VI. USING COMPOST PRODUCTS BENEFICIALLY IN NURSERY CROP PRODUCTION

in begonia (Begonia X tuberhybrida Voss) at five rates (0.5, 1, 1.5, 2, and 2.5 kg·m–2).

Gouin and Walker (1977) reported greater stem length in tulip poplar (Liriodendron

tulipifera L.) and dogwood (Cornus florida L.), and significantly less winter dieback

in tulip poplar, when planting beds were treated with three rates (2.5, 5, and 10 cm

thickness) of compost made from one part digested biosolids and three parts wood

chips compared to unamended beds. Gouin (1977), in a separate study, reported

similar or reduced growth of Norway spruce [Picea abies (L.) Karst] and white pine

(Pinus strobus L.) in planting beds treated with compost of the same type and at the

same rates as in Gouin and Walker (1977) compared to a control topdressed with a

slow-release fertilizer and mulched with aged sawdust. Table 6.1 provides a summary

of these published reports.

Table 6.1 Response of Ornamental Crops to Compost Products Used in Field

Nursery Production

Crop



Compost

Typez



Gloxinia



MSW



Begonia



MSW



Tulip poplar



B/WC



Dogwood



B/WC



Norway spruce



B/WC



White pine



B/WC



z

y



Rate

1, 2, 3, 4, and

5 kg·m–2

1, 2, 3, 4, and

5 kg·m–2

2.5, 5, and 10

cm thickness

2.5, 5, and 10

cm thickness

2.5, 5, and 10

cm thickness

2.5, 5, and 10

cm thickness



Growth

Responsey



Reference



+



DeGroot, 1956



+



DeGroot, 1956



+



Gouin and Walker,

1977

Gouin and Walker,

1977

Gouin, 1977



+

=, –

=



Gouin, 1977



MSW = municipal solid waste compost; B/WC = biosolids/wood chip co-compost.

+, –, = represent: positive, negative, or neutral, respectively (usually relative to a control).



B. Container Production

One of the earliest reports on container production of ornamentals with compost,

describing research conducted between 1948 and 1954, was published in Belgium

in 1956 (DeGroot, 1956). In a series of research studies, DeGroot found that MSW

compost (“compost de ville”) would not support growth in azaleas (Azalea indica

L.), if the compost rate was greater than 10% of the rooting medium. DeGroot

indicated that elevated pH levels in the compost product probably were responsible

for the growth inhibition. In the same series of experiments, favorable results were

observed with begonia when grown in mixes containing 30% MSW compost. He

reported reduced growth (“moyenne” or “mediocre”) in begonia when compost

concentrations were higher than 40%. In a much larger report published 5 years

later, DeGroot (1961) observed favorable results in growing 74 species of ornamental

plants and unfavorable results in 6 species, when the growing medium contained 25

to 35% compost. Numerous studies published subsequently by many other authors

have elaborated on compost use in containerized ornamental plant production, and



© 2001 by CRC Press LLC



also advised against using too high a concentration of compost product in the

growing medium blend.

1. Temperate Woody Ornamentals

In a study of three species of woody ornamentals, Sanderson and Martin (1974)

reported enhanced growth in Chinese holly (Ilex cornuta Lindl. & Paxt.) and white

cedar when grown in media containing 33% MSW compost, relative to an untreated

control. They reported that viburnum (Viburnum X burkwoodii Hort. Burkw. &

Skipw.), when grown in the 33% MSW compost rate, did not differ significantly in

growth from plants grown in the control medium. Working with a different species

of viburnum, V. suspensum Lindl., Fitzpatrick and Verkade (1991) reported that

plants grown in both 40% and 100% MSW compost grew at rates that were not

significantly different than the control. They speculated that certain plant species,

like viburnum, may be physiologically ambivalent to the composition of the growing

medium and may be able to adapt to a wide range of rooting conditions.

The issue of effects of compost rate in the growing medium is clearly illustrated

in a recent study of four species of temperate woody ornamentals (Raymond et al.,

1998). In this study, all four species (deutzia, Deutzia gracilis L.; silverleaf dogwood,

Cornus alba L. ‘Elegantissima’; red-osier dogwood, C. sericea L.; and ninebark,

Physocarpus opulifolius [L.] Maxim.) grew at rates significantly higher than the

controls when the growing medium contained 25% waxed corrugated cardboard

(WCC) compost. When tested in media containing 50% WCC compost, only the

silverleaf dogwood grew at rates higher than the control; deutzia and red-osier

dogwood grew at rates comparable to the control and ninebark grew at rates significantly lower than the control. The authors characterized the WCC compost as

immature; it is therefore possible that some of the growth suppression observed in

some species may have been due to the ephemeral phytotoxicity associated with

immature compost products. Research findings of compost efficacy on selected

species of temperate woody ornamentals are summarized in Table 6.2.

2. Subtropical and Tropical Ornamentals

In a study of three subtropical ornamental species (jasmine, Jasminum volubile

Jacq.; ligustrum, Ligustrum japonicum Thunb. var. rotundifolium Blume; and dwarf

oleander, Nerium oleander L.), Fitzpatrick (1981) reported enhanced growth in

ligustrum and dwarf oleander and no difference in growth of jasmine when grown

in a mix consisting of 80% biosolids compost, compared to the control. In a different

study, dwarf oleander grown in 100% MSW compost and 100% paper mill sludge

compost grew at rates that were significantly greater than the control (Fitzpatrick,

1989). This suggests that dwarf oleander may be a particularly responsive species

to even slight differences in the rooting environment, quite the opposite of ambivalent

species like viburnum. In the same study, Fitzpatrick (1989) reported that growth

of orange-jessamine (Murraya paniculata [L.] Jack) in 100% MSW compost and

100% paper mill sludge compost was not significantly different than the control.

The composts used in this study were well aged, so there would be little concern

© 2001 by CRC Press LLC



Table 6.2 Response of Temperate Woody Ornamental Crops to Compost Products

in the Rooting Substrate



Crop



Compost

Typez



Compost in

Rooting

Medium (%)



Growth

Responsey



Chinese holly



MSW



33



+



White cedar



MSW



33



+



Burkwood viburnum



MSW



33



=



Viburnum suspensum



MSW



40, 100



=



Silverleaf dogwood



WCC



25



+



Silverleaf dogwood



WCC



50



+



Red-osier dogwood



WCC



25



+



Red-osier dogwood



WCC



50



=



Deutzia



WCC



25



+



Deutzia



WCC



50



=



Ninebark



WCC



25



+



Ninebark



WCC



50



–



z

y



Reference

Sanderson and

Martin, 1974

Sanderson and

Martin, 1974

Sanderson and

Martin, 1974

Fitzpatrick and

Verkade, 1991

Raymond et al.,

1998

Raymond et al.,

1998

Raymond et al.,

1998

Raymond et al.,

1998

Raymond et al.,

1998

Raymond et al.,

1998

Raymond et al.,

1998

Raymond et al.,

1998



MSW = municipal solid waste compost; WCC = waxed corrugated cardboard compost.

+, –, = represent positive, negative, or neutral, respectively (usually relative to a control).



about possible phytotoxicity attributable to compost immaturity. In a study of the

interactive effects of sewage effluent irrigation and growing media consisting of 80%

biosolids compost and 20% sifted incinerator ash, Fitzpatrick (1985) reported growth

rates in four species of tropical trees (West Indian mahogany, Swietenia mahagoni

[L.] Jacq.; pink tabebuia, Tabebuia pallia [Lindl.] Miers; pigeon-plum, Cocoloba

diversifolia Jacq.; and key lime, Citrus aurantiifolia [Christm.] Swingle) were comparable to the control, while one species (schefflera, Brassaia actinophylla Endl.),

grew faster in the control than in the compost-incinerator ash-effluent treatment.

Table 6.3 provides a summary of reports on compost efficacy on selected subtropical

and tropical ornamental species.

3. Floriculture and Foliage Crops

Poole (1969) reported reduced rooting for cordatum (Philodendron scandens C.

Koch & H. Sello. subsp. oxycardium [Schott] Bunt.) and golden pothos (Scindapsus

aureus [Linden & Andre´] Engl.) when a 100% MSW compost was used as a rooting

medium, compared to 3 commercial rooting media. Both the pH and soluble salt

levels of the compost were significantly elevated compared to levels in the three



© 2001 by CRC Press LLC



Table 6.3 Response of Subtropical and Tropical Ornamental Crops to Compost

Products in the Rooting Substrate



Crop

Jasmine

Ligustrum

Dwarf oleander

Dwarf oleander

Dwarf oleander

Orange-jessamine

Orange-jessamine

West Indian mahogany

Pink tabebuia

Pigeon-plum

Key lime

Schefflera

z



y



Compost

Typez

B

B

B

MSW

PM

MSW

PM

B

B

B

B

B



Compost in

Rooting

Medium (%)



Growth

Responsey



80

80

80

100

100

100

100

80

80

80

80

80



=

+

+

+

+

=

=

=

=

=

=

+



Reference

Fitzpatrick,

Fitzpatrick,

Fitzpatrick,

Fitzpatrick,

Fitzpatrick,

Fitzpatrick,

Fitzpatrick,

Fitzpatrick,

Fitzpatrick,

Fitzpatrick,

Fitzpatrick,

Fitzpatrick,



1981

1981

1981

1989

1989

1989

1989

1985

1985

1985

1985

1985



B = biosolids compost; MSW = municipal solid waste compost compost; PM = paper mill

sludge compost.

+, –, = represent positive, negative, or neutral, respectively (usually relative to a control).



control media. Fitzpatrick (1986) reported that two foliage plant species (dwarf

schefflera and ‘Mauna Loa’ spathiphyllum) grew faster in two different types of

biosolids compost used as 100% of the growing medium, as compared to plants

grown in a control medium. One of the composts was made from biosolids that had

been treated with ferric chloride and lime prior to composting. The second compost

was made from biosolids that had not been so treated. Although both compost

products, which had been aged for ca. 10 months prior to being used as growing

media, produced larger plants than the control, the compost made from the chemically treated biosolids produced smaller plants than the compost made from the

untreated biosolids. Chrysanthemum (Chrysanthemum X morifolium Ramat. ‘Yellow

Delaware’ and ‘Oregon’) exhibited a general increase in number of flowers per pot

and a decrease in time required for flowering as the concentration of MSW compost

in the growing medium was increased up to and including 100% compost as the

complete medium (Conover and Joiner, 1966). Gogue and Sanderson (1975) reported

marginal leaf injury in C. X morifolium grown in MSW compost, and having found

elevated levels of B in both the compost and plant tissue, suggested B toxicity as

an explanation for this observation. Shanks and Gouin (1984) observed that chrysanthemums grew well in a wide range of media types but did particularly well in

media containing vermiculite, whether or not compost was present in the mix. Pansy

(Viola tricolor L. ‘Super Swiss Mix’), and snapdragon (Antirrhinum majus L. ‘Floral

Carpet Red’) exhibited enhanced growth in media amended with biosolids compost,

as compared to the control medium. Both species had greater fresh weight as compost

rate was increased up to 50% of the medium concentration, and snapdragon had

more flower buds than the control when grown at the 50% compost rate (Hemphill

et al., 1984). Wootton et al. (1981) reported enhanced growth in marigold (Tagetes

erecta L. ‘Golden Jubilee’), zinnia (Zinnia elegans Jacq. ‘Fire Cracker’), and petunia



© 2001 by CRC Press LLC



(Petunia hybrida Hort. ‘Sugar Plum’) grown in biosolids compost that had been

screened through a 2.38 mm sieve (No. 8 sieve). They reported no significant medium

compaction for the 2 to 3 month period needed to produce annuals and observed no

phytotoxicity symptoms.

Although most reported studies on floricultural uses of compost examined just

one type of compost, Klock and Fitzpatrick (1997) reported on the effects of three

different composts: biosolids–yard trash (SYT), refuse-derived fuel residuals–biosolids–yard trash (RYT), and MSW used as growing media for impatiens (Impatiens

wallerana Hook. ‘Accent Red’). Examining compost rates up to and including 100%

of the growing medium, the authors reported that shoot dry mass of plants grown

in SYT compost increased as the percentage of compost in the medium increased,

while mass of plants grown in MSW compost decreased as percentage of compost

in the medium increased. There were no significant differences in plant mass attributable to rate of RYT compost in the growing medium. Comparable results in average

number of flowers per plant and plant size were also reported. Reasons for the

disparity between these compost types included (1) higher levels of soluble salts in

the MSW compost compared to the other two, and (2) less maturity in the MSW

compost, with a C:N ratio of 29, as compared to C:N ratio of 17 for the SYT compost

and 15 for the RYT compost. Composts with a C:N ratio <20 are generally considered

mature (Jimenez and Garcia, 1989). Floriculture and foliage crop findings are summarized in Table 6.4.



VII. THE FUTURE OF COMPOST USE IN ORNAMENTAL

PLANT PRODUCTION

Over the last several decades, numerous authors have made predictions about

the future of compost utilization in horticultural crop production. There is a wide

diversity of opinion on this subject, but certain threads of commonality are apparent,

such as the belief that there is great potential for increased use of compost. Some

of the predictions for the great potential of compost are several decades old, so it

is certainly appropriate to consider why there has not been greater exploitation of

compost products by nursery crop growers and other horticultural producers.

One of the major barriers to greater utilization of compost products is the

economic instability of the composting industry. Many commercial compost producers have made major changes in the specific types and amounts of products they

have manufactured, such as changing the types of organic materials they compost,

the mix ratios of feedstocks, various preprocessing procedures, active composting

periods, and postprocessing procedures. In many cases, such management decisions

were made for valid business reasons, but with little regard to the influence such

changes could have on the efficacy of the compost product. Moreover, numerous

composting companies have gone out of business during the past decade or two.

Growers who have tried compost products and decided to continue using them have

often been unable to acquire the same product, or even something close to the same

product from the manufacturer, because of changes in the compost product’s physical



© 2001 by CRC Press LLC



Table 6.4 Response of Floriculture and Foliage Crops to Compost Products in the

Rooting Substrate



Crop

Cordatum

Golden pothos

Dwarf schefflera

‘Mauna Loa’

spathiphyllum

Chrysanthemum

(2 cultivars)

Chrysanthemum



Compost

Typez



Compost in

Rooting

Medium (%)



Growth

Responsey



MSW

MSW

B

B



100

100

100

100



–

–

+

+



Poole, 1969

Poole, 1969

Fitzpatrick, 1986

Fitzpatrick, 1986



MSW



100



+



MSW



100



–



B



50



+



B



50



+



Conover and Joiner,

1966

Gogue and

Sanderson, 1975

Hemphill et al.,

1984

Hemphill et al.,

1984

Wootton et al., 1981



‘Super Swiss Mix’

pansy

‘Floral Carpet Red’

snapdragon

‘Golden Jubilee’

marigold

‘Fire Cracker’ zinnia

‘Sugar Plum’ petunia

‘Accent Red’ impatiens



B



100



+



B

B

B/YT



100

100

100



+

+

+



‘Accent Red’ impatiens



R/YT



100



=



‘Accent Red’ impatiens



MSW



100



–



z



y



Reference



Wootton et al., 1981

Wootton et al., 1981

Klock and

Fitzpatrick, 1997

Klock and

Fitzpatrick, 1997

Klock and

Fitzpatrick, 1997



MSW = municipal solid waste compost; B = biosolids compost; B/YT = biosolids/yard

trimmings co-compost; R/YT = refuse-derived fuel residuals/biosolids/yard trimmings cocompost.

+, –, = represent positive, negative, or neutral, respectively (usually relative to a control).



and chemical parameters or because the manufacturer was no longer in the composting business.

There are relatively few published studies that illustrate how changes in feedstock

composition or process parameters can influence efficacy of the compost product.

Some studies (Fitzpatrick, 1986; Fitzpatrick, 1989; Fitzpatrick and Carter, 1983;

Fitzpatrick et al., 1993; Klock and Fitzpatrick, 1997) have provided insight on how

compost product quality may be influenced by the feedstocks from which the

compost is made, the ways these materials are processed prior to composting, the

amount of time these materials are allowed to compost, and the ways these materials

are processed after composting. These and other studies clearly showed that such

factors can cause major changes (such as pH and soluble salt elevation, introduction

of phytotoxic materials, and other perturbations) in the compost product’s ability to

provide a suitable rooting environment for nursery crops.

The U.S. Composting Council, recognizing the need for greater standardization

of testing and characterization procedures for composting and compost products,

has developed the publication Test Methods for the Examination of Composting and

Compost (Leege and Thompson, 1997). This document, although currently in draft



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