|Method of potassium
Since potassium uptake depends primarily
on root interception, placement of potassium
fertilizers with or near the seed is usually
the most effective method of application
provided the rate of application is not
greater than the seed can tolerate. If too
much potassium or other fertilizer is placed
with the seed, germination and emergence
may be delayed or reduced.
The safe level of potassium that can be
applied with the seed depends on the crop.
In general, smaller seeded crops such as
canola have a lower tolerance than cereal
grains. The clay and organic matter content
of the soil and the soil moisture content
will also have an effect on possible germination
With average soil moisture conditions and
for medium textures, the total amount of
seed placed fertilizer materials should
not exceed 175 lb/ac, and the amount of
N plus K2O should not exceed 40 lb/ac. For
less tolerant crops such as canola, flax
and peas, the application of potassium with
the seed should not exceed 15 lb K2O/ac,
provided other fertilizers are not seed
placed. These recommendations are based
on the use of a double-disc or similar drill,
which places the seed and fertilizer in
a very narrow band. If the opener spreads
the seed over a wider band, higher rates
of fertilizer can be safely placed with
Side-band placement is
an efficient means of applying potassium.
In this placement, the fertilizer is in
a band approximately 2.5 cm (1 inch) to
the side and 2.5 cm (1 inch) beneath the
seed. This separation of fertilizer and
seed reduces the possible detrimental effects
on germination when high rates are applied.
Machinery for placing seed and fertilizer
in this configuration is not readily available
commercially, and the method is not widely
Banding (also referred
as deep-banding of potassium into the soil
prior to seeding has, to date, not received
a great deal of research attention, but
there is no reason to believe that this
should not be a good method of applying
The two methods, banding prior to seeding
and side-banding, should give similar results.
before seeding is less efficient than applying
potassium in a band with or near the seed.
The major role for broadcast applications
of potassium fertilizer will be in "building
up" soils extremely deficient in potassium.
For perennial forage crops, potassium is
best applied by broadcasting and incorporating
before seeding. This approach will overcome
the problem of limited movement of potassium
into the soil when applications are made
after stand establishment.
Where established stands require potassium
fertilizer, then broadcast applications
are the only option, and relatively high
rates may be required on severely potassium-deficient
soils. Fall or spring applications could
be made, but fall applications would likely
be preferred in dry areas because of the
additional moisture available to leach the
potassium to the root zone. For potassium
deficient soils, potassium fertilizer will
reduce alfalfa winter-kill and help maintain
the proportion of alfalfa in mixed stands.