Model application in small agricultural catchments Methods for calculation of leaching from...
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Model application in small Model application in small agricultural catchmentsagricultural catchments
Methods for calculation of leaching from agricultureMethods for calculation of leaching from agricultureandand
Effects of possible changes in agricultural practicesEffects of possible changes in agricultural practices
Katarina KyllmarKatarina Kyllmar
Swedish University of Agricultural SciencesSwedish University of Agricultural SciencesDivision of Water Quality ManagementDivision of Water Quality Management
Examples of factors influencing leaching
Land use Soil types
Crop distribution Fertiliser levels
Simulation of nitrogen leaching fromroot-zone with the SOILNDB model
• Information from each field concerning:– crop, fertiliser/manure application, yield, soil cultivation etc.
for each year
– soil type
• Climate data as daily values
Data requirements
Picture from www.vastra.org
Dynamic simulation of nitrogen leaching on field level with the SOILNDB model
What is produced
• Time series of leaching for each field in the catchment
0
40
80
120
1 2 3 4 5
Year
N (
kg/h
a)
Wheather conditions have large influence on annual leaching
Calculation of nitrogen leaching on field level with coefficients
• Leaching coefficients are calculated with the SOILNDB model
• Information concerning crop husbandry is based on official statistics
• The generated leaching coefficients are normalised for variations in weather between years
• The method is a further development of a method that was used for assessment of nitrogen load from arable land in Sweden
Leaching coefficients
Picture from www.vastra.org
Application of leaching coefficients
• Each field is given a coefficient based on field information
Normal leaching from root-zone on arable land in 1999
Leaching regions
Plain districts in southern Götaland, Skåne
Plain districts in southern Götaland, Halland
Central districts in southern Götaland, Skåne
Central districts in southern Götaland, Blekinge
Data requirements for calculation of leaching coefficients
• International soil classes
Soil types
Cultivation
Climate
• Official agricultural statistics in production areas Crop distribution
Fertiliser and manure as mean amounts for different crops including spreading periods for manure (autumn or spring)
for these crops
Standard yields for different crops• Dates for soil cultivation, sowing and harvesting from practice when
statistics is missing
• Leaching regions based on production areas• Climate data in 20 year periods for each leaching region
Calculation of leaching coefficients
• Crops including applied fertiliser or/and manure are randomly put into climate series (20 years) according to occurrence in statistics
• The random procedure is repeated 3.000 times which results in 60.000 outcomes for each soil type and leaching region
Crop rotations produced by random
Simulation of nitrogen leaching with SOILNDB
• Each climate serie with randomised crop rotations are simulated• Mean values are calculated for each combination of crop and
following crop including fertiliser/manure application for these crops • Some of the crops are put together into crop groups
The produced leaching coefficients are stored in a database
• Leaching region (4)• Soil type (5)• Crop (7)• Crop, following year (5)• Fertiliser/manure application (4)• Fertiliser/manure, following year (4)
Leaching coefficients could be chosen regarding to:
Example of leaching coefficients:
Influence of soil type
0
20
40
60
80
Spring cereals followed by spring-sown crops
Nitr
og
en
leac
hing
(kg
/ha)
Loamy sand
Sandy loam
Loam
Clay loam
Clay
0
20
40
60
80
Winter cereals followed bywinter cereals
Nitr
og
en
lea
chin
g (
kg/h
a) Manure autumn
Manure spring
Manure spring and adjusted fertiliser level
No manure
Example of leaching coefficients:
Effects of manure application
Application of leaching coefficients on nine monitoring catchments in south Sweden
• Calculations of nitrogen load in each catchment
• Basis for follow-up of environmental quality goals
• Scenarios for measurements in agricultural practices to reduce nitrogen leaching
Comparison between coefficient calculated leaching and measurements in stream outlets in
two catchments
0
10
20
30
40
50
Loam Sandy loam
Nitr
ogen
leac
hin
g (
kg/h
a)
Leaching calculated with coefficients
Measurements in stream outlets
Measurements for reducing nitrogen leaching in the catchments
Spreading of manure in spring
Spring sown crops after termination of ley and fallow
Catch crop in spring cereals and spring rape
Catch crop in both winter and spring forms of cereals and rape
Winter cereals replaced by spring cereals and catch crop
Nitrogen leaching was reduced from 34 to 54 % in the catchments
Nitrogen leaching from root-zone (kg/ha)
Changes in nitrogen leaching after measurements in agriculture
Initial leaching levels
After measurements in agriculture
Coefficient method - Conclusions
• Large data basis and time consuming simulations for producing coefficients
• Simple to use the coefficients• Effects on nitrogen leaching of changes in agricultural
practices can easy be calculated• New coefficients to describe effects of e.g. over-doses
of fertiliser and variations in occasion of soil cultivation could be produced with additional simulations