| Aeration
The primary purpose of aeration is to maintain
the condition of the crop stored in a bin. Hot spots cause
spoilage and provide an environment in which bug infestations
can develop. An aeration system moves a low volume of air
through the crop, dissipating heat and preventing hot spots.
Aeration offers only minimal drying, so a system
designed for aeration should not be used to dry crop. Aeration
does not offer the advantage of an earlier crop harvest
as offered by Natural Air Drying and Pressure Curing.
As a rule of thumb aeration requires an air
flow of 0.1 - 0.15 CFM per bushel.
Natural Air Drying
Natural Air Drying is a process which removes
moisture from stored crops. With a Natural Air Drying system you can harvest
a crop with a 16-20% moisture content and remove moisture down
to an optimal moisture content. Once drying is complete the
Natural Air Drying system can provide aeration for long term crop storage.
A Natural Air Drying system dries a crop by
evaporation. Air flows by kernels, absorbing moisture and
carrying it out of a bin. A drying front starts at the bottom
of the stored crop. As the bottom kernels dry, the drying
front moves upwards towards the top.
The drying process may take several weeks,
depending upon the crop condition, airflow, outside humidity
and temperature. Natural Air Drying requires that a crop is
dried within the allowable storage time before spoilage has
a chance to occur, so sufficient airflow is essential. Airflow
of 0.5-1 CFM is normal for a Natural Air
Drying system.
In certain conditions of high relative humidity
(a factor of cooler temperatures) air cannot absorb moisture
so drying cannot occur. For this condition low temperature
supplemental heaters should be used. The purpose of the
heaters is not as much to raise the temperature, but to
lower the relative humidity of the air by increasing its
temperature. (For more information on heaters, click
here.)
Natural Air Drying offers a number
of advantages:
| Earlier harvests |
A crop dried in storage is crop not
dried in the field. Crops can easily loose grade waiting
to dry 14% in the field. |
| Reduced shellage |
Department of Agriculture tests show that
wheat kernel damage is at a minimum when combined at 20%
moisture. Having the option to dry in the bin allows the
option to combine at a higher moisture content. |
| Optimum moisture content |
Field drying can result in a crop dropping
below 14% moisture. A Natural Air Drying system allows drying
to be stopped at 14%, keeping the weight in the kernel and
putting the cash in your pocket. |
| Insect control |
Insects will remain dormant when a stored
crop is below 50ºF (or 10ºC). Using airflow when
the outside air temperature is cool enough can keep a crop
below the critical temperature. |
| Test weights |
Crops harvested at a higher moisture content
are often 2-6 pounds per bushel greater than crops harvested
with lower moisture content. This happens because the kernel
retains more nutrients. When a crop is left in the field
some of the nutrient is absorbed by the stalk. |
| Crop quality |
Kernel quality is often much higher for
crops conditioned with natural air compared to crops subjected
to heated drying. Natural air leads to less shell cracking
and better color, tests weight and germination percentage. |
| Low drying cost compared to
heat dryers |
Natural Air Drying systems have low capital costs and
operating costs compared to batch drying systems which use
heat to dry. |
| Peace of mind |
Natural air drying offers opportunities
for crop management and reduces the risks imposed by
the weather. |
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