Monitoring
soil mineral nitrogen concentration
in Germany:
Preliminary results
and some methodical challenges
P. Schweigert* and R.R. van der Ploeg
Institute of Soil Science, University of Hannover,
Hannover, Germany
N surplus of agricultural land
in Germany
140
nitrogen (kg ha-1)
120
100
80
60
40
20
0
1950
1960
1970
1980
time (calendar year)
1990
2000
Consequences of N surplus
• Soil mineral nitrogen increased
Consequences of N surplus
• Soil mineral nitrogen increased
• Nitrate leaching increased
Consequences of N surplus
• Soil mineral nitrogen increased
• Nitrate leaching increased
• Nitrate concentration in groundwater often increased over 50 mg l-1
• Problem for drinking water supliers, because:
50 mg l-1 is the upper limit in drinking water
Consequences of N surplus
• Soil mineral nitrogen increased
• Nitrate leaching increased
• Nitrate concentration in groundwater often increased over 50 mg l-1
• Problem for drinking water supliers, because:
50 mg l-1 is the upper limit in drinking water
80 % of the drinking water comes from groundwater
Measures to reduce nitrate leaching
• Prevention of overfertilization
• Promotion of cover crop cultivation during fall
Result check: Monitoring programs
• In drinking water catchments
• Soil mineral nitrogen (NO3-N) in 0-90 cm depth
• In fall before leaching begins
Result check: Monitoring programs
Baden-Württemberg:
- Since 1987
- First program in Germany
- 60000 samples per year
Trend of soil mineral nitrogen
in Baden-Württemberg
70
60
50
40
30
y = -2.2x + 61.0
2
r = 0.58
20
10
time (calendar year)
2003
2002
2001
2000
1999
1998
1997
1996
1995
1994
1993
1992
1991
1990
1989
1988
0
1987
NO3-N content (kg ha-1)
80
Trend of soil mineral nitrogen
in Baden-Württemberg
70
60
50
40
30
y = -2.2x + 61.0
2
r = 0.58
20
10
time (calendar year)
2003
2002
2001
2000
1999
1998
1997
1996
1995
1994
1993
1992
1991
1990
1989
1988
0
1987
NO3-N content (kg ha-1)
80
Trend of soil mineral nitrogen
in Baden-Württemberg
70
60
50
40
30
y = -2.2x + 61.0
2
r = 0.58
20
10
time (calendar year)
2003
2002
2001
2000
1999
1998
1997
1996
1995
1994
1993
1992
1991
1990
1989
1988
0
1987
NO3-N content (kg ha-1)
80
Preliminary result
- Soil nitrate concentration decreases
- Nitrate leaching probably decreases
Methodical challenges?
Are there still problems, that should be solved?
Are there anyhow methodical challenges?
Trend of soil mineral nitrogen
in Baden-Wuerttemberg
70
60
50
40
30
y = -2.2x + 61.0
2
r = 0.58
20
10
time (calendar year)
2003
2002
2001
2000
1999
1998
1997
1996
1995
1994
1993
1992
1991
1990
1989
1988
0
1987
NO3-N content (kg ha-1)
80
Trend of soil mineral nitrogen
in Baden-Wuerttemberg
70
60
50
40
30
y = -1.3x + 55.6
2
r = 0.19
20
10
time (calendar year)
2003
2002
2001
2000
1999
1998
1997
1996
1995
1994
1993
1992
1991
1990
1989
1988
0
1987
NO3-N-content (kg ha-1)
80
Methodical challenge:
Quantification of the influences of the weather
on the mineral N content of the soils
Result check: Monitoring programs
Liebenau
- Since 1992
- 100 samples per year
Soil mineral nitrogen
in Liebenau
70
60
50
40
y = -1.3x + 58.4
2
r = 0.09
30
20
10
time (calendar year)
2002
2001
2000
1999
1998
1997
1996
1995
1994
1993
0
1992
NO3-N content (kg ha -1)
80
400
70
350
60
300
50
250
NO3-N
40
200
precipitation
30
150
time (calendar year)
2002
2001
2000
1999
1998
0
1997
0
1996
50
1995
10
1994
100
1993
20
precipitation (mm)
80
1992
NO3-N content (kg ha -1)
Soil mineral nitrogen and the
precipitation until sampling date
400
70
350
60
300
50
250
NO3-N
40
200
precipitation
30
150
time (calendar year)
2002
2001
2000
1999
1998
0
1997
0
1996
50
1995
10
1994
100
1993
20
precipitation (mm)
80
1992
NO3-N content (kg ha -1)
Soil mineral nitrogen and the
precipitation until sampling date
400
70
350
60
300
50
250
NO3-N
40
200
precipitation
30
150
time (calendar year)
2002
2001
2000
1999
1998
0
1997
0
1996
50
1995
10
1994
100
1993
20
precipitation (mm)
80
1992
NO3-N content (kg ha -1)
Soil mineral nitrogen and the
precipitation until sampling date
400
70
350
60
300
50
250
NO3-N
40
200
precipitation
30
150
time (calendar year)
2002
2001
2000
1999
1998
0
1997
0
1996
50
1995
10
1994
100
1993
20
precipitation (mm)
80
1992
NO3-N content (kg ha -1)
Soil mineral nitrogen and the
precipitation until sampling date
400
70
350
60
300
50
250
NO3-N
40
200
precipitation
30
150
time (calendar year)
2002
2001
2000
1999
1998
0
1997
0
1996
50
1995
10
1994
100
1993
20
precipitation (mm)
80
1992
NO3-N content (kg ha -1)
Soil mineral nitrogen and the
precipitation until sampling date
Soil mineral nitrogen as a function
of precipitation until sampling date
NO3-N content (kg ha -1)
80
70
60
50
40
30
20
10
0
0
50
100
150
200
precipitation (mm)
250
300
Soil mineral nitrogen as a function
of precipitation until sampling date
NO3-N content (kg ha -1)
80
70
60
50
40
30
y = -0.15x + 66.7
r2 = 0.46
20
10
0
0
50
100
150
200
precipitation (mm)
250
300
Simple regression
with 1 variable
NO3-N = - 0.15 P10 + 66.7
r2 = 0.46*
NO3-N = mean NO3-N fall content of all soils (kg ha-1), 0-90 cm depth
P10
= Precipitation since 1. October, until date of sampling (mm)
NO3-N = - 0.15 P10 + 66.7
r2 = 0.46*
70
60
50
40
30
NO3-N measured
20
NO3-N calculated
10
time (calendar year)
2002
2001
2000
1999
1998
1997
1996
1995
1994
1993
0
1992
NO3-N content (kg ha -1)
80
NO3-N = - 0.15 P10 + 66.7
r2 = 0.46*
70
60
50
40
30
NO3-N measured
20
NO3-N calculated
10
time (calendar year)
2002
2001
2000
1999
1998
1997
1996
1995
1994
1993
0
1992
NO3-N content (kg ha -1)
80
NO3-N = - 0.15 P10 + 66.7
r2 = 0.46*
70
60
50
40
30
NO3-N measured
20
NO3-N calculated
10
time (calendar year)
2002
2001
2000
1999
1998
1997
1996
1995
1994
1993
0
1992
NO3-N content (kg ha -1)
80
Multiple regression
with 2 variables
NO3-N = - 0.20 P10 - 2.8 Y + 86.6 r r2 = 0.86 ***
NO3-N = mean NO3-N fall content of all soils (kg ha-1), 0-90 cm depth
P10
Y
= Precipitation since 1. October, until date of sampling (mm)
= Year (1992 = 0; 1993 = 1; 1994 = 2; etc.), temporal trend
Multiple regression
with 2 variables
NO3-N = - 0.20 P10 - 2.8 Y + 86.6
r2 = 0.86 ***
NO3-N = mean NO3-N fall content of all soils (kg ha-1), 0-90 cm depth
P10
Y
= Precipitation since 1. October, until date of sampling (mm)
= Year (1992 = 0; 1993 = 1; 1994 = 2; etc.), temporal trend
r2 = 0.86 ***
NO3-N = - 0.20 P10 - 2.8 Y + 86.6
70
60
50
40
30
NO3-N measured
20
NO3-N calculated
10
time (calendar year)
2002
2001
2000
1999
1998
1997
1996
1995
1994
1993
0
1992
NO3-N content (kg ha -1)
80
Multiple regression
with 4 variables
NO3-N = - 0.17 P10 - 3.2 Y - 0.08 P9 + 3.1 T10 + 52.3
r2 = 0.97 ***
NO3-N = mean NO3-N fall content of all soils (kg ha-1), 0-90 cm depth
Y
P10
P9
T10
=
=
=
=
Year (1992 = 0; 1993 = 1; 1994 = 2; etc.), temporal trend
Precipitation since 1. October until date of sampling (mm)
Precipitation of September (mm)
Mean air temperature at 2 p.m. in October (° C)
Multiple regression
with 4 variables
NO3-N = - 0.17 P10 - 3.2 Y - 0.08 P9 + 3.1 T10 + 52.3
r2 = 0.97 ***
NO3-N = mean NO3-N fall content of all soils (kg ha-1), 0-90 cm depth
Y
P10
P9
T10
=
=
=
=
Year (1992 = 0; 1993 = 1; 1994 = 2; etc.), temporal trend
Precipitation since 1. October until date of sampling (mm)
Precipitation of September (mm)
Mean air temperature at 2 p.m. in October (° C)
Multiple regression
with 4 variables
NO3-N = - 0.17 P10 - 3.2 Y - 0.08 P9 + 3.1 T10 + 52.3
r2 = 0.97 ***
NO3-N = mean NO3-N fall content of all soils (kg ha-1), 0-90 cm depth
Y
P10
P9
T10
=
=
=
=
Year (1992 = 0; 1993 = 1; 1994 = 2; etc.), temporal trend
Precipitation since 1. October until date of sampling (mm)
Precipitation of September (mm)
Mean air temperature at 2 p.m. in October (° C)
NO3-N = - 0.17 P10 - 3.2 Y - 0.08 P9 + 3.1 T10 + 52.3
r2 = 0.97 ***
70
60
50
NO3-N measured
40
NO3-N calculated
30
20
10
time (calendar year)
2002
2001
2000
1999
1998
1997
1996
1995
1994
1993
0
1992
NO3-N content (kg ha -1)
80
160
140
120
100
80
60
40
20
0
time (calendar year)
2001
2000
1999
1998
1997
1996
1995
1994
1993
1992
1991
1990
1989
y = -9.4x + 18959
r2 = 0.76
1988
NO3 concentration (mg l -1)
Decrease of nitrate in groundwater
Conclusions
Preliminary results:
- Measures
to reduce the nitrate leaching are successful
Conclusions
Methodical challenge:
- Values of soil nitrate are superimposed by atmospheric influences
Conclusions
Methodical challenge:
- Values of soil nitrate are superimposed by atmospheric influences
- Multiple regression models can detect these influences