Today’s knowledgeToday’s knowledgeand potential for future research P ti f N-Perspectives from Norway

Anne Falk ØgaardAnne Falk ØgaardMarianne Bechmann

Svein SkøienBioforsk Jord og miljø

Eutrophic lake in a complex agricultural landscape

- How do we reduce P loads to the lake most efficiently?y

P loss processes

Source Transport Sink

........................................

..

After Sharpley et al. 2001

Soil erosion – the main focus in Norwayy

Maps of erosion risk -derived from soil maps

S il i ff t f d d ilSoil erosion – effect of reduced soiltillage

Results from lysimeter experiments

Effect of red ced tillage in a t mn on soil lossEffect of reduced tillage in autumn on soil loss

Middel årlig jordtap 1992-2000 for 5 forsøksfelter

500

600

700

Høstpløying

Ikke pløying

Clay soils on all sites

Slope 10-13%

300

400

500

Knowledge gaps:- Effect of reduced tillage on

0

100

200

gareas with low erosion risk

- Effect of reduced tillage on subsurface runoff0

Bjørnebekk Askim Hellerud Øsaker Syverud

Jordtap kg/daa

subsurface runoff

Helge Lundekvam

Tillage winter wheatPlot 2:Harrowing before seedinggSS-kons: 1110 mg/l

Plot 3:Di t d illiDirect drillingSS-kons: 5 mg/l

Pl t 42 3 4 Plot 4:Ploughing before seedingSS-kons: 5820 mg/l

2 3 4

Surface runoff 16.09.04 - 05.10.04

ErosionErosion risk at different tillagerisk at different tillage

Autumn ploughing 1,00

Autumn harrowing 0,50

Spring ploughing (No autumn tillage) 0,14

Grass 0,05

From plot scale to catchment scale

Mørdre catchment (JOVA catchment): • Increased area with no autumn tillage from 1990 to 2009 Increased area with no autumn tillage from 1990 to 2009

• But still increased particle and phosphorus concentration in the stream

• Climate change increased runoff

500300SS TP Avrenning

300350400450500

200

250

300

g (m

m)

TP (g

/daa

)100150200250

50

100

150

Avre

nnin

g

S (k

g/da

a), T

050

0

91/9

292

/93

93/9

494

/95

95/9

696

/97

97/9

898

/99

99/0

000

/01

01/0

202

/03

03/0

404

/05

05/0

606

/07

07/0

808

/09

SS

C ti itConnectivity

Sedimentation of eroded soilbefore it reaches watercourses?

Distance to watercourses and landscape shapesp p

Improved soil structure reduced erosion riskImproved soil structure reduced erosion risk

Average yearly soil and P loss in surface runoff

Soil aggregate

Suspendedsolids

Phosphorus

Average yearly soil and P loss in surface runoff

aggregatestability

solidskg/ha kg/ha

AskimSlope 13%Clay 29%

Low 2990 3,4

SyverudSyverudSlope 13%Clay 23%

High 131 0,39

H. Lundekvam

Erosion in streams

Algal availability of P in subsoil? Algal availability of P in subsoil?

Soil and P losses also through tile drainsSoil and P losses also through tile drains

Kværnø og Bechmann (2010)

P fertilization and soil P status P fertilization and soil P status

1200

800

1000/L

)P-AL 24

400

600

800

otal

P (µ

g

200

400To

P-AL 7

00 100 200 300 400

Suspended solids (mg/L)

Marianne Bechmann

p ( g )

Particle bound P not always particle bound

12

Clay soil, Ås

12

Sandy soil, Råde

6

8

10

12

(mg/10

0g)

P‐AL 3,5

P‐AL 4,9

P‐AL 8,7

P‐AL 13 6

8

10

12

(mg/10

0 g)

P‐AL 6,3

P‐AL 9,2

P‐AL 24

P‐AL 38

0

2

4

0 200 400 600 800

CaCl2‐P 

0

2

4

0 200 400 600 800

CaCl2‐P 

0 200 400 600 800

solution:soil

0 200 400 600 800

solution:soil

Critical soil test P value for P loss?

20

Silty clay loam

10

15

aCl2

(mg

P/kg

)

0

5

0 10 20 30 40

P-C

a

Tore Krogstad

P-AL (mg/100g)

Particle bound P available for algae?Particle bound P available for algae?

Biotests (Krogstad & Løvstad, 1991):( g , )

• 20-70 % of total P in cultivated soilpotential available for blue green algae; potential available for blue-green algae; dependent of the part of inorganic P

• Organic P was not readily available for algae

Chemical test (Krogstad & Løvstad, 1991):

• Total Reactive P (TRP) in soil suspensionsotal eact ve ( ) so l suspe s o s≈ P available to blue-green algae

Algal available P related to P-AL

Algal available P (TRP) as a function of P-AL

600

g)

400

500

TRP

(mg/

kg

200

300

0 50 100 150 200 250 3000

100TRP = 1.63 PTRP = 1.63 P--AL + 89.6AL + 89.6

RR22 = 0.73= 0.73

P-AL (mg/kg)

Tore Krogstad

P distribution on particle-size fractionsp

• Particles <20 µm would stay suspended long enough to be a t ti l f P t lpotential source of P to algae (Huettl et al. 1979)

• Increasing P concentration with decreasing particle size

Sandy soil Clay soilP‐AL 23,5 P‐AL 28mg P/kg mg P/kgmg P/kg mg P/kg

Whole soil 800 1600

< 20 µm 4400 1800< 20 µm 4400 1800

< 2 µm 7100 3800

Rikard Pedersen 2008

• A large part of excess P fertilization is found in the clayfraction (Øgaard 1996)

Reduced P fertilization in the catchment of western Vansjø

kg P/ha g

2004 2007 2008 2009

Average for 75 % of the fields 22 11 5,8 4,4 of the fields

Effects of reduced P fertilization on P runoff?

TP/SS relationship in streams

Small constructed wetlands for P retention

Effect of constructed wetlands

Braskerud (2001):• Retention of soil particles: • Retention of soil particles:

45 -75%

• Retention of total P: 21 – 44%

• Retention of dissolved P: Low

Tore KrogstadTore Krogstad

Maintenance of constructed wetlands importantMaintenance of constructed wetlands important

mm

)

n (%

)

renn

ing

(m

g re

tens

jon

AvÅrli

g

TP SS Avrenning (mm)

Filtralite P® filter at the end of constructed wetlands

Fil li P (0 5 4 ) E d d l i h li• Filtralite P (0,5-4 mm): Expanded clay aggregates with lime

• Cost of Filtralite P: 65-90 € per m3

WetlandWetland

Filter

Outlet

P retention in the filter -ft t bli h tone year after establishment

350

200

250

300P/l

50

100

150TP µg 

Before filter

After filter

0

50

Data from E. Hougsrud 2009

But: Only 0.2 l/s through the filter

R i d h t i ti f Required characteristics for filters for agricultural runoff

• High hydraulic conductivity

• High adsorption capacity and short reaction time

• Flocculation of clay particles

G d b ff Grassed buffer zones

• Where are grassed buffer zones efficient?

- topography- soil type

soil tillage- soil tillage

• If the grass is not cut; release f di l d P d i of dissolved P during

winter/spring

Grassed buffer zones

100100 Grorudnson

e

8090

100

Mørdre8090

100

Mørdre

geta

sjon

506070

S506070

Snet i

veg

20304050 Sum m e r

W inte r

20304050 Sum m e r

W inte r

SS fj

ern

01020

01020

TP o

g S

TP -5m

TP -10m

S S -5m

SS -10 m

SS -5m

TP -5 m

TP -5m

TP -10m

S S -5m

SS -10 m

SS -5m

TP -5 m N. Syversen%

Release of P from different plant species after winter frost

Ongoing research:

18-42% av total P released last winter, d d ldepending on plant species

Application of manure

Injection techniques for li ti i fl manure application – influence

on risk for P losses?

Identify high-risk areas – Calculator for P-indexhttp://webgis.no/pindeks

P runoff from forests?P runoff from forests?

Thank you for the attention!