Journal of Environmental Protection, 2011, 2, 502-510
doi:10.4236/jep.2011.25058 Published Online July 2011 (http://www.scirp.org/journal/jep)
A Soil Quality Index to Evaluate the
Vermicompost Amendments Effects on Soil
Properites
Romina Romaniuk*, Lidia Giuffré, Rosario Romero
Edafología, Facultad de Agronomía, Universidad de Buenos Aires, Buenos Aires, Argentina.
Received April 12th, 2011; revised May 16th, 2011; accepted June 18th, 2011.
ABSTRACT
The aims of this work were 1) to evaluate the changes in soil properties with the application of different amounts of
vermicompost (10 and 20 Mg·ha–1), and 2) to construct a soil quality ind ex that allows the evalua tion of changes in the
most sensitive soil parameters. The study was carried out in a cattle field of General Alvear, Bueno s Aires, Argentina.
Vermicompost application showed a positive effect on most of the chemical and biological soil properties evaluated,
especially with the higher dose (20 Mg·ha–1). There were slight but significant increases in electrical conductivity and
soil pH with the higher dose of vermicompost. Physical soil properties were not affected by the vermicompost amend-
ment. The SQI showed a significant increase of soil quality with the vermicompost dose of 20 Mg·ha–1, especially by
enhancing the biochemical an d bi ol o gi cal properti e s.
Keywords: Organic Amendments, Soil Physical Properties, Soil Biochemical Properties, Soil Bio logical Properties,
Soil Quality Indicators
1. Introduction and Methods
Soil is one of the most valuable natural resources and
maintains its health is a moral responsibility. However,
the urgency to produce more food and fuels is causing an
irreparable damage on soil. Excessive mineral fertiliza-
tion and irrational cultural practices contribute to reduce
fertility and the organic matter contents. These circum-
stances have led many researchers to search new and
better management strategies. Soil application of organic
waste, represents a management strategy that can reduce
the losses of soil organic matter [1]. The use of organic
amendments improves soil structure an d fertility, increas-
ing microbial populations, activity and diversity [2-4].
The vermicompost is an “organic fertilizer” produced
by interactions between earthworms and soil microorga-
nisms, resulting in a material with a high degree of ma-
turity, high porosity, aeration, drainage, water storage
capacity and microbial activity [5 ]. The use of this amen-
dment promotes biological activity enhancing the produ-
ctive capacity of soils directly related to increases of
nutrients availability and indirectly through improve-
ments in physical properties [6].
There are several studies about changes produced by
the application of vermicompost on physical, chemical
and biological soil properties. Mahesewarappa et al. [7]
found increases in N content, total organic carbon, and
pH values in soil amended with vermicompost. According
to Pascual et al. [8] the contents of humus and microbial
biomass carbon in soils fertilized with vermicompost
were increased compared with those receiving inorganic
fertilizers only. Albiach et al. [2] reported increases in
soil microbial activity with the addition of organic ferti-
lizers. A study by Marinari et al. [9] showed that the in-
corporation of vermicompost to soil under maize signi-
ficantly improved physical and biological soil properties.
Arancon et al. [10] reported increases of humic acids
contents after vermicompost application in soils, related
with the largest amount of microorganisms associated
with the earthworms activity. Tejada et al. [11] found
that vermicompost application had a positive effect on
the soil physical, chemical and biological properties, in-
creasing plant c ov er and de cr e a si n g the soil losses.
Although there are numerous research about the changes
in soil properties after organic amendments, there are not
informations about which are the main parameters (in-
dicators) to be monitored over time to assess the effects

A Soil Quality Index to Evaluate the Vermicompost Amendments Effects on Soil Properites503
of vermicompost applications on soil quality. These in-
dicators should be easily and accurately determined by
routine laboratories protocols. Then, it is important to
integrate this information into a soil quality index that
allows monitoring the changes in soil properties. Several
indexing methods have been used to calculate an inte-
grated index of soil quality. The approach proposed by
Andrews and collaborators [12] is th e most used and it is
based on the selection of a minimum data set of indica-
tors (MDS) by principal component analysis (PCA),
normalization, and integration by a weighted additive
index (WAI). This approach was successful to evaluate
the effects of soil management in different production
systems [13-18].
The objectives of this work were 1) to evaluate the ef-
fect of vermicompost application on physical, chemical,
biochemical and biological soil properties and 2) to con-
struct a soil quality in dex in teg rated by th e most sensitive
soil parameters that allow an accurate evaluation and
monitoring of changes in so il quality.
2. Materials and Methods
2.1. Field Site, Treatments and Soil Sampling
The experiment was carried out in a cattle field located in
General Alvear, Buenos Aires, Argentina. This site is
part of the “ Salado Depre ssion” and is ch aracterize d by a
vast plain with very low surface runoff and groundwater
layers near the surface. The average temperature for the
month of January is 22.5˚C and for July of 8.1˚C, with an
average rainfall of 843 mm per year. The soil of the
study is located in the highest part of the field, classified
as a Thapto argic Hap ludoll, and it is under natural vege-
tation. Vermicompost (VC) application is done to impro-
ve the quantity and quality of the natural vegetation to
cattle use. The compost used for the VC is produced
from animal manures and plant residues, which are sta-
cked in piles of 1 .5 m above the ground. Every 3 0 cm of
plant litter, animal manure in a thickness of 3 cm is in-
serted into the piles to facilitate the colonization by mi-
croorganisms. The pile is periodical removed to give
aeration that allows the pasteurization, which occurs
when high temperatures are reached (60˚C - 65˚C) and
pH values reaches acid values (pH 3.5), ensuring
complete destruction of pathogens. After two weeks of
the pasteurization, the substrate is placed in raised soil
beds of 1.0 × 10.0 × 0.5 m and inoculated with high
densities of earthworms Eisenia foetida (20.000
worms·m–2) by adding a pre-treated biowaste. After one
to three months depending on the season, the quality of
the VC is analyzed with the following requirements:
organic matter higher than 20% and nitrogen higher than
0.8%, both on dry basis, being the carbon/nitrogen ratio
less than 20. The actual pH value must be between 5.5
and 8, and the electrical conductivity less than 4 dS·m–1.
The experimental design was completely randomized
and consisted of the following treatments: soil with
vermicompost amendment of 10 Mg·ha–1 (VC 10), soil
with vermicompost amendment of 20 Mg·ha–1 (VC 20), a
control without addition of vermicompost (C), and an
undisturbed situation (UN) located next to the cattle plots.
The predominant species are Paspalum Dilatatum, Pas-
palum quadrifarium, Bromus unioloides, Cynodon dac-
tylon, Stipa neesiana, Stipa papposa, Bothriochloa, Bac-
charis sps. and Piptochaetium montevidense. Application
of the amendment was made superficially. The VC pre-
sented 11.24% of oxidable carbon, 0.84% of total nitro-
gen, 237 mg·kg–1 of exchangeable phosphorous, 7.3 of
pH and 2.96 d S·m–1 of electrical conductivity.
Soil sampling was performed after 6 months from the
VC application. Three soil samples from 0 to10 and 10 to
20 cm soil depth were collected from each treatment.
Soil was air-dried, sieved (<2 mm) and stored at room
temperature prior chemical, biochemical and physical an-
alysis, or stored at 4˚C prior being analyzed for biological
properties.
2.2. Soil Physical Analysis
Bulk density (BD) was determined by the core method
[19], and particle size analysis by the sedimentation pro-
cedure [20]; the later property was expressed in percent-
age of clay (%CL), silt (%SL) and sand (%SA). Struc-
tural stability was determined by gently breaking moist
soil and sieving throu gh an 8-mm sieve; then soil was air
dried and sieved so as to obtain the 4.76, 3.36, and 2.00
mm aggregate fractions [21]. This sieving was done with
a mechanical shaker at 1440 vibrations min–1 for 5 min.
These fractions were wetted until holding capacity, in-
cubated for 24 h, and wet-sieved through a set of sieves
with 4.76, 3.36, 2.00, 1.00, 0.50 and 0.30 mm openings,
respectively. Sieved materials were dried at 50˚C fo r 24 h.
The sum of products between the weights of each aggre-
gate fraction and the mean diameter of the fraction gave
the mean weight diameter (MWD). The change in MWD
from dry sieving to wet sieving was a number inversely
related to soil aggregate stab ility.
2.3. Soil Chemical and Biochemical Analysis
Soil pH was measured in a 1:2 soil/distilled water sus-
pension using a pre-calibrated glass electrode; and elec-
trical conductivity (EC) was determined in saturated soil
paste. Extractable phosphorus (P) was determined as
reported by Bray and Kurtz [22]. The total organic car-
bon (TOC) content of soil was evaluated using the wet
oxidation method of Walkley and Black [23]. The Stock
C (SC) was calculated affecting TOC by the BD for both

A Soil Quality Index to Evaluate the Vermicompost Amendments Effects on Soil Properites
504
depths considered. Particulate organic C (POC) was mea-
sured as described by Cambardella and Elliot [24]. The
ratio between POC and TOC (POC/TOC) was also calcu-
lated. The C extracted with K2SO4 was u sed as a meas u re
of the soluble C pool (SOC) [25].
2.4. Soil Biological Analysis
Soil basal respiration (Resp) was measured according to
Jenkinson and Powlson [26]. Soil microbial biomass C
(MBC) was measured by the chloroform fumigation -
extraction method [27]. Both the respiration and micro-
bial biomass were used to calculate the metabolic quo-
tient (qCO2) which expresses the quantity o f CO2 emitted
per microbial biomass unit and time, and also the micro-
bial coefficient MBC/TOC was calculated.
2.5. Soil Quality Index
Data were processed using the Infostat statistics program.
Seventeen soil parameters were measured for each soil
layer and the relative data were firstly checked for nor-
mality and then subjected to univariate analysis of vari-
ance (ANOVA). Variables w ith F statistically significan t
at p < 0.05 were further analyzed by Principal Compo-
nent Analysis (PCA). The separation of treatments means
was carried out by the Rienzo, Guzmán and Casanoves
(DGC) test. The PCA is a mathematical procedure giving
a small number of uncorrelated variables (PC) from seve-
ral correlated and thus it can reduce the size of the pa-
rameter dataset. The first PC account for most of the re-
maining variability. We have assumed that PC 1 receiv-
ing high eigenvalues best represented variation of the
system. Therefore, only the PCs with eigen values >1 and
those that explained at least 10% of the variation in the
data were included. Under a particular PC, each soil pro-
perties was given a weight or factor loading that repre-
sent the contribution of the variable to the composition of
the PC. Within each PC, only highly weighted factors
were retained for MDS. We have defined highly weight-
ed factor loadings those having absolute values within
10% of the highest factor loading. Multivariate correla-
tion coefficients were carried out when more than one
factor was retained under a single PC. The variable with
the highest correlation sum was considered for the MDS.
When highly weighted variables were not correlated
(correlation coefficient <0.7), each of them were retained
in the MDS.
After the selection of the MDS indicators, each indi-
cator was transformed by the linear scoring method. Indi-
cators were arranged depending on whether a higher value
was considered “good” or “bad” in terms of soil func-
tions. For “more is better” indicators, each observation
was divided by the highest observed value such that the
highest observed value received a score of 1. For “less is
better” indicators, the lowest observed value was divided
by each observation such that the lowest observed value
received a score of 1. Once transformed, the indicators
were weighted by the PCA. Each PC gave the percentage
of the variation with respect to the total data set. This
percentage, divided by the total percentage of variation
of all PCs with eigenvectors >1, provided the weighted
factor for the chosen indicator. Then, the scored indica-
tors for each observation were summed by the following
equation:
1
n
ii
i
SQIW S


where S was the score of the indicator, and W the
weighted factor derived from the PCA. Higher index
scores were assumed to give the best soil quality. The
calculated SQI values were tested for their significance at
p = 0.05 by ANOVA and the means were compared by
the DGC procedure.
3. Results
3.1. Selection of Indicators
3.1.1. Univariate Analysis of Soil Parameters
The results from ANOVA are summarized in Table 1.
Among the seventeen soil properties evaluated for both
soil depths, twelve were selected for soil depth 1, and
eight were selected for soil depth 2.
The MWD 1 was the only physical parameter selected
for both depths. This parameter presented the highest
value for the UN plot, but there were not significant dif-
ferences for the cattle plots (C, VC 10 and VC 20).
All the chemical and biochemical analyzed properties
were selected for soil depth 1. In the10 to 20 cm soil
layer (soil depth 2) only the EC, pH, P and SOC were
selected. The UN plot presented the highest values of P,
TOC and SC, without significance differences among the
others plots. The pH presented the highest value for VC
20, and the EC for both VC 10 and VC 20 treatments.
The labile organic carbon pools (SOC and POC) were
significant higher for UN, followed by VC 20, with the
lowest values for VC 10 and C. The ratio POC/TOC was
significant higher for UN and VC 20 in comparison with
C and VC 10.
Among the soil biological properties, only the qCO2 of
soil depth 1 was excluded (p > 0.05). All the others bio-
logical soil properties (Resp, MBC, MBC/TOC, qCO2)
were selected for both depths. The Resp and the MBC
and the microbial coefficient (MBC/TOC) were signifi-
cantly increased by dose of 20 Mg·ha–1 of VC applied to
the soil. The microbial quotient (qCO2) for soil depth 2
was higher for both VC treatments in comparison with
UN and C.
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A Soil Quality Index to Evaluate the Vermicompost Amendments Effects on Soil Properites
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Table 1. Mean vales of soil physical, chemical and biochemical properties of 0 - 10 cm (1) and 10 - 20 cm (2) soil depth.
UN C VC 10 VC 20
Mean values for depth 1 (0 – 10 c m)
% CL 14.17 ns15 ns14.17 ns 15 ns
% SA 59.17 ns60 ns59.17 ns 60 ns
% SL 26.67 ns25 ns26.67 ns 25 ns
MWD (mm) 39.5 a 113.5 b 113.4 b 99.4 b
BD (g·cm–3) 1.28 ns1.26 ns1.26 ns 1.24 ns
pH 6.16 a 6.06 a 6.13 a 6.45 b
EC (ds·m–1) 0.35 a 0.49 b 0.60 c 0.63 c
P (mg·kg–1) 43.15 b 10.18 a 13.66 a 17.94 a
TOC (%) 3.93 b 2.94 a 3.08 a 3.16 a
SC (tn·ha–1) 50.30 b 37.05 a 38.50 a 39.18 a
SOC(gC g·soil–1) 189 c 117 a 120 a 156 b
POC (%) 1.03 c 0.78 a 0.61 a 0.59 b
POC/TOC (%) 24 b 8 a 12 a 21 b
Resp (g C-CO2 g·soil–1·h–1) 1.18 a 0.96 a 1.42 a 1.96 b
MBC (g C g·soil–1) 585 a 500 a 547 a 764 b
qCO2 0.20 ns0.19 ns0.26 ns 0.26 ns
MBC/TOC 172 a 150 a 177 a 241 b
Mean values for depth 2 ( 10 – 2 0 c m)
% CL 14.17 ns15.83 ns15 ns 15.83 ns
% SA 60 ns60 ns58.33 ns 60 ns
% SL 25.83 ns23.33 ns26.67 ns 23.33 ns
MWD (mm) 87.8 ns115.4 ns110.7 ns 103.1 ns
BD (g·cm3) 1.3 ns1.25 ns1.25 ns 1.24 ns
pH 5.84 a 5.84 a 6.12 b 6.33 b
EC (ds·m–1) 0.37 a 0.49 b 0.55 b 0.57 b
P (mg·kg–1) 38.22 b 5.74 a 5.74 a 8.68 a
TOC (%) 2.41 ns2.34 ns2.37 ns 2.56 ns
SC (tn·ha–1) 31.33 ns29.25 ns29.62 ns 31.75 ns
SOC(g C g·soil–1) 114 b 60.4 a 61.7 a 75.7 a
POC (%) 0.17 ns0.11 ns0.14 ns 0.18 ns
POC/TOC (%) 6.95 ns4.92 ns5.88 ns 7.06 ns
Resp (g C-CO2 g·soil–1·h–1) 0.30 a 0.23 a 0.4 a 0.66 b
MBC (g C g·soil–1) 318 a 305 a 327 a 528 b
qCO2 0.10 a 0.08 a 0.14 b 0.13 b
MBC/TOC 132 a 131 a 138 a 208 b
%CL is clay, %SL is silt, %SA is sand, MWD is mean weight diameter, BD is bulk density, EC is electrical conductivity, P is extractable pho sphorus, TOC is
total organic carbon, SC is stock C, SOC is soluble organic carbon, POC is particulate organic C, POC/TOC is the ratio of POC to TOC and Resp is basal soil
respiration, MBC is microbial biomass carbon, qCO2 is metabolic quotient, MBC/TOC is microbial coefficient. UN is undisturbed plot, C is the control plot,
VC 10 is the plot amendment with 10 Mg· ha–1 of vermicompo s t and VC 20 is t he plot amendment with 20 Mg·ha–1 of verm i compost.

A Soil Quality Index to Evaluate the Vermicompost Amendments Effects on Soil Properites
506
Table 2. Results of principal components analysis.
3.1.2. Multi v a r i ate An al ysi s of the Selected Soil
Parameters
Tables 2 and 3 show results of PCA analysis and corre-
lation between soil properties, respectively.
Both PC 1 an d PC 2 were selected. Accord in g to PC 1 ,
MWD 1, EC 1, P 1, SC 1 and P 2 were considered for the
correlation analysis. The highest sum of correlation coef-
ficient (cc) was shown by P1 with final selection of P 1,
MWD1 and EC 1 (cc < 0.7). According to PC 2, MBC 1,
pH 1 and POC/TOC 1 were selected with MBC 1 gettin g
the highest sum of correlations coefficients. The correla-
tion between MBC 1 and POC/TOC 1 was < 0.7 (p <
0.1), and both were selected to represent CP2.
3.2. Transformation and Integration of Indicators
To carry out linear scores of selected properties, values
of each observation of P1, POC/TOC and MBC were
divided by the highest observed value; and values of
MWD and EC 1 were divided by the lowest observed
value. The transformation allows scoring observation as
“higher is better” up to a threshold value whereas the latter
transformation allows scoring “lower is better” above the
threshold.
Selected properties for a given PC have the same weight
into the index. This gave a weighted factor of 0.545 for
selected properties of PC 1 (MWD 1, P 1 and EC 1) and
0.415 for selected properties of PC 2 (MBC 1 and POC/
COT 1).
Soil quality index was:


0.545 111
0.415 11
SQIP MWD EC

M
BCCOP COT
 
 
3.3. Application of the Soil Quality Index
Figure 1 shows the values of soil quality in dex.
The SQI differentiated the undisturbed situation (UN)
from those under grazing (T, VC 10 and VC 20). The UN
presented the highest value of the SQI. The applications
of 20 Mg·ha–1 of vermicompost (VC 20 treatment) sig-
nifically increase the final value of the SQI, in compari-
son with the control (C) and the treatment with vermi-
compost amendment of 10 Mg·ha–1 (VC 10). The SQI
values were similar for C and VC 10. Differences be-
tween the undisturbed situation (UN) and the cattle plots
(C, VC 10 and VC 20) were mainly represented by
MWD 1 and P1 values. The higher SQI value of the VC
20 treatment in comparison with T was mainly repre-
sented by the phosphorus contents (P 1) and by the bio-
logical indicators (MBC 1 and COP/COT 1).
4. Discussion
The cattle practice reduces the structural stability of soil,
and thus could be the reason of the different values of the
Principal Component Analysis
PC 1 2
Eigenvalues 10.14 7.09
Proportion 0.48 0.34
Weighted factor 0.585 0.415
Factor loadings
MWD 1 –0.28 –0.11
BD 1 0.25 0.03
pH 1 –0.11 0.33
EC 1 –0.29 0.06
P 1 0.28 0.15
TOC 1 0.25 0.13
POC 1 0.22 0.27
POC/TOC 1 0.17 0.31
SOC 1 0.22 0.24
SC 1 0.27 0.12
Resp 1 –0.14 0.26
MBC 1 –0.07 0.34
MBC/COT 1 –0.2 0.23
pH 2 –0.2 0.24
EC 2 –0.26 0.03
P 2 0.29 0.11
SOC 2 0.24 0.16
Resp 2 –0.18 0.28
MBC 2 –0.16 0.29
qCO2 2 –0.14 0.15
MBC/COT 2 –0.16 0.27
MWD is mean weight diameter, BD is bulk density, EC is electrical conduc-
tivity, P is extractable phosphorus, TOC is total organic carbon, SC is stock
C, SOC is soluble organic carbon, POC is particulate organic C, POC/TOC
is the ratio of POC to TOC and Resp is basal soil respiration, MBC is mi-
crobial biomass carbon, qCO2 is metabolic quotient, MBC/TOC is microbial
coefficient for 0 - 10 cm (1) and 10 - 20 cm (2) soil depth.
MWD between the undisturbed plot and the plots under
grazing. The soil physical parameters evaluated (% CL,
% SL, % SA, BD, MWD) were not affected by the both
doses of VC applied, probably because the time elapsed
since the beginning of the experiment until the sampling
was not enough to affect significantly these soil proper-
ties. However, the MWD and the BD, decrease in soils
amendment with the highest dose of VC (20 Mg·ha–1).
Organic soil amendments could help to con- serve and/or
enhance the structure, because organic matter is
considered an active agent that promotes aggre- gation
through physical and chemical mechanisms [28]. Whalen
et al. [29] noted a larger amount of aggregates stable in
water five months after the in- corporation of VC,
concluding that the MWD increased linearly with
increasing doses vermicompost applied.
The higher values of most of the chemical and bioche-
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A Soil Quality Index to Evaluate the Vermicompost Amendments Effects on Soil Properites507
Table 3. Correlation between soil properties.
MWD
1 BD1 pH 1 EC 1 P 1 TOC 1 POC 1 POC/C 1 SOC 1 SC 1 Resp 1 MBC 1 MBC/ C 1 pH 2 EC 2 P 2 SOC 2 Resp 2 MBC 2 qCO2 2 MBC /C 2
MWD 1 1
BD 1 –0.72 1
pH 1 0.09 –0.23 1
EC 1 0.82 –0.71 0.46 1
P 1 –0.63 0.67 0.05 –0.68 1
TOC 1 –0.74 0.49 0.01 –0.61 0.83 1
POC 1 –0.79 0.57 0.38 –0.5 0.89 0.85 1
POC/
C 1 –0.7 0.51 0.54 –0.36 0.81 0.72 0.97 1
SOC 1 –0.87 0.66 0.25 –0.56 0.85 0.76 0.94 0.91
SC 1 –0.8 0.64 –0.03 –0.69 0.87 0.98 0.87 0.750.811
Resp 1 0.07 –0.44 0.71 0.49 –0.05 –0.13 0.16 0.310.12–0.21
MBC 1 –0.04 0.03 0.88 0.33 0.12 0.1 0.5 0.660.470.10.611
MBC/
C 1 0.36 –0.26 0.77 0.63 –0.35 –0.46 -0.03 0.180.01–0.460.610.831
pH 2 0.44 –0.32 0.79 0.7 –0.3 –0.34 0.03 0.23–0.04–0.360.630.790.881
EC 2 0.73 –0.86 0.33 0.72 –0.63 –0.48 –0.45 –0.33–0.55–0.610.560.230.470.541
P 2 –0.64 0.72 –0.06 –0.83 0.98 0.83 0.84 0.740.820.78–0.180.01–0.46–0.43–0.741
SOC 2 –0.81 0.6 0.12 –0.59 0.87 0.74 0.81 0.750.750.78–0.060.15– 0.28–0.32–0.590.88 1
Resp 2 0.32 –0.41 0.87 0.72 –0.2 –0.16 0.12 0.280.0048 –0.220.680.720.730.860.45–0.31 –0.08 1
MBC 2 0.16 –0.45 0.92 0.54 –0.12 –0.13 0.18 0.330.12–0.210.820.760.760.720.46–0.23 –0.08 0.84 1
qCO2 2 0.37 –0.25 0.45 0.66 –0.2 –0.11 0.02 0.11–0.14–0.150.380.380.390.670.38–0.29 –0.06 0.77 0.34 1
MBC/
C 2 0.18 –0.48 0.89 0.52 –0.14 –0.17 0.12 0.280.07–0.250.780.710.740.710.45–0.24 –0.13 0.84 0.98 0.331
MWD is mean weight diameter, BD is bulk density, EC is electrical conductivity, P is extractable phosphorus, TOC is total organic carbon, SC is stock C, SOC
is soluble organic carbon, POC is particulate organic C, POC/TOC is the ratio of POC to TOC and Resp is basal soil respiration, MBC is microbial biomass
carbon, qCO2 is metabolic quotient, MBC/TOC is microbial coefficient for 0 - 10 cm (1) and 10-20 cm (2) soil depth.
mical parameters (P, TOC, SC, SOC, POC and POC/
TOC) in the UN plot show that the cattle reduced the
nutrient and carbon contents of soils, probably because
removals by grazing were greater than inputs from litter
and cows depositions.
The increase in pH could be due to the higher Ph value
of the amendment (pH of 7.3) in relation to soil (pH of
6.06). However, this increase is not considered danger-
ous to soil quality because the values remained close to
neutrality.
Soil electrical conductivity was significantly affected
(P < 0.05) by both amendments of VC. This result can be
interpreted as a warning signal, since there is a clear
trend to increases of the electrical conductivity with the
applied doses of the VC. Similar results were found by
Gonzalez et al. [3].
There was a significant increase in the soil extractable
phosphorus with the increase of the VC doses applied.
Vermicompost amendments could help to recovering the
nutrient contents. The data obtained in our experiment
agree with those of numerous studies in which the VC
applied increases the concentratio n of soil P [30]. Devlie-
gher and Verstraete [31] found a significant increase in
the P contents after the VC amendment, reaching th e

A Soil Quality Index to Evaluate the Vermicompost Amendments Effects on Soil Properites
508
Figure 1. Values of the soil quality index. Different letters
denote significant differences between situations at  = 0.05.
UN is undisturbed plot, C is the control plot, VC 10 is the
plot amendment with 10 Mg·ha–1 of vermicompost, and VC
20 is the plot amendment with 20 Mg·ha–1 of vermicom-
post. . MWD is mean weight diameter, P is the extractable
phosphorus, EC is the electrical conductivity, MBC is mi-
crobial biomass carbon and POC/TOC is the ratio between
the particulate organic carbon and the total organic carbon.
double of the initial value for some treatments, and even
the triple in others, attributing the results to increases in
the enzymatic activity of phosphatases from earthworms.
The addition of both doses of VC did not affect (P <
0.05) the soil total organic carbon (TOC). However, the
labile organic carbon pools (SOC and POC) were signi-
ficant higher for the VC 20 treatment, showing that these
labile fractions may be more sensitive than TOC as an
indicator of soil quality.
Leifeld et al. [32] noted that the accumulation of orga-
nic carbon in the fine soil fraction occurs immediately
after application of vermicompost, presumably by the rapid
absorption on uno ccupied sites in the soil mine ral matrix.
In our study the ratio between COP and TOC for depth 1
were selected to act as an indicator of soil quality be-
cause it shows the preferential increment of the higher
size fraction of organic matter instead of the total org anic
carbon in the VC treatments, showing a tendency to the
recover of the original values (UN). A similar pattern
was shown by the microbial coefficient (MBC/TOC).
The use of organic amendments increases the soil orga-
nic carbon and improves soil structure [33]. Fortuna et al.
[34] argued that the VC amendment could increase the
carbon contents up to 45% of the original levels, and thus
contribute to increase the soil structural stability, p articu-
larly that of the macroaggregates.
Many authors reported that organic fertilization in-
creases the soil biological activity [35,36]. Organi c amend-
ments stimulate respiration due to a synergistic effect of
soil microorganisms and the amendment or by a stimula-
tion of microbial growth by the addition of organic sub-
strates [9]. Most of the carbon present on the organic
amendments includes partially decomposed material that
could be easily used as an energy source by soil micro-
organisms, resulting in higher respirations rates.
The application of 20 Mg·ha–1 of VC produced signi-
ficant increases in the microbial biomass carbon, in rela-
tion with the increase in available carbon which allows a
rapidly multiplication of microbial population. Arancon
et al. [10] reported that two of the major contributions of
vermicomposts to the field soils were the increases in
microbial populations and activities. However, in other
study [2] there was no effect of the addition of VC to soil
microbial biomass, attributing these results to the large
spatial and temporal variability o f soil.
The microbial quotient (qCO2) is considered an indi-
cator of nutritional stress of microbial communities.
However, the higher values of the qCO2 for soil depth 2
in the VC treatments could be interpreted as a higher re-
spiration rate because of the greater amount of labile car-
bon available for the microbial community, in compari-
son with the control and the undisturbed situation, which
did not receive any carbon supply. The increase of qCO2
due to organic amendments was reported also by others
[37,38].
SQI was capable to summarize the whole information
given by the soil measurements parameters. The final
values show that the cattle grazing reduce the SQ by
reduction in the physical, chemical and biological para-
meters. However, the higher values of the SQI obtained
for the VC 20 treatment in comparison with the control
(C) and the VC 10 plots; show that this practice could
increase the SQ, specially by an enhancing soil labile
carbon and also microbial population, which is a key fac-
tors in nutrient cycling and availability for plant growth.
Macci et al. [39] reported that the organic fertilizations
increase the soil quality in an almond tree plantation by
the improvement of chemico-nutritional, biochemical
and physical soil properties.
The inclusion of the EC in the SQI decreases the final
values of the SQI for both VC treatments. The EC is an
important indicator to be carefully monitored due to the
high values of the VC used in this experiment.
5. Conclusions
The VC amendment did not produced significant changes
in physical parameters.
There were a general increases in the P content, soil
labile organic carbon fractions, microbial activity and
population with the VC amendment, especially with the
higher dose of 20 Mg·ha–1. However, the applied VC
significantly increase the so il EC for both doses used.
The SQI shows an increase in soil quality with the
highest doses of VC amendment, allowing a complete
view of changes in the more sensitive soil properties af-
fected by VC application.
C opyright © 2011 SciRes. JEP

A Soil Quality Index to Evaluate the Vermicompost Amendments Effects on Soil Properites509
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