L. Bergstrom - Plant Nutrition Group

plantnutrition.ethz.ch

L. Bergstrom - Plant Nutrition Group

SOIL AS AN IMPORTANT INTERFACE

BEWEEN HUMAN ACTIVITIES AND

GROUND WATER - SOIL FUNCTIONS

IN THE VADOSE ZONE

Lars Bergström

Swedish University of Agricultural

Sciences


Topics to be covered:

• Sources (N)

• Transport pathways (P)

• Availability (pesticides)


N sources …


Leaching and plant uptake of fertilizer/ manure

derived N (kg/ha) during 2- to 3-year3

periods

(from Bergström and Kirchmann, , 1999; 2004)

60

50

40

30

20

Plant uptake

Leaching

10

0

AmNi

Poultry

manure

Red clover

manure


Supply the crop with N when it

is needed

Spring Summer Autumn Winter

Plant/Soil

Sophie Gunnarsson, Håkan Marstorp

Dept of Soil Science, SLU


P transport pathways …


Cumulative P leaching (g/ha) from a

sand and a clay soil (Djodjic

et al.,

1999)

4500

4000

3500

3000

2500

2000

1500

1000

500

0

Clay soil

n=5

Sand soil

n=3

0 5 10 15 20 25 30

Time (days)


Effect of macropore flow

on solute movement

through soils (Bergström &

Shirmohammadi, 1999)

Mellby sand

Lanna clay


Pesticide availability …


Effect of soil structure on ndegradation

of 2,4-D (Bergström & Stenström, 1995)


Herbicide leaching in sand and clay

soils (Bergström et al., 2001)

25

Pesticide conc (µg/L)

20

15

10

5

0

Clay

Sand

0 50 100 150 200 250 300 350

Days after application


Increasing awareness and

development of counter

measures have improved

the situation …


Nitrate-N concentrations in groundwater

at 1.7-m depth during the period 1977-

1999 (from Johansson et al., 2000)

25

20

NO3-N mgl -1

15

10

5

0

1977

1979

1981

1983

1985

1987

1989

1991

1993

1995

1997

1999


Conclusions:

• Leaching of nutrients and pesticides from

agricultural soils is in most cases a manageble

environmental problem.

• Macropore flow has a major impact on solute

movement in clay soils.

• The availability of organic chemicals to

microorganisms in soil will determine their

persistence.

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