rice Husk (RH) 0 87 ± 2 b 0.71± 0.06 b 0.60± 0.07 c 1.33± 0.20 b 63± 7 a
10 91± 3 a 0.77± 0.05 a 0.69 ± 0.10 a 1.43± 0.24 a 65 ±5 a
100 90± 4 a 0.76± 0.06 a 0.65 ± 0.07 b 1.43±0.17 a 68±3 a
New Jarrah (NJ) 0 87 ± 2 a 0.71 ± 0.06 a 0.60 ± 0.07 b 1.33±0.20 a 63± 7 a
10 87± 4 a 0.71± 0.07 a 0.70 ± 0.07 a 1.36± 0.21 a 65 ±4 a
100 86± 5 a 0.71± 0.05 a 0.73 ± 0.07 a 1.26± 0.31 b 70± 7 a
Old Jarrah (OJ) 0 87± 2 a 0.71 ± 0.06 a 0.60 ± 0.07 a 1.33 ± 0.20 b 63± 7 a
10 89± 3 a 0.72± 0.06 a 0.63 ± 0.07 a 1.39± 0.23 a 67 ±6 a
100 84± 6 b 0.65 ±0.09 b 0.61 ± 0.08 a 1.41 ± 0.26 a 62 ± ± 8 a
Wheat Chaff (WC) 0 87 ± 2 b 0.71±0.06 b 0.60± 0.07 b 1.33 ± 0.20 b 63± 7 a
10 95± 4 a 0.78± 0.03 a 0.75 ± 0.08 a 1.53± 0.19 a 73 ±6 a
100 81± 6 c 0.65± 0.05 c 0.54 ± 0.07 c 1.19± 0.22 c 62 ± 8 a
Mean data (±SE) having similar letter(s) are not statistically significant within each biochar.
278 Plant Soil (2012) 353:273287
Author's personal copy
biochar had no effect on germination (p>0.05).
Finally, the OJ biochar increased wheat seed germi-
nation when applied at rates of 10, 20 and 50 t/ha
(p<0.05) but not at 100 t/ha (p>0.05).
Both biochar type and rate of application generally
increased root length of the seedlings in the Petri dish
bioassay, especially at the first three rates of applica-
tion (p<0.001, Table 4). Root length gradually
increased (p<0.05) with increasing biochar rates for
OM and RH biochars, including the highest rate
(100 t/ha). There was a similar effect for the NJ, OJ
and WC biochars when applied at 10, 20 and 50 t/ha
(p<0.05), but not for 100 t/ha application (p>0.05,
Fig. 2). NJ and OJ biochars applied at 100 t/ha had no
effect on root growth of wheat (p> 0.05), but WC
biochar applied at 100 t/ha significantly decreased
root growth (p<0.5; Fig. 2).
Soil-based glasshouse bioassay for wheat in ten soils
(Experiment 2)
Soil texture varied widely among the 10 soils from
loamy sand to clay, and clay content varied from 5
40% (Table 2). Soil pH ranged from 5.77.5 in H
2
O
Table 4 Results of ANOVA (degrees of freedom, df and level of significance) for seed germination, plant dry weight (DW) and root
length across Experiments 1, 2 and 3
Factor df Germination Shoot DW Root DW Total DW Root length
Petri dish bioassay (Expriment 1)
Biochar type 4 <.001 <.001
Biochar rate 4 <.001 <.001
Biochar type × Biochar rate 16 <.001 <.001
Glasshouse bioassay (Experiment 2)
Biochar type 4 0.012 0.002 NS 0.051 NS
Biochar rate 2 <.001 0.001 0.004 <.001 0.101
Soil 9 <.001 <.001 <.001 <.001 <.001
Biochar type × Biochar rate 8 0.003 0.003 0.005 <.001 NS
Biochar type × Soil 36 NS 0.014 0.018 0.002 NS
Biochar rate × Soil 18 0.001 <.001 NS NS 0.012
Biochar type × Biochar rate × Soil 72 NS NS NS NS NS
Glasshouse bioassay (Experiment 3)
Crop 2 <.001 <.001 <.001 <.001 <.001
Biochar type 4 <.001 <.001 <.001 <.001 <.001
Biochar rate 2 <.001 <.001 <.001 <.001 <.001
Crop × Biochar type 8 <.001 <.001 <.001 <.001 <.001
Crop × Biochar rate 4 <.001 <.001 <.001 <.001 <.001
Biochar type × Biochar rate 8 <.001 <.001 <.001 <.001 <.001
Crop × Biochar type × Biochar rate 16 <.001 <.001 <.001 <.001 <.001
NS Not significant
Table 5 Linear correlation (r) between seed germination, seedlings growth and soil characteristics (Experiment 2)
Clay content Carbon pH EC Cations Al CEC NH4 NO3 P K S
Seed germination 0.31 0.12 0.23 0.55** 0.59** 0.36 0.60** 0.61** 0.50** 0.23 0.60** 0.54**
Shoot DW 0.63** 0.33 0.14 0.77** 0.86** 0.48 0.86** 0.75** 0.84** 0.77** 0.81** 0.80**
Root DW 0.02 0.82** 0.38 0.14 0.15 0.02 0.15 0.44* 0.42* 0.38* 0.36* 0.01
Root length 0.05 0.40* 0.11 0.20 0.10 0.30 0.10 0.02 0.04 0.00 0.11 0.02
pH measured in CaCl2, *p<0.05, **p<0.01
Plant Soil (2012) 353:273287 279
Author's personal copy
and from 5.07.0 in CaCl
2
. Organic carbon, electrical
conductivity, exchangeable cations, exchangeable
acidity, CEC, macro- and micro-nutrient contents also
varied among the soils.
0
20
40
60
80
100
OM0
OM10
OM100
RH0
RH10
RH100
NJ0
NJ10
NJ100
OJ0
OJ10
OJ100
WC0
WC10
WC10 0
Seed germination (%)
a
b
c
aa aa
b
b
b
b
c
c
c
c
0.00
0.05
0.10
0.15
0.20
0.25
0.30
0.35
0.40
OM0
OM10
OM100
RH0
RH10
RH100
NJ0
NJ10
NJ100
OJ0
OJ10
OJ100
WC0
WC10
WC100
Shoot DW (g)
a
b
c
aa
b
a
b
c
a
b
b
cb
a
0.00
0.05
0.10
0.15
0.20
0.25
OM0
OM10
OM100
RH0
RH10
RH100
NJ0
NJ10
NJ100
OJ0
OJ10
OJ100
WC0
WC10
WC100
Root DW (g)
a
a
b
c
a
b
a
a
b
b
b
c
c
c
0
2
4
6
8
10
12
14
16
18
OM0
OM10
OM100
RH0
RH10
RH100
NJ0
NJ10
NJ100
OJ0
OJ10
OJ100
WC0
WC10
WC100
Root length (m)
a
b
c
a
b
c
aa
b
a
b
c
a
c
b
a
a
Fig. 3 a Effect of different types and rates of biochars on
subterranean clover seed germination (%), shoot and root DW
(g/pot) and root length (m/pot), in a standard soil Oil Mallee
(OM), Rice Husks(RH), New Jarrah(NJ), Wheat Chaff
(WC) and Old Jarrah(OJ) biochars were tested at rates 0, 10
(1%) and 100 (10%) t/ha. Error bars show standard errors of the
mean. Mean data followed by a similar letter are not
statistically significant within each biochar (Experiment 3). b
Effect of different types and rates of biochars on mung bean
seed germination (%), shoot and root DW (g/pot) and root
length (m/pot), in a standard soil. Oil Mallee(OM), Rice
Husks(RH), New Jarrah(NJ), Wheat Chaff(WC) and Old
Jarrah(OJ) biochars were tested at rates 0, 10 (1%) and 100
(10%) t/ha. Error bars show standard errors of the mean. Mean
data followed by a similar letter(s) are not statistically
significant within each biochar (Experiment 3). cEffect of
different types and rates of biochars on wheat seed germination
(%), shoot and root DW (g/pot) and root length (m/pot), in a
standard soil. Oil Mallee(OM), Rice Husks(RH), New
Jarrah(NJ), Wheat Chaff(WC) and Old Jarrah(OJ)
biochars were tested at rates 0, 10 (1%) and 100 (10%) t/ha.
Error bars show standard errors of the mean. Mean data
followed by a similar letter(s) are not statistically significant
within each biochar (Experiment 3)
280 Plant Soil (2012) 353:273287
Author's personal copy
Mean values of seed germination, root length,
root DW and shoot DW were obtained for wheat
sown in 10 soils (Table 3). There was significant
variation in wheat seed germination among soils in
the presence of biochar (p<0.001, Table 4). Seed
germination with 10 t/ha biochar was increased by 9%
for OM, 8% for WC and 4% for RH (p<0.05) but not
for OJ and NJ biochars (p>0.05). In contrast, there
was an inhibitive main effect on seed germination at
the higher rate (100 t/ha) of application of all biochars
(p<0.001). The trend in the effect of biochar
application on parameters measured was generally
similar across soils (i.e. increasing at lower rates of
biochar application and decreasing at higher rates,
Table 3).
A linear correlation was noted between soil
characteristics, seed germination, root and shoot
growth (Table 5;*p<0.05; **p<0.01). A positive
correlation was observed between seed germination
and EC (r=0.55**), exchangeable cations (r = 0.59**),
CEC (r=0.60**), NH
4
(r=0.61**), NO
3
(r=0.50**),
K (0.60**) and S (r=0.54**), whereas there was a
0
20
40
60
80
100
OM0
OM10
OM100
RH0
RH10
RH100
NJ0
NJ10
NJ100
OJ0
OJ10
OJ100
WC0
WC10
WC100
Seed germination (%)
abc
abc
a
a
aaab ba
b
0.00
0.20
0.40
0.60
0.80
1.00
1.20
1.40
1.60
OM0
OM10
OM100
RH0
RH10
RH100
NJ0
NJ10
NJ100
OJ0
OJ10
OJ100
WC0
WC10
WC100
Shoot DW (g)
a
b
ab aa
b
aa
aaa
b
a
a
0.00
0.10
0.20
0.30
0.40
0.50
0.60
0.70
OM0
OM10
OM100
RH0
RH10
RH100
NJ0
NJ10
NJ100
OJ0
OJ10
OJ100
WC0
WC10
WC100
Root DW (g)
a
b
c
a
b
c
a
bc
a
b
c
a
b
c
0
5
10
15
20
25
30
OM0
OM10
OM100
RH0
RH10
RH100
NJ0
NJ1
0
NJ100
OJ0
OJ10
OJ100
WC0
WC10
WC100
Root length (m)
a
b
c
aa
c
a
bb
a
b
c
ab b
b
a
b
Fig. 3 (continued)
Plant Soil (2012) 353:273287 281
Author's personal copy
negative correlation between seed germination and Al
content in soil (r= 0.36*).
Glasshouse bioassay for three plant species (one
standard soil) (Experiment 3)
Subterranean clover
Biochar application rate significantly altered seed
germination of clover (p<0.001); it decreased signif-
icantly with the increased rate of biochar application
for all five biochars (Fig. 3a; Table 4). Similar effects
were observed for root length (p< 0.01). Root length
increased with application of 10 t/ha of OM and RH
biochars but for the other biochars it was significantly
decreased, especially at 100 t/ha (p<0.05). Shoot and
root DW showed very similar patterns in response to
application of all biochars. At the higher rate of
application, only OJ biochar showed a positive
growth effect over the lower rate of application but not
over the control both for shoot and root DW (p<0.05).
Root/shoot ratio of subterranean clover increased
0
20
40
60
80
100
OM0
OM10
OM100
RH0
RH10
RH100
NJ0
NJ10
NJ100
OJ0
OJ10
OJ100
WC0
WC10
WC100
Seed germination (%)
a
bba
c
a
ab
a
c
ba
bb
0.00
0.20
0.40
0.60
0.80
1.00
1.20
OM0
OM10
OM100
RH0
RH10
RH100
NJ0
NJ10
NJ100
OJ0
OJ10
OJ100
WC0
WC10
WC100
Shoot DW (g)
b
a
a
b
a
a
a
bab ab
a
c
b
a
b
0.00
0.20
0.40
0.60
0.80
1.00
1.20
OM0
OM10
OM100
RH0
RH10
RH100
NJ0
NJ10
NJ100
OJ0
OJ10
OJ100
WC0
WC10
WC100
Root DW (g)
ab
c
a
bc
a
bab
a
b
c
0
20
40
60
80
100
120
OM0
OM10
OM100
RH0
RH10
RH100
NJ0
NJ10
NJ100
OJ0
OJ10
OJ100
WC0
WC10
WC100
Root length (m)
ab
ca
b
c
a
bb
a
b
c
a
b
c
a
b
c
c
Fig. 3 (continued)
282 Plant Soil (2012) 353:273287
Author's personal copy
significantly with OJ biochar whereas it decreased
with NJ biochar at the rate of 10 t/ha application
(Fig. 4). It also decreased with both RH and WC
biochars applied at the rate of 100 t/ha.
Mung bean
As for subterranean clover, both biochar type and rate
of application altered seed germination of mung bean
seed (p<0.001). Germination decreased at both 10
and 100 t/ha application rates of OM, RH and WC
biochars, whereas there was a positive effect of OJ
biochar at 10 t/ha (p<0.05; Fig. 3b). NJ biochar did
not affect seed germination of mung bean (p>0.05).
The influence of biochars and rate of application on root
length of mung bean was also significant (p<0.01)
(Fig. 3b). Root length increased significantly with
application of 10 t/ha for OM and NJ biochars (p<0.05).
A significant decrease of root length was observed
with application of OM, RH and WC biochars at
100 t/ha whereas OJ increased root length when
applied at this rate (p> 0.05). Root and shoot DW had
a similar pattern of root length for all biochars (p< 0.05)
except shoot DW was not influenced by rates of
application for NJ and OJ biochar (p> 0.05). Root/
shoot ratio of mung bean decreased with OM, RH and
WC biochars applied at 100 t/ha whereas it increased
with OM, NJ and WC biochars applied at 10 t/ha
(Fig. 4).
Wheat
Unlike mung bean and subterranean clover, wheat
seed germination was increased with 10 t/ha biochar
Wheat
0.0
0.4
0.8
1.2
1.6
2.0
OM0
OM10
OM100
RH0
RH10
RH100
NJ0
NJ10
NJ100
OJ0
OJ10
OJ100
WC0
WC10
WC100
Root/Shoot ratio
aa
a
b
b
a
baba
a
a
b
c
Subterranean clover
0.0
0.2
0.4
0.6
0.8
1.0
OM0
OM10
OM100
RH0
RH10
RH100
NJ0
NJ10
NJ100
OJ0
OJ10
OJ100
WC0
WC10
WC100
Root/Shoot ratio
a
a
a
b
aa
ab
b
a
bbaa
b
Mung bean
0.0
0.2
0.4
0.6
0.8
1.0
OM0
OM10
OM100
RH0
RH10
RH100
NJ0
NJ10
NJ100
OJ0
OJ10
OJ100
WC0
WC10
WC100
Root/Shoot ratio
a
b
c
aab
a
bb
a
a
aa
b
c
a
a
Fig. 4 Effects of different
types and rates of biochars
on root/shoot ratio of sub-
terranean clover, mung bean
and wheat. Error bars show
standard errors of the mean.
Mean data followed by a
similar letter(s) are not
statistically significant
within each biochar.
(Experiment 3)
Plant Soil (2012) 353:273287 283
Author's personal copy
application for most of the biochar sources used such
as OM, WC and OJ (p<0.05) (Fig. 3c). In contrast, at
100 t/ha, wheat seed germination decreased as for
mung bean and subterranean clover (especially for
RH and OJ biochars, p<0.05; Fig. 3c). Root length,
root DW and shoot DW tended to follow the same
pattern as seed germination of wheat in response to
biochar. Wheat seed germination and growth in the
10 soils (Table 3, Experiment 2) and in one standard
soil (Fig. 3c, Experiment 3) had similar patterns of
biochar effects. Root/shoot ratio of wheat was
increased with NJ and WC whereas it was
decreased with RH biochar applied at the rate of
10 t/ha. It also decreased with RH and WC
biochars applied at 10 t/ha (Fig. 4).
Discussion
Biochars may not all be equally suitable as soil
amendments, especially if they contain unwanted
compounds that may inhibit seed germination and
initial growth of roots (Garnett et al. 2004; Hille and
den Quden 2005). Depending on the biomass type
from which biochar is produced, biochars may
contain traces to high concentrations of nutrients that
could affect seed germination (Gaskin et al. 2008).
Because of this variability among biochars, we sought
to evaluate the use of a soil-less Petri dish bioassay as
a simple and rapid ecotoxicological test for prelimi-
nary screening of biochars prior to their application as
a soil amendment. Rapid biological tests, including
seed germination tests, are considered useful in
assessing the presence of toxic compounds in biochar
(Major 2009). We anticipated that a soil-less Petri
dish bioassay would be a simpler preliminary screen-
ing procedure than a soil-based bioassay using a
standard soil as previously suggested (OECD 1984).
The general trend in effects of the biochars on
wheat seed germination and early root growth in
the soil-less Petri dish bioassaywassimilartothat
obtained in the glasshouse soil-based bioassay
(Table 6). Three of the biochars which had a negative
effect in the soil-less Petri dish bioassay when applied
at 100 t/ha (NJ and WC on germination; OJ on root
length) also had a negative effect in the soil-based
bioassay (OJ and WC on germination; WC on root
growth; OJ and WC on shoot growth; NJ and WC
on total shoot growth). OM and RH had no
negative effects on seed germination or plant
growth measurements in either the soil-less Petri
dish bioassay or the soil-based bioassay. Applica-
tions of all biochars at rates less than 100 t/ha
either increased or had no effect on the plant
parameters measured in either the soil-less Petri
dish bioassay or the soil-based bioassay.
Thus, for these biochars, the use of the soil-less
Petri dish bioassay gave a consistent indication of
potential biochar effects on early seedling develop-
ment in soil. Use of the Petri dish bioassay for
preliminary screening of biochars in the absence of
soil has the advantage that the standardsoil used in a
soil-based test does not need to be transported across
quarantine borders (such as those existing between
states in Australia). Furthermore, it avoids the need to
maintain pots in a glasshouse as is required for a test
using a standardsoil. While soil can complicate
interpretation of preliminary ecotoxicology tests due
to variability in physical, chemical properties and
microbial activity (OECD 1984), a preliminary
screening could be used to eliminate those biochars
which are most likely to be toxic at early stages of
plant growth. In the soil-less Petri dish bioassay,
inhibition of seed germination and/or root growth
observed at the highest rate of biochar application
might be due to trace levels of compounds that occur
only above economic agronomic rates of application
(Thies and Rillig 2009).
The effect of biochars on seed germination and
seedling growth varied with soil properties. In our
study, there was less inhibitory effect of biochars on
seed germination and seedling growth in soil with
higher soil fertility. For example, for soil no.9 (which
had higher organic C, CEC, exchangeable cations and
acidity, NH
4
,NO
3
, P, K and micronutrients) amended
with OJ biochar, germination was not inhibited at
100 t/ha (data not shown). Biochar application can
increase soil fertility and nutrient retention to a greater
extent than uncharred organic matter (Lehmann et al.
2006). Novak et al. (2009) also observed that biochar
addition to soil improved fertility by increasing soil
pH, soil organic carbon, Ca, K, Mn, and P and this
might help to overcome inhibitory effects of higher
rates of biochar application on seed germination. The
biochars used in our study were generally alkaline
except for the OJ biochar. Both high alkalinity and
acidity may inhibit seed germination (Pierce et al.
1999; Horne et al. 1996) for some biochars applied at
284 Plant Soil (2012) 353:273287
Author's personal copy
high rates. In a previous study, wood biochar
increased soil pH and exchangeable P and K, and
seed germination was improved in biochar-amended
soils compared with unamended soil (Chidumayo
1994).
The need to investigate the effect of biochar on
agricultural plant species has been highlighted by
previous studies of lettuce, radish and clover (US EPA
1994; Major 2009). In our study, the influence of
biochar type and rate on seed germination and
seedling growth varied among three agricultural plant
species. Root/shoot ratio decreased with the higher
rate of biochar application. Wheat seed germination
was stimulated at the 10 t/ha application rate but not
for mung bean, but inhibition of germination
occurred at the highest rate 100 t/ha for most of
the biochars. For subterranean clover, seed germination
and growth were both significantly decreased at
low and high rates of application of all the
biochars. This aligned with previous studies that
compared forest plant species differing in their
sensitivity to biochars (Enright and Kintrup 2001;
Keeley and Bond 1997), but the mechanism is
unknown. Rondon et al. (2007) reported that for
common bean (Phaseolus vulgaris L.) yield, biomass
production and N-fixation increased with biochar
application at 30 and 60 g/kg soil whereas it decreased
at 90 g/kg soil. In this case, the improved growth of
Table 6 Comparison of soil-less Petri dish and soil-based bioassays (Experiments 1 and 2), and wheat in Experiment 3;+ indicates
increase, and NS not significant
Biochar
Type
Experiment 1
(soil-less bioassay)
Experiment 2 (soil-based bioassay) Experiment 3 (wheat only)
(glasshouse experiment)
Rate Germination Root
length
Germination Root DW Shoot DW Total DW Germination Shoot DW Root DW Root
length
OM
10+++NS++++++
20 NS NS
50 NS NS
100 NS NS NS + + + NS + + +
RH
10 NS + + + + + NS + + +
20 + NS
50 + NS
100 NS + + + + + decrease + decrease decrease
NJ
10 NS NS NS + NS NS NS decrease + decrease
20 + NS
50 NS NS
100 decrease NS NS + NS decrease decrease NS NS decrease
OJ
10 + + + NS NS + NS NS decrease decrease
20 + NS
50 + NS
100 NS decrease decrease decrease decrease decrease decrease decrease
WC
10 + + + + + + NS + + +
20 NS NS
50 NS NS
100 decrease decrease decrease decrease decrease decrease NS NS decrease decrease
Plant Soil (2012) 353:273287 285
Author's personal copy
common bean appeared to be associated with increased
availability of nutrients and higher soil pH.
The response of wheat growth in Experiment 3 to
biochar application in soil was similar to that in
biochar bioassays (Experiments 1 and 2) except RH
biochar applied at the highest rate (Table 6). The
negative effect of 100 t/ha of RH biochar on wheat
growth was not predicted from either the soil-less
Petri dish bioassay or the soil-based bioassay. This
shows that bioassays may not be definitive procedures
for screening biochars for their potential toxicity,
although in the case of RH biochar, there was
consistency at lower, more agronomically relevant
application rates.
In conclusion, the five biochar types used in this study
generally increased wheat seed germination at rates of
application <50 t/ha and three of them tended to inhibit
germination at the highest rate of application under the
bioassay conditions. Wheat chaff biochar (WC) had the
greatest inhibitory effect on seed germination among the
biochars compared when applied at higher rates. Based
on the comparison of the effects of biochar on plant
growth in a glasshouse experiment with three agricultural
plant species, this investigation supports the proposal of
Major (2009) that a germination test could be a useful
screening process for evaluating biochars. However, it
is important to use several rates of biochar in the
bioassay because of differences in response observed
in this study. We recommend the soil-less Petri dish
bioassay as a preliminary ecotoxicological test for
biochar screening because it is rapid and simple, and
it avoids the need for use of a standardsoil which is
difficult to collect, transport and maintain across
quarantine boundaries. While we recommend the
soil-less Petri dish germination bioassay as a test
procedure for preliminary assessment of biochars, this
does not preclude unforseen toxicities when plants are
grown in some soils (e.g. RH biochar; Table 6).
Furthermore, there were marked differences among
plant species in their response to application of the
biochars. For subterranean clover, all plant attributes
measured decreased at the highest application rate of
all biochars; for mung bean, root growth was affected
to a greater extent than was germination; and effects
of biochars on early growth of wheat depended on the
type of biochar. Finally, it is recommended that
toxicity bioassays for biochar are repeated (in addition
to the replication used within each test) to ensure
reproducibility.
Acknowledgements This research was funded by the Australian
Grains Research and Development Corporation (GRDC). We thank
VERVE Pty Ltd, WA for supplying Oil Mallee,MrJerome
Mathews for the rice husk, SIMCOA Pty Ltd, WA for the
Simcoa, Rainbow Bee Eaters for supplying Wheat Chaffand
Dr Paul Blackwell for Wundowiebiochars. We thank Dr Ian
Abbott for commenting on the manuscript.
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Author's personal copy
... The study of Solaiman et al. (2012) indicated that the application of biochar made from Oil ...
... K (0.60**) and S (r=0.54**), but a negative correlation between seed germination and Al content in soil (r=−0.36*) (Solaiman et al., 2012). ...
... Biochar has been reported to both increase (Arif et al., 2012;Chan et al., 2007;Yamato et al., 2006) and decrease (Deenik et al., 2010) plant growth and yield but there have been few studies reporting the influence of biochar on early stages of plant growth such as on seed germination and seedling growth. Recent research findings showed that biochar increased wheat seed germination (Solaiman et al., 2012;Van Zwieten et al., 2010). In contrast, maize seed germination and early growth were not significantly affected by biochars made from a range of organic sources (Free et al., 2010). ...
Research Proposal
Full-text available
This study examined the use of biochar in the particular context of three crops (maize, peanut, and barley) with these crops subjected to a number of amendments - biochar, compost, combi-mix (biochar added to biomass prior to composting and inorganic fertilizer). The objectives of the study were to investigate the effect of these treatments on soil biophysical and chemical parameters, crop performance, and mitigation of greenhouse gases.
... The study of Solaiman et al. (2012) indicated that the application of biochar made from Oil ...
... K (0.60**) and S (r=0.54**), but a negative correlation between seed germination and Al content in soil (r=−0.36*) (Solaiman et al., 2012). ...
... Biochar has been reported to both increase (Arif et al., 2012;Chan et al., 2007;Yamato et al., 2006) and decrease (Deenik et al., 2010) plant growth and yield but there have been few studies reporting the influence of biochar on early stages of plant growth such as on seed germination and seedling growth. Recent research findings showed that biochar increased wheat seed germination (Solaiman et al., 2012;Van Zwieten et al., 2010). In contrast, maize seed germination and early growth were not significantly affected by biochars made from a range of organic sources (Free et al., 2010). ...
Research Proposal
This study examined the use of biochar in the particular context of three crops (maize, peanut, and barley) with these crops subjected to a number of amendments - biochar, compost, combi-mix (biochar added to biomass prior to composting and inorganic fertilizer). The objectives of the study were to investigate the effect of these treatments on soil biophysical and chemical parameters, crop performance and mitigation of greenhouse gases.
... For instance, maize grain yield increased by 98-150%, and water use efficiency by 91-139% due to the application of cow manure biochar (Uzoma et al., 2011), 30-40% increase in wheat plant biomass following charred paper mill sludge additions (Van Zwieten et al., 2010), 18% increase in wheat grain yield from the use of oil mallee biochar (Solaiman et al., 2010), and 200% increase in maize yield when charcoal was applied with fertilizer (Yamato et al., 2006). Plant growth and yield increases with biochar additions have been in most cases attributed to the optimization of the availability of plant nutrients (DeLuca et al., 2009;Gaskin et al., 2010;Glaser et al., 2002;Lehmann, 2007;Lehmann et al., 2003), increase in soil microbial biomass and activity (Biederman & Harpole, 2012;Hammes and Schmidt, 2009;Pietikainenn et al., 2000;Steiner et al., 2008a;Thies & Rillig, 2009) and reduction of exchangeable Al 3+ (Glaser et al., 2002;Solaiman et al., 2012;Steiner et al., 2007). Likewise, application of biochar at the rate of 25 t ha -1 with 5 t ha -1 of farmyard manure (FYM) improved maize growth and resulted in a lower weed population at 30 and 60 days after sowing (Arif et al., 2012). ...
... Plant available soil P and NO3-N had a more significant influence on the shoot-and root biomass production than other nutrients, indicating that these nutrients were most limiting as proved by the soil P and NO3-N content before planting and plant nutrient uptake. A recent study has also shown significant positive linear correlations between soil characteristics (K, P, EC, CEC, NO3, NH4 and S), wheat seed germination, root-and shoot growth as a result of biochar addition, but negative correlation between seed germination and Al content (Solaiman et al., 2012). Plant available nitrate was correlated with total soil N NH4 + as nitrification acts rapidly when the weather is warm enough for rapid plant growth, and so the amount of available ammonia becomes small (Troeh and Thompson, 2005 ...
Experiment Findings
Full-text available
A pot experiment was conducted to investigate the effects of willow and acacia biochar, compost, and the mixture of compost and biochar on soil physicochemical properties and growth of maize using Ferralsols from Northern Queensland, Australia. The treatments improved plant growth and soil properties. The biochar and biochar-compost amendments improved soil water content and decreased the leaching of nutrients.
... Photosynthetic activity is indicated by chlorophyll content, and they are related to nitrogen content present in plant biomass. Our results contrast with the results of Agegnehu et al. (2015) and Solaiman et al. (2012), who reported that biochar application increased the chlorophyll content in the leaf of crops compared with fertilizer in our NPK fertilizers which increased chlorophyll contents. Studies showed that in water shortage areas (under arid climate), biochar addition improves water absorption, water retention, soil aeration and porosity, soil quality, soil microbial activity, soil organic matter contents, and soil nutrient status, thus ultimately improving crop growth and yield (Yang and Ali 2019). ...
Article
Despite its focus on carbon sequestration, biochar derived from manure can provide other benefits after being added to the soil, such as nutrient supply. Inefficient use of chemical fertilizers, usually nitrogen-containing fertilizers, results in reduced crop growth and reduction in yield. This problem can be addressed by adding organic matter and biochar, providing nutrients, and retaining them in the soil for a longer time. The study was conducted to find the impact of various biochar treatments on sorghum and millet growth parameters. Two pot experiments were conducted to study the growth response of sorghum and millet under different biochar treatments. Results showed that all the recorded treatments were significantly different, and NPK applied at optimum rate showed maximum plant height, number of leaves, leaf area, and root-shoot fresh and dry weight. Plant growth parameters also showed a similar trend. From recorded data, it has been observed that high doses (15 t ha−1) of farmyard manure biochar (FYMB) and poultry manure biochar (PMB) cause a reduction in all recorded growth parameters while treatments of 5 and 10 t ha−1 of PMB and FYMB gave significant results compared with treatment where no biochar has been applied. The study concluded that application of biochar as an organic fertilizer will improve the efficiency of growth and physiological parameters of crops and the biochar can be used as an alternate for fertilizer and management practice for waste management.
... This ethylene is required for the germination of seeds and stopped the dormancy stage in a wide range of plant species (Newman, 1966). Furthermore, at 500 • C pyrolysis temperature, the amount of such organic compounds was maximum, and the subsequent release of sorbed ethylene from the biochar may be helped speed up the germination process (Solaiman et al., 2012). ...
Article
Various experts have been concerned about the safety usage of sludge generated during wastewater treatment and its disposal in the environment. Biochar made from sewage sludge was studied for its efficiency in enhancing soil quality, reducing heavy metal uptake, and potential benefits in agriculture areas to enrich the soil. The objectives of the present study were to examine the feasibility of raw sewage sludge (RSS) and sewage sludge biochar (SSB), which were produced at 400 and 500°C, as a soil amendment, and the effect of sewage sludge biochar on seed germination of Solanum lycopersicum. Present study included seven treatments: (i) T0 (Control); (ii) T1 (RSS, 1%); (iii) T2 (RSS, 2.5%); (iv) T3 (SSB400°C, 1%); (v) T4 (SSB400°C, 2.5%); (vi) T5 (SSB500°C, 1%); and (vii) T6 (SSB500°C, 2.5%). The addition of sewage sludge and its biochar enhanced electrical conductivity (EC), total organic carbon (TOC), sodium (Na) and potassium (K), and soil enzymatic activity when compared to control. The pH value of the soil amended with RSS increased by 0.04–0.1 units as compared to control. The treatments with the higher concentration (2.5%) of RSS and SSB significantly increased the concentration of Na whereas, SSB400°C, 2.5% significantly increased the K concentration in soil in comparison to control. The TOC in soil increased in all the RSS and SSB amended treatments and ranged between 1.16 and 1.83 %. Seeds of Solanum lycopersicum treated with SSB at 500°C had shown maximum germination (90%) and germination index (103.01 ± 1.41). The increase in the alkaline phosphatase activity was significant and was maximum 25.2 μg 4‐nitrophenol g−1 soil h−1 for T2 followed by T4 which was 24.9 μg 4‐nitrophenol g−1 soil h−1. The results demonstrate that the RSS and SSB at 2.5% concentration are potential organic amendments to promote the soil nutrients.
... Previously, Uzoma et al. (2011) also discussed the application of cow manure-derived biochar on maize yield under the sandy soil condition and found that the production of maize was increased bỹ 150 %. Similarly, the biochar derived from deep-banded oil mallee showed an 18 % increase in wheat grain yield versus control (Solaiman et al., 2012). Agegnehu et al. (2015) performed a field experiment and applied the biochar derived from waste willow wood (Salix spp.) onto Ferral-sol in northern Queensland, Australia, and found that the peanut production was increased by 23 %. ...
Article
Rising global temperature, pollution load, and energy crises are serious problems, recently facing the world. Scientists around the world are ambitious to find eco-friendly and cost-effective routes for resolving these problems. Biochar has emerged as an agent for environmental remediation and has proven to be the effective sorbent to inorganic and organic pollutants in water and soil. Endowed with unique attributes such as porous structure, larger specific surface area (SSA), abundant surface functional groups, better cation exchange capacity (CEC), strong adsorption capacity, high environmental stability, embedded minerals, and micronutrients, biochar is presented as a promising material for environmental management, reduction in greenhouse gases (GHGs) emissions, soil management, and soil fertility enhancement. Therefore, the current review covers the influence of key factors (pyrolysis temperature, retention time, gas flow rate, and reactor design) on the production yield and property of biochar. Furthermore, this review emphasizes the diverse application of biochar such as waste management, construction material, adsorptive removal of petroleum and oil from aqueous media, immobilization of contaminants, carbon sequestration, and their role in climate change mitigation, soil conditioner, along with opportunities and challenges. Finally, this review discusses the evaluation of biochar standardization by different international agencies and their economic perspective.
... In particular, these ameliorations were observed later in the cherry tomato plant phenology during Vs and Fs. These findings are in line with studies reporting a lack of biochar influence on the early stages of plant growth for Triticum aestivum, Raphanus sativus, and Sorghum bicolor (respectively, [61,62]). For instance, Free et al. [63] showed that maize's early growth was not significantly affected by biochar produced from a range of feedstock sources. ...
Article
Full-text available
Biochar soil amendment can improve growing medium water and nutrient status and crop productivity. A pot experiment was conducted using Solanum lycopersicum var. cerasiforme plants to investigate the effects of biochar amendment (20% application rate) on a soilless substrate, as well as on plant growth, fruit yield, and quality. During the experiment, substrate characteristics, plant morphological traits, and root and leaf C/N content were analyzed at three sampling points defined as early stage (36 days after germination), vegetative stage (84 days a. g.), and fruit stage (140 days a. g.). Fruit morphological traits, titratable acidity, lycopene, and solid soluble content were measured at the end of the experiment. Biochar ameliorated substrate characteristics (Nav increase of 17% and Ctot increase of 13% at the beginning of the study), resulting in a promotion effect on plant root, shoot, and leaf morphology mainly at the vegetative and fruit stages. Indeed, at these two sampling points, the biochar-treated plants had a greater number of leaves (38 and 68 at the vegetative and fruit stages, respectively) than the untreated plants (32 and 49, respectively). The biochar also increased leaf area with a rise of 26% and 36% compared with the values measured in the untreated plants. Moreover, the amendment increased twofold root length, root surface area, and root, stem, and leaf biomasses in comparison with untreated plants. Regarding plant productivity, although fruit morphology remained unchanged, biochar increased flower and fruit numbers (six times and two times, respectively), acidity (75%), lycopene (28%), and solid soluble content (16%). By unveiling promoting changes in morphological traits, fruit number, and antioxidant content occurring in cherry tomato plants growing in a biochar-treated soilless substrate, it could be possible to highlight the importance of biochar for future applications in the field for enhancing plant production and fruit quality in a sustainable agriculture framework.
Article
Biochar has been used as an alternative in organic wastes management and to alleviate trace elements toxicity. The aim of this research was to use a rapid and simple test to detect the potential toxic effects of biochar and its ability to alleviate aluminum and cadmium toxicity to seeds and seedlings of Sorghum bicolor L. Two experiments were carried out in Petri dishes with two different biochars where sorghum seeds were exposed to aluminum (experiment 1) and cadmium (experiment 2) solutions. The experimental designs were completely randomized, with five doses of aluminum or cadmium in aqueous solution (0, 0.5, 1, 2, and 4 mmol/L of Al or Cd), combined with or without the addition of 0.25 g of biochar from sugarcane bagasse or from sewage sludge. Compared to treatments without biochar, in the treatments with biochar, higher seed germination rate and growth of sorghum seedlings were obtained. Moreover, the biochars were not toxic to sorghum and they decreased the toxicity of aluminum and cadmium, mainly the biochar from sewage sludge that presented higher pH and greater occurrence of functional groups in its particles.
Technical Report
Full-text available
This report contains the outcomes of the CCRP/DAFF‐funded “National Biochar Initiative: From Source to Sink” project. This project commenced in September 2009 and concluded in June 2012, spanning 27 months of dedicated research on biochar and its effects on soil carbon (C) and greenhouse gas (GHG) mitigation. The main tasks of the project were: Task A: biochar characterisation, analyses of key properties and categorisation to determine biochar variability Task B: quantification of biochar stability, taking into account interactions among the soil mineral matrix and native soil organic matter Task C: life cycle assessment (LCA) of greenhouse gas mitigation benefits of different biochar production scenarios Task D: quantification of greenhouse gas fluxes (with particular emphasis on nitrous oxide (N2O) emissions) from contrasting agricultural areas in NSW and WA and development of an understanding of the basic mechanisms for changes in N2O emissions Task E: Assessment of biochar risk factors, including production‐inherent and feedstock‐derived toxicants and application rates of biochar to soil, specifically with regard to pesticide efficacy.
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This study aims to improve the quality and quantity of winter wheat by using the potential of combining the use of cold plasma and waste biorefinery products for improving wheat yield. Plasma was applied by a radio frequency (RF) plasma reactor operated with air for 180 s and 50 W. The waste biorefinery products, including pyroligneous acid, biochar, and azolla compost, were used as plant nutrition. The effects of cold plasma treatment and waste biorefinery products were determined by measuring plant photosynthesis, grain yield, and content of chlorophyll, carotenoids, anthocyanin, protein, and starch. The experiment was conducted during the cropping seasons 2016−18 in a randomized complete block design with four replications. The combination of cold plasma and pyroligneous acid increased the grain yield up to 40.0%. The photosynthesis rate was improved up to 39.3%, and total chlorophyll content up to 48.3% in both years. Seed plasma treatment combined with biochar application increased the starch content by 36.8%. Adding azolla compost increased the protein content by 35.4%. Using seed plasma treatment with biochar increased the microbial biomass carbon by 16.0%. The application of plasma and azolla compost increased the microbial biomass nitrogen by 29.0%.
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Full-text available
Large crabgrass is a problem weed in horticultural crops, particularly in turfgrass in the southeastern United States. If growth of large crabgrass could be suppressed via soil pH or calcium levels, control of this weed in turfgrass might be improved while minimizing herbicide usage. To determine the effect of soil calcium and pH on germination and growth of large crabgrass, seeds were sown in a loamy sand soil amended with calcium carbonate (CaCO3) or magnesium carbonate (MgCO3) that established a range of soil pH from 4.8 to 7.8. Seeds were also sown in soil amended similarly with calcium sulfate (CaSO4), which does not affect pH, that established a range of exchangeable Ca levels corresponding to the Ca range in CaCO3 from pH 4.8 to 7.8. Seed germination of large crabgrass was unaffected by pH when soil was amended with CaCO3, whereas seed germination decreased with increasing pH when soil was amended with MgCO3. Crabgrass germination was not affected by Ca (CaSO4) independent of pH changes. Increasing soil pH reduced shoot and root dry weights of seedlings regardless of material used to raise pH. Maximum shoot dry weights occurred at pH 4.8 in the unamended soil, whereas maximum root dry weights occurred at ranges from pH 5.8 to 6.3 for CaCO3 and pH 5.3 to 5.8 for MgCO3. Shoot and root dry weights were not affected by Ca when soil was amended with CaSO4. By raising soil pH levels, the growth of large crabgrass and its ability to compete with turfgrass may be reduced. Raising exchangeable Ca does not appear to be an effective management tool for control of this weed species.
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Full-text available
California chaparral and South African fynbos are fire-prone communities dominated by species exhibiting remarkable similarities in germination response. In both regions there are a substantial number of species with germination stimulated chemically by charred wood and smoke. This type of germination behaviour has arisen independently in distantly related families and is interpreted as convergent evolution. Heat-shock is also an important germination trigger that is widespread, although in both regions it is most common in the same families. Phylogeney may play an important role in the presence of this postfire germination cue in both regions, but a much more rigorous analysis is required to show that this trait represents a single unique event in each lineage. In both regions, germination response is not randomly distributed across growth forms and there are marked regional similiarities in the type of germination behaviour associated with certain growth forms. Geophytes largely lack refractory seeds, which require fire-type cues for germination, but the presence of fire-stimulated flowering of bulbs and corms may time recruitment to subsequent postfire years. Annuals that cue germination to postfire conditions are predominantly triggered by chemicals from smoke and/or charred wood.
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A series of short-term greenhouse experiments and laboratory incubations were conducted to evaluate the effect of macadamia (Macadamia integrifolia Maiden & Betche) nut shell (MNS) charcoal with varying volatile matter (VM) content on soil properties and plant growth in two tropical soils. Lettuce (Lactuca sativa L.) and corn (Zen mays L.) were planted in an Andisol amended with four rates of MNS charcoal (0, 5, 10, and 20% w/w) containing relatively high Vie! content (225 g kg(-1)) with and without N fertilizer. Increasing rates of charcoal without N caused a significant decline in both lettuce and corn growth. Corn growth declined significantly with or without N at the two highest charcoal rates. In a third experiment, corn growth also declined significantly in an Ultisol amended with the MNS charcoal (5% w/w) with and without fertilizers. In a fourth experiment, charcoals with high VM (225 g kg(-1)) showed negative effects on plant growth while the low-VM (63.0 g kg(-1)) charcoal supplemented with fertilizer showed a significant positive effect on corn growth. Results from the 2-wk incubation experiments showed that high-VM charcoal caused a significant decline in soil NH(4)(+)-N and a significant increase in soil respiration compared with the soil amended with low-VM charcoal and the soil alone. We propose that phenolic compounds and other products in the high-VM charcoal stimulated microbial growth and immobilization of plant-available N. Our results demonstrate that VM content appears to be an important property of charcoal that has short-term effects on soil N transformations and plant growth. Longer incubation experiments and field trials are needed to further elucidate the role of charcoal VM content on soil processes and plant growth.
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The application of bio-char (charcoal or biomass-derived black carbon (C)) to soil is proposed as a novel approach to establish a significant, long-term, sink for atmospheric carbon dioxide in terrestrial ecosystems. Apart from positive effects in both reducing emissions and increasing the sequestration of greenhouse gases, the production of bio-char and its application to soil will deliver immediate benefits through improved soil fertility and increased crop production. Conversion of biomass C to bio-char C leads to sequestration of about 50% of the initial C compared to the low amounts retained after burning (3%) and biological decomposition (< 10–20% after 5–10 years), therefore yielding more stable soil C than burning or direct land application of biomass. This efficiency of C conversion of biomass to bio-char is highly dependent on the type of feedstock, but is not significantly affected by the pyrolysis temperature (within 350–500 ∘C common for pyrolysis). Existing slash-and-burn systems cause significant degradation of soil and release of greenhouse gases and opportunies may exist to enhance this system by conversion to slash-and-char systems. Our global analysis revealed that up to 12% of the total anthropogenic C emissions by land use change (0.21 Pg C) can be off-set annually in soil, if slash-and-burn is replaced by slash-and-char. Agricultural and forestry wastes such as forest residues, mill residues, field crop residues, or urban wastes add a conservatively estimated 0.16 Pg C yr−1. Biofuel production using modern biomass can produce a bio-char by-product through pyrolysis which results in 30.6 kg C sequestration for each GJ of energy produced. Using published projections of the use of renewable fuels in the year 2100, bio-char sequestration could amount to 5.5–9.5 Pg C yr−1 if this demand for energy was met through pyrolysis, which would exceed current emissions from fossil fuels (5.4 Pg C yr−1). Bio-char soil management systems can deliver tradable C emissions reduction, and C sequestered is easily accountable, and verifiable.
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This study examines the potential, magnitude, and causes of enhanced biological N2 fixation (BNF) by common beans (Phaseolus vulgaris L.) through bio-char additions (charcoal, biomass-derived black carbon). Bio-char was added at 0, 30, 60, and 90 g kg−1 soil, and BNF was determined using the isotope dilution method after adding 15N-enriched ammonium sulfate to a Typic Haplustox cropped to a potentially nodulating bean variety (CIAT BAT 477) in comparison to its non-nodulating isoline (BAT 477NN), both inoculated with effective Rhizobium strains. The proportion of fixed N increased from 50% without bio-char additions to 72% with 90 g kg−1 bio-char added. While total N derived from the atmosphere (NdfA) significantly increased by 49 and 78% with 30 and 60 g kg−1 bio-char added to soil, respectively, NdfA decreased to 30% above the control with 90 g kg−1 due to low total biomass production and N uptake. The primary reason for the higher BNF with bio-char additions was the greater B and Mo availability, whereas greater K, Ca, and P availability, as well as higher pH and lower N availability and Al saturation, may have contributed to a lesser extent. Enhanced mycorrhizal infections of roots were not found to contribute to better nutrient uptake and BNF. Bean yield increased by 46% and biomass production by 39% over the control at 90 and 60 g kg−1 bio-char, respectively. However, biomass production and total N uptake decreased when bio-char applications were increased to 90 g kg−1. Soil N uptake by N-fixing beans decreased by 14, 17, and 50% when 30, 60, and 90 g kg−1 bio-char were added to soil, whereas the C/N ratios increased from 16 to 23.7, 28, and 35, respectively. Results demonstrate the potential of bio-char applications to improve N input into agroecosystems while pointing out the needs for long-term field studies to better understand the effects of bio-char on BNF.
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The roots are laid out on a flat surface, and a count is made of the number of intersections between the roots and random straight lines. Then the total root length = πNA/2H, where N is the number of intersections, A the area within which the roots lie, and H the total length of the straight lines. Details are given of a technique in which a microscope hair-line provides the straight lines. In practical tests the method was compared with direct measurement, and with direct measurement of a sub-sample followed by weighing of the sub-sample and the remainder. The results from the different methods agreed well. The line intersection method was much quicker than direct measurement, and in a given time achieved higher precision than measurement of a sub-sample and weighing.
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It is well documented that some non-native inva-sive species can release allelochemicals into soils at levels that may be phytotoxic. However, it is still not known whether allelochemicals, that remain in the soil after an invasive species has been removed, have long-term allelopathic effects on other plants. To answer this ques-tion, 2 native forbs (Sida szechuensis and Artem-isia myriantha) and 2 introduced forage grasses (Brachiaria decumbens and Setaria anceps) were grown separately for 2 years in a fi eld that had been infested with Ageratina adenophora (a nox-ious invasive species worldwide) for more than 10 years. All plants, including both underground and aerial parts, were removed at the beginning of the fi eld experiment. In a separate experiment, allelopathic effects of the fi eld soil on seed ger-mination were determined in the laboratory. Acti-vated carbon (AC) was used in an attempt to eliminate allelopathic effects of A. adenophora. The effects of AC treatments were signifi cant in all variables except crown area. Overall, relative growth rate, above-ground biomass, plant height, branch number, total leaf area, crown area, pho-tosynthesis, seed germination rate, shoot length and shoot dry weight were increased by AC treat-ment in all species, except for photosynthesis in B. decumbens. These results suggest that allelo-chemicals of A. adenophora remained in the soil and suppressed other plant species for 2 years after removal of the plants. These fi ndings have signifi cant implications for restoration programs as allelochemicals of A. adenophora can not only facilitate its invasion but also infl uence the efforts of ecological restoration of invaded habitats. Feasible measures, such as cutting and burning invasive plants or using species insensitive to allelochemicals, should be adopted to achieve desired ecological restoration in practice.
Article
This study compares the potential of natural charcoal from Scots pine (Pinus sylvestris L.) and activated carbon to improve germination under the hypothesis that natural charcoal adsorbs phytotoxins produced by dwarf-shrubs, but due to it's chemical properties to a lesser extent than activated carbon. Activated carbon has been used in many bioassays as an adsorbate to clean aqueous solutions. We used aqueous extracts from young leaves of Calluna vulgaris (L.) Hull and Vaccinium myrtillus (L.) as phytotoxin sources in two different concentrations (10 and 14 gr. of dried leaves in 100 ml distilled water). Germination of pine seeds was prevented by the higher concentration of both species, while the lower ones did not show significantly reduced germination. Both ericaceous species showed a very similar potential to prevent germination of Scots pine seeds. Supplemented carbon (activated carbon, powdered or granulated pine charcoal) restored germination in strong extracts. Adding activated carbon resulted in germination of almost 100%. With pine charcoals added, lower germination percentages were observed. The charcoal powder was more effective (60% for C. vulgaris; 28% for V. myrtillus) than the charcoal granulate (30% and 16%, respectively) in restoring germination. Chemical and surface analysis of the three carbon supplements revealed that activated carbon had by far the biggest active surface area (641 m2 g−1), and thus many more cavities to bind phytotoxins than natural charcoal (total surface area of 142 m2 g−1). We conclude, that charcoal produced by forest fires can have a positive effect on seed germination, but to a much lesser extent than activated carbon. Previous studies, which used activated carbon as an equivalent for charcoal, overestimated the effect of charcoal on germination.
Article
Biochar application to soil has been proposed as a mechanism for improving soil quality and the long term sequestration of carbon. The implications of biochar on pesticide behavior, particularly in the longer term, however, remains poorly understood. Here we evaluated the influence of biochar type, time after incorporation into soil, dose rate and particle size on the sorption, biodegradation and leaching of the herbicide simazine. We show that typical agronomic application rates of biochar (10–100 t ha−1) led to alterations in soil water herbicide concentrations, availability, transport and spatial heterogeneity. Overall, biochar suppressed simazine biodegradation and reduced simazine leaching. These responses were induced by a rapid and strong sorption of simazine to the biochar which limits its availability to microbial communities. Spatial imaging of 14C-labeled simazine revealed concentrated hotpsots of herbicide co-localized with biochar in the soil profile. The rate of simazine mineralization, amount of sorption and leaching was inversely correlated with biochar particle size. Biochar aged in the field for 2 years had the same effect as fresh biochar on the sorption and mineralization of simazine, suggesting that the effects of biochar on herbicide behavior may be long lasting. We conclude that biochar application to soil will reduce the dissipation of foliar applied pesticides decreasing the risk of environmental contamination and human exposure via transfer in the food chain, but may affect the efficacy of soil-applied herbicides.