Agriculture Reference
In-Depth Information
Increase in pH of an acid soil leads to increase soil CEC as soil pH rises above soil
mineral PZC, or as it leads to dissociation of functional groups of amphoteric material (e.g.
organic matter) or variable charge minerals such as free oxides of Fe, Al, and Mn. Increasing
pH also increases soil base saturation, while reducing the activity and subsequent toxicity of
Al and Mn. Consistent and beneficial effects of biochar application on crop yield in acid soils
is well documented (Chan et al., 2008; Kimetu et al., 2008; Hossain et al., 2010; Major et al.,
2010; Van Zwieten et al., 2010; Peng et al., 2011; Uzoma et al., 2011a, 2011b). Van Zwieten
et al. (2010) reported positive effect on yield of wheat, soybean, and radish (
Raphanus
sativus
)
grown in a ferrosol (pH
CaCl
2
4.2), but not in a calcareous soil (pH
CaCl
2
7.7), when
amended with biochar produced at 550 °C from paper mill sludge mixed with waste wood
chips and applied at rate of 10 Mg ha
-1
. Aluminum and Mn toxicity are known to be growth
limiting factors in acid soils (Fay et al., 1978; Fox et al., 1991; He et al., 1999) and
overcoming such limitation was likely achieved as biochar application resulted in increase in
soil pH (from 4.2 to >5.0), increase in CEC and exchangeable Ca, and decrease in soil
exchangeable Al (Van Zwieten et al., 2010). Inasmuch as Al
3+
is thought to be the
predominant species responsible for plant growth reduction, Kinraide and Parker (1990)
suggested that plant growth was more sensitive to Al(OH)
2+
and Al(OH)
2
+
than Al
3+
since
the
presence of H
+
(at the low pH where Al
3+
predominates) alleviates Al
3+
toxicity through
competition with Al
3+
at the root cell plasma membrane (Kinraide & Parker, 1990; Kinraide,
1993). Aluminum uptake inhibition by base cations was found to decrease in the order of Ca
2+
> Mg
2+
≈ Sr
2+
>> K
+
≈ Na
+
(Kinraide & Parker, 1987). Traditional management practices
used to ameliorate Al toxicity and increase pH of acid soils include use of limestone,
dolomite, by-products such as fly ash, fluidized-bed combustion by-products, wood ash, as
well as organic amendments such as mulch and green manures (Duong & Diep, 1986; Hue &
Amien, 1989; Wang et al., 1999; Ritchey & Snuffer, 2002; Ritchey et al., 2004; Qin &
Chen,
2005).
In acid soils where Al and/or Mn toxicity have lesser effect on plant growth (e.g. pH ≥
5.5, high organic matter, or the use of tolerant plants to acid conditions), biochar application
may have limited effect on plant response. No effect of biochar (pH 7.8) from Monterey pine
(
Pinus radiate
) on perennial ryegrass (
Lolium perenne
L.) herbage biomass yield and herbage
N content was observed when biochar was applied to pasture land with an Andic Dystrudepts
soil (pH 5.5) at application rates of up to 30 Mg ha
-1
(Taghizadeh-Toosi et al., 2011). In
another study, biochar and organic amendments (sawdust, manure, and tithonia [
Tithonia
spp.
] green biomass), improved maize grain yield in two consecutive seasons along a
chronosequence of a degraded soil previously treated with mineral fertilizers (Kimetu et al.,
2008). Yet, no significant differences were found between biochar and sawdust treatments in
all but the first year at the most drastically disturbed soil (Kimetu et al., 2008). The above
effect is likely in part due to the role of organic matter in ameliorating aluminum toxicity by
binding Al poly/monomeric species (Marschner, 1995, Haynes & Mokolobate, 2001; Ma et
al., 2001). Green manure and mulch showed to be an effective agents in alleviating Al
residues (
Calopogonium
, soybean, and
Leucaena
) were more effective in reducing
monomeric Al in solution of an Indonesian red-yellow podzolic soil than non-leguminous
residues (
Imperata
, sugarcane, and rice) (Berek et al., 1995).
Biochar also showed to have different effect on yield in subsequent years when applied to
different soils. While wood biochar application (8 and 20 Mg ha
-1
) to a Typic Haplustox
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