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Journal of Agricultural Science
Vol. 3, No. 4; December 2011
A Reliable Quality Index for Mushroom Cultivation
Diego Cunha Zied (Corresponding author)
Departamento de Produção Vegetal, Universidade Estadual Paulista
Fazenda Lageado, PO box 237, CEP 18603-970, Botucatu, SP, Brazil
Tel: 55-14-3811-7167
E-mail: dczied@gmail.com
J. Emilio Pardo-González
Escuela Técnica Superior de Ingenieros Agrónomos, Universidad de Castilla-La Mancha
Campus Universitario, s/n, 02071 Albacete, Spain
E-mail: Jose.PGonzalez@uclm.es
Marli Teixeira Almeida Minhoni
Departamento de Produção Vegetal, Universidade Estadual Paulista
Fazenda Lageado, PO box 237, CEP 18603-970, Botucatu, SP, Brazil
E-mail: marliminhoni@fca.unesp.br
Arturo Pardo-Giménez
Centro de Investigación, Experimentación y Servicios del Champiñón (CIES)
PO box 63, 16220 Quintanar del Rey, Cuenca, Spain
E-mail: apardo.cies@dipucuenca.es
Received: February 9, 2011
doi:10.5539/jas.v3n4p50
Accepted: February 23, 2011
Published: December 1, 2011
URL: http://dx.doi.org/10.5539/jas.v3n4p50
The research was financed by the Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES – No.
1184/09-1), the Graduate Program (Energia na Agricultura) in Faculdade de Ciências Agronômicas
(FCA/UNESP, Brazil), the Consejería de Agricultura de Castilla-La Mancha (Spain) and the Diputación
Provincial de Cuenca (Spain)
Abstract
The aim of this study was to develop a systematic quality index for application in the cultivation of Agaricus
bisporus (Lange) Imbach mushrooms, based on the physical, chemical and biological properties (indicators) of
the compost and casing layers (factors). The relative importance (weight) of each of the factors and indicators,
their normalized scores, the quality index values and the correlation with the mushroom yield were evaluated.
Three casings (soil + peat moss, Dutch commercial casing, and peat moss + spent mushroom substrate) and two
composts were used. The resulting quality index is reliable and useful for identifying problems and can also
serve as a rapid tool for possible intervention when problems occur. There was little difference between the two
composts used, both of them showing high factor index values. Although the peat + spent mushroom casing
presented certain limitations because of its high electrical conductivity, the other two casings showed satisfactory
factor index values.
Keywords: Methodological interactions, Yield modeling, Worldwide databases, Mushroom technology
1. Introduction
The methodology used to obtain a "quality index" has been applied in agricultural research, especially in the
field of soil science (Glover et al., 2000; Doran and Park in, 1994). For example, according to Larson and Pierce
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(1994), soil quality is a combination of the physical, chemical and biological properties of soil as well as its
capacity to promote the growth of vegetables and animals, to regulate the flow of water in the environment and
to act as a filter in the degradation and degeneration of environmentally hazardous substances.
However, quality index methodology has never been applied to mushroom production. Here, were study
Agaricus bisporus (Lange) Imbach, the most widely cultivated mushroom in the world, for which an abundant
literature exists concerning appropriate cultivation technology, especially optimal growth conditions and the
factors that affect yield. In this work, were focus on the compost and casing layer.
The development of a quality index for mushroom cultivation is important in that it can help identify problems in
the cultivation process, provide realistic yield estimates and avoid potential errors, while enabling government
sectors to monitor the sustainability and quality of mushroom production and the changes related with the
compost and casing layers used.
Sustainability in mushroom production is a multi-dimensional concept that includes aspects such as the stability
of production and profit, the protection and improvement of basic natural resources (biotic and abiotic) and the
maintenance of social order (e.g., the maintenance of family farms and industry).
Based on the different aspects and stages of A. bisporus production, four basic steps must be followed for precise
quality evaluation and monitoring: 1) select and define the principal factor (or factors) involved in the
commercial production of mushrooms that need to be assessed (e.g., compost and/or casing); 2) establish the
attributes that are relevant to the quality indicators for the selected factors (e.g., “pH and C/N ratio” for compost);
3) determine the key points of data analysis and specify the evaluation and integration process (analysis method,
weight (a and b) and slope at baseline); 4) establish specific criteria for the interpretation of the data to guarantee
reliable estimates of the production quality of each attribute (e.g., normalized score).
To be of practical use to professionals (researchers, extension agents, growers, designers and others), quality
indicators must meet the following criteria: a) be accessible to users worldwide and facilitate measurement; b) be
applicable to any growth condition; c) own criteria for quantification and interpretation of values; d) be flexible
in the face of changes (variations in temperature, humidity and CO2, irrigation alterations that cause problems
with casing layer compaction, etc.); e) allow both short- and long-term assessments of production quality; f) if
possible, be components of existing databases.
Based on the above mentioned criteria, compost and casing layers were selected from the many factors involved
in mushroom cultivation to be the key factors in our analyses. The following parameters were evaluated and
integrated:
- Indicators of compost quality: moisture content, C/N ratio, pH, nitrogen and presence of mites, nematodes and
competitor moulds.
- Indicators of casing layer quality: water-holding capacity, porosity, pH, electrical conductivity and presence of
mites, nematodes and competitor moulds.
Two compost and three casing layers were used in our study. The aim was to develop a systematic quality index
of the physical, chemical and biological properties (indicators) of the compost and casing layers (factors). The
relative importance (weight) for each of the factors and indicators, their normalized scores, the quality index
values and the correlation with the mushroom yield at the end of the harvest period were also evaluated.
2. Materials and methods
The experiment was carried out at the Centro de Investigación, Experimentación y Servicios del Champiñón
(CIES), Quintanar del Rey (Cuenca, Spain) in a controlled room used specifically for mushroom growing. The
total research time was 52 days (14 days of spawn run and 38 days of harvest phase).
2.1 Mushroom strain
The commercial strain “Gurelan 45” (large off-white hybrid) was used. The spawn is recommended for
cultivation in the winter and spring, and the optimal fruiting conditions are 18ºC (although it may bear fruit at
15ºC), a relative humidity of 87% and adequate ventilation to keep CO2 levels between 1000 and 1500 ppm.
2.2 Composts
Two commercial composts from different composting facilities were used. For both composts, Phase I was
carried out in bunkers with controlled air flow, and Phase II in a pasteurization tunnel to eliminate pests and
diseases. The physical, chemical and biological properties of these composts are summarized in Tables 2, 3 and
4.
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2.3 Casing layers
Three casing layers were used in this study: soil + peat moss “brown peat” (4:1, v/v), Dutch commercial casing
(DCC) and peat moss “brown peat” + spent mushroom substrate (SMS) (3:2, v/v). Their physical, chemical and
biological properties are presented in Tables 2, 3 and 4, respectively.
2.4 Growing of mushrooms
After applying the casing layer over the composts, the plastic boxes were transferred to the production chamber
where disinfectant treatment (formalin, 18 ml m-2), insecticide treatment (diflubenzuron 25%, 3.6 g m-2) and
fungicide treatment (prochloraz 46%, 0.62 g m-2) were done on days 1, 3 and 5, respectively. The casing was
deeply raked on day 6, and ventilation was carried out 11 d after casing to stimulate primordia formation. The
growth cycle after casing lasted 38 d, and three flushes of mushrooms were harvested.
2.5 Quality index
Were assessed the quality indexes for the two composts and three casing layers in the cultivation of A. bisporus.
2.5.1 Factors to evaluate
Any proposals to improve or increase A. bisporus yield necessarily involves through two stages of the production
process: composting and the selection and preparation of the casing layer.
As regards composts, the different factors that should be considered include changes in raw materials or
supplements, the methods used in composting (Phase I and Phase II), the formulations used, and all the other
aspects that can directly affect the physical, chemical and biological properties of the composts. For this reason,
two different composts from two commercial facilities, each prepared with a particular method, formulation and
technique, were selected.
Three casing materials were selected for the same reason. These included two organic casings (Dutch
commercial casing as a reference, and peat moss + SMS, considered an interesting alternative for growers that
reuse spent mushroom compost) and soil + peat moss (widely used worldwide), a mixture with high mineral soil
content.
2.5.2 Quality indicators
To establish the best quality indicators for the compost and casing layers that directly affect the yield of
mushrooms, were selected the following principal parameters, which can be analyzed by well-defined analytical
methods at low cost.
- Compost: moisture (Mapa, 1994), pH (Ansorena, 1994; Aenor, 2001a), total N content (Mapa, 1994; Tecator,
1987), C/N ratio (calculated from the total nitrogen and the total organic matter), and the presence of mites
(Brady, 1969; Krantz, 1986), nematodes (Nombela and Bello, 1983) and competitor moulds (Tello et al., 1991).
- Casing layer: water holding capacity (Ansorena, 1994; Aenor, 2001c), porosity (Ansorena, 1994; Aenor, 2001c),
pH (Ansorena, 1994; Aenor, 2001a), electrical conductivity (Aenor, 2001b), and the presence of mites (Brady,
1969; Krantz, 1986), nematodes (Nombela and Bello, 1983) and competitor moulds (Tello et al., 1991).
2.5.3 Critical limits for quality indicators
Based on previous data (Gerrits, 1988; Visscher, 1988; Pardo, 1994; Hearne, 1994; Pardo, 1999; Shekhar Sharma
and Kilpatrick, 2000), the laboratory records at the Centro de Investigación, Experimentación y Servicios del
Champiñón and the practical experience of the author and their collaborators in experimental and industrial
cultivation, the critical limits and the optimal values of the indicators were defined, as shown in Table 1.
2.5.4 Weights for each factor (a) and for each quality indicator (b)
Based on their relative importance for yield, the compost factor was given a weight of 0.65 and the casing layer
factor a weight of 0.35 (the numerical weights must total 1.0). We also established the weights of the quality
indicators (their sum must also be 1). The most influential indicator for the final behavior of the crop was
selected according to its importance and the possible consequences due to deviations from optimal values.
For example, in addition to being a key element in "Phase I and II" of the composting process, the total N
content of the compost is directly linked to other factors that may affect yield. A high N content would favor the
presence of contaminants such as Coprinus and Chaetomium in the compost; moreover, if poorly composted,
NH3 becomes toxic to the mushrooms, while a low N content would cause problems with fermentation during
Phase I (difficult for the temperature to reach 75-80ºC) lower yield and longer mean spawn-run time, which,
jointly, mean a higher risk of compost contamination and a longer growing cycle.
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The weight was set for each factor and quality indicator, as shown in Table I. For the different factors, the
numerical weights assigned to all the quality indicators must add up to 1.0 at each level.
2.5.5 Normalized scores obtained (c) for the indicators
The normalized score of the indicators ranged from 0 to 1.0, with 0 representing the worst value and 1
representing the best value. The scoring curves were generated using the following equation (1) (Wymore,
1993):
1
1 B L / X L
2 S B x2 L
(1)
where is the normalized score, B is the critical value or the baseline value of the indicator (a score of 0.5 sets
the difference between a bad and good quality indicator), L is the initial value, which can be lower than a
property and can be expressed as 0, S is the slope of the tangent to the curve at the critical value of the indicator
and x is the indicator value measured in the laboratory.
To apply the above-mentioned equation of Wymore (1993), the slope (S) of the tangent to the curve at the critical
value of the indicator ( = 0.5) was first calculated using the following equation (2):
1
log 1
S
BL
2B x 2 L log
xL
(2)
With the scoring curve equations, three types of normalized scoring functions were generated (Figure 1): (a)
“More is better”, e.g., water holding capacity and porosity; (b) “Less is better”, e.g., electrical conductivity and
the presence of mites; (c) “Optimum”, e.g., pH and C/N ratio.
2.5.6 Calculation of final quality index
The quality index (Q) for the cultivation of A. bisporus was obtained in two stages. The indexes of each
individual factor were first calculated (1st step), and their sum provided the factor index for each compost-casing
combination (2nd step):
m
Q1 a1 (bi ci )
i 1
(1st step).
n
Q2 a2 (b j c j )
j 1
(2nd step).
Q = Q1 + Q2
where Q1 and Q2 are the index values of the main factors (compost and casing layer), a1 and a2 are the weights of
these factors, bi and bj are the weights of the m indicators of factor 1 (compost) and the n indicators of factor 2
(casing layer), ci and cj are the normalized scores of these indicators. Q is the final quality index value.
2.6 Test of the feasibility of modeling
To verify the safety and significance of this methodology, a correlation analysis was carried out for the final
quality index values obtained for the six compost-casing combinations and the yield values recorded at the end
of the growing for the same combinations. SigmaStat 3.5 with the Linear Regression tool was used for data
analysis.
3. Results and discussion
Tables 2, 3 and 4 summarize the quality indexes obtained for each different casing layer, which include the main
factors, the indicators within each factor, the weights of each factor (a) and indicator (b), the mean observed
values, the normalized scores of each indicator (c), the factor index and the calculated values of the quality
indexes.
The data were grouped according to the casing layers, with each table showing the values obtained for one type
of casing layer cultivated with two different composts. The same method was previously used by Karlen and
Stott (1994) to define a soil quality index. These authors stated that if the observed values of the indicators were
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Vol. 3, No. 4; December 2011
equal to their critical limits, the quality index would be equal to 0.5. Values below 0.5 would represent soils with
more limitations, and values above 0.5 soils with fewer limitations.
Thus, the maximum possible value for any normalized score (c) or factor-quality index is 1.0. The closer the
value is to 1.0, the better the result selected for each evaluation.
Analyses of both the compost and the casing layers showed that all the quality index values were above the
critical limit (0.5), and arranged in the following descending order: Compost1/DCC (0.993) > Compost2/DCC
(0.990) > Compost1/Soil + peat (0.978) > Compost2/Soil + peat (0.975) > Compost1/peat + SMS (0.953) >
Compost2/peat + SMS (0.950).
It follows that compost 1 has a better factor index value than compost 2, and, as regards the casing layers, DCC
has the highest factor index value and peat + SMS (3:2, v/v) the lowest.
It is important to emphasize that this method can be used worldwide to study quality indexes for the cultivation
of A. bisporus. A database with different types of compost and casing layers used in both situations (past and
present) can be built, which will give realistic estimates of the quality indexes expected for each country.
A further examination of the data revealed little differences in the compost index values (0.995 and 0.992 for
compost 1 and 2, respectively). The lowest normalized score (c) of 0.984 was obtained for pH in compost 2,
which can still be considered a high value indicating good quality.
Based on the observed results, we conclude that the composting process was well established and developed in
these two facilities, and that the substrates were well suited for our research, especially with regard to their
physical, chemical and biological characteristics.
For fungiculture practice, it would be of great interest to periodically sample all existing composting facilities to
identify potential problems (such as technical errors in the process, limitations of the constructions and bad
materials used) and provide suggestions at critical time points.
Unlike the results obtained for the composts, substantial differences were found between the casing layers, with
the factor index values ranging from 0.989 (DCC, Table 3) to 0.876 (peat + SMS, Table 4). Possible actions to
improve the quality indicator valued below 1.0 in the peat + SMS casing would include correcting the value of
the electrical conductivity (with a normalized score (c) of 0.183), increasing the leaching of the SMS by adding
more water and extending the maturation period. Another alternative strategy would be to mix small amounts of
SMS with peat moss, black peat or mineral soil for use as casing layer.
Rendering to the yield obtained at the end of the harvest phase, this methodology showed high correlation
coefficient (R=0.829) between the yields and quality index values (Figure 2) and is therefore reliable.
According to van Griensven (1982), Flegg (1985), Oei (2003) Zied et al. (2010) and Pardo et al. (2010), the yield
values of this work (ranging from 31.0 to 37.1%) were within the range considered satisfactory (25-40%) for A.
bisporus cultivation, and can be ordered in the following decreasing order: compost1/DCC (37.1%) >
Compost2/DCC (35.9%) > Compost1/Soil + peat (34.7%) > Compost2/peat + SMS (32.1%) > Compost2/Soil +
peat (31.1%) > Compost1/peat + SMS (31.0%).
It should be noted that the factors and indicators proposed in this paper and their critical limits and weights may
not necessarily be fixed. Due to the flexibility of the factor selection process, additional indicators can always be
included for better adaption to local conditions. Logically, they can also include other factors of production such
as the grower’s knowledge (training and experience), characteristics of the facilities (construction aspects and
degree of automation) or the mycelium used.
To predict precise quality index values, more work needs to be done, and more indexes should be analyzed. With
the continuation of our current work (to test other factors-indicators and their respective weights), the proposed
quality index method will become more reliable and should eventually become an indispensable tool for
mushroom cultivation (A. bisporus and others) worldwide.
4. Conclusions
This methodology used to obtain the quality index analysis is reliable and practical for identifying problems and
can also serve as a rapid tool for possible intervention when problems occur. There was little difference between
the two composts, both of which showed high factor index values. Although the peat + SMS based casing layer
presented certain limitations as a result of its high electrical conductivity, the other two casings showed
satisfactory factor index values.
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Table 1. Compost and casing layer quality score card for the integrated management treatment
1
Compost (Phase II) = analysis done in the compost at the end of the pasteurization process for its physical,
chemical and biological conditions.
2
Casing layer = analysis done in the casing layer before the addition of colonized compost.
3
Indicators: Moisture, %; C/N ratio; pH; Total N content, %; Mites, individuals/100 g compost; nematodes,
individuals/100 g compost; Competitor moulds: the presence or absence; Water holding capacity, % and
Porosity, %.
4
Optimum: Type curve of normalized scores “optimum”; Type curve of normalized scores “less is better” and
Type curve of normalized scores “more is better”.
(a) Function level weight scores are the sums of associated Level 1 indicator values.
(b) For Level 1 indicators that are determined by Level 2 indicators (i.e., moisture), the weight scores are the sums
of Level 2 indicator values.
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Table 2. Weight (a and b) of factor and indicators, normalized score (c) and final quality index values for
evaluating soil + peat moss (4:1, v/v) casing
(a) Function level weight scores are the sums of associated Level 1 indicator values.
(b) For Level 1 indicators that are determined by Level 2 indicators (i.e., moisture), the weight scores are the sums
of Level 2 indicator values.
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Table 3. Weight (a and b) of factor and indicators, normalized score (c) and final quality index values for evaluating
DCC (4:1, v/v) casing
(a) Function level weight scores are the sums of associated Level 1 indicator values.
(b) For Level 1 indicators that are determined by Level 2 indicators (i.e., moisture), weight scores are the sums of
Level 2 indicator values.
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Table 4. Weight (a and b) of factor and indicators, normalized score (c) and final quality index values for evaluating
brown peat + spent mushroom substrate (2:3, v/v) casing
(a) Function level weight scores are the sums of associated Level 1 indicator values.
(b) For Level 1 indicators that are determined by Level 2 indicators (i.e., moisture), weight scores are the sums of
Level 2 indicator values.
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a
Mites, individual 100g-1 compost
c
Figure 1. (a) “More is better” normalized score function as applied to water holding capacity. (b) “Less is better”
normalized scoring function as applied to the presence of mites. (c) “Optimum” normalized scoring function as
applied to C/N ratio
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Figure 2. Correlation between the quality index values and the yields of A. bisporus obtained for two composts and
three casing layers (*SEE = standard error of estimate)
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