Effect of soil type and vermicompost applications on tomato growth

Abstract

Background Vermicomposts (VC) improve plant growth and development beyond that normally observed from just soil nutrient transformation and availability. These increases in plant productivity have been attributed to improved soil structure and soil microbial populations that have higher levels of activity and greater production of biological metabolites, such as plant growth regulators. Although there have been many studies on the benefits of VC as a fertilizer source, little research has focused on the effects and/or interactions of soil type and VC application rates on vegetable crop productivity. This paper identifies optimum application rate(s) of VC on tomato growth responses for three different textural classes of soils (loamy sand, silt loam, and silty clay). Results Soils with high VC rates (0.4 and 0.8 g/g) produced taller plants with more leaf and flower numbers, higher leaf chlorophyll content, greater plant biomass, and more total leaf area compared to soils with low VC rates (0.05, 0.1, and 0.2 g/g). Tomato growth increases were also observed at the low VC soil amendment rates compared to the nontreated control. Tomatoes grown in the sandy soil amended with VC generally had the greatest growth responses (plant height, leaf and flower number, and leaf chlorophyll content) compared to the clay or silt loam soils, with the silt loam soil generally providing the least response. Conclusions This research indicated that VC is a suitable alternative fertilizer for tomato, with approximately 0.5-0.6 g/g VC added to soil resulting in optimal tomato plant growth. Moreover, this rate provided tomato growth results similar to the standard inorganic fertility program. The sandy soil with VC amendments generally increased tomato plant growth parameters the most compared to the clay and loam soils, with the loam soil generally providing the least.

Full text

ORIGINAL RESEARCH
Effect of soil type and vermicompost applications on tomato
growth
Marc A. Zucco
1
•S. Alan Walters
2
•She-Kong Chong
2
•Brian P. Klubek
2
•
Joseph G. Masabni
3
Received: 25 March 2014 / Accepted: 8 April 2015 / Published online: 18 April 2015
ÓThe Author(s) 2015. This article is published with open access at Springerlink.com
Abstract
Background Vermicomposts (VC) improve plant growth
and development beyond that normally observed from just
soil nutrient transformation and availability. These in-
creases in plant productivity have been attributed to im-
proved soil structure and soil microbial populations that
have higher levels of activity and greater production of
biological metabolites, such as plant growth regulators.
Although there have been many studies on the benefits of
VC as a fertilizer source, little research has focused on the
effects and/or interactions of soil type and VC application
rates on vegetable crop productivity. This paper identifies
optimum application rate(s) of VC on tomato growth re-
sponses for three different textural classes of soils (loamy
sand, silt loam, and silty clay).
Results Soils with high VC rates (0.4 and 0.8 g/g) pro-
duced taller plants with more leaf and flower numbers,
higher leaf chlorophyll content, greater plant biomass, and
more total leaf area compared to soils with low VC rates
(0.05, 0.1, and 0.2 g/g). Tomato growth increases were also
observed at the low VC soil amendment rates compared to
the nontreated control. Tomatoes grown in the sandy soil
amended with VC generally had the greatest growth re-
sponses (plant height, leaf and flower number, and leaf
chlorophyll content) compared to the clay or silt loam soils,
with the silt loam soil generally providing the least
response.
Conclusions This research indicated that VC is a suitable
alternative fertilizer for tomato, with approximately
0.5–0.6 g/g VC added to soil resulting in optimal tomato
plant growth. Moreover, this rate provided tomato growth
results similar to the standard inorganic fertility program.
The sandy soil with VC amendments generally increased
tomato plant growth parameters the most compared to the
clay and loam soils, with the loam soil generally providing
the least.
Keywords Earthworms Organic wastes Recycling 
Solanum lycopersicon
Introduction
Vermicomposts (VC) are finely divided, peat-like materials
with high porosity, aeration, drainage, water-holding ca-
pacity, and microbial activity (Edwards 2004; Pandya et al.
2014). These composts result from a non-thermophilic
biodegradation and stabilization of organic materials
through interactions of earthworms and microorganisms
(Edwards 2004; Arancon et al. 2003; Agnieszka et al.
&Joseph G. Masabni
jmasabni@ag.tamu.edu
Marc A. Zucco
m_zucco@yahoo.com
S. Alan Walters
awalters@siu.edu
She-Kong Chong
skchong@siu.edu
Brian P. Klubek
bklubek@siu.edu
1
USDA, Natural Resources Conservation Service, Grayling,
MI 49738, USA
2
Department of Plant, Soil, and Agricultural Systems,
Southern Illinois University, MC 4415, 1205 Lincoln Dr.,
Carbondale, IL 62901, USA
3
Department of Horticultural Sciences, Texas A&M
University, 2134 TAMU, College Station, TX 77843-2134,
USA
123
Int J Recycl Org Waste Agricult (2015) 4:135–141
DOI 10.1007/s40093-015-0093-3

2013). A wide range of organic residues, including sewage
sludge, animal wastes, crop residues, and industrial refuse
are increasingly being converted by earthworms to form
VC (Edwards 2004; Roberts et al. 2007; Pascal et al. 2010).
The earthworms breakdown the organic residues, which
stimulate greater microbial activity, increase nutrient
mineralization rates, and rapidly convert the wastes into a
humus-like substance that has a finer structure than ordi-
nary composts while possessing greater and more diverse
microbial populations (Atiyeh et al. 2000; Yadav and Garg
2011).
Various types of composts, including VC, are often used
in sustainable farming systems to improve soil physical
properties, provide plant nutrients, and recycle organic
wastes. Vermicomposts have been shown to increase plant
growth and crop yields in managed and natural ecosystems
(Edwards 2004; Arancon et al. 2003; Gutie
´rrez-Miceli
et al. 2007; Pascal et al. 2010). Organic wastes converted to
VC have beneficial effects on plant growth and develop-
ment that are unrelated to increases observed only from soil
nutrient transformation and availability. Vermicomposts
improve seed germination, seedling vigor, and plant pro-
ductivity more than what would have been possible from
inorganic mineral nutrient sources, while using as little as
10–40 % of the total plant rooting volume (Subler et al.
1998; Gopalakrishnan et al. 2012; Alsina et al. 2013).
These increases in plant productivity have been attributed
to improved soil structure and soil microbial populations
with higher levels of activity and greater production of
biological metabolites, such as plant growth regulators
(Pascual et al. 1997; Canellas et al. 2002; Atiyeh et al.
2002; Roberts et al. 2007).
Although there have been many studies relating to the
benefits of using VC as a fertilizer source (Arancon et al.
2003,2004a,b; Alsina et al. 2013), little research has fo-
cused on the effects and/or interactions of soil type and VC
applications on vegetable crop productivity. Therefore, the
objective of this research was to identify the optimum
application rate(s) of VC on tomato growth responses for
three different textural classes of soils (loamy sand, silt
loam, and silty clay).
Methods
A study was conducted at the Southern Illinois University
Horticulture Research Center Greenhouse in Carbondale,
Illinois, USA to determine the effects and/or interactions of
soil type and VC applications on tomato growth. The ex-
periment was a 3 97 factorial in a randomized complete
block design with four replications and was repeated twice
in the greenhouse. Three different textural classes of soils
(sandy, loamy, and clayey) were amended with seven VC
treatments: (1) untreated control (0 g/g VC), (2) standard
fertilizer treatment (SFT) with 0 g/g VC and 2 g per pot of
an inorganic 12-12-12 fertilizer [N–P–K; nitrogen, phos-
phorus from P
2
O
5
, potassium from K
2
O]; (3) 0.05 g/g VC;
(4) 0.1 g/g VC; (5) 0.2 g/g VC; (6) 0.4 g/g VC; and (7)
0.8 g/g VC. The VC was obtained from New Horizon
Organics (Jerseyville, IL, USA). The sandy soil came from
an inclusion of sandy orthents within a Medway silty clay
loam (Fine-loamy, mixed, mesic Fluvaquentic Hapludolls)
in Union county, Illinois, USA (Miles 1979; Fehrenbacher
et al. 1984). The other soils were collected in Jackson
county, Illinois, USA with the loamy soil collected from a
Hosmer silt loam (Fine-silty, mixed, mesic Typic, Fragiu-
dalf) and the clayey soil collected from a Darwin silty clay
(Fine, smectitic, mesic Vertic Haplaquolls) (Herman 1979;
Fehrenbacher et al. 1984). All soil samples were collected
(surface to 15 cm depths) from fields historically used to
produce corn (Zea mays) and soybean (Glycine max).
Particle size distribution of each soil was analyzed by the
hydrometer method to confirm soil textural class (Table 1;
Sabey et al. 2003). All soils were steam pasteurized at
approximately 70 °C for 6 h to reduce the presence of
soilborne pathogens and then sieved to 4 mm. The mois-
ture content of the sandy soil was adjusted to 10 % and the
loamy and clayey soils were adjusted to 20 % to allow for
optimal mixing. After mixing, the soil mix was packed into
15-cm-diameter plastic pots to provide 1.7 L of soil vol-
ume in each pot.
The nutrient and organic matter content and pH for the
VC used in the experiment were determined by analyzing
three 20 g VC bulk dried samples (Brookside Laboratories
Inc., New Knoxville, OH, USA). The VC had a pH of 6.1,
organic matter content of 0.52 g/g, and N, P, and K content
of 20,710, 3610, and 4580 mg/kg, respectively. The levels
of Ca, Mg, and S were 33,330, 5040, and 2540 mg/kg,
respectively; and the micronutrients B, Fe, Cu, Zn, Mn, and
Table 1 Results of textural analysis of Illinois soils (Sabey et al.
2003) used for the tomato vermicompost greenhouse study
Soil separate content (%)
Soil series
a
Sand Silt Clay
Hosmer silt loam 5.7 70.0 24.3
Darwin silty clay 7.7 48.0 44.3
Sandy orthents (loamy sand) 81.0 8.7 10.3
a
Hosmer silt loam (fine-silty, mixed, mesic Typic, Fragiudalf) and
Darwin silty clay (fine, smectitic, mesic Vertic Haplaquolls) were
both collected in Jackson county, Illinois, USA (Fehrenbacher et al.
1984; Herman 1979); and an inclusion of sandy orthents was col-
lected within a Medway silty clay loam (Fine-loamy, mixed, mesic
Fluvaquentic Hapludolls) in Union county, Illinois, USA (Miles 1979;
Fehrenbacher et al. 1984)
136 Int J Recycl Org Waste Agricult (2015) 4:135–141
123

Na were 31, 5750, 55, 192, 690, and 1290 mg/kg,
respectively.
‘Sun Chief’ tomato seeds (Seedway Inc., Elizabethtown,
PA, USA) were germinated in a greenhouse and trans-
planted into pots at the one-leaf stage. Plants were watered
2–3 times per week for the first month after planting and
then daily after that to prevent wilting. Tomato suckers
were removed and plants were pruned to two fruiting stems
at 1 month after transplanting, and each tomato plant was
then tied to a 0.5–0.7-m-long bamboo stake. The tomato
was chosen for this study for two primary reasons: (1) it is
a widely grown vegetable in both greenhouse and field
production systems throughout the world, and growers of
this crop have a great interest in alternative nutrient sys-
tems, and (2) it was also selected since the tomato plant is a
high nutrient feeder, which would determine if VC could
provide sufficient nutrient resources for a crop that requires
high amounts of nitrogen and other nutrients for maximum
growth and development.
Plant height (cm), leaf and flower number per plant, leaf
chlorophyll content, total leaf area per plant, and dry foliage
and root weight (g) were measured at the termination of each
experiment at 2 months after transplanting. The height of each
plant was measured from the soil line to the tip of the tomato
main plant stem. The leaf chlorophyll content was measured
using a Minolta SPAD-502 chlorophyll meter (Special Prod-
ucts Analysis Division, Konica Minolta Sensing Inc., Osaka,
Japan) on ten randomly selected mature leaves from the mid-
portion of tomato plants within each pot. Shoots were cut at the
soil surface with all leaves removed from each plant and total
leaf area (cm
3
) measured with a portable leaf area meter
(Model LI-3000, LI-COR, Lincoln, NE, USA). Roots were
washed free of soil using tap water. Root and foliage samples
were oven dried at 80 °C for 48 h and weighed.
Data were subjected to analysis of variance procedures
using the general linear models procedure of SAS (SAS Inst.,
Cary, NC, USA) appropriate for a factorial experimental
design to determine the effects of soil type and VC rate on
tomato growth response variables. Fisher’s Least Sig-
nificance Difference (LSD) test at PB0.05 was used to make
comparisons among soil types. Orthogonal contrasts were
used to make comparisons between the various combinations
of low and high VC rates, nontreated control, and standard
inorganic fertilizer treatments. Furthermore, data were also
analyzed using regression analysis to determine the influence
of VC rate on tomato growth responses.
Results
No interactions (P[0.05) were detected between the two
greenhouse experiments with either soil type or VC rate,
and between soil type and VC rate for most tomato growth
responses (data not presented). Thus, tomato growth data
are presented by soil type and VC rate main effects
(Tables 2,3).
Soil type
Tomatoes grown in the sandy soil had the greatest plant
heights, leaf and flower numbers per plant, and leaf
chlorophyll content compared to the clay and loam soils
(Table 2), with the loam soil generally providing the least.
Although the clay and sandy soils provided similar high
dry shoot foliage weights, the clay soil produced the
greatest root dry weights compared to the other soils. The
three soils differed (PB0.05) for root-to-shoot ratios and
leaf area with the loam soil having the highest, followed by
the clay and sandy soils, respectively. Although total leaf
area per plant was not influenced by soil type, the amount
of leaf area per leaf was highest for the loam soil, followed
by the clay soil, with the sand soil type providing the least.
Vermicompost rate
The low VC rates (0.05, 0.1, and 0.2 g/g) did not improve
the tomato plant height, leaf and flower numbers per plant,
leaf chlorophyll content, and dry root biomass compared to
that of the control (0 g/g) (Table 3). Although no differ-
ences (P[0.05) were detected between the high VC rates
(0.4 and 0.8 g/g) and the SFT for most tomato growth re-
sponses (except leaf and flower number per plant), differ-
ences (PB0.05) were generally observed between the low
and high VC rates for most growth responses (except leaf
SPAD value). Tomato leaf and flower number per plant
responded to VC applications, as differences were detected
among most contrasts evaluated. However, no VC rate
provided tomato leaf and flower numbers on a per plant
basis that were similar to SFT. Higher leaf SPAD values
were also obtained for SFT compared to either 0 g/g con-
trol or low VC rates. Although differences were not de-
tected (P[0.05) for leaf chlorophyll content between the
low and high VC rates, the low rate provided lower SPAD
values compared to SFT. The highest VC rate evaluated
(0.8 g/g VC) also had high leaf chlorophyll content, which
was similar to SFT. Most contrasts were significant
(PB0.05) for dry shoot and root weight, except the high
VC rates provided tomato shoot and root biomass that was
similar to SFT and the 0.0 g/g control and low VC rates
had similar dry root weight. For tomato root-to-shoot ratio,
most contrasts were again significant (PB0.05), except
the high VC rates were similar to SFT. Tomato leaf area
was also influenced by VC rate, as differences were de-
tected (PB0.05) between the 0 g/g control with both low
and high VC rates as well as SFT; the high VC rates also
differed from the low VC rates for tomato leaf area.
Int J Recycl Org Waste Agricult (2015) 4:135–141 137
123

Tomatoplant growth responses generallyincreased withthe
increasing VC application rates (Tab le 3). Tomato plant height
increased in a quadratic manner with the increasing VC rate.
Approximately 0.66 g/g VC provided the optimal rate to
maximize tomato plant height [y=78.42 ?0.39 (VC
rate) -0.003 (VC rate)
2
,R
2
=0.95, P=0.0097]. Quadratic
relationships also explained the increase in leaf and flower
number per plant with increasing VC rate, although there was
only a 2.6 leaf and 4.0 flower increase per plant from the 0 g/g
control to the highest VC rate (0.8 g/g). The optimum VC
application rates to achieve maximum leaf [y=8.92 ?0.04
(VC rate) -0.0002 (VC rate)
2
,R
2
=0.96, P=0.0077] and
flower numbers [y=3.77 ?0.15 (VC rate) -0.001 (VC
rate)
2
,R
2
=0.95, P=0.0103] per plant were about 0.80 and
0.59 g/g, respectively. Tomato leaf chlorophyll content in-
creased in a linear manner with the increasing VC application
rate [y=39.67 ?0.05 (VC rate), R
2
=0.70, P=0.0381].
Tomato dry shoot and root biomass increased in a quadratic
[y=13.67 ?0.24 (VC rate) -0.0015 (VC rate)
2
,
R
2
=0.99, P=0.0005] and linear [y=11.74 ?0.02 (VC
rate), R
2
=0.64, P=0.0576] manner, respectively, with the
increasing VC application rate; and approximately, 0.70 and
0.80 g/g VC provided the highest tomato shoot and root bio-
mass, respectively, which was similar to the SFT in both cases.
The decrease in the root-to-shoot ratio with the increasing VC
rate was best described by a quadratic model
[y=0.82 ?0.007 (VC rate) -0.00005 (VC rate)
2
,
R
2
=0.97, P=0.0064], with about 0.60 g/g VC rate pro-
viding the lowest root-to-shoot ratio. Lastly, total tomato leaf
area increased in a quadratic manner as VC application rate
increased [y=181.74 ?2.66 (VC rate) -0.025 (VC rate)
2
,
R
2
=0.87, P=0.0459], with leaf area optimized at the
0.53 g/g VC rate.
Discussion
The use of VC as a fertilizer source for tomato growth
provided no advantage compared to a standard inorganic
fertilizer, although the higher amounts of VC applied im-
proved tomato growth over the untreated control. However,
other benefits provided by VC such as soil structure im-
provement and increase in soil microbial populations
(Edwards and Burrows 1988; Canellas et al. 2002) com-
pared to petroleum-based synthetic fertilizers should be
considered and may be more ideal for certain situations.
Results from this study indicated: (1) VC enhanced tomato
growth particularly for the sandy soil type; (2) VC appli-
cation rate affected tomato plant growth response, and soils
with higher amounts of VC (0.4 and 0.8 g/g) generally
resulted in taller tomato plants with greater leaf and root
biomass, more leaves and flowers, higher chlorophyll
content and increased leaf area than the non-treated control
or low VC rates; and (3) the soil VC application rate to
achieve optimal tomato growth parameter responses was
between 0.5 and 0.6 g/g.
Although VC additions will improve soil structure pri-
marily through increases in organic matter, tomato growth
differed among soil types that were amended with VC. The
sandy soil with VC amendments generally produced
greater tomato plant heights, leaf and flower numbers per
plant, and leaf chlorophyll content compared to the clay
and loam soils, with the loam soil generally providing the
least (Table 2). The influence of soil type on the tomato
growth parameters was most likely due to VC improve-
ments in soil structure allowing for greater water retention
and aeration, especially in the sandy soil. However, in this
experiment, the loamy and clayey soils appeared to become
Table 2 Influence of soil type on ‘Sunchief’ tomato growth responses combined for the vermicompost rates and for two greenhouse experiments
Soil type
A
Plant Flower Leaf Leaf SPAD Dry Wt (g)
D
Root-to-shoot Leaf area (cm
3
)
F
Ht (cm)
B
No./plant No./plant Value
C
Shoot Root Ratio
E
Leaf Total
Clay 86.0b 10.1b 6.7b 40.4b 20.6a 13.9a 0.67b 36.0b 241.3a
Loam 80.4c 9.1c 4.3c 40.0b 15.5b 11.6b 0.75a 51.4a 221.2a
Sand 90.7a 11.2a 8.6a 43.5a 21.7a 11.7b 0.54c 26.2c 225.0a
All measurements were taken at the termination of the experiments at 2 months after transplanting. Tomato growth response means followed by
the same letter within a column do not differ significantly at PB0.05
A
Clay was Darwin silty clay (Fine, smectitic, mesic Vertic Haplaquolls), loam was a Hosmer silt loam (Fine-silty, mixed, mesic Typic,
Fragiudalf), and sand came from an inclusion of sandy orthents within a Medway silty clay loam (Fine-loamy, mixed, mesic Fluvaquentic
Hapludolls)
B
Plant heights were measured for each plant from the soil line to the tip of the tomato main plant stem
C
Leaf SPAD values were measured using a Minolta SPAD-502 chlorophyll meter (Special Products Analysis Division, Konica Minolta Sensing
Inc., Osaka, Japan) on 10 randomly collected leaves from the mid-portion of plants in each plot
D
Roots and foliage samples were oven dried at 80 °C for 48 h
E
Root-to-shoot ratio is the root weight divided by shoot weight
F
Leaf area was measured using a portable leaf area meter (Model LI-3000, LI-COR, Lincoln, NE, USA)
138 Int J Recycl Org Waste Agricult (2015) 4:135–141
123

more compacted over the duration of the experiment,
which would definitely have an effect on plant growth
(Brady and Weil 2008).
Vermicompost application rate affected all tomato plant
growth characteristics in this study and provided further
evidence of VC as a suitable alternative-type fertilizer for
tomato which is comparable to other studies including
Arancon et al. (2003), Gutie
´rrez-Miceli et al. (2007), and
Roberts et al. (2007). This study indicated that addition of
0.5 to 0.6 g/g VC to soils provided optimal tomato plant
growth, since this rate provided tomato growth results
similar to the standard inorganic fertility program and ap-
plication rates [0.6 g/g tended to result in excessive
amounts of shoot growth as well as low root-to-shoot ratios
(Table 3). Arancon et al. (2003) indicated that the
improvements in tomato plant growth due to VC application
may be due to increases in microbial populations in soils
provided by these materials. However, other research has
indicated that increased plant growth and yields with VC
may be due to the production of plant growth regulators by
microorganisms or to the effects of humates (Canellas et al.
2002). Regardless, the addition of organic composts or VC
to soil tends to improve soil structure, increase microbial
population and activity, and increase water retention (Ed-
wards and Burrows 1988; Edwards 2004). Therefore, the
use of organic composts, such as VC, can provide various
benefits to soils while, at the same time, providing a fertility
source for selected vegetable crops.
Vermicomposts can be used as a source of nutrients for
vegetable crops, as well as increasing soil organic matter,
Table 3 Influence of vermicompost (VC) rate on ‘Sunchief’ tomato plant growth responses combined over the three soil types evaluated
Vermicompost Plant Leaf Flower Leaf SPAD Dry Wt (g)
d
Root-to-shoot Leaf area
f
(cm
3
)
Rate (g/g)
a
Ht (cm)
b
No./plant No./plant Value
c
Shoot Root Ratio
e
0.0 77.9 8.8 3.8 38.8 14.1 11.9 0.84 168.7
Low
0.05 80.1 9.0 4.1 39.1 14.4 11.2 0.77 201.4
0.1 82.0 9.7 5.3 41.9 16.0 11.7 0.73 211.5
0.2 87.0 9.7 6.9 41.0 17.8 12.9 0.72 234.6
High
0.4 88.0 10.3 7.4 41.3 21.1 12.8 0.61 237.0
0.8 91.1 11.4 7.8 43.5 23.2 13.2 0.57 237.4
SFT 93.9 12.2 10.5 43.7 24.6 13.5 0.55 232.8
Contrasts
g
None vs. low NS NS NS NS ** NS ** **
None vs. high * *** *** * *** ** *** ***
None vs. SFT ** *** *** ** *** * *** ***
Low vs. high * *** ** NS *** * *** **
Low vs. SFT ** *** *** * *** ** *** NS
High vs. SFT NS ** ** NS NS NS NS NS
Significance of VC rate trend
h
Linear ** ** * * ** * ** NS
Quadratic ** ** ** NS ** NS ** *
All measurements were taken at the termination of the experiments at 2 months after transplanting. The three soil types evaluated were clay (silty
clay), loam (silt loam), and sand (silty clay loam)
NS,
*
,
**
,
*** Nonsignificant or significant at PB0.05, PB0.01, or PB0.0001, respectively
a
SFT is the standard fertilizer treatment and was an inorganic 12-12-12 (N–P–K) complete fertilizer applied at 2 g per 1.7 L pot
b
Plant heights were measured for each plant from the soil line to the tip of the tomato main plant stem
c
The leaf SPAD value was measured using a Minolta SPAD-502 chlorophyll meter (Special Products Analysis Division, Konica Minolta
Sensing Inc., Osaka, Japan) on 10 randomly collected leaves from the mid-portion of each plant
d
Root and foliage samples were oven dried at 80 °C, with dry weights taken after 48 h
e
Root-to-shoot ratio was root dry weight divided by shoot dry weight
f
Leaf area was measured using a portable leaf area meter (Model LI-3000, LI-COR, Lincoln, NE, USA)
g
Low is the combination of 0.05, 0.1 and 0.2 g/g vermicompost rates and High is the combination of 0.4 and 0.8 g/g vermicompost rates, while
None =0 g/g vermicompost
h
SFT is used only in contrast comparisons and is not included in the calculation of linear and quadratic models
Int J Recycl Org Waste Agricult (2015) 4:135–141 139
123

improving soil structure, and providing increases in soil
microbial populations which all have beneficial effects on
plant growth and development (Arancon et al. 2003,2004a;
Gutie
´rrez-Miceli et al. 2007). Furthermore, the recycling of
organic wastes into composts for use as alternative fertil-
izers can reduce the need and dependence on synthetic,
inorganic fertilizers by both small- and large-scale veg-
etable producers. Many amateur home gardeners as well as
commercial vegetable growers are interested in using en-
vironment-friendly alternative type fertilizers, such as VC,
that can supply sufficient amounts of nutrients for crop
growth and development while at the same time improving
the physical properties of soils. Thus, there is great po-
tential to increase the use of these fertilizers by both
commercial vegetable growers and home vegetable
gardeners.
Conclusions
This research provided further evidence for VC as a suit-
able alternative fertilizer for tomato, with approximately
0.5–0.6 g/g VC added to soil resulting in optimal tomato
plant growth. Moreover, this rate provided tomato growth
similar to the standard inorganic fertility program. The
sandy soil with VC amendments generally increased
tomato plant growth parameters the most compared to the
clay and loam soils, with the loam soil generally providing
the least.
Acknowledgments The investigators would like to express their
sincere thanks to Illinois Dept of Agriculture Sustainable 2000 Grant
Program and Illinois Department of Commerce and Economic Op-
portunity for funding this research. Special thanks are also extended
to Mr. Chad Hurley at New Horizon Organics Inc. in Jerseyville, IL
and all personnel at the Horticulture Research Center, SIUC for their
assistance in conducting this research. The tomato seed used in this
study was generously provided by Rupp Seeds Inc., Wauseon, OH.
Conflict of interest The authors declare that they have no conflict
of interest.
Author contribution This paper is based on a thesis submitted by
Mr. Marc Zucco, who is a former graduate student at the Department
of Plant, Soil, and Agricultural Systems at SIUC, Carbondale, Illinois,
USA. He is now a soil scientist with the Natural Resources Conser-
vation Service (NRCS) in Grayling, Michigan, USA. Dr. Alan Wal-
ters is Professor of Vegetable Science and Director of the Southern
Illinois University Sustainable Farming Center. This center includes a
vermicomposting facility in which University food wastes are recy-
cled and used as a fertilizer source and soil enhancer for the Organic
Vegetable Farm located next to the facility. Dr. Chong is an Emeritus
Professor of Soil Science, who was involved in vermicompost re-
search prior to his retirement and is now involved in various inter-
national activities, especially in China. Dr. Brian Klubek is Emeritus
Professor of Soil Microbiology and former Chair of the Dept of Plant,
Soil, and Agricultural Systems at Southern Illinois University, Car-
bondale, Illinois, USA. Dr. Joseph Masabni is an Assistant Professor
and Extension Vegetable Specialist at Texas A&M University and
collaborated with the authors in writing this manuscript.
Open Access This article is distributed under the terms of the
Creative Commons Attribution 4.0 International License (http://
creativecommons.org/licenses/by/4.0/), which permits unrestricted
use, distribution, and reproduction in any medium, provided you give
appropriate credit to the original author(s) and the source, provide a
link to the Creative Commons license, and indicate if changes were
made.
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