Spraying
summary
These
are the 'field notes' compiled by Clive Marsh while attending the
field-day led by David Manktelow on November 26, 2006.
Spray ~ 1.5
kg Cu/Ha per application.
Currently
do high volume, dilute spraying: 250 g /100l and 2000 l / (canopy)Ha. This
is ‘forgiving’ as high volume means that
less likely to have uncovered areas of foliage in ‘sprayer
blind spots’. There is motivation to
go to low volume, high
concentration, say 1kg / 100l and 500 l/Ha or even 1.5 kg / 100l and
333.3 l/Ha
but would need to be sure of homogeneity of spray else significant
‘blind
spots’. Motivation is less cost
to apply
– pass through orchard quicker and less tank refills.
Need
to
monitor spray – poles with water sensitive tags, showing both
sides and top
& bottom. Underside of uppermost
tag
one of hardest to hit as spray needs to pass up through canopy. Top
side of this one is got by anything the
gets above tree and falls back down.
For
dilute
spraying need ~ 50% coverage but for concentrate only need 4% coverage. Write
up interpretation on tags.
Need
to get
most of the spray moving between 11 and 1 O’clock from the
sprayer… most of the
‘target’ is in that direction. The
‘twisting’ effect from axial fans is significant
and the performance on the
lifting (fan blades rising) and dumping (fan blades falling) sides of
the
sprayers can be quite different, less lift on the dumping side. Straightening
vanes not
effective/popular. One option is to
accept that the dumping side won’t perform and make the
sprayer single sided
with ducting etc to push all air out on the lifting side.
Supply
plumbing for nozzles should not restrict airflow.
An
effective way to get spray high is an elevated nozzle.. as high as can
be
driven through the orchard. Distribution
from this nozzle could be air assist (if fan/ducting allows) or simply
hydraulic (but need to be operating at ~ 20 bar for
‘hydraulic’ nozzles).
Futher notes from the day (by Heather
North)
- David
expects that you can spray 14 cubic metres of walnut canopy with a
litre of spray (I guess this is dilute spraying)
- And he
recommends the use of tree-row-volume calculation
- But hard to
calculate the right volume because so many variables, so recommend
assess wetness visually and use water sensitive tags, and watch sprayer
working to see where spray is going
- “run-off”
is when outer canopy is wet and dripping, and inner canopy is wet but
not dripping
- Critical for
spray use minimisation is to turn off sprayer between trees
- When you
double the application volume, you don’t double the deposit
volume (you only about 1.5 it) – diminishing returns
- Trees >8m
high – need to use a chopper every 3rd spray
- Don’t
use normal organosilicone wetting agents (e.g. Pulse) on tree crops
because they’re penetrants as well – Cu can penetrate
leaves which is not good because it’s phytotoxic [probably need
to think about this one a bit more!]
- Fruit may be
harder to wet than leaves. Don’t need wetting agent for
mankocide on walnut leaves but not sure about fruit? Could also
be used in bud burst spray to help get it in behind bracts?
- Could use
wetting agent with concentrate spraying e.g. 400l/ha with wetting
agent. But wetting agent can make dilute spray run off onto
ground.
- 50% cover
for dilute spraying, 4% cover for conc spraying
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