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