Impact of pre harvest burning versus tra
Plant Soil (2010) 333:71–80
DOI 10.1007/s11104-010-0320-7
REGULAR ARTICLE
Impact of pre-harvest burning versus trash conservation
on soil carbon and nitrogen stocks on a sugarcane plantation
in the Brazilian Atlantic forest region
Érika Flavia Machado Pinheiro & Eduardo Lima &
Marcos Bacis Ceddia & Segundo Urquiaga &
Bruno J. R. Alves & Robert M. Boddey
Received: 3 December 2009 / Accepted: 4 February 2010 / Published online: 2 March 2010
# Springer Science+Business Media B.V. 2010
Abstract Owing to the increased demand for ethanol
biofuel from sugar cane, the area planted to this crop in
Brazil has increased from 4.8 to 9.5 Mha since 2000. At
the same time there has been pressure from environmental groups and others to cease the pre-harvest
burning of cane, and today over 40% of the crop is
harvested without burning, thus conserving the trash on
the soil surface. While most trash decomposes during
the year, it is generally assumed that this transition from
burning to trash conservation will have benefits for cane
productivity and increase soil carbon stocks. To
investigate the possible benefits of this change of
practice an experiment was carried out in the state of
Espírito Santo, south-eastern Brazil, to investigate the
long-term effects of the practice of pre-harvested
burning compared to trash conservation on soil fertility
and soil C and N stocks. The results showed that over a
14-year period, trash conservation marginally decreased
soil acidity and significantly increased soil C and N
stocks in 0–10 cm depth interval. Although the trash
Responsible editor: Elizabeth M. Baggs.
É. F. Machado Pinheiro : E. Lima : M. B. Ceddia
Departamento de Solos, Instituto de Agronomia da UFRRJ,
BR 465, km 7,
23890-000 Seropédica, RJ, Brazil
S. Urquiaga : B. J. R. Alves : R. M. Boddey (*)
Embrapa – Agrobiologia,
Rodovia BR 465, km 7, Caixa Postal 74505, 23890-000
Seropédica, RJ, Brazil
e-mail: [email protected]
conservation treatment accumulated 13 Mg C ha−1
more than the burned treatment, this difference was not
statistically different. However, the stocks of N to 100
cm depth were 900 kg ha−1 higher under the trash
conservation treatment and this difference was statistically significant. The 13C abundance data suggested
that where trash was conserved, more soil C was
derived from the sugar cane than from the original
native vegetation.
Keywords 13C . Carbon accumulation .
Green manure . Pre-harvest burning . Soil organic
matter . Sugarcane . Trash conservation
Introduction
Brazil is the world’s largest producer of sugarcane. In
2008 a total of 8.2 Mha of cane fields were harvested
for the production of over 27 billion litres of ethanol
for fuelling light vehicles and 30.8 million tonnes
(Tg) sugar. Since the year 2000 cane production has
increased from 255 Tg to over 653 Tg in 2008
(projected to be 660 Tg in 2009), and taking into
account the fields recently planted, this crop nowadays covers just over 9.5 Mha (IBGE-SIDRA 2009;
UNICA 2009). The large increase has been stimulated
by the international interest in bio-ethanol as a vehicle
fuel (ethanol exports reached 5.4 billion litres in
2008) and the introduction of FlexFuel (Otto cycle)
motors which can run on any mixture of hydrous
72
(95%) ethanol and Brazilian gasoline (a mixture of
approximately 76% gasoline and 24% of anhydrous
[99.5%] ethanol). Light vehicles with FlexFuel
motors were launched on the Brazilian market in
2003 and over 8.3 million had been sold until October
2009 (ANFAVEA 2009).
The State of São Paulo is responsible for over 60%
of the cane production and the crop occupies
approximately 4.5 Mha, 18% of the whole area of
the State. The air pollution caused by burning the
cane at harvest is thought to have significant
detrimental effects on human health, especially
respiratory problems for young children and the
elderly (Godoi et al. 2004; Arbex et al. 2007). In
2003 this led to legislation being passed in this State
that mandates all pre-harvest burning of cane in São
Paulo must be phased out by the year 2022. Only on
land that has greater than a 12% slope, where machine
harvesting is non-viable, will burning be allowed until
2032. Today approximately 40% of Brazil’s sugarcane is not subject to pre-harvest burning (green cane
harvesting), and most of this area is in São Paulo, but
the change in practice is increasing steadily.
It is natural to assume that the preservation of the
cane trash (usually between 10 and 15 Mg ha−1
crop−1, Resende et al. 2006; Mello et al. 2006) will
lead to the accumulation of soil carbon (Vallis et al.
1996). The trash is on the soil surface but much
decomposes during the crop cycle, and thus it is
expected that only a small proportion becomes
integrated into the soil. At the experimental site
described by Resende et al. (2006) in the Agreste
region of Pernambuco, at harvest, 12 Mg ha−1 of trash
were deposited on the soil surface when the cane
(yield, 120 Mg stems ha−1) was not burned, and after
12 months at the time of the next harvest, only 500 kg
ha−1 remained (Resende 2003). These authors found
that trash conservation increased cane yields over a 16
year period by 25%, but that soil C only increased by
2.5 Mg C ha−1 over the whole period or a mean
annual gain of only 156 kg C ha−1.
From short-term studies (4 years) in São Paulo,
other authors have suggested that the change from
pre-harvest burning to trash conservation would
promote a mean soil C accumulation of 1.62 Mg C
ha−1 year−1 (Cerri et al. 2004; Mello et al. 2006).
However, this estimate was based on data taken from
fields where the cane crop was not replanted, which in
São Paulo generally occurs every 5 to 6 years. The
Plant Soil (2010) 333:71–80
deep ploughing and harrowing involved in replanting
stimulates soil organic matter (SOM) decomposition
and probably causes the loss of a large proportion of
this C.
The energy balance of bio-ethanol from sugarcane
has been recently computed by Macedo et al. (2008)
and Boddey et al. (2008). This is the ratio of fossil
energy used to produce 1 litre of ethanol in
comparison with the total energy produced when the
ethanol is used as fuel. Both studies concluded that
the balance was approximately 9:1 and Boddey et al.
(2008) reported that for a 100 km journey in a
FlexFuel family car there is a 79% offset in
greenhouse gas emissions compared to the same
vehicle travelling the same distance running on pure
gasoline. If the change from burned cane (which
facilitates manual harvesting) to machine harvesting
of “green” cane leads to significant soil C sequestration, this will have an impact on the greenhouse gas
emission offset. Hence the question of the magnitude
of this soil C change is relevant to any assessment of
the overall environmental impact of bio-ethanol
production from sugarcane.
The objective of this study was to compare the soil
C stocks under sugar cane subject to pre-harvest
burning, or trash conservation over a 14 year period,
with a view to contributing reliable data to evaluate
the impact of the conversion to trash conservation on
the mitigation of greenhouse gas emissions.
Material and methods
Site and experimental layout
The experiment was established in the experimental
area of the LAGRISA “Usina” (distillery/cane factory), Linhares, Espírito Santo (19°18′ S, 40°19′ W),
situated in the Atlantic Forest region. Mean monthly
temperatures range from 20.5°C in July to 26°C in
February. Mean annual rainfall was 1226 mm over the
14 years of the experiment. The soil is classified as a
Haplic Acrisol (Abruptic, Hyperdytric – FAO Classification) or an Argissolo Amarelo by the Brazilian
classification. Soil granulometric analysis data are
displayed in Table 1.
The area of the experiment was originally native
forest and the vegetation was cleared and initially
replaced by Brachiaria pasture in 1986. The sugar
Plant Soil (2010) 333:71–80
73
Table 1 Physical properties of the Yellow Ultisol under the
long-term sugarcane experiment at the LAGRISA cane factory,
Linhares, North Espirito Santo, Brazil)
Depth (cm)
Sand
(g kg−1)
Clay
(g kg−1)
890
100
Silt
(g kg−1)
Experimental plots
0–5
10
5–10
890
100
10
10–20
890
100
10
20–30
880
120
0
30–40
800
200
0
40–60
760
200
40
60–80
750
230
20
80–100
700
280
20
Forest
0–5
700
280
20
5–10
720
260
20
10–20
850
140
10
20–30
790
180
30
30–40
660
260
80
40–60
610
330
50
60–80
590
310
100
80–100
560
380
60
cane experiment was established in 1989 with a
randomized block design with five replicates and just
two treatments (A) with, or (B) without, pre-harvest
burning of the cane.
The 10 plots consisted of 6 rows of sugarcane of 95
m in length spaced at 1.2 m between rows. The variety
of sugar cane was RB 73-9735. Basal fertilization at the
start of the experiment was 500 kg ha−1 dolomitic lime,
81 kg ha−1 of K as potassium chloride, and 55 kg ha−1
of P as single super phosphate, applied in the furrow at
planting. In the following years (1990–2002), soon
after harvest, the ratooning cane crop was fertilised
with 400 kg/ha of compound fertiliser (25-00-20) and
150 kg N in the form of urea.
Sugar cane was planted after deep ploughing and
harrowing in May 1989. The cane was all manually
harvested, the consequence being that almost no
machinery entered the experimental area. Machines,
especially the heavy cane harvesters, compact the soil
which often leads to progressively decreasing yields
and the cane plantations are usually replanted every 5
to 6 years. This experiment and the surrounding
commercial area were not replanted until 2003, just
after the soil sampling reported here.
Cane harvest
The first harvest was made after 18 months in late 1990
and then the next 13 ratoon crops harvested at 12-month
intervals. All unburned plots were cut first as well as the
border area (two rows on each side) around each plot.
The trash on the soil surface of these plots was then
saturated with water from a tanker truck to prevent it
being burned, and the remaining plots then burned off
for harvesting the following day.
The aerial tissue of the plants was manually
harvested and separated into fresh stems, trash (unburned) and flag leaves. These materials were weighed
fresh and then sub-sampled for evaluation of dry weight.
All plant material was dried (65°C for >72 h) and
subsequently ground using a Wiley mill (
DOI 10.1007/s11104-010-0320-7
REGULAR ARTICLE
Impact of pre-harvest burning versus trash conservation
on soil carbon and nitrogen stocks on a sugarcane plantation
in the Brazilian Atlantic forest region
Érika Flavia Machado Pinheiro & Eduardo Lima &
Marcos Bacis Ceddia & Segundo Urquiaga &
Bruno J. R. Alves & Robert M. Boddey
Received: 3 December 2009 / Accepted: 4 February 2010 / Published online: 2 March 2010
# Springer Science+Business Media B.V. 2010
Abstract Owing to the increased demand for ethanol
biofuel from sugar cane, the area planted to this crop in
Brazil has increased from 4.8 to 9.5 Mha since 2000. At
the same time there has been pressure from environmental groups and others to cease the pre-harvest
burning of cane, and today over 40% of the crop is
harvested without burning, thus conserving the trash on
the soil surface. While most trash decomposes during
the year, it is generally assumed that this transition from
burning to trash conservation will have benefits for cane
productivity and increase soil carbon stocks. To
investigate the possible benefits of this change of
practice an experiment was carried out in the state of
Espírito Santo, south-eastern Brazil, to investigate the
long-term effects of the practice of pre-harvested
burning compared to trash conservation on soil fertility
and soil C and N stocks. The results showed that over a
14-year period, trash conservation marginally decreased
soil acidity and significantly increased soil C and N
stocks in 0–10 cm depth interval. Although the trash
Responsible editor: Elizabeth M. Baggs.
É. F. Machado Pinheiro : E. Lima : M. B. Ceddia
Departamento de Solos, Instituto de Agronomia da UFRRJ,
BR 465, km 7,
23890-000 Seropédica, RJ, Brazil
S. Urquiaga : B. J. R. Alves : R. M. Boddey (*)
Embrapa – Agrobiologia,
Rodovia BR 465, km 7, Caixa Postal 74505, 23890-000
Seropédica, RJ, Brazil
e-mail: [email protected]
conservation treatment accumulated 13 Mg C ha−1
more than the burned treatment, this difference was not
statistically different. However, the stocks of N to 100
cm depth were 900 kg ha−1 higher under the trash
conservation treatment and this difference was statistically significant. The 13C abundance data suggested
that where trash was conserved, more soil C was
derived from the sugar cane than from the original
native vegetation.
Keywords 13C . Carbon accumulation .
Green manure . Pre-harvest burning . Soil organic
matter . Sugarcane . Trash conservation
Introduction
Brazil is the world’s largest producer of sugarcane. In
2008 a total of 8.2 Mha of cane fields were harvested
for the production of over 27 billion litres of ethanol
for fuelling light vehicles and 30.8 million tonnes
(Tg) sugar. Since the year 2000 cane production has
increased from 255 Tg to over 653 Tg in 2008
(projected to be 660 Tg in 2009), and taking into
account the fields recently planted, this crop nowadays covers just over 9.5 Mha (IBGE-SIDRA 2009;
UNICA 2009). The large increase has been stimulated
by the international interest in bio-ethanol as a vehicle
fuel (ethanol exports reached 5.4 billion litres in
2008) and the introduction of FlexFuel (Otto cycle)
motors which can run on any mixture of hydrous
72
(95%) ethanol and Brazilian gasoline (a mixture of
approximately 76% gasoline and 24% of anhydrous
[99.5%] ethanol). Light vehicles with FlexFuel
motors were launched on the Brazilian market in
2003 and over 8.3 million had been sold until October
2009 (ANFAVEA 2009).
The State of São Paulo is responsible for over 60%
of the cane production and the crop occupies
approximately 4.5 Mha, 18% of the whole area of
the State. The air pollution caused by burning the
cane at harvest is thought to have significant
detrimental effects on human health, especially
respiratory problems for young children and the
elderly (Godoi et al. 2004; Arbex et al. 2007). In
2003 this led to legislation being passed in this State
that mandates all pre-harvest burning of cane in São
Paulo must be phased out by the year 2022. Only on
land that has greater than a 12% slope, where machine
harvesting is non-viable, will burning be allowed until
2032. Today approximately 40% of Brazil’s sugarcane is not subject to pre-harvest burning (green cane
harvesting), and most of this area is in São Paulo, but
the change in practice is increasing steadily.
It is natural to assume that the preservation of the
cane trash (usually between 10 and 15 Mg ha−1
crop−1, Resende et al. 2006; Mello et al. 2006) will
lead to the accumulation of soil carbon (Vallis et al.
1996). The trash is on the soil surface but much
decomposes during the crop cycle, and thus it is
expected that only a small proportion becomes
integrated into the soil. At the experimental site
described by Resende et al. (2006) in the Agreste
region of Pernambuco, at harvest, 12 Mg ha−1 of trash
were deposited on the soil surface when the cane
(yield, 120 Mg stems ha−1) was not burned, and after
12 months at the time of the next harvest, only 500 kg
ha−1 remained (Resende 2003). These authors found
that trash conservation increased cane yields over a 16
year period by 25%, but that soil C only increased by
2.5 Mg C ha−1 over the whole period or a mean
annual gain of only 156 kg C ha−1.
From short-term studies (4 years) in São Paulo,
other authors have suggested that the change from
pre-harvest burning to trash conservation would
promote a mean soil C accumulation of 1.62 Mg C
ha−1 year−1 (Cerri et al. 2004; Mello et al. 2006).
However, this estimate was based on data taken from
fields where the cane crop was not replanted, which in
São Paulo generally occurs every 5 to 6 years. The
Plant Soil (2010) 333:71–80
deep ploughing and harrowing involved in replanting
stimulates soil organic matter (SOM) decomposition
and probably causes the loss of a large proportion of
this C.
The energy balance of bio-ethanol from sugarcane
has been recently computed by Macedo et al. (2008)
and Boddey et al. (2008). This is the ratio of fossil
energy used to produce 1 litre of ethanol in
comparison with the total energy produced when the
ethanol is used as fuel. Both studies concluded that
the balance was approximately 9:1 and Boddey et al.
(2008) reported that for a 100 km journey in a
FlexFuel family car there is a 79% offset in
greenhouse gas emissions compared to the same
vehicle travelling the same distance running on pure
gasoline. If the change from burned cane (which
facilitates manual harvesting) to machine harvesting
of “green” cane leads to significant soil C sequestration, this will have an impact on the greenhouse gas
emission offset. Hence the question of the magnitude
of this soil C change is relevant to any assessment of
the overall environmental impact of bio-ethanol
production from sugarcane.
The objective of this study was to compare the soil
C stocks under sugar cane subject to pre-harvest
burning, or trash conservation over a 14 year period,
with a view to contributing reliable data to evaluate
the impact of the conversion to trash conservation on
the mitigation of greenhouse gas emissions.
Material and methods
Site and experimental layout
The experiment was established in the experimental
area of the LAGRISA “Usina” (distillery/cane factory), Linhares, Espírito Santo (19°18′ S, 40°19′ W),
situated in the Atlantic Forest region. Mean monthly
temperatures range from 20.5°C in July to 26°C in
February. Mean annual rainfall was 1226 mm over the
14 years of the experiment. The soil is classified as a
Haplic Acrisol (Abruptic, Hyperdytric – FAO Classification) or an Argissolo Amarelo by the Brazilian
classification. Soil granulometric analysis data are
displayed in Table 1.
The area of the experiment was originally native
forest and the vegetation was cleared and initially
replaced by Brachiaria pasture in 1986. The sugar
Plant Soil (2010) 333:71–80
73
Table 1 Physical properties of the Yellow Ultisol under the
long-term sugarcane experiment at the LAGRISA cane factory,
Linhares, North Espirito Santo, Brazil)
Depth (cm)
Sand
(g kg−1)
Clay
(g kg−1)
890
100
Silt
(g kg−1)
Experimental plots
0–5
10
5–10
890
100
10
10–20
890
100
10
20–30
880
120
0
30–40
800
200
0
40–60
760
200
40
60–80
750
230
20
80–100
700
280
20
Forest
0–5
700
280
20
5–10
720
260
20
10–20
850
140
10
20–30
790
180
30
30–40
660
260
80
40–60
610
330
50
60–80
590
310
100
80–100
560
380
60
cane experiment was established in 1989 with a
randomized block design with five replicates and just
two treatments (A) with, or (B) without, pre-harvest
burning of the cane.
The 10 plots consisted of 6 rows of sugarcane of 95
m in length spaced at 1.2 m between rows. The variety
of sugar cane was RB 73-9735. Basal fertilization at the
start of the experiment was 500 kg ha−1 dolomitic lime,
81 kg ha−1 of K as potassium chloride, and 55 kg ha−1
of P as single super phosphate, applied in the furrow at
planting. In the following years (1990–2002), soon
after harvest, the ratooning cane crop was fertilised
with 400 kg/ha of compound fertiliser (25-00-20) and
150 kg N in the form of urea.
Sugar cane was planted after deep ploughing and
harrowing in May 1989. The cane was all manually
harvested, the consequence being that almost no
machinery entered the experimental area. Machines,
especially the heavy cane harvesters, compact the soil
which often leads to progressively decreasing yields
and the cane plantations are usually replanted every 5
to 6 years. This experiment and the surrounding
commercial area were not replanted until 2003, just
after the soil sampling reported here.
Cane harvest
The first harvest was made after 18 months in late 1990
and then the next 13 ratoon crops harvested at 12-month
intervals. All unburned plots were cut first as well as the
border area (two rows on each side) around each plot.
The trash on the soil surface of these plots was then
saturated with water from a tanker truck to prevent it
being burned, and the remaining plots then burned off
for harvesting the following day.
The aerial tissue of the plants was manually
harvested and separated into fresh stems, trash (unburned) and flag leaves. These materials were weighed
fresh and then sub-sampled for evaluation of dry weight.
All plant material was dried (65°C for >72 h) and
subsequently ground using a Wiley mill (