BIOMASS

Biomass measurements are useful in studying:

1 The flow of energy through the soil population.

2 The flow of material through the soil population.

3 The storage of C, N, P, and S in an active pool.

Defined as the living part of the soil organic matter,excluding roots and soil animals larger than 5 x 10 um .-3 3

TECHNIQUES FOR MEASURINGMICROBIAL BIOMASS

TECHNIQUES FOR MEASURINGMICROBIAL BIOMASS

Direct Microscopy

Analysis of Specific BiomassContituents ( ATP )

Chemical Techniques (CHCl )

Initial Respiration Rate

Direct Microscopy

Analysis of Specific BiomassContituents ( ATP )

Chemical Techniques (CHCl )

Initial Respiration Rate

3

2CO

REQUIREMENTS OF BIOMASS CONSTITUENTCHOSEN AS AN INDEX OF MICROBIAL BIOMASSREQUIREMENTS OF BIOMASS CONSTITUENTCHOSEN AS AN INDEX OF MICROBIAL BIOMASS

Be present in all parts of biomass atknown concentration.

Be present only in living cells.

Be extracted quantitatively from soils

Be accurately and precisely measured byanalytical techniques.

Be present in all parts of biomass atknown concentration.

Be present only in living cells.

Be extracted quantitatively from soils

Be accurately and precisely measured byanalytical techniques.

3Effect of CHCl fumigation, with and without inoculation, on O consumption

by soil. ( Source: Jenkinson and Powlson, 1976a )

Effect of CHCl fumigation, with and without inoculation, on O consumption

by soil. ( Source: Jenkinson and Powlson, 1976a )2

5

50

100

100

150

INCUBATION ( DAYS )INCUBATION ( DAYS )

Untreated

Treated( Chloroform inoculated )( Chloroform inoculated )

Treated( Chloroform not inoculated )( Chloroform not inoculated )O

XY

GE

NC

ON

SU

ME

D

(m

g100g

SO

IL)

OX

YG

EN

CO

NS

UM

ED

(m

g100g

SO

IL)

-1

ASSUMPTIONS MADE IN CALCULATINGBIOMASS FROM CO FLUSH

ASSUMPTIONS MADE IN CALCULATINGBIOMASS FROM CO FLUSH2

C in dead organisms is mineralizedto CO faster than C in living organisms.C in dead organisms is mineralizedto CO faster than C in living organisms.

Kill is essentially complete.Kill is essentially complete.

Biomass dying in untreated soil is negligiblecompared to treated soil.Biomass dying in untreated soil is negligiblecompared to treated soil.

The fraction of the killed biomass C mineralizedis the same for different soils ( K is constant ).The fraction of the killed biomass C mineralizedis the same for different soils ( K is constant ).

Fumigation has no effect on soils other thankilling microorganisms.Fumigation has no effect on soils other thankilling microorganisms.

2

c

Estimates of Soil Microbial Biomass by Different MethodsEstimates of Soil Microbial Biomass by Different Methods

SoilNo.SoilNo.

Use and Location of Soil,or Experimental TreatmentUse and Location of Soil,or Experimental Treatment

1

2

3

4

5

6

7

8

1

2

3

4

5

6

7

8

FromChloroformFumagation

FromChloroformFumagation

FromDirectCounts

FromDirectCounts

FromATP

Content

FromATP

Content

Continuous wheat, receiving farm-yard manure annually, EnglandContinuous wheat, receiving farm-yard manure annually, England

Continuous wheat, no manure,EnglandContinuous wheat, no manure,England

Calcareous deciduous woodland,EnglandCalcareous deciduous woodland,England

Acid deciduous woodland, EnglandAcid deciduous woodland, England

Secondary rainforest, Nigeria

Arable cropping, Nigeria

Parent Material, with clay, low P

Parent material with clay, high P

Secondary rainforest, Nigeria

Arable cropping, Nigeria

Parent Material, with clay, low P

Parent material with clay, high P

560

220

1230

50

540

280

250

190

560

220

1230

50

540

280

250

190

650

220

1820

390

510

310

190

190

650

220

1820

390

510

310

190

190

430

170

1040

470

---

---

180

240

430

170

1040

470

---

---

180

240

a

b

b

b

b

b

b

c

c

a

b

c

a

b

c

cUsing K = 0.45Using K = 0.45

Assuming that the biomass has a specific gravity of 1.1 and contains 25%dry matter, of which 47% is C.Assuming that the biomass has a specific gravity of 1.1 and contains 25%dry matter, of which 47% is C.

Using a biomass C / ATP ratio of 250.Using a biomass C / ATP ratio of 250.

Biomass ( g C g soil )Biomass ( g C g soil )u-1

Total Organic C and Biomass C in Various SoilsTotal Organic C and Biomass C in Various Soils

Organic C Biomass C Biomass COrganic C Biomass C Biomass C

* Using k = 0.45* Using k = 0.45c

SamplingDepth

SamplingDepth

(cm ) ( tonnes ha ) ( kg ha ) (as % total organic C )(cm ) ( tonnes ha ) ( kg ha ) (as % total organic C )

*-1 -1

SoilNo.SoilNo. Location Land UseLocation Land Use

1

2

3

4

5

6

1

2

3

4

5

6

England

England

England

Nigeria

Nigeria

Nigeria

England

England

England

Nigeria

Nigeria

Nigeria

Arable

Deciduouswoodland

Permanentgrassland

Secondaryrain forest

Bush regrowth

Bush regrowthcultivated tomaize 2 yr

Arable

Deciduouswoodland

Permanentgrassland

Secondaryrain forest

Bush regrowth

Bush regrowthcultivated tomaize 2 yr

0 - 23

0 - 23

0 - 23

0 -15

0 -17

0 - 16

0 - 23

0 - 23

0 - 23

0 -15

0 -17

0 - 16

29

65

70

19

27

22

29

65

70

19

27

22

660

2180

2240

760

700

370

660

2180

2240

760

700

370

2.2

3.4

3.2

4.0

2.6

1.7

2.2

3.4

3.2

4.0

2.6

1.7

Microbial Biomass in an Unmanured Soil under Continuous WheatMicrobial Biomass in an Unmanured Soil under Continuous Wheat

Weight of soil

Organic matter in soil

N in soil

Annual input of organic matter

Gross turnover time of soil organic C

Radiocarbon age of soil organic C

(1944 sample)

Microbial biomass from biovolume

Microbial biomass from flush

Microbial biomass from flush

Turnover time of biomass

Maximal value for specific maintenance rate

N in biomass

Flux of N through biomass

P in biomass

Flux of P through biomass

Weight of soil

Organic matter in soil

N in soil

Annual input of organic matter

Gross turnover time of soil organic C

Radiocarbon age of soil organic C

(1944 sample)

Microbial biomass from biovolume

Microbial biomass from flush

Microbial biomass from flush

Turnover time of biomass

Maximal value for specific maintenance rate

N in biomass

Flux of N through biomass

P in biomass

Flux of P through biomass

tonnes ha

tonnes C ha

tonnes N ha

tonnes C ha yr

yrs

yrs

tonnes ha

tonnes C ha

tonnes N ha

tonnes C ha yr

yrs

yrsa

-1

-1

-1 -1

-1

-1 -1

-1

-1

-1 -1

a

b

b

b

c

c

c

d

d

d

e

f

g

Broadbalk plot 03, from Rothamsted, sampled to a depth of 23 cm.All results are on an oven-dry basis.Jenkinson and Powlson (1976b).Jenkinson and Rayner (1977).Jenkinson et al. (1976)Assuming a C/N ratio of 6 for the microbial biomass.N in biomass turnover time of biomass C.Assuming a C/P ratio of 50.

Broadbalk plot 03, from Rothamsted, sampled to a depth of 23 cm.All results are on an oven-dry basis.Jenkinson and Powlson (1976b).Jenkinson and Rayner (1977).Jenkinson et al. (1976)Assuming a C/N ratio of 6 for the microbial biomass.N in biomass turnover time of biomass C.Assuming a C/P ratio of 50.

b

c

d

e

f

g

b

c

d

e

f

g

a

..

-1

-1

-1

ug C g

ug C g

kg C ha

yrs

yr

kg N ha

kg N ha yr

kg P ha

kg P ha yr

ug C g

ug C g

kg C ha

yrs

yr

kg N ha

kg N ha yr

kg P ha

kg P ha yr

2200

26

2.70

1.20

22

1310

2200

26

2.70

1.20

22

1310

220

220

570

2.50

0.21

95

38

11

5

220

220

570

2.50

0.21

95

38

11

5

So

ilM

icro

bia

lB

iom

ass

Tu

rno

ver

an

dY

earl

yE

nerg

yR

eq

uir

em

en

tsS

oil

Mic

rob

ialB

iom

ass

Tu

rno

ver

an

dY

earl

yE

nerg

yR

eq

uir

em

en

ts

Tro

pic

al

fore

st

Tro

pic

al

fore

st

Tem

pera

tefo

rest

Tem

pera

tefo

rest

Tem

pera

teg

rassla

nd

Tem

pera

teg

rassla

nd

Tu

nd

raS

avan

na

Main

ten

an

ce

en

erg

yre

qu

irem

en

t,G

tyr

C NMain

ten

an

ce

en

erg

yre

qu

irem

en

t,G

tyr

C NMic

rob

ialb

iom

ass

turn

over,

years

C N NMic

rob

ial

bio

mass

turn

over,

years

C N N

Bo

real

fore

st

Bo

real

fore

st

0.1

4

0.1

3

0.0

6

0.1

4

0.1

3

0.0

6

7.5

0.6

7.5

0.6

8.5

0.7

8.5

0.7

2.6

0.2

2.6

0.2

5.5

0.4

5.5

0.4

11.9

0.9

11.9

0.9

1.0

0.1

1.0

0.1

0.6

0

1.0

0

0.4

4

0.6

0

1.0

0

0.4

4

0.2

8

0.2

1

0.0

9

0.2

8

0.2

1

0.0

9

0.3

4

0.7

2

0.3

2

0.3

4

0.7

2

0.3

2

0.6

4

2.8

8

1.2

7

0.6

4

2.8

8

1.2

7

0.5

4

0.5

0

0.2

2

0.5

4

0.5

0

0.2

2

a a

-1

b bB

ased

on

60%

yie

ldo

fb

iom

ass

per

un

ito

flitt

er

C.

Based

on

mic

rob

ialN

thro

ug

ho

ut

of

2.3

tim

es

pla

nt

Nu

pta

ke.

Based

on

60%

yie

ldo

fb

iom

ass

per

un

ito

flitt

er

C.

Based

on

mic

rob

ial

Nth

rou

gh

ou

to

f2.3

tim

es

pla

nt

Nu

pta

ke.

Co

mp

ari

so

no

fG

lob

alP

oo

lM

ag

nit

ud

es

an

dY

earl

yN

utr

ien

tU

pta

ke

of

C,

N,

P,

an

dS

by

Pla

nt

Bio

mass

Co

mp

ari

so

no

fG

lob

alP

oo

lM

ag

nit

ud

es

an

dY

earl

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utr

ien

tU

pta

ke

of

C,

N,

P,

an

dS

by

Pla

nt

Bio

mass

CN

PS

(G

t)

(G

t)

(G

t)

(G

t)

CN

PS

(G

t)

(G

t)

(G

t)

(G

t)

Pla

nt

bio

mass

Yearl

yu

pta

ke

Mic

rob

ialb

iom

ass

Pla

nt

bio

mass

Yearl

yu

pta

ke

Mic

rob

ialb

iom

ass

786

13

1.8

1.4

60

1.2

0.2

0.1

6.0

0.9

0.7

0.2

786

13

1.8

1.4

60

1.2

0.2

0.1

6.0

0.9

0.7

0.2

Soil - Carbon

Acetate - Carbon

Soil - Organic Nitrogen (unlabeled)

Mineral - Nitrogen

Primary Pop’N &Extracellular Prod.

Conceptual model of carbon and nitrogen transferthrough various microbial and soil components.

Secondary Pop’N &Extracellular Prod.

2CO

C

C N

N

2CO

2CO 2CO 2CO

2CO

CONCEPTS OF RELATIONSHIPSCONCEPTS OF RELATIONSHIPS

MICROBIAL GROWTH

COEVOLUTION

COEVOLUTION

C AND NTURNOVERC AND N

TURNOVER2

1. Two biochemically separate populations develop sequentially.

2. The primary population acts as the sink for any added carbon.

3. The secondary population utilizes microbial metabolites andsoil organic, but not added C.

1. Two biochemically separate populations develop sequentially.

2. The primary population acts as the sink for any added carbon.

3. The secondary population utilizes microbial metabolites andsoil organic, but not added C.

4. All populations are assumed to undergo some cryptic growth.

5. The quantity of C and N entering a given population is afunction of the biomass originally present in that soil.

4. All populations are assumed to undergo some cryptic growth.

5. The quantity of C and N entering a given population is afunction of the biomass originally present in that soil.

6. The quantity of C or N released is dependent on the amountpresent in the population and its rate of turnover.

7. Organic N turnover is strictly dependent on C turnover.

6. The quantity of C or N released is dependent on the amountpresent in the population and its rate of turnover.

7. Organic N turnover is strictly dependent on C turnover.

8. Maximum microbial activity after addition of C occursapproximately after 10 days.

8. Maximum microbial activity after addition of C occursapproximately after 10 days.