Guidelines for Storing Grains in Plastic Bags
This is a low-cost technology, but various
points must be kept in mind in order to avoid losses
during the storage of the grains:
The basic principle is to keep the grains
dry in a modified atmosphere, with low oxygen content and a high
concentration of carbon dioxide (CO2). This gives
control of insects and fungi that are the major causes of
increases in the temperature of the grains.
It should also be considered that grains are
living organisms and must be healthy, clean and without
mechanical damage in order to have a greater chance of maintaining
their quality during storage.
The place where the bag is laid must be as
high as possible, far from trees and from any possible source of
breakages. The ground must be firm and plain, to enable the bag
to be laid properly without its bottom part breaking. This also
helps when emptying it. It must be laid in a north – south
The suitable make-up of the bag depends on
many factors, one of which is the quality of the bagging
machine. With a well-built and well-designed machine, it is
easier to obtain well-made-up bags.
The principle for making up the bag, so that
it stretches appropriately, is based on maintaining a dynamic
and steady rhythm while filling it. This is done by regulating
the braking, which depends on the brake of the machine itself
and on good preparation of the land.
Bag quality is fundamental for good
conservation. The bag must permit sufficient stretching over a
prolonged period of time, without losing its grain-holding
capacities and its impermeability.
It should be noted that the pressure when
filling is mainly produced by the specific weight of each
particular grain, and to a lesser extent by the auger of the
bagger. As the grain pours in, it gradually pushes the cereal
lightly against the bag-filling wall. The bag in turn exerts
resistance to the stretching that is regulated mainly with the
All these factors must come together for the
bag to be made up with a diameter that is even and with uniform
stretching. This requires the bag to be filled well enough to
expel the greatest possible quantity of air, neither leaving the
bag "loose", nor surpassing the stretching capacity
recommended by the manufacturers. This is measured by the rule
found on the side of the bag.
The most important aspect to bear in mind is
the augers, both of the bagger and of the extractors. The augers
should be of the greatest diameter possible, well-centred in the
tube, well-finished, with low revolutions and working with the
least possible slope. They must also be operated completely
full. When the augers are worn, it is better to avoid using the
machine, since this causes significant mechanical damage to the
grains. The augers should be changed, for a new one, once they
As a general rule, the humidity with which
the grains should be stored must not be greater than the base
humidity for commercialization. The lower the humidity of the
grain, the better it will keep and the more time it will be
possible to keep it. In the case of seeds, the conditions are
As the humidity of the grain to be bagged
increases, so too does the risk of damage. Tests made by INTA
have shown that the quality of grains tends to deteriorate when
they are stored in silo bags for a long period of time and with
high humidity content. Damp grains can only be stored in plastic
bags when it is an emergency and there is no other alternative.
In these cases it is advisable to mount, 40 cm above the bag, a
cover with a plastic net (80% of shadow) when the spring comes.
It will attenuate the incidence of the outside temperature and
reduce the risk of grain damage.
It should be remembered that this is a
simple technology, but that it needs extreme care to protect and
maintain the integrity of the bag. There must be permanent
monitoring so that any breakages are immediately repaired.
Lastly, particular care must be taken after
emptying the bag to pick up all the remains of plastic. Plastic
remains are one of the most dangerous contaminants of the
environment. The farmer is recommended to collect every kind of
plastic (used bags and containers from pesticides) and keep them
in one place to be sold later. Every measure should be taken to
ensure they do not scatter around the environment.
When planning storage in plastic bags, it is
recommended to keep in mind the following guidelines:
Guidelines for Storing Dry Grains
in Plastic Bags
It is not recommended to store wheat
with a humidity above
14% for a long period (greater than 90 days)
As the ambient temperature increases, the risks
When the grains are damaged, the risks increase When the grains are dirty
(impurities), the risks increase.
The risk is measured taking into consideration
the humidity of the grain, the normal aging of the bag and the
possibility of the bag being broken by external agents. It As
the ambient temperature increases, the risks increase When
the grains are damaged, the risks increase When
the grains are dirty (impurities), the risks increaseimportant
to bear in mind that these risk values are guidelines, are not
absolute and that they may vary in different situations.
With these guidelines the farmer can plan the
storage and the monitoring that must be carried out so as not to
lose quantity and quality in the grains being kept. That is, for
example, that the bags containing grains that are damper, and/or
damaged, and/or with impurities, will be the ones that must be taken
care of most intensively. These must be the first ones to be
delivered for commercialisation, and the others that contain dry,
healthy and clean grains left for the end.
This is a simple technology
but it needs maximum care: in the quality of the grain to be stored,
in the quality of the bag, in its filling and in its subsequent
Information prepared by: Cristiano Casini,
INTA EEA Manfredi – January 2005