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FORAGE AND NUTRITION Guide 2017
FORA
GE AND NUTRITION
Guide 20
1
7
25
Spreading urea
Fertiliser spreader types will di er in their capacity to spread
urea evenly at wider bout widths. When buying a spreader,
select one that has proven capacity to spread urea at the
desired bout width. Value independent spread tests more than
manufacturers' sales literature.
Modern spreaders need to be carefully set-up to spread urea.
The settings needed largely depend on the characteristics of
the urea (density, size distribution and particle strength) and
the bout width being used. Manufacturers increasingly provide
this setting information on their websites or on a phone app as
well as in printed spread charts. The settings on the spreader
that may need to be set to spread a particular type of urea at a
specific bout width may include:
disc or vane type used;
vane position;
fertiliser drop point on disc;
spreader angle and height over the crop; and
disc speed.
Some machines will not be capable of spreading urea at
wider bouts. In this situation, narrower bout widths should be
used with the rate adjusted accordingly. In windy conditions,
spreading urea is much riskier than conventional fertiliser. On
grassland, if spreading in some level of wind is necessary,
the bout width should be reduced. If for example an 18m bout
width is targeted, in windy conditions this could be halved to
9m with a corresponding adjustment to the application rate.
This will generally produce a better spread pattern.
Blends of urea
Some blends of urea with conventional density fertiliser
are becoming available on the market and will cause some
challenges for spreading as the components of the blend may
have totally di erent spreading characteristics. These products
can include urea with CAN or P and K products. Correct size
matching could help produce a good spread, but it is up to
the fertiliser manufacturer to prove that these can be evenly
spread.
Finally
If urea is to be spread at wider bout widths, be careful.
Urea products di er. Select the one with the best physical
characteristics unless very narrow bout widths are being used.
Make sure the spreader is capable of spreading urea at the
required bout width and ensure it is set properly to achieve
the correct spread. Avoid spreading in windy conditions, but
if some level of wind must be tolerated, consider reducing the
bout width.
100
80
60
40
20
0
<2mm
2-3.3mm
Figure 1: Particle size distribution of an NPK fertiliser.
NPK
3.3-4.75mm
>4.75mm
100
80
60
40
20
0
<2mm
2-3.3mm
Figure 2: Particle size distribution of urea with very small prill
sizes.
3.3-4.75mm
>4.75mm
100
80
60
40
20
0
<2mm
2-3.3mm
Figure 3: Particle size distribution of urea with mainly medium
particle sizes.
3.3-4.75mm
>4.75mm
100
80
60
40
20
0
<2mm
2-3.3mm
Figure 4: Particle size distribution of urea with a mix of medium
and large sizes.
3.3-4.75mm
>4.75mm