Carbon sequestration in pasture and forage

systems

A. Moulin, P. McCaughey, D. McCartney, S. Bittman, M. Entz, W.F. Nuttall

• Background

• Objectives

• Methods

• Carbon sequestration in rotations with forages

• Carbon sequestration in fertilized and unfertilized pasture systems

Carbon sequestration in rotations with forages and pastures

• Greenhouse gases: nitrous oxide (N2O), methane (CH4), carbon dioxide (CO2)

• Carbon Sequestration: Carbon stored in the soil as soil organic matter

• Carbon Storage: Carbon stored in the soil as plant debris, roots, and soil organic matter

• One tonne of carbon removes 3.667 tonnes of CO2

Definitions

Carbon Sequestration in forages

• Increases of 5.4 and 9.3 Mg ha-1 in soil organic carbon (SOC) over 27 years for two studies in smooth bromegrass grassland. (Malhi et al. 1997, Nyborg et al 1994,

1998)

• 1.2 to 2.0 Mg C ha-1 yr -1 were stored on soils with poor fertility (Agro.Manger Sept 99 p 7-8)

• 0.2 Mg C ha-1 yr -1 over 20 years for intensive management of grassland. (Bruce et al 1999)

Objective

• To report organic carbon sequestered in pasture systems and rotations with forages.

• Discuss issues related to carbon sequestration in forage systems and pastures

Carbon Sinks

Atmosphere AtmosphereSoil

Management ManagementFertilizerRotationForages

TillageResidue

SinkTap Drain

Annual Cropping Systems

• Comparison of zero and conventional tillage at 200 locations in the Brown, Dark Brown, and Black soils in Saskatchewan

• Approximately 150 sites with a field comparison, 45 replicated studies, 5 detailed studies

Current Estimates of Carbon Sequestration• Published literature for zero vs

conventional tillage indicates 0.2 Mg C ha-1 yr-1 over 15 years for agricultural soils

• Research shows higher levels possible for Black soils over 15 years

Annual Crops (15 years)

Texture No-till vs Conventional

(Mg C ha-1 yr-1)

Continuous crop from

Crop-Fallow

(Mg C ha-1 yr-1)

Coarse (sand) 0.2 0.5-0.6

Medium (loam)

0.3 0.5-0.6

Fine (clay) 0.4 0.5-0.6

Carbon Sinks

Atmosphere AtmosphereSoil

SinkTap Drain

Management ManagementFertilizerRotationForages

Tillage

Forage Studies

• Forages in Rotation

• Melfort, Saskatchewan

• Glenlea, Manitoba

• Pasture Systems

• Pathlow, Saskatchewan

• Brandon, Manitoba

Melfort Rotations• Established in 1957 at Melfort,

Saskatchewan

• Silty clay soil, Thick Black soils

• Fertilized and unfertilized Fallow-Wheat-Wheat-Brome Alfalfa Hay- Brome Alfalfa Hay-Wheat

0

50

100

150

200

250

1970 1978 1982 1986 1994 1970 1978 1982 1986 1994

H6 H6 H6 H6 H6 Hu6 Hu6 Hu6 Hu6 Hu6

Rotation

So

il O

rgan

ic C

arb

on

(M

g h

a-1)

Carbon Sinks

Atmosphere AtmosphereSoil

Management ManagementFertilizerRotationForages

SinkTap Drain

Glenlea Rotations

• Established in 1993 at Glenlea, Manitoba• Clay soil, Thick Black soils• Rotations 1) wheat-pea-wheat-flax (W-P-W-

Fl); 2) wheat (under seeded to sweet clover)-wheat-flax (W.Cl-W-Fl); 3) wheat- alfalfa (two years)-flax (W-Al-Al-Fl); and 4) a restored native tallgrass prairie

• Flax phase was sampled in 1999

0

20

40

60

80

100

120

140

160

180

WPWF WScWF WAAF Native Grass

Flax Phase of Rotation 1999

Org

an

ic C

arb

on

(M

gh

a-1)

Fertilizer

No Fertilizer

Carbon Sinks

Atmosphere AtmosphereSoil

Management ManagementFertilizerRotationForages

SinkTap Drain

Pathlow Pasture

• Established in 1978 at Pathlow, Saskatchewan

• Undifferentiated medium to moderately fine textured soil, Gray soils

• Treatments 0, 45, 90, 180 Kg ha -1 N; 0, 20 kg ha-1 P; 0, 23, 45 kg ha-1 elemental S

• Sampled in 1989 and 1999

0

10

20

30

40

50

60

70

80

0-0-0 45-0-0 90-0-0 4-20-0 45-20-0 90-20-0 180-80-0 90-20-23 90-20-45

Fertilizer Rate (N-P-S) 1989

So

il O

rgan

ic C

arb

on

(M

g h

a-1)

0

2

4

68

10

12

14

16

0-0-0 45-0-0 90-0-0 4-20-0 45-20-0 90-20-0 180-80-0 90-20-23 90-20-45

Fertilizer N-P-S 1999

So

il O

rgan

ic C

arb

on

(M

g h

a-1)

0

5

10

15

20

25

30

0-0-0 45-0-0 90-0-0 4-20-0 45-20-0 90-20-0 180-80-0 90-20-23 90-20-45

Fertilizer Rate (N-P-S) 1999

So

il O

rgan

ic C

arb

on

(M

g h

a-1

)

Carbon Sinks

Atmosphere AtmosphereSoil

Management ManagementFertilizer

SinkTap Drain

Brandon Pasture

• Established in 1994 at Brandon, Manitoba• Fine sandy loam soil, Black soils• Treatments fertilized and unfertilized

bromegrass, fertilized and unfertilized alfalfa and bromegrass

• Fertilizer applied at soil test recommendations

• Sampled in 1999

0102030405060708090

Fertilized Unfertilized Fertilized Unfertilized

Alfalfa-bromegrass

Alfalfa-bromegrass

Bromegrass Bromegrass

Rotation 1999

So

il O

rga

nic

Ca

rbo

n (

Mg

ha-1

)

Carbon Sinks

Atmosphere AtmosphereSoil

Management ManagementFertilizerForages

SinkTap Drain

Carbon Sequestration in forages

• Potential carbon sequestration ranged from 5 to 15 Mg C ha-1, over a period from 15 to 20 years, depending on fertility management of forages in pasture and initial levels of soil organic carbon.