What might be one reason why the carrot on the left is
nicely shaped and the carrot on the right is bent?
It could be several things, but one reason may be that
the seed planted to produce the carrot on the left was
evenly spaced in the soil and the seed spacing for the
carrot on the right was less uniform. Seeds that are
planted too close together can produce plants that
compete with each other for space and soil resources.
The carrot on the right may have been so close to
another carrot plant that the root had to bend a little
to continue to grow downward.
What does this have to do with a seed pellet?
Consumers Demand Attractive, Uniform, and Fresh
A grower may have a very high yield in
a particular field, but not be able to sell a high
percent of the crop. Vegetables must meet the standards
required by the industry, and demanded by consumers
across the country. A uniform, nicely shaped product is
usually a must. To get the highest percentage of your
crop to meet these standards, precisely planting seed in
the soil with the desired amount of space between each
seed is critical. Seed pelleting can increase the
likelihood that the seed will be placed in the soil with
the most precision and accuracy possible.
The idea behind seed pelleting is to take a seed that
is comparatively light in density and oddly shaped and
turn it into a seed with a pellet around it that makes
that seed heavier, more uniform, and as perfectly round
as possible. A planter will be able to plant that
seed/pellet in the most accurate and precise way that is
Science – Selecting the Powder and Adhesive
Creating a pellet is both a science and an art. Most of
the science comes when selecting the powders and
adhesive used to create the pellet around the seed. The
materials should form a pellet structure that is porous
enough to provide immediate oxygen to the germinating
seed, and absorb water in a way that is most beneficial
to the seed. It is necessary sometimes to have a mixture
of 4 or more powders in order to achieve the desired
characteristics and also end up with the desired pellet
The adhesive is also very important. It needs to be
strong enough to hold the powder together, without
making the pellet so hard that it slows the germination
process. You can also go one step further by putting
together the right combination of adhesives and powders
to create a pellet that actually splits open much like
an egg cracks open. This splitting action is said to
lead to even faster oxygen availability and thus less
stress on the germinating seed.
The Art – Making the pellet
There are a couple of ways to create a pellet around a seed, but
today the most common method was taken from the candy industry.
In this method, seed is placed in a large rolling pan
like the one pictured below. The pan is continuously
turning and tumbling the seed during this process. The
pelleter sprays water until the seed surface is wet.
After that, he sprinkles the pelleting powder over the
wet, tumbling seed. The powder sticks to the wet seed.
The pelleter then sprays adhesive until the seed and
powder is again wet. Then more powder, then more
adhesive, then powder, then adhesive etc. etc. etc.
During the process the pellets are removed from the
rolling pan several times in order to run them over a
sizing screen so that smaller pellets can be built up,
while any larger pellets wait outside the pan. This is
done until all pellets are exactly the same standard
size. Knowing when and how much adhesive to add, and
when and how much powder to add is an art that takes
some time and practice to perfect. For example, if you
get the seed too wet in the beginning the seed sticks to
each other and you get two seeds per pellet. Not enough
adhesive makes for a pellet that is too soft.
Several companies are starting to use machinery that
is more mechanized, using less art, but the method
described is still the most common pelleting method used
in the industry today.