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AN INSIDE LOOK AT THE SILO-BAG SYSTEM
Ricardo Bartosik*
National Institute of Agricultural Technologies (INTA), Ruta 226 km 73,5 (7620), Balcarce,
Buenos Aires Province, Argentina
*Corresponding author's e-mail: rbartosik@balcarce.inta.gov.ar
ABSTRACT
The silo-bags are a hermetic type of storage widely adopted. This paper summarizes the
results of the effect of silo-bag storage on the commercial quality of corn, soybean,
wheat, sunflower, malting barley, canola and beans. The effect of the modified
atmosphere on insect population and storage fungi, and recommendations for proper
storage conditions in the silo-bags are also presented.
Overall, when dry grain is stored in silo-bag, the CO2 ranges from 3 to 10% and the O2
from 18 to 10%. The degree of modification of the interstitial atmosphere increases with
the grain m.c. and temperature having typical CO2 concentration of 15-25% and O2 of 2-
5% for wet grain.
There are few reports of insect presence in silo-bags. Analysis of data indicates that
unfavorable environmental conditions negatively affect insect development. Thus, storage
in silo-bags under the analyzed climate conditions help to maintain grain without notable
insect populations.
When grain is stored in silo-bags at m.c. that would allow for mold development, the
mold activity is lower compared with that of normal atmosphere storage conditions.
Additionally, grain temperature inside the silo-bag is mainly affected by the ambient
temperature. Silo-bags have a high heat exchange rate with the air and soil (double
surface/volume ratio than regular bins), so no heat damage is observed, even when wet
grain is stored in temperate weathers.
The overall results indicate that dry grain (equilibrium relative humidity below 67%) can
be stored in silo-bag for more than six months without losing quality (measured as
percentage of mold damaged grain, test weight, germination, fat acidity, and nutritional
and organoleptic parameters, among others). When grain m.c. increases, commercial
quality could be maintained for up to six months in winter time, to less than three months
in summer time. In all cases, maintaining the airtightness of the bag is a key factor for
successful storage. A monitoring system for silo-bags based on measuring CO2
concentration was also developed.
Key words: hermetic storage, modified atmosphere, storage, quality, cereal, oilseeds
INTRODUCTION
The silo-bags are a hermetic type of storage made with a plastic bag, with the shape of a tube,
of 60 m long and 2.74 m diameter. The plastic cover is made of three layers (white outside
and black inside) with 235 µm of thickness.
Each bag can hold approximately 200 tonnes of grain and with the available handling
equipment is very easy to fill. The new generation of high capacity combines found in the
Bartosik R (2012) An inside look at the silo-bag system. In: Navarro S, Banks HJ, Jayas DS, Bell CH, Noyes RT,
Ferizli AG, Emekci M, Isikber AA, Alagusundaram K, [Eds.] Proc 9th. Int. Conf. on Controlled Atmosphere and
Fumigation in Stored Products, Antalya, Turkey. 15 – 19 October 2012, ARBER Professional Congress Services,
Turkey pp: 117-128
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silo-bag system is the ideal partner, since the loading capacity of the bagging machine is
basically limited to the transportation capacity between the combine and the place where the
bag is filled. Several companies also developed machineries to unload the plastic bag
transferring the grain directly from the silo-bag to the truck or wagon with a high capacity
(more than 180 tonnes/h).
Argentina is the country in which the silo-bag was developed for storing dry grains.
Since mid 1990’s when it was introduced, the silo-bag system gained rapid adoption in the
agricultural and industrial sector. Each year, more than 40% of the total production of the
country is stored in the silo-bags (more than 40 million tonnes in year 2011).
Due to the successful experience in Argentina, the silo-bag system is now being adopted
in more than 40 countries worldwide, from countries with tropical weather (i.e. Sudan) to
countries with cold weather (i.e., Russia).
There was an important development regarding to the bagging (loading) and unloading
equipment. The operating capacity of the loading and unloading equipment is higher than 180
tonnes/h. Fig. 1 shows a picture of a typical loading and unloading equipment.
Fig. 1- Images of loading (left) and unloading (right) machines.
A LOOK INSIDE OF THE SILO-BAG
Environment and Relationships
Fig. 2 shows a diagram of the main factors affecting the ecosystem of the silo-bag and the
relationship among them. Based on this model, the respiration of grains, fungi, insects and
other microorganisms present in the grain ecosystem consume the O2 and generate CO2, heat
and water. The respiration process also consumes the grain energy sources (starch, oil or
protein), which could be quantified as dry matter loss (DML).
The respiration rate is affected by grain type and condition, m.c., temperature, storage
time, and O2 and CO2 concentrations. These last two factors make a difference between the
respiration rate of grains in regular storage structures and hermetic structures.
The temperature of the grain depends on the initial grain temperature (this effect is less
important as the storage period increases), the effect of the sun radiation, the heat release from
the respiration process, and the transfer of heat with the air and soil. The grain m.c. depends
on the initial grain m.c., the entrance of moisture from the outside (through openings after a
rain event into broken or poorly sealed silo-bags), and the moisture released from the
respiration process. Additionally, due to the day and night temperature differential, some
moisture condensation can occur in the top grain layers resulting in a localized spot of wetter
grain.
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For any particular time, the CO2 and O2 concentration in the silo-bag depends on the
balance between respiration (consumption of O2 and generation of CO2), the entrance of
external O2 to the system, and the loss of CO2 to the ambient air. The movement of gases in
and out of the silo-bags depends on the gas partial pressure differential and the permeability
of the system (through openings in the plastic cover, or through the natural permeability of the
plastic material to the gases).
Respiration:
Molds
Insects
Grain
Yeasts
Grain type and condition
Moisture content
Temperature
Storage time
O
2
and CO
2
concentration
Factors affecting respiration
Moisture through
plastic perforations
[O2]
[CO2]
Sun radiation
Dry matter
Heat
Moisture
Oxygen enters
through
plastic
permeability or
perforations
Carbon
dioxide exits
through
plastic
permeability
or
perforations
Exchange of heat with
the air and soil
Moisture condensation
and migration
Moisture condensation
and migration
Soil
Air
Heat
exchange
Heat
exchange
Respiration:
Molds
Insects
Grain
Yeasts
Grain type and condition
Moisture content
Temperature
Storage time
O
2
and CO
2
concentration
Factors affecting respiration
Moisture through
plastic perforations
[O2]
[CO2]
Sun radiation
Dry matter
Heat
Moisture
Oxygen enters
through
plastic
permeability or
perforations
Carbon
dioxide exits
through
plastic
permeability
or
perforations
Exchange of heat with
the air and soil
Moisture condensation
and migration
Moisture condensation
and migration
Soil
Air
Heat
exchange
Heat
exchange
Fig. 2- Section diagram of the silo-bag showing the main factors affecting the grain
ecosystem, the relationship among them and with the external environment.
EFFECT OF AMBIENT TEMPERATURE
Bartosik et al. (2008a) indicated that the grain temperature at the surface showed the
distinctive pattern of the ambient air temperature, reaching its maximum at noon and
minimum during the early morning ( 3). The daily temperature oscillation decreased with
the grain depth, being not noticeable after 0.7 m depth. It was also demonstrated that the
average grain temperature in the silo-bags followed the pattern of the average ambient
temperature through the season.
In a field experiment, silo-bags with wheat were set up during the summer time with
grain temperatures close to 40°C. The silo-bag was able to dissipate the heat in the grain to
the ambient air and the soil in a couple of months, reducing the grain temperature to less than
17°C by early May (Fig. 3). This could be explained with the relation volume/surface, which
is substantially lower for silo-bags (0.7 for a 200 tonnes silo-bag) than for a regular bin of
similar storage capacity (1.27 for a 7 m diameter and 9 m height bin of 200 tonnes capacity).
On the other hand, soybean and corn, harvested during the fall and winter, were able to
maintain the temperature below 17°C until early November. Similar results were reported by
Barreto et al. (2012) simulating the effect of ambient conditions on wheat silo-bags
temperature in different regions of Argentina.
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0.0
5.0
10.0
15.0
20.0
25.0
30.0
35.0
40.0
45.0
50.0
Jan-01 Feb-01 Mar-01 Apr-01 May-01 Jun-01
Time
Temperature ºC
Fig. 3-Temperature pattern at different grain depths (top, middle and bottom) during storage
of wheat in a silo-bag from January to June. Source: Bartosik et al. (2008).
Effect of Grain Moisture Content
Since the silo-bag is made of a hermetic plastic cover, no moisture variation should be
expected during storage, unless rainwater enters to the bag through openings. Gaston et al.
(2009) mentioned that the temperature differential between the top layer and the rest of the
bag caused migration of moisture from the core of the grain mass to the top layer, and, to a
lesser extent, to the bottom layer. Moisture migration can lead to m.c. rise in some grain
layer, increasing the risk of grain spoilage (and grain quality deterioration) in localized areas
of the silo-bag. Up to the present, it is not clear the magnitude of the moisture stratification
process during storage in the silo-bag. Gaston et al. (2009) considered that grain m.c., grain
temperature, grain temperature fluctuation magnitude and storage time affect the magnitude
of m.c. stratification.
Darby and Caddick (2007) reported moisture stratification during storage of dry barley
       -punctured silo-bags. This stratification
increased m.c. in the peripheral layer up to 13% over winter, but remained dry over summer
   ain could be stored in perfect condition
for up to 6 months. On the other hand, Ochandio et al. (2009) did not find m.c. stratification
in 12% m.c. barley silo-bags, even after 1 year of storage.
Respiration of Biological Components
Grain, insects, fungi and other microorganisms respire, consuming grain constituents and O2
from the environment, and releasing to the interstitial environment CO2, water and heat.
Grain type, m.c., temperature, storage time and O2 and CO2 concentrations affect the
respiration rate. Most of the factors influencing respiration in silo-bags could be modeled.
However, there are no correlations available for predicting respiration rate of grains stored
under hermetic conditions (oxygen depleting environments). In order to further improve the
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modeling of modified and controlled atmospheres it is necessary to generate suitable
correlation for predicting respiration in O2 restricted environments.
Permeability
The transfer of gases between the inside and outside of the silo-bag depends on the gas partial
pressure differential and the effective permeability of the silo-bag to gases (permeability of
the plastic layer film and perforations). While the permeability of the plastic cover could be
measured or estimated based on the characteristics of the plastic material (most of the silo-
bags are made of similar materials and have similar thickness), the permeability due to
perforations is more difficult to estimate since the size, shape, location and number of
perforations differ substantially among different silo-bags.
Plastic Cover
The permeability of the silo-bag plastic cover depends on the thickness and material
composition, both set by the manufacturing process. The silo-bag is made of a three layer
plastic of 230 to 250 µm thickness, black inside and white outside. The plastic layers are a
mixture of high density (HDPE) and low density polyethylene (LDPE). The plastic layer has a
differential permeance to O2 and CO2. For a silo-bag with an average thickness of 240 µm,
Abalone et al. (2011) estimated that the permeance to O2 was 4.06× 10-4 m3d-1m-2atm-1 and to
CO2 was of 1.34× 10-3 m3d-1 m-2 atm-1.
Perforations
Perforations in the plastic cover increase the exchange rate of gases between the inside and
the outside. Simulations were performed by Abalone et al. (2011) to explore the effect of
structural damage of the silo-bag. It was shown that even a small perforation can significantly
change the evolution of gas composition, from 1 percentage point for one perforation of 1 mm
diameter per linear meter of a silo-bag, to more than 5 percentage points for one perforation of
10 mm diameter.
The effect of number of perforations on gaseous composition was also investigated.
Wheat at 13% m.c. and 25°C stored in a completely airtight silo-bag reached a CO2
concentration of 6.5% and a O2 concentration of 12%. One perforation of 3 mm diameter per
meter of silo-bag reduces the CO2 concentration to 4.5% and increases the O2 concentration to
15%, while 5 perforations per meter resulted in a decrease in the CO2 concentration to 1.5%
and an increase in the O2 concentration to 19.5% (Abalone et al., 2011).
Oxygen and Carbon Dioxide Concentration
The CO2 and O2 concentration in any given time is the result between the respiration rate
(depletion of O2 and generation of CO2) and the gas exchange rate with the outside (entrance
of O2 and exit of CO2). Gas concentration data were measured over time for different grains
and storage conditions (m.c.) ( 4). Typically, for dry grains, the O2 concentration
equilibrates between 10 and 18%, while the CO2 concentration equilibrates between 3 and
10%. For wet grains (equilibrium relative humidity higher than 67%) the O2 concentration
drops to 2 to 5%, while the CO2 rises to 15 to 25%. In some cases, with exceptionally wet
grain, the CO2 concentration can reach values as high as 70% (O2 close to 0%).
Silo-bags would act as a typical modified atmosphere system when the grain is wet
enough to hold biological activity that would consume the O2 at a higher rate than O2 is
entering to the bag from the outside through the plastic cover. Under this situation the O2
concentration will drop below the limit at which aerobic respiration starts to be limited. This
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observation is in agreement with Darby and Caddick (2007) in their comprehensive report
made about silo-bags in Australia.
Fig. 4-O2 and CO2 concentration during storage of dry (a) and wet (b) grains in silo-bags.
Adapted from Bartosik et al. (2008). Legends: solid line, CO2; dashed line, O2

The temperature also has a positive effect on the biological activity, but the interaction
with m.c. shows that the effect of temperature is higher in wet grain storage than in dry grain
storage ( 5). This would imply that dry grain would not hold significantly different
biological activity in winter or summer, but storing wet grain could be substantially more
challenging (affected by biological activity) in summer than in winter time.
Fig. 5- Predicted evolution of O2 and CO2 concentrations during storage from summer
(January 1) to winter (July 30) for different initial storage temperatures of grains. Initial grain
moisture content: a) 12% w.b; b) 13% w.b; c) 14%w.b. Initial grain temperature- -
 
Effect on Quality
Wheat
The storage of dry wheat (12.5% m.c.) during 6 months in a silo-bag resulted with no
substantial reduction in the test weight, neither affecting the baking quality parameters (loaf
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volume, gluten %, w, etc). When 16.4% m.c. wheat was bagged in January the average grain
temperature was of 42°C. The combination of high m.c. and high temperature resulted in a
substantial decrease on most of the quality parameters evaluated. Test weight decreased from
78.7 to 77.3 kg/hl, although this decrease did not change the commercial grade of the wheat.
Additionally, all the baking quality parameters were negatively affected, making this wet
wheat not suitable for flour milling purposes.
Corn
The grain bagged at 14.8% m.c. resulted with a slightly higher test weight after 150 days of
storage, while the percentage of damaged kernels increased by 1.3 percentage points (the
initial percentage of damaged kernel was greater than 3%). The wet corn samples (19.5%
m.c.) resulted with a reduction in the test weight of 2 kg/hl, and a substantial increase of the
damaged corn faction of 4.4 percentage points.
Soybean
The soybean bagged at 12.5% m.c. did not substantially modify the test weight and oil
percentage of the samples after 150 days. On the other hand, the oil acidity index and the
germination were, slightly affected. The wet soybean samples (15.6% m.c.) did not result in
effect on the test weight and the percentage of oil, but resulted with an increase in the oil
acidity index from 1.7% to 2.3%.
Barley
Malting barley stored dry (below 12% m.c.) for a storage period from 6 to 12 months did not
have negative effect on the germination (always remained above 98%). In one study including
56 silo-bags, only 2 resulted with germination test values of 94%, and one with values of
86%. The protein content typically did not change during storage, being the highest change
observed of 1 percentage point after 6 months of storage (Ochandio et al., 2009; Cardoso et
al., 2010; Massigoge et al., 2011).
Sunflower
When sunflower was bagged at 8.4% m.c. no reduction in oil composition was observed,
while the oil acidity index slightly increased from 0.9 to 1.4%. This increase in the oil acidity
index did not affect the commercialization standard grade of sunflower, since the oil acidity
index limit for the argentine standard is 1.5% until August 31, and 2% thereafter. Thus,
storage of dry sunflower (below 11% m.c.) is a safe practice, since the industrial quality
parameters were not affected after 150 storage days. Storing of wet sunflower (16.4%)
resulted in a reduction of oil composition of 1.3 percentage points (from 47.0 to 45.7%) after
150 storage days, and a more substantial increase in the oil acidity index (0.9 to 3.9%).
Canola
The r.h. in the interstitial air of canola remained below 50% along the entire storage period
(canola m.c. of 6%). The m.c., foreign matters and fat values remained unchanged throughout
the storage period. The fat acidity increased during storage in 0.7 % points, reaching a final
value of 1.4%, but did not represent a commercial quality loss (Ochandio et al., 2010).
Seeds
When seeds are stored with low m.c. (equilibrium r.h. below 67%), no substantial reduction in
the germination was observed for wheat (Bartosik et al., 2008a) and barley (Ochandio et al.,
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2009; Cardoso et al., 2010; Massigoge et al., 2010). In the case of soybean it was observed
that when the initial germination values were low, there was a substantial decrease of this
parameter during storage, even for m.c. as low as 12.5% (Bartosik et al., 2008a). Additional
data showed that when the initial germination value was high (i.e., above 95%), the soybean
seed viability did not change during storage when the m.c. was below 12.5%. However, when
the seed was stored at a m.c. higher than 12.5%, the number of samples in which a reduction
in the germination was observed increased.
Molds and Mycotoxins
In grain ecosystems, the most important abiotic conditions that influence mold growth and
mycotoxins production are aw, temperature, and gas composition. Fungal species involved in
the deterioration of stored grain are obligate aerobes, but they can grow under conditions of
reduced levels of oxygen, and some species can tolerate high levels of CO2. Additionally,
modified atmospheres also had been reported to have control effect on mycotoxin production
at both, high CO2 concentration and low O2 concentration (Chulze, 2010).
Pacin et al. (2009) reported fumonisin in corn silo-bags. The contamination levels
recorded at the closing of the silo suggest that contamination with molds and fumonisins are
more dependent on the grain conditions at the moment of entrance to the silo bags than on the
duration of storage.
Castellari et al. (2010) indentified two potential producers of aflatoxins (A. flavus and A.
parasiticus) and a potential producer of fumonisins (F. verticillioides) in corn silo-bags with
m.c. from 14 to more than 20%, although toxins levels were not tested.
Most of the mold species typically present in grains cannot develop in environments
with r.h. below 67-65%, which corresponds with an equilibrium m.c. of 14% in wheat and
corn, 12.5% in soybean and 8-9% in sunflower. Under this storage condition in the silo-bag
the mold activity is basically stopped, and hence the mycotoxin production.
When storing grain at a m.c. that would support mold growth (equilibrium r.h. higher
than 67%), the mold activity and the mycotoxin production would be affected by the
atmosphere composition. If the grain is wet, thus the microbial activity would deplete the
oxygen rather quickly (few hours), preventing mold damage and mycotoxin production.
However, if the grain is slightly wet, the modification of the interstitial atmosphere would be
rather slow, and many days (and may be months) would be required to reach the level of mold
suppression. Under this condition mycotoxin production could be possible. Additionally, if
the grain is wet (high biological activity) but the silo-bag has a low airtight level (i.e., bad
sealing of the closing end, perforations, etc), oxygen will enter from the outside allowing
mold development and mycotoxin production. The relationship among grain m.c., the effect
on biological activity, the resulting CO2 and O2 concentration and how this affect the
mycotoxin production is yet not fully understood for typical silo-bag storage conditions and
more research is needed.
Insects in the Silo-bag
There are relatively few reports of insect infestation of grain stored in silo-bag. Massigoge et
al. (2010) reported that insects were observed in 10 barley silo-bags out of 56 monitored. The
wheat milling industry, which uses silo-bag for storing dry wheat, indicates that the presence
of insects is more frequent during summer time and in silo-bags filled with grain that has been
previously stored in regular bins (not coming from the field).
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Conditions that Affect Insect Development in Silo-bags
The insect development in silo-bags is limited because: 1) most of the silo-bags are filled with
grain coming directly from the field. The presence of stored grain insects in the field is rather
scarce, depending on the ambient condition of the harvest time (temperature, r.h.), proximity
to storage structures, etc, but most of the time the grain comes form the field free of insects.
Additionally, during the harvest operation the grain passes through the combine, then to a
truck or wagon and then to the bagging machine, reducing the risk of infestation when
compared to grain stored at the elevators. 2) The plastic bag itself comes free of insects, in
comparison with regular bins which could be infested prior to the harvest. 3) Once the grain is
stored in the silo-bag, the plastic cover acts as a physical barrier, preventing the entrance of
insects. 4) The temperature of the grain inside of the silo-bag follows the average ambient
temperature throughout the year. Thus, in temperate and cold climates, during the fall and
winter the grain temperature will drop below the range of insect activity (15-17°C), reducing
substantially their development. 5) When grain is stored with m.c. above the mold activity
limit, the O2 concentration can drop below the 2% and the CO2 concentration can rise above
20%, creating a lethal environment for insects.
Based on these considerations, the most critical situation that would favor insect
development (and damage) in the silo-bags is when the bag is filled with previously infested
grain, the grain is stored over summer time (grain temperature between 25 and 30°C), and the
grain is too dry to create a lethal atmosphere for insects.
Phosphine Fumigation
Phosphine fumigation in silo-bags has been successfully implemented when insect control is
required. Cardoso et al. (2009) showed that applying aluminum phosphine pellets each 5 m
along the silo-bag with a dose of 1 g of PH3 (3 g of aluminum phosphide) per tonne was
sufficient to hold 200 ppm during 5 days in the almost entire grain mass. The critical point
was the closing end, where a re-application after 3-4 days was recommended. In a similar
study using a phosphine dose of 1.5 g m-3 in wheat, Ridley et al. (2011) found that complete
control of all life stages of R. dominica was achieved at all locations in the fumigated silo
bags.
Monitoring Grain Quality (CO2 Monitoring)
The respiration of the biotic components of the grain mass (fungi, insects, and grain) increases
CO2 and reduces O2 concentrations. Thus, the degree of modification of the gas composition
in the interstitial air could be related to the biological activity inside the silo-bag, and can be
used as a monitoring tool to detect early spoilage problems (Bartosik et al., 2008b). INTA
developed the CO2 monitoring technology with a private company (Silcheck, Lincoln,
Argentina). Trained personnel with a portable CO2 meter measures interstitial atmosphere
CO2 composition every 6 m along the bag, perforating the plastic cover with a needle (this
operation takes less than 10 min for the entire bag). The information is uploaded to a server
where the data are automatically analyzed and processed, a storage risk index is elaborated for
each environment of the silo-bag, and the storage condition of the silo-bag can be monitored
through internet. In case of detecting unsafe storage conditions, an automatic report is sent to
the owner of the silo-bag through e-mail, fax or by cell phone SMS.
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Fig. 6-a) CO2 concentration during storage of one silo-bag without storage problems (--)
and two silo---) with soybean at m.c. around 13.5%
(Source: Bartosik et al., 2008b). b) CO2 meter and internet report with visual information
showing in a color scale the storage risk index.
Recommendation for Successful Storage with Silo-bags
The overall results indicate that dry grain (equilibrium r.h. below 67%) can be stored in silo-
bag for more than six months without losing quality (measured as percentage of mold
damaged grain, test weight, germination, fat acidity, and nutritional and organoleptic
parameters, among others). When grain m.c. increases, commercial quality could be
maintained from three to six months in winter time, and from one to three months in summer
time.
Silo-bags storing dry grain will not create a lethal environment for insects. However,
low temperatures during winter in temperate climates will affect insect development. Storing
grain at m.c. that can hold mold activity would create a lethal environment for insects, but the
storage time will be limited due to effects on grain quality. Phosphine fumigation in silo-bags
is a simple and effective insect control methodology.
Prior to set up the silo-bag, the site selection is a key factor. The piece of land should be
high and with a slight slope to avoid rain water accumulation that, potentially, could enter into
the silo-bag through perforations. A smoothing and leveling operation of the ground should be
done. The soil should not have materials that could damage the bottom of the silo-bag during
the filling operation, such as stones, residues of the crop, etc. Additionally, sites that are close
to trees should be avoided to place silo-bags, since falling branches can damage the bag.
Maintaining a high airtightness level is a key factor for successful storage. Good care
should be taken to maintain the plastic cover integrity during the bag filling operation and
during storage. It is also critical to make a proper sealing of the closing end. Thermo sealing
seems to be the most appropriated technique for ensuring a high airtightness level.
Place the silo-bags in pairs, leaving one open road for the unloading operation before
the next pair of silo-bags. With this configuration, any silo-bag could be unloaded at any time
(i.e., because a spoilage problem was detected), without having to unnecessary unload an
extra bag.
127
Set up a fence around the silo-bags to keep out the animals, either wild or domestics
(i.e., dogs and cats). The fence could be permanent, or made with electrified wires, such as
those used for cattle. The wires should be placed at different heights, according to the typical
animals of the location.
Some animals, such as birds and rodents, cannot be controlled by a fence. Thus, a
rodent monitoring and control program must be implemented. Keeping clean and mowing or
spraying herbicide in the silo-bag area will also help to prevent animal activity around the
silo-bags.
The silo-bags should be periodically inspected. Any perforation should be properly
sealed immediately. Avoid probing the silo-bag, since the patches often get detached. It is
convenient to collect grain samples for quality control during the bag filling operation.
Monitoring of the grain storage condition should be done by measuring CO2 concentration,
since it does not affect the physical integrity of the bag.
REFERENCES
Abalone R, Gastón A, Bartosik R, Cardoso L, Rodríguez J (2011) Gas concentration in the
interstitial Atmosphere of a wheat silo-bag. Part II: Model sensitivity and effect of grain
storage conditions. J Stored Prod Res 47: 276-283.
Bartosik R, Rodríguez J, Cardoso L (2008a) Storage of corn, wheat soybean and sunflower in
hermetic plastic bags. Proceedings of the International Grain Quality and Technology
Congress, July 15-18, Chicago, Illinois, USA.
Bartosik R, Cardoso L, Rodríguez J (2008b) Early detection of spoiled grain stored in
hermetic plastic bags (silo-bags) using CO2 monitoring. Proceedings of the 8th
International Conference Controlled Atmospheres and Fumigation of Stored Products,
from September 21-26, Chengdu, China.
Barreto A, Abalone R, Gastón A, Bartosik R (2012) Computer simulation of gas
goncentration in the interstitial atmosphere of a wheat silo-bag for typical agricultural
areas of Argentina. Presented at the 9th International Conference on Controlled
Atmospheres and Fumigation on Stored Products, October 15-19, Antalya, Turkey.
Cardoso L, Ochandio D, de la Torre D, Bartosik R, Rodríguez J (2010) Storage of quality
malting barley in hermetic plastic bags. Proceedings of the International Working
Conference on Stored Product Protection, June 27 to July 2, Estoril, Portugal.
Cardoso L, Bartosik R, Milanesio D (2009) Phosphine concentration change during
fumigation in hermetic plastic bags. Proceedings of the CIGR Section V International
Symposium, September 1-4, Rosario, Argentina.
Castellari C, Marcos Valle F, Mutti J, Cardoso L, Bartosik R (2010) Toxigenic fungi in corn
(maize) stored in hermetic plastic bags. Proceedings of the International Working
Conference on Stored Product Protection, June 27-July 2, Estoril, Portugal.
Chulze S (2010) Strategies to reduce mycotoxin levels in maize during storage: a review.
Food Additives and Contaminants 27(5): 651657.
Darby J, Caddick L (2007) Review of grain harvest bag technology under Australian
conditions. Technical report Nº: 105. CSIRO Entomology. Available at:
http://www.csiro.au/resources/HarvestBagReport.html. Accessed in June 2009.
Gastón A, Abalone R, Bartosik R, Rodríguez J (2009) Mathematical modeling of heat and
moisture transfer of wheat stored in plastic bags (silo-bags). Biosystems Eng 104: 72-
85.
128
Massigoge J, Cardoso L, Bartosik R, Rodríguez J, Ochandio D (2010) Almacenamiento de
cebada cervecera en silo bolsas. In Spanish: “Storing of malting barley in silo-bag”.
Proceedings of the IX Congreso Latinoamericano y del Caribe de Ingeniería Agrícola -
CLIA 2010 y XXXIX Congresso Brasileiro de Engenharia Agrícola - CONBEA 2010.
July 25-29, Vitória - ES, Brasil.
Ochandio D, Cardoso L, Bartosik R, de la Torre D, Rodríguez J, Massigoge J (2010) Storage
of canola in hermetic plastic bags. Proceedings of the International Working Conference
on Stored Product Protection, June 27-July 2, Estoril, Portugal.
Ochandio D, Rodríguez J, Rada E, Cardoso L, Bartosik R (2009) Almacenamiento de cebada
cervecera en bolsas plásticas herméticas. In Spanish: “Storage of malting barley in
hermetic plastic bag”. Proceedings of the X Congreso Argentino de Ingeniería Rural y
II del Mercosur (CADIR), September 1-4, Rosario, Argentina.
Pacin A, Ciancio Bovier E, González H, Whitechurch E, Martínez E, Resnik S (2009) Fungal
and fumonisins contamination in Argentine maize (Zea mays L.) silo bags. J Agric Food
Chem 57: 27782781.
Ridley A, Burrill P, Cook C, Daglish G (2011) Phosphine fumigation of silo bags. J Stored
Prod Res 47: 349-356.
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