Danish Institute of Agricultural Sciences Department of Agroecology Research Centre Foulum
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Danish Institute of Agricultural SciencesDepartment of Agroecology
Research Centre Foulum
Denitrification in the root zone
Finn P. Vinther,Danish Institute of Agricultural Sciences,Department of Agroecology,Research Centre Foulum
N2 N2O N2N2O N2 N2O N2
N2O
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NO3 N2O N2
Denitrification
(nitrate) (nitrous oxide) (atmospheric nitrogen)
In the field:
Acetylene
In the lab:
Measuring denitrification
NO3 N2O N2
Denitrification
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• Resource demanding and difficult to measure
• Modelling often the only possibility
Measuring or modelling?
• Simple model for estimation of N2O emission and denitrification – SimDen…..
which only needs information about• amount and type of added nitrogen • clay content of the soil
• Most models, however, often needs more input information than what is available
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Denitrification = N2O * (N2/N2O) Denitrification = N2O * (N2/N2O)
Fertilizer N2O emission
Background N2O emission
Total N2O emission = Background N2O emission + EF1.25 * N-input
Inorganic N: EF0.8
Organic N: EF2.5
Principles of SimDen:
Input, kg N ha-10100200300400500N2O
-em
issi
on, k
g N
ha-1
-20246810y = 0.0125x + 1
Bouwman, 1996
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WFPS* < 60% N2/N2O-ratio 0 - 3
60% < WFPS < 80% N2/N2O-ratio 3 - 5
WFPS > 80% N2/N2O-ratio 5 - 10* Water filled pore space
Literature values (app. 500):
Avg. N2/N2O-ratio: app. 3
Principles of SimDen:
Denitrification = N2O * (N2/N2O)
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Water filled pore space (WFPS)
Soil texture (clay content)
Denitrification
SimDen
Principles of SimDen:
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Input of nitrogen kg N ha-1
Inorganic fertiliser 1 1 Amount of N added with inorganic fertiliser2 Amount of total-N added with manure or slurry
Animal manure/slurry N - surface applied and incorporated 2 3 Is calculated separately in the sheet: "N in urine and faeces"
Animal manure/slurry N - directly injected 2 4 For N2 fixation give total N fixed, i.e. both above and
below ground N (stolons, roots, etc.)
Pastures - N deposited during grazing 0 3
- N2 fixation by clover in grass-clover 4
- N2 fixation by other leguminous crops 4
Results:N2O emission
Proportion of (kg N/ha/year)
Clay content in the profile: Depth % clay denitrification min mean max
10 (80%) 1.1 1.3 1.5
10 (10%) 0.1 0.2 0.2
10 (5%) 0.1 0.1 0.1
10 (5%) 0.1 0.1 0.1
(100%) 1.4 1.6 1.90 - 100 cm
50 - 75 cm
75 - 100 cm
0 - 25 cm
25 - 50 cm
Amount of N added with inorganic fertiliser
Amount of total-N added with manure or slurry
Is calculated separately in the sheet: "N in urine and faeces"
For N2 fixation give total N fixed, i.e. both above and
Denitrification
(kg N/ha/year)min mean max
5.0 6.6 8.3
0.6 0.8 1.0
0.3 0.4 0.5
0.3 0.4 0.5
6.3 8.2 10.4
Example 1: Background denitrification
How to use SimDen
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Input of nitrogen kg N ha-1
Inorganic fertiliser 150 1 1 Amount of N added with inorganic fertiliser2 Amount of total-N added with manure or slurry
Animal manure/slurry N - surface applied and incorporated 2 3 Is calculated separately in the sheet: "N in urine and faeces"
Animal manure/slurry N - directly injected 2 4 For N2 fixation give total N fixed, i.e. both above and
below ground N (stolons, roots, etc.)
Pastures - N deposited during grazing 0 3
- N2 fixation by clover in grass-clover 4
- N2 fixation by other leguminous crops 4
Results:N2O emission
Proportion of (kg N/ha/year)
Clay content in the profile: Depth % clay denitrification min mean max
10 (80%) 2.1 2.3 2.5
10 (10%) 0.3 0.3 0.3
10 (5%) 0.1 0.1 0.2
10 (5%) 0.1 0.1 0.2
(100%) 2.6 2.8 3.10 - 100 cm
50 - 75 cm
75 - 100 cm
0 - 25 cm
25 - 50 cm
Amount of N added with inorganic fertiliser
Amount of total-N added with manure or slurry
Is calculated separately in the sheet: "N in urine and faeces"
For N2 fixation give total N fixed, i.e. both above and
Denitrification
(kg N/ha/year)min mean max
9.4 11.4 13.6
1.2 1.4 1.7
0.6 0.7 0.9
0.6 0.7 0.9
11.7 14.3 17.1
How to use SimDen
Example 2: Background + fertilizer denitrification
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Input of nitrogen kg N ha-1
Inorganic fertiliser 150 1 1 Amount of N added with inorganic fertiliser2 Amount of total-N added with manure or slurry
Animal manure/slurry N - surface applied and incorporated 2 3 Is calculated separately in the sheet: "N in urine and faeces"
Animal manure/slurry N - directly injected 2 4 For N2 fixation give total N fixed, i.e. both above and
below ground N (stolons, roots, etc.)
Pastures - N deposited during grazing 0 3
- N2 fixation by clover in grass-clover 4
- N2 fixation by other leguminous crops 4
Results:N2O emission
Proportion of (kg N/ha/year)
Clay content in the profile: Depth % clay denitrification min mean max
20 (80%) 2.5 2.7 2.9
15 (10%) 0.3 0.3 0.3
10 (5%) 0.1 0.1 0.2
10 (5%) 0.1 0.1 0.2
(100%) 3.1 3.3 3.60 - 100 cm
50 - 75 cm
75 - 100 cm
0 - 25 cm
25 - 50 cm
Amount of N added with inorganic fertiliser
Amount of total-N added with manure or slurry
Is calculated separately in the sheet: "N in urine and faeces"
For N2 fixation give total N fixed, i.e. both above and
Denitrification
(kg N/ha/year)min mean max
14.6 17.1 19.9
1.5 1.8 2.2
0.6 0.7 0.9
0.6 0.7 0.9
17.3 20.4 23.7
How to use SimDen
Example 3: Background + fertilizer denitrification at higher clay content
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Measured values, kg N/ha/year
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Danish studies
How does SimDen perform
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Measured values, kg N/ha/year
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How does SimDen perform
Other studiesSpain (Vallejo et al., 2004)Canada (Paul & Zebarth, 1997)
Sweden (Dahlin et al., 2005)The Netherlands (Zwart et al., 2004)
Period % clay depth N-inputfull year 10 0-20 298full year 20 0-21 327Apr-Oct 3 0-11 250Apr-Oct 3 0-11 400Apr-Oct 3 0-11 250Apr-Oct 3 0-11 400Apr-Oct 23 0-11 250Apr-Oct 23 0-11 400
March-June 45 0-11 160March-June 25 0-11 260March-June 25 0-11 260March-June 25 0-11 30 tons
Jan-May 20-30 0-30 67 tonsJan-May 20-30 0-30 67 tonsJan-May 20-30 0-30 0
March-Oct 20 0-15 250March-Oct 20 0-15 600
Aug (17 days) 20 0-15 25 tonsApr-Oct 23 0-11 250Apr-Oct 23 0-11 400Apr-Oct 22+peat 0-11 93Apr-Oct 22+peat 0-11 193full year 35 0-40 0full year 35 0-40 365full year 35 0-40 365full year 35 0-40 0full year 35 0-40 242
Jarvis et al. (1994) 14 days 18 0-10 50Apr-June 15 0-20 0Apr-June 15 0-20 300
Corré (1995) May-Jan 28 0-120 220
Corré (1996)
De Klein et al (1994)
Velthof et al. (1997)
De Klein et al (1996)
Corré (1990)
De Klein et al (1994)
Koops et al. (1996)
Postma & Loon (1996)
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How does SimDen perform
Other studies
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Measured denitrification, kg N/ha
Est
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ith S
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kg N
/ha
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Measured denitrification, kg N/ha
Est
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/ha
How does SimDen perform
Other studies
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Regional mapping, as for example as shown here, where SimDen has been implemented into ”CT-tools”, ConTerra ApS, which use databases with information about soil types, fertiliser use, etc.
How can SimDen be used?
Herning
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• SimDen is based on average values, and the deni-trification is calculated for a climatically ‘normal’ year, or an average denitrification over years.
• If more detailed estimates about the annual variation of the denitrification is wanted, dynamic models as for example Daisy must be used.
• Wish you good luck and thank you for your attention!
• SimDen can be downloaded fromwww.agrsci.dk/simden
Ending remarks