Agriculture Reference
In-Depth Information
very successfully to plant either very small plots or much
larger plots. Pouring a measured or counted quantity of
seed over a cone such that the seed is evenly distributed
around the base of the cone operates the seeder. Dur-
ing planting the cone revolves and seed passes through
a hole and is subsequently dropped via disc or tube
coulters into the soil at the required depth. It is often
possible to plant several rows from the same unit seed
lot. In this case, after the seeds drops from the cone
they are evenly distributed to a number of tubes, which
will each plant a single row. Cone planters are usually
designed so that a range of plot lengths is possible. This
is achieved by gearing the rate that the cone revolves.
After one complete revolution then all the seed from
one lot will have passed down the open hole. Planting
can be done with continuous movement with each plot
being dropped onto the revolving cone at a designated
trip point
.
Cone planters are available where the seed for each
plot/row are loaded into a cassette or magazine. This is
then mounted above a seeder unit with several revolving
cones. With this system it is possible to plant several
rows simultaneously with each row being a different
genotype. Cone seeders are particularly useful as they
can be used with small seed lots and all seed loaded is
planted to completion. Therefore there is no need to
maintain a seed reservoir, which needs to be emptied
between different plots/genotypes. Cone planters are
also self cleaning.
With small seed, cone planters can result in an even
distribution of planted seed, but it is sometimes desir-
able to have a more precise placement of seed. If this
is necessary then
precision planters
can be used. With
these machines it is possible to obtain spaced plants at
relatively even density. Precision planters are in general
of three types:
specific place in the plate's rotation. At this point the
single seed is dropped into the soil.
•
Cup planters, where a series of rotating cups are
dipped into a reservoir of seed. The size of each cup
is such that only a single seed is scooped up as the
cups revolve through the seed. At a specific point on
the rotation the cups are tipped and the single seed is
dropped into the soil.
The major limitation of precision planters when
used by plant breeders is that they usually require a
volume of seed in the reservoir in order to operate effec-
tively. Therefore they have only limited use when small
amounts of seed are available.
In some crops, transplanting is common even on
commercial scale (e.g. fresh tomatoes). Small scale
transplanters are available which will allow automatic
transplanting of field plots. Seedlings are grown in
'
seedling flats
'. At transplanting time the seedlings are
removed from the flats by hand and placed into the
transplanter. Systems have also been developed where
the seedling flat fits onto the transplanting machine and
the whole operation is automated. In this latter case it
is usually possible only to transplant large plots.
The areas between different plots in field trials are
usually left unplanted. There is very little competition
in these areas and weeds can be a big problem. Weed
control in field plot trials can be carried out mechan-
ically or chemically. Mechanical weed control can be
by hand hoeing (a task often enjoyed by many summer
student helpers). Automatic mechanical devices such as
rota-tillers and harrow cultivators can achieve inter-row
and inter-plot weeding. Often it requires a combi-
nation of chemical herbicide application, rota-tilling,
harrowing and hand hoeing to ensure that plots remain
weed free.
Evaluation of disease and pest resistance is an impor-
tant factor of field testing. Test lines and controls will be
grown in regions or areas where specific diseases or pests
are common. Disease is often encouraged by including
particularly susceptible genotypes as
spreaders
and by
artificial inoculation of these spreader lines.
In other field studies it is not desirable to have disease
or pest epidemics and this need to be controlled. Con-
trol is usually by chemical application although some
biological control of insects may be available. It should
be remembered that many diseases are spread (and most
are not helped) by having poor weed control.
Belt planters, where a reservoir of seed is maintained
over a revolving belt. The belt has holes cut which
are of precise size and shape so that only a single
seed will fit through the hole. The density of plant-
ing is achieved by the number of holes in the belt
and the rate of which the belt revolves (e.g. Stanhay
seeders).
•
•
Vacuum planters, where suction is applied to a revolv-
ing plate that has holes drilled to allow only a single
seed to be sucked to the plate at each hole position.
As the plant revolves the vacuum is turned off at a
