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APRIL 2018
Tillage
www.irishfarmersmonthly.com
Sulphur rates
The next question to address is: "What is the rate of sulphur
required?" Current advice would be to target 15-20kg S/ha in
cereal crops and 20-30kg S/ha (16-24 units/acre) in oilseed rape
(OSR).
Again, ensure this is applied in two applications, bringing
improved nutrient use effi ciency. At these rates we will avoid
the negative nutrient interactions which occur as we go towards
40kg S/ha and above.
Financial return
What return on investment (ROI) can you expect from taking
the correct approach of multiple applications, and supplying
the optimum rates? In cereal crop trials, yield increases of
0.3t/ha have been observed, while in OSR this has been higher
at 0.5t/ha. Using a calcium ammonium nitrate (CAN) plus
sulphate product will result in an ROI of 20 for every 1
invested.
When phosphate and potash are required, use an NPKS fertiliser
Now, of course, the yield benefi t from S will only be expressed
if this is the limiting factor. If other nutrients are an issue, they
need to be addressed as well. In early spring (February, March),
soils are cold, and wet phosphate and K are typically at their
lowest point of availability.
This is where a `spring starter' fertiliser should be considered
to promote early spring growth of roots and shoots. This fresh
spring growth of roots enables the plant to explore the soil's
phosphate reserves while at the
same time building above-ground
biomass that is essential for high
yield attainment.
A complex equation
This adds a further complication
into the product selection, but is
simple to resolve.
Rather than using a granulated
nitrate plus S product, all that
is required is to switch the fi rst
spring application to an NPKS
complex compound fertiliser
(CCF). The target should be to
apply 15-20kg of P and 30-40kg
of K/ha along with 50kg N/ha and
8-10kg S/ha.
This nutrient combination is
ideal to give arable crops the
best possible start in the spring
as they look to recover root and
shoot growth, which has often
been lost over the winter period.
Investigations into the benefi t
of this approach have been
ongoing for many years, across
a range of sites/countries, and a
consistent yield increase that can
be expected is a further 0.25-0.3t/
ha above the expected sulphur
response.
The ideal solution
The answer, therefore, to the
question, "how much straight N
do you actually need?" is "very
little", in that 25 per cent of the N
should be in the form of an NPKS
CCF and 50-75 per cent will be
in the form of CAN plus sulphate
fertiliser.
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