CompostingCompostingNREM 461

D G B l dDr. Greg Bruland

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I. CompostingA. Def.

1. creation of humuslike OM outside of soil by mixing, piling, or storing OM under conditions conducive of aerobic decomp & nutrient cons.

B.Other traits

1. Periods of high temps not found in soils

C.Finished product = compost

1. used as

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D. Vermicomposting: process in which litter dwelling (epigeic) earthworms added to help transform OM

1. Piles kept shallow-why?

2. Composting worms: Eisenia fetida, E. andrei, Lumbricus rubellus, p g , , ,Perionyx excavatus, Eudrilus eugeniae

3. Earthworkers: Lumbricus terrestris

Lumbricus rubellusEisenia fetida

3Lumbricus terrestris

Main Types of Worms

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E. Composting Process

1 3 St f d1. 3 Stages of decomp.

Mesophilic: brief, sugars rapidly metabolized, temp. ↑

Thermophilic: next few weeks/months, decomp. of cellulose & more resistant OM, temp. ↑

Curing: weeks months temp ↓Curing: weeks-months, temp. ↓

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F. Requirements:

1 C diti f bl f i bi l th S h ?1. Conditions favorable for microbial growth. Such as?

2. To destroy pathogens need to reach 71oC (160oF) for >1 hour

3. Materials not good for compost?

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4. If OM deficient in nutrients, can be added

a. N, P, & lime

5. Often need to mix high C/N OM (leaves, straw, paper) w/ low C/N OM (grass clippings, legume hay, blood meal, sewage sludge, manure) to get proper C/N

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G. Finished product

1. C/N of OM ↓ until it reaches 10:1 – 20:1

2. 50-75% of C lost, mineral nutrients gen. conserved

3. Gen. have < 2%

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Pros & Cons of Composting

Pros Cons

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Case Study: OM Amendment Experiment

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(Bruland et al., 2009)

Study Site in Charles City County, Virginia

Virginia

N

Virginia

Dry BlockWet Block

N

3.5m*4m=14m2

Dry BlockWet Block1

5

3 2 4 5

2 5 3 130 m 5

4

1324

215313 m

5

3

2344

1425

To VA Highway 5 and James

2

1

3 1 4 2

3 4 4 51: 0 Mg ha-1

2: 56 Mg ha-1

Compost Amendment Level

30 m 51324

30 m

52344

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and James River3: 112 Mg ha-1

4: 224 Mg ha-1

5: 336 Mg ha-1

Grind All IncCBI Grinder

Grind All, Inc.Rockville, VA

Compost

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Amendment Hypotheses

(1) Denitrification will increase with increasing levels of compost amendmentsamendments

(2) P sorption will decrease with increasing levels of compost amendments

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Amendment load effects vegetative growth

0 Mg compost.ha-1 336 Mg compost.ha-1112 Mg compost.ha-1

Betula nigra (river birch)

16Soil %C = 1.4, C/N = 17 Compost %C = 35, C/N = 38

y = ‐0.0007x + 7.13R² = 0.85

7.2

7.4

y = 1 07e-0.003x1.01.21.4

m-3

)A. B.

dd c

b

y = -0.0003x + 6.93R² = 0 13

6.6

6.8

7.0y 1.07e

R² = 0.92

y = 1.03e-0.004x

R² = 0.970.20.40.60.8

BD

(g. c

m

pH

cc

c

b bb

bc abc

ab

abc

ababcab

ab

abba

R 0.136.4

y = 0.25x + 213.52R² = 0.54

240

300

360

0.0

C. c

m-3

)

C. c

m-3

)

C. D.

cd

dd

ab

cbcbc

y = 0.35x + 57.14R² = 0.93

150180210

W tt

Drier

y = 0.27x + 145.24R² = 0.86

0

60

120

180

0

MB

C (μ

g C

SOC

(μg

C

aba

bc

ab

bcdbc

bcd abab

a

a

ab

ab

ab bc

y = 0.39x + 61.66R² = 0.83

0306090

120 Wetter

y = -0.01x2 + 2.88x + 477.13R² = 0.49

700800900

1000

0

O. c

m-3

. hr-1

)

100c

m-3

)E. F.

c

b

d

0

y = -0.002x + 1.60R² = 0.87

1 82.22.63.0

y = -0.01x2 + 3.39x + 369.13R² = 0.91

200300400500600

DEA

(ng

N2O

PSI (

mM

Ps.

aba

abcabc

abcbc

abab

ab

c

cd

bccbc

bcab ab

aby = -0.004x + 2.08R² = 0.92

0.20.61.01.41.8

000 60 120 180 240 300 360

Loading Rate (Mg.ha-1) Loading Rate (Mg.ha-1)

D 0.20 60 120 180 240 300 360

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50 110336

Loading Rate

050-110

Organic Amendments

(+): Plant growth, BD, MBC, DEA*

(-): pH, PSI

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