1. Explaining the recent changes in agricultural nutrient load in Finland
Katri Rankinen, Petri Ekholm, Hannu Rita, Heidi Sjöblom, Ljudmila Vesikko

2. Research question Is it possible to estimate quantity development
Petri Ekholm, SYKE
Is it possible to estimate
quantity
development
contributing factors
of agricultural nutrient load based on national river monitoring data?

3. Data National monitoring data from 22 rivers
Petri Ekholm, SYKE
National monitoring data from 22 rivers
Southern and western Finland
⅓ of agricultural land in Finland
Total P, Total N, Flow
Years 1985–2006 divided into 4 periods
I = 1985–1989
II = 1990–1994
III = 1995–1999, 1st Programme period
IV = 2000–2006, 2nd Programme period

4. ”Diffuse-source component”
CTN
(µg l−1)
Approach
Step 1: Estimating daily concentrations, C, from flow, Q
Petri Ekholm, SYKE
”Point-
source
component”
”Diffuse-source component”
”Basic component” Q
(m3 s−1)

5. Approach Step 2: Riverine nutrient fluxes, L
Petri Ekholm, SYKE
Step 3: Source apportionment
Step 4: Explaining spatial differences and temporal changes
Step 5: Analysis of development: flow used for all the periods

6. Factors related to ”agricultural” P load (LP, kg km−2 y−1)
LP = 1.6 × Field-% − 3.6, r2 = 0.57
LP = 1.4 × Field-% − 2.2× Lake-% − 9.0, r2 = 0.70
LP = 1.4 × Field-% + 1.7× Lake-% + 92 × Runoff − 22, r2 = 0.73
Increase in LP : soil-test P, r2 = 0.81
Decrease in LP : fallow, r2 = 0.74
No effect on LP : P in manure
Regional analysis
Southern Finland: Grassland appears to decrease LP
Western Finland: Grassland increases LP
Petri Ekholm, SYKE

7. Regional differences Southern Finland
Petri Ekholm, SYKE
Southern Finland
P losses high and correlate with TSS losses
Western Finland
P losses, and correlation with TSS losses, lower
Soil P decreased from Period III to Period IV

8. Factors related to ”agricultural” N load (kg km−2 y−1)
LN = 16 × Field-% −20 × Lake-% × Runoff, r2 = 0.87
Increase in LN : N in manure, r2 = 0.88, fields on organic soils , r2 = 0.88
No effect on LN : N deposition
Regional analysis
Western Finland: Grassland, soil temperature, N balance increases LN
Petri Ekholm, SYKE

9. Change in ”agricultural” load 1985–2006
Phosphorus
Nitrogen
The Kalajoki
The Perhonjoki
No change
Western Finland
No change
No data
Southern Finland
No data

10. Change in ”agricultural” load 1985–2006 (2011)
The Kalajoki
3658 km2 Lakes 1.9%
Fields 15%

11. Conclusions Approach Allows the use of national monitoring data
Approach
Allows the use of national monitoring data
Gives a several-year average load for a larger area
Relatively robust, if sampling strategy remains unchanged, sensitive to outliers
Cannot separate agricultural load from natural background
”Agricultural” load
P load decreased (especially in Ostrobothnia), N load increased in 2000s
P: fertilizer use and animal numbers decreased
N: increase in temperature, clearing of new field, manure handling?
The analysis is currently being expanded in the project
Larger number of sites
Larger set of explaining variables
Petri Ekholm, SYKE