Vermicompost as a substitute for peat in potting media:
Effects on germination, biomass allocation, yields and
fruit quality of three tomato varieties
Johann G. Zaller
Institute of Organic Agriculture, University of Bonn, Germany
Received 8 March 2006; received in revised form 10 November 2006; accepted 6 December 2006
Commercial potting media often contain substantial amounts of peat that was mined from endangered bog and fen ecosystems. The main
objectives of this study were to assess (1) whether the amendment of 0, 20, 40, 60, 80 and 100% (v/v) of vermicompost (VC) to a fertilized
commercial peat potting substrate has effects on the emergence, growth and biomass allocation of tomato seedlings (Lycopersicon esculentum
Mill.) under greenhouse conditions, (2) whether possible impacts on seedlings can affect tomato yields and fruit quality even when transplanted
into equally fertilized ﬁeld soil, and (3) whether effects are consistent among different tomato varieties. Amended VC was produced in a windrow
system of food and cotton waste mainly by earthworms Eisenia fetida Sav. Vermicompost amendments signiﬁcantly inﬂuenced, speciﬁcally for
each tomato variety, emergence and elongation of seedlings. Biomass allocation (root:shoot ratio) was affected by VC amendments for two
varieties in seedling stage and one ﬁeld-grown tomato variety. Marketable and total yields of ﬁeld tomatoes were not affected by VC amendments
used for seedling husbandry. However, morphological (circumference, dry matter content, peel ﬁrmness) and chemical fruit parameters (contents
of C, N, P, K, Ca, Mg,
-ascorbic acid, glucose, fructose) were signiﬁcantly affected by VC amendments in seedling substrates; these effects again
were speciﬁc for each tomato variety. Overall, vermicompost could be an environmentally friendly substitute for peat in potting media with similar
or beneﬁcial effects on seedling performance and fruit quality. However, at least for tomatoes, variety-speciﬁc responses should be considered
when giving recommendations on the optimum proportion of vermicompost amendment to horticultural potting substrate.
# 2006 Elsevier B.V. All rights reserved.
Keywords: Soilless substrate; Peat moss replacement; Seedling husbandry; Earthworms; Solid organic wastes; Vermicompost
Sphagnum peat moss is used extensively as a soilless potting
substrate in horticulture because of its desirable physical
characteristics and high nutrient exchange capacity (Raviv
et al., 1986). However, in recent years there has been increasing
environmental and ecological concerns against the use of peat
because its harvest is destroying endangered wetland ecosys-
tems worldwide (Barkham, 1993; Buckland, 1993; Robertson,
1993). Several studies revealed that peat can be substituted by
various compost types without any negative effects on a variety
of crops raised in these substrates (e.g., Inbar et al., 1986;
Bugbee and Frink, 1989; Beeson, 1996; Eklind et al., 2001;
Hashemimajd et al., 2004).
Vermicompost, in contrast to conventional compost is the
product of an accelerated biooxydation of organic matter by the
use of high densities of earthworm populations without passing a
thermophilic stage (Domı
nguez et al., 1997; Subler et al., 1998).
Research has shown that different earthworm species are able to
consume a wide range of organic residues such as sewage sludge
(Mitchell et al., 1980; Domı
nguez et al., 2000), animal wastes
(Edwards et al., 1985; Chan and Grifﬁths, 1988; Wilson and
Carlile, 1989; Atiyeh et al., 2000b), crop residues (Mba, 1996;
Shanthi et al., 1993; Orozco et al., 1996) and industrial wastes
(Albanell et al., 1988; Kaushik and Garg, 2003; Maboeta and van
Rensburg, 2003).These earthworm-processed organic wastes are
ﬁnely divided peat-like materials with high porosity, aeration,
drainage, and water-holding capacity (Edwards and Burrows,
1988). Compared to conventional compost which passes a
thermophilic stage, vermicompost usually has a much ﬁner
Scientia Horticulturae 112 (2007) 191–199
* Present address: Institute of Zoology, Department of Integrative Biology
and Biodiversity Research, University of Natural Resources and Applied Life
Sciences Vienna, Gregor Mendel Strasse 33, A-1180 Vienna, Germany.
Tel.: +43 1 47654 3205; fax: +43 1 47654 3203.
E-mail address: firstname.lastname@example.org.
0304-4238/$ – see front matter # 2006 Elsevier B.V. All rights reserved.