II. ALTERNATIVE ORGANIC MEDIA AMENDMENTS

Table 10.1 Evaluation of Feedstocks for Composts Used in Growing Media for Vegetable

Transplants

Compost



Rate

(% Volume)



Growth Responsez



Factor(s) Affecting

Response



Hardwood bark 50, 80



Cucumber, tomato dry wt. < Immaturity

peat-lite



Biosolids

(BS)-LMy



33, 50



BS-HMy



33, 50



BS



33, 50, 67



BS



33



BS



33



BS



25, 50



BS



25, 50, 75,

100



BS



10



Tomato & cabbage dry wt.

and stem diameter = peatlite

Tomato & cabbage dry wt.

< LM compost & peat-lite

Tomato, pepper, cabbage

dry wt. = peat-lite (33,

50%); pepper dry wt. <

peat-lite (67%)

Broccoli, cabbage,

eggplant, lettuce, pepper,

and tomato dry wt.

increased linearly over 8

week period

Dry wt. of tomato and

lettuce grown in compost:

peat:vermiculite + N

fertilizer = peat-lite; dry wt.

of plants in compost:

peat:perlite < peat-lite

Tomato dry wt. >100%

white peat; shoot radius of

tomato > with 50%

compost than with peat

Germination of tomato

delayed with increased %

compost (one trial) and %

germination < peat-lite.

Shoot and root dry weight

< peat-lite and decreased

with increased % compost

% emergence slightly <

peat-lite, plant height >

peat-lite

% germination Ӎ peat-lite,

germination delayed

slightly in one trial



Municipal solid 25, 50, 75

waste (MSW)



MSW



100



MSW



100



BS/MSW

(2:1 ratio)



25, 50, 75,

100



© 2001 by CRC Press LLC



Reference

Bearce and

Postlethwaite,

1982

Sterrett et al.,

1983



Compost stable,

leached at

transplanting

Heavy metal toxicity Sterrett et al.,

1983

Physical

Sterrett and

characteristics,

Chaney, 1982

media leached at

planting

Compost stable,

Falahileached at planting Ardakani et

al., 1987a



K requirements

Falahisatisfied, in part, by Ardakani et

vermiculite; other

al., 1988

nutrients supplied

by compost

C:N ratio Ӎ 20:1, P Pinamonti et

& K supplied by

al., 1997

compost

High soluble salts

(unleached)



Vavrina, 1994



Dilution of soluble

salts



Vavrina, 1995



Some concern

Vavrina, 1994

about consistency

between batches of

compost

% germination and height of Fertility program

Vavrina, 1995

tomato < peat-lite

needed adjustment

relative to peat-lite

Pepper germination slower Stabilized compost Roe and

than in peat-lite but final % but soluble salts

Kostewicz,

germination of pepper,

high

1992

rape, radish, and dill =

peat-lite

% germination ≤ peat-lite Unknown

Vavrina, 1994

and slightly decreased

with increasing % compost



Table 10.1 Evaluation of Feedstocks for Composts Used in Growing Media for Vegetable

Transplants (Continued)

Compost

BS/MSW (2:1

ratio)



Rate

(% Volume)

100



BS/MSW;x co- 33, 50

compost aged

30 or 90 days

BS/yard

100

trimmings

(YT)

MSW + YT

100



YT + BS



18, 35, 52,

70



YT



100



YT + poultry

100

manure (PM)



YT + grass

clippings



100



BS + YT



100



BS + YT +

mixed waste

paper



50, 100



BS + YT +

refusederived fuel



50, 100



BS + YT +

refusederived fuel

residuals

Spent

mushroom

compost

(SMC)



100



33



© 2001 by CRC Press LLC



Growth Responsez



Factor(s) Affecting

Response



Reference



% germination and height of Inconsistencies in

Vavrina, 1995

tomato varied between

process or

batches of compost but

feedstock

was < peat-lite

Lettuce and cabbage dry

Compost stable,

Purman and

wt. = peat-lite

stored in windrows Gouin, 1992

Radish and dill %

germination < peat-lite



Stabilized compost

but soluble salts

high

Pepper germination slower Stabilized compost

than peat-lite but faster

but soluble salts

than 100% MSW; final % high

germination of pepper,

rape, radish, and dill =

peat-lite

Tomato dry wt., leaf area, C:N ratio = 16.9:1;

and stem diameter > peat- supplemental

lite

nutrients



Roe and

Kostewicz,

1992

Roe and

Kostewicz,

1992



OzoresHampton et

al., 1998a,

1998b

Tomato and watermelon % Stabilized compost Roe and

germination and dry

Kostewicz,

weight > peat-lite

1992

% germination of tomato, Total N and soluble Roe and

watermelon, and lettuce

salts in YT+PM > in Kostewicz,

delayed with YT and 25% YT alone

1992

PM. Plant dry wt. in YT +

25% PM > than in peat-lite

after 4 weeks

% germination of tomato, Increased N

Roe and

watermelon = peat-lite

promoted

Kostewicz,

vegetative growth

1992

Tomato and cucumber %

Increased aeration Roe et al.,

emergence = peat-lite

in peat-lite

1997

Tomato, pepper, cucumber Increased aeration Roe et al.,

% emergence = peat-lite

in peat-lite

1997

(50%); tomato, pepper,

cucumber % emergence <

peat-lite (100%)

Tomato, pepper, cucumber NH4 -N considered Roe et al.,

% emergence = peat-lite

high

1997

(50%); tomato and pepper

% emergence < peat-lite

(100%)

Cucumber % emergence < High soluble salts; Roe et al.,

1997

peat-lite

NH4-N, Zn, Cu

elevated

Tomato height ≥ peat-lite



Fertilizer application Rathier, 1982

to peat-lite at 4

weeks



Table 10.1 Evaluation of Feedstocks for Composts Used in Growing Media for Vegetable

Transplants (Continued)

Compost



Rate

(% Volume)



SMC



25–50



SMC



100



Papermill

sludge



33, 50, 67



Grape

100

branches

fragmented to

3–4 mm

(prunings/

husks/seeds)

Poultry manure 100



z



y



x



Growth Responsez



Factor(s) Affecting

Response



Tomato, lettuce, and

High soluble salts

cucumber height and dry

prior to leaching;

wt. in 25% aged compost NH4 toxicity in fresh

= peat-lite; in 50%

compost

compost and fresh

compost < peat-lite

Tomato germination < peat- Lower H2O holding

lite; plants in SMC more

capacity; organic N

succulent

source interfered

with hardening off

of transplants

Tomato, cucmber, eggplant, Incomplete

and cabbage stunted, off

stabilization, high

color

pH, high soluble

salts

Tomato dry wt., stem

Improved physical

diameter, and height >

properties,

peat:perlite:sand

aeration, and

available P



Inhibition of tomato and

watermelon germination



Excess NH4-N



Reference

Lohr et al.,

1984



Vavrina et al.,

1996



Hornick et al.,

1984



Kostov et al.,

1996



Roe and

Kostewicz,

1992



Compared to peat-lite medium (peat moss and usually vermiculite; may contain perlite and/or

polystyrene). A commercial peat-lite medium was used in most studies, but several commercial

media are represented in these trials.

LM (low metals) = biosolids with concentrations of Zn, Pb, Cd, and Ni meeting EPA Section

503 guidelines; HM (high metals) = biosolids contaminated with Zn, Pb, Cd, and Ni from industrial

sources, exceeding the guidelines.

Garbage ground and separated magnetically and by density to remove metals and glass.



concentrations of zinc (Zn), copper (Cu), manganese (Mn), nickel (Ni), and cadmium

(Cd) in tomato and cabbage (Brassica oleracea L. Capitata group) transplants grown

in media containing compost made with industrially contaminated biosolids compared to those grown in compost from a residential (low metal) source or in peat–

vermiculite (peat-lite). Biosolids that meet the alternative pollution limits (<41

mg·kg–1 arsenic [As], 39 mg·kg–1 Cd, 1500 mg·kg–1 Cu, 300 mg·kg–1 lead [Pb], 17

mg·kg–1 mercury [Hg)], 420 mg·kg–1 Ni, 100 mg·kg–1 selenium [Se], and 2800

mg·kg–1 Zn) can be marketed for general use without cumulative site loadings for

the regulated metals provided pathogen levels in the product are reliably reduced to

nondetectable levels by heat and time (Chaney et al., 1999).

B. Compost Characteristics Affecting Plant Response

The most frequently cited problems with using compost in the growing medium

for vegetable transplants include unstable or immature compost, high soluble salt



© 2001 by CRC Press LLC



concentrations, and poor water-holding capacity (Table 10.1). Because the potential

usefulness of composts as organic amendments to vegetable transplant media is

directly related to consistent, uniform growth, it is important to understand the factors

that may adversely affect plant response.

As defined by Ozores-Hampton et al. (1998a), stability of compost refers to the

degree to which the compost consumes N and oxygen in significant quantities to

support biological activity and generates heat, carbon dioxide, and water vapor, a

process that can cause plant stunting and yellowing of leaves. A desirable C:N ratio

is between 15:1 and 20:1 (Hoitink and Fahy, 1986; Hornick et al., 1984; Inbar et

al., 1990; Ozores-Hampton et al., 1998a; Roe et al., 1997; Rosen et al., 1993).

Compost maturity refers to the absence of phytotoxic substances that can cause

delayed seed germination or seedling and plant death (Ozores-Hampton et al., 1998a).

Numerous studies have described delayed or reduced germination due to the presence

of phytotoxic substances in compost (Chanyasak et al., 1983; Keeling et al., 1994;

Lunt, 1959; Roe and Kostewicz, 1992; Vavrina, 1994; Wong and Chu, 1985; Zucconi

et al., 1981). Lohr et al. (1984) noted that symptoms of ammonium toxicity were

observed in tomato, cucumber (Cucumis sativus L.), and lettuce (Lactuca sativa L.)

grown in fresh spent mushroom compost. Delayed or inconsistent germination greatly

increases transplant production costs and interrupts production schedules.

Variation between sources or between batches of compost from the same source

can result in unpredictable plant response. Vavrina (1995) reported significant differences between compost sources and between batches from the same source in

emergence and height of tomato after 6 weeks of growth. Immaturity of the compost

or differences in composting conditions may have contributed to this response. Gouin

(1993) noted that compost piles that are allowed to become anaerobic produce

compost containing methanol or methane and acetic acid (foul odors) with a corresponding depression in pH (3.0 to 3.5). High levels of acetic acid (6000 to 28,000

mg·kg–1) in immature MSW compost have inhibited germination of several vegetable

crops (Keeling et al., 1994). Wong and Chu (1985) reported increased retardation

of root elongation by aqueous extracts of refuse compost with increasing ammonia

(NH3) and ethylene oxide concentrations. Lunt (1959) reported delayed germination

with addition of municipal wastes to cropland, with the lag period being dose

dependant. Zucconi et al. (1981) noted that toxicity from decomposing organic

matter is temporary; both germination and root elongation are improved with mature

compost over fresh or immature compost.

Storage of the composted, cured product may also affect plant growth. Roe and

Kostewicz (1992) reported a strong NH3 odor from packaged poultry litter compost

in a study comparing media composed of various combinations of yard trimmings,

poultry litter, and grass clippings to a commercial peat-lite meduim in compartmentalized flats (5 cm2 cells). Total germination inhibition of tomato and watermelon

(Citrullus lanatus [Thunb.] Matsum. & Nakai) was reported for all media containing

poultry litter compost. Available N is in the ammonium (NH4) form after initial

composting, with conversion to nitrate occurring over time while stored in static

piles (Vega-Sanchez et al., 1987). Hence, the premature use of immature compost

or packaging of compost (i.e., anaerobic conditions) could disrupt the microbial

activity needed for the conversion of organic N to nitrate or promote reversion to

© 2001 by CRC Press LLC