Directory UMM :Data Elmu:jurnal:S:Soil & Tillage Research:Vol52.Issue3-4.Oct1999:
Soil & Tillage Research 52 (1999) 129±139
Effects of tillage depth on organic carbon content and
physical properties in ®ve Swedish soils
A. Etanaa,*, I. HaÊkanssona, E. Zagala,1, S. BucÆasb
a
Department of Soil Sciences, Swedish University of Agricultural Sciences, PO Box 7014, S-750 07 Uppsala, Sweden
b
Lithuanian Institute of Agriculture, 5051 Academia, Dotnuva sen., Kedainiai d., Lithuania
Received 24 December 1998; received in revised form 6 May 1999; accepted 23 June 1999
Abstract
The soil tillage system affects incorporation of crop residues and may in¯uence organic matter dynamics. A study was
carried out in ®ve 15±20 year old tillage experiments on soils with a clay content ranging from 72 to 521 g kgÿ1. The main
objective was to quantify the in¯uence of tillage depth on total content of soil organic carbon and its distribution by depth.
Some soil physical properties were also determined. The experiments were part of a series of ®eld experiments all over
Sweden with the objective of producing a basis to advise farmers on optimal depths and methods of primary tillage under
various conditions. Before the experimental period, all sites had been mouldboard ploughed annually for many years to a
depth of 23±25 cm. Treatments included primary tillage to 24±29 cm depth by mouldboard plough (deep tillage) and to 12±
15 cm by ®eld cultivator or mouldboard plough (shallow tillage). Dry bulk density, degree of compactness and penetration
resistance pro®les clearly re¯ected the depth of primary tillage and substantially increased below that depth. Compared to
deep tillage, shallow tillage increased the concentration of organic carbon in the surface layer but decreased it in deeper layers.
Total quantity of soil organic carbon and carbon±nitrogen ratio were unaffected by the tillage depth. Thus, a reduction of the
tillage depth from about 25 cm to half of that depth would appear to have no signi®cant effect on the global carbon cycle.
# 1999 Elsevier Science B.V. All rights reserved.
Keywords: Soil organic matter; Soil organic carbon; Soil organic nitrogen; Tillage depth; Reduced tillage; Bulk density; Penetration resistance
1. Introduction
Soil organic matter greatly in¯uences soil properties and plant nutrition and is an important source or
*
Corresponding author. Tel.: 4618-671259; fax: 4618672795
E-mail address: [email protected] (A. Etana)
1
Present address: University of Conception, Faculty of Agronomy, Department of Soil Science, PO Box 535, ChillaÂn, Chile.
sink for CO2. The soil tillage system (time, depth, type
and intensity of tillage) affects the incorporation of
crop residues and the rate of decomposition of the
organic matter. Mouldboard ploughing is the traditional primary tillage in northwestern Europe. In
Sweden, it is still used on more than 80% of the area
of annual crops, although various forms of reduced
tillage are increasingly used. The ploughing depth is
usually 20±25 cm, but a depth about 30 cm is not
uncommon, particularly on sandy soils.
0167-1987/99/$ ± see front matter # 1999 Elsevier Science B.V. All rights reserved.
PII: S 0 1 6 7 - 1 9 8 7 ( 9 9 ) 0 0 0 6 2 - 8
130
A. Etana et al. / Soil & Tillage Research 52 (1999) 129±139
Tillage depth determines the maximum depth to
which above-ground plant residues are incorporated
into arable soils, and therefore it affects the vertical
distribution of soil organic carbon (SOC) and soil
organic nitrogen (SON). Overwhelming results show
that shallow tillage leads to a concentration of SOC
near the soil surface (e.g., Dick, 1983; Rydberg, 1987;
Comia et al., 1994). Bùrresen and Njùs (1994) and
Riley and Ekeberg (1998) reported that reduced
ploughing depth led to accumulation of SOC near
the surface, but the total amount was unaffected.
As pointed out by Ellert and Bettany (1995), measurement de®ciencies in many earlier studies have
made the determinations of total contents of SOC
and SON uncertain. For accurate quanti®cations,
not only the SOC and SON concentrations in individual layers must be satisfactorily determined, but also
the depth and mass of dry soil in the same layers. A
further requirement is that all these determinations be
made on a continuous pro®le from the soil surface to
the full depth of interest. In most investigations not all
these requirements have been ful®lled. Hence, it is not
well known whether tillage depth affects the total
quantity of SOC and SON in the whole Ap-horizon,
and consequently, the global carbon cycle. Therefore
more investigations are needed under various soil,
cropping and climatic conditions.
The present study was carried out in ®ve existing
long-term trials with annual tillage to different depths.
The trials were located in various parts of Sweden and
were initiated to produce a basis for advising farmers
on optimal depths and methods of primary tillage
under various conditions. The main objective of the
present study was to investigate the effects of tillage
depth on concentration, distribution by depth and total
content of SOC and SON. Some soil physical parameters were also determined.
2. Materials and methods
2.1. Sites and treatments
Five long-term trials with various depths of primary
tillage were selected for the investigation (Table 1).
They represented common soil types in their respective regions. In the original plough layer, the clay
content ranged from 72 to 521 g kgÿ1 and the organic
matter content from 26 to 59 g kgÿ1. No detailed soil
classi®cation was made, but according to a tentative
classi®cation using the FAO system the soils were
Eutric Cambisols except the soil at site 3 that was a
Thionic Fluvisol with a shallow ground water level.
The climate at the experimental sites is cool temperate
and moderately humid with the lowest mean temperature, longest winter and shortest growing season at site
5. Climatic data from the national meteorological
station closest to each of the sites is given in Table 2.
During the experimental period there were differences in treatments between the sites. However, at all
of them shallow (12±15 cm) and deep (24±29 cm)
primary tillage were carried out annually for 15±20
years. These treatments were applied at the traditional
time of autumn ploughing in Swedish agriculture,
which is in late September or October, some weeks
after harvest of the previous crop. Before initiation of
the experiments, all sites had been conventionally
tilled for many years, including annual mouldboard
Table 1
Description of five Swedish sites for long-term studies of shallow and deep annual tillage
Site
1.
2.
3.
4.
5.
Position
(lat.N/long.E)
Kattarp
Lanna
UlfhaÈll
Hamre
RoÈbaÈcksd.
a
b
0
0
56813 /12848
588210 /138070
598210 /178030
608180 /8168000
638480 /208140
Soil texture
Sandy loam
Clay
Clay
Silt loam
Silt loam
Particle size distributiona (g kgÿ1)
5 > 2.
The main reasons were the differences in plot size (the
smallest plots at site 1, the largest at site 2) and the
immediate appearance of differences in SOC and SON
concentrations at sites 1, 4 and 3 as soon as the
experiments were initiated, while at the other sites,
the differences developed gradually.
Differing preconditions made it impossible to
directly use the models or results by Sibbesen and
Andersen (1985) or Sibbesen (1986) to estimate the
magnitude of the net transport. However, by comparison with their results and considering the factors
mentioned above, a rough and somewhat subjective
estimate was made. At site 1, the estimated maximum
gain of SOC in D-plots during the experimental period
was 4 Mg haÿ1 and the maximum loss in S-plots
2 Mg haÿ1. Thus, the estimated maximum net gain
in D-plots relative to S-plots was 6 Mg haÿ1. The
corresponding values for sites 4, 3, 5 and 2 were 5,
3, 1 and
Effects of tillage depth on organic carbon content and
physical properties in ®ve Swedish soils
A. Etanaa,*, I. HaÊkanssona, E. Zagala,1, S. BucÆasb
a
Department of Soil Sciences, Swedish University of Agricultural Sciences, PO Box 7014, S-750 07 Uppsala, Sweden
b
Lithuanian Institute of Agriculture, 5051 Academia, Dotnuva sen., Kedainiai d., Lithuania
Received 24 December 1998; received in revised form 6 May 1999; accepted 23 June 1999
Abstract
The soil tillage system affects incorporation of crop residues and may in¯uence organic matter dynamics. A study was
carried out in ®ve 15±20 year old tillage experiments on soils with a clay content ranging from 72 to 521 g kgÿ1. The main
objective was to quantify the in¯uence of tillage depth on total content of soil organic carbon and its distribution by depth.
Some soil physical properties were also determined. The experiments were part of a series of ®eld experiments all over
Sweden with the objective of producing a basis to advise farmers on optimal depths and methods of primary tillage under
various conditions. Before the experimental period, all sites had been mouldboard ploughed annually for many years to a
depth of 23±25 cm. Treatments included primary tillage to 24±29 cm depth by mouldboard plough (deep tillage) and to 12±
15 cm by ®eld cultivator or mouldboard plough (shallow tillage). Dry bulk density, degree of compactness and penetration
resistance pro®les clearly re¯ected the depth of primary tillage and substantially increased below that depth. Compared to
deep tillage, shallow tillage increased the concentration of organic carbon in the surface layer but decreased it in deeper layers.
Total quantity of soil organic carbon and carbon±nitrogen ratio were unaffected by the tillage depth. Thus, a reduction of the
tillage depth from about 25 cm to half of that depth would appear to have no signi®cant effect on the global carbon cycle.
# 1999 Elsevier Science B.V. All rights reserved.
Keywords: Soil organic matter; Soil organic carbon; Soil organic nitrogen; Tillage depth; Reduced tillage; Bulk density; Penetration resistance
1. Introduction
Soil organic matter greatly in¯uences soil properties and plant nutrition and is an important source or
*
Corresponding author. Tel.: 4618-671259; fax: 4618672795
E-mail address: [email protected] (A. Etana)
1
Present address: University of Conception, Faculty of Agronomy, Department of Soil Science, PO Box 535, ChillaÂn, Chile.
sink for CO2. The soil tillage system (time, depth, type
and intensity of tillage) affects the incorporation of
crop residues and the rate of decomposition of the
organic matter. Mouldboard ploughing is the traditional primary tillage in northwestern Europe. In
Sweden, it is still used on more than 80% of the area
of annual crops, although various forms of reduced
tillage are increasingly used. The ploughing depth is
usually 20±25 cm, but a depth about 30 cm is not
uncommon, particularly on sandy soils.
0167-1987/99/$ ± see front matter # 1999 Elsevier Science B.V. All rights reserved.
PII: S 0 1 6 7 - 1 9 8 7 ( 9 9 ) 0 0 0 6 2 - 8
130
A. Etana et al. / Soil & Tillage Research 52 (1999) 129±139
Tillage depth determines the maximum depth to
which above-ground plant residues are incorporated
into arable soils, and therefore it affects the vertical
distribution of soil organic carbon (SOC) and soil
organic nitrogen (SON). Overwhelming results show
that shallow tillage leads to a concentration of SOC
near the soil surface (e.g., Dick, 1983; Rydberg, 1987;
Comia et al., 1994). Bùrresen and Njùs (1994) and
Riley and Ekeberg (1998) reported that reduced
ploughing depth led to accumulation of SOC near
the surface, but the total amount was unaffected.
As pointed out by Ellert and Bettany (1995), measurement de®ciencies in many earlier studies have
made the determinations of total contents of SOC
and SON uncertain. For accurate quanti®cations,
not only the SOC and SON concentrations in individual layers must be satisfactorily determined, but also
the depth and mass of dry soil in the same layers. A
further requirement is that all these determinations be
made on a continuous pro®le from the soil surface to
the full depth of interest. In most investigations not all
these requirements have been ful®lled. Hence, it is not
well known whether tillage depth affects the total
quantity of SOC and SON in the whole Ap-horizon,
and consequently, the global carbon cycle. Therefore
more investigations are needed under various soil,
cropping and climatic conditions.
The present study was carried out in ®ve existing
long-term trials with annual tillage to different depths.
The trials were located in various parts of Sweden and
were initiated to produce a basis for advising farmers
on optimal depths and methods of primary tillage
under various conditions. The main objective of the
present study was to investigate the effects of tillage
depth on concentration, distribution by depth and total
content of SOC and SON. Some soil physical parameters were also determined.
2. Materials and methods
2.1. Sites and treatments
Five long-term trials with various depths of primary
tillage were selected for the investigation (Table 1).
They represented common soil types in their respective regions. In the original plough layer, the clay
content ranged from 72 to 521 g kgÿ1 and the organic
matter content from 26 to 59 g kgÿ1. No detailed soil
classi®cation was made, but according to a tentative
classi®cation using the FAO system the soils were
Eutric Cambisols except the soil at site 3 that was a
Thionic Fluvisol with a shallow ground water level.
The climate at the experimental sites is cool temperate
and moderately humid with the lowest mean temperature, longest winter and shortest growing season at site
5. Climatic data from the national meteorological
station closest to each of the sites is given in Table 2.
During the experimental period there were differences in treatments between the sites. However, at all
of them shallow (12±15 cm) and deep (24±29 cm)
primary tillage were carried out annually for 15±20
years. These treatments were applied at the traditional
time of autumn ploughing in Swedish agriculture,
which is in late September or October, some weeks
after harvest of the previous crop. Before initiation of
the experiments, all sites had been conventionally
tilled for many years, including annual mouldboard
Table 1
Description of five Swedish sites for long-term studies of shallow and deep annual tillage
Site
1.
2.
3.
4.
5.
Position
(lat.N/long.E)
Kattarp
Lanna
UlfhaÈll
Hamre
RoÈbaÈcksd.
a
b
0
0
56813 /12848
588210 /138070
598210 /178030
608180 /8168000
638480 /208140
Soil texture
Sandy loam
Clay
Clay
Silt loam
Silt loam
Particle size distributiona (g kgÿ1)
5 > 2.
The main reasons were the differences in plot size (the
smallest plots at site 1, the largest at site 2) and the
immediate appearance of differences in SOC and SON
concentrations at sites 1, 4 and 3 as soon as the
experiments were initiated, while at the other sites,
the differences developed gradually.
Differing preconditions made it impossible to
directly use the models or results by Sibbesen and
Andersen (1985) or Sibbesen (1986) to estimate the
magnitude of the net transport. However, by comparison with their results and considering the factors
mentioned above, a rough and somewhat subjective
estimate was made. At site 1, the estimated maximum
gain of SOC in D-plots during the experimental period
was 4 Mg haÿ1 and the maximum loss in S-plots
2 Mg haÿ1. Thus, the estimated maximum net gain
in D-plots relative to S-plots was 6 Mg haÿ1. The
corresponding values for sites 4, 3, 5 and 2 were 5,
3, 1 and