I am forwarding this message from Jason to apple-crop. Jon
-- Forwarded message --
From: Deveau, Jason (OMAFRA) jason.dev...@ontario.ca
Date: Mon, Jan 25, 2010 at 9:51 AM
Subject: RE: How to Post
To: Jon Clements cleme...@umext.umass.edu
This is my first time posting on Apple-Crop.
Methods for optimizing orchard applications are of particular interest to me
and I’ve learned a great deal from this collection of experiences and
opinions.
I’ve tried to keep this brief, but there’s a lot to say on the subject.
Ontario has been developing a new approach to optimizing orchard
applications. The model draws from the best parts of existing Crop-Adapted
Spraying methods published and practiced since the sixties. Crop-Adapted
Spraying can be defined as “a process for matching carrier volume and
product dosage to a growing leaf area within a canopy, or to variation
between canopies, combined with the correct calibration and orientation of
the sprayer.” The goal of our model is to remove variation in applications.
If it saves water and product in the process, that’s a nice side-effect.
Carrier Volume:
Tree row volume is only one form of Crop-Adapted Spraying and it’s based on
assumptions that need to be reconsidered. I agree with Dave Rosenberger that
we have good reason for questioning the validity of any method proffered 30
years ago. Trees, planting parameters and chemistries have changed. It’s a
sad irony that orchard application equipment (read airblast sprayers) is the
only variable that has remained roughly the same.
TRV is based on the carrier volume of 400 US Gallons / acre, which was
pointed out in this discussion to be the volume of growth-regulating spray
that will provide ideal coverage of a standard orchard using an airblast
sprayer. Generally, TRV models compare the volume of today’s high density
canopies to that of a standard orchard and make a proportional reduction in
the volume of spray required to achieve dilute coverage for all orchard
agrichemicals. There are a lot of inherent problems with making this
conversion.
I’ve seen a “standard” orchard defined many ways, spanning from 29,410 to
39,906 cubic metres per hectare (420,300 to 570,310 cubic feet per acre).
The ideal volume of 400 US gallons / acre seems to be based largely on best
practices of the day and has been handed down somewhat reflexively. Is it
the correct starting point for determining the “right” carrier volume for
today’s plantings?
Canopy Density and PACE+:
As was noted in this discussion, planting parameters and crop morphology is
considerably different today from the standard planting. Can carrier volumes
really be pro-rated as a percentage based on canopy volume given changes in
crop density?
I suggest growers consider a new method of Crop-Adapted Spraying currently
in practice in the UK. Dr. Peter Walklate and the Silsoe Institute’s PACE+
scheme (Pesticide application rate adjustment to the crop environment) has
made some impressive contributions. In my opinion, the most interesting find
is that the density of an apple canopy accounts for about 80% of the
variability in spray coverage when using a fixed rate across orchards. Most
variants of the TRV formula do not account for density.
http://www.pesticides.gov.uk/HDC.pdf
http://www.cigrjournal.org/index.php/Ejounral/article/viewFile/1240/1097
Still, PACE+ makes no recommendation as to the ideal carrier volume required
for an application. As many of you have pointed out, the purpose of the
carrier is to convey the agrichemical product to the target and distribute
it in the desired pattern. Generally, a high droplet density (i.e. the
number of discrete droplets per unit target area) is conducive to an
effective application. Therefore, given the importance of the carrier, it is
surprising that a specific volume is seldom indicated on the label except in
generalities such as maximum and minimum.
Coverage Constant:
The method we’re developing does not pro-rate that classic 400 UG gallons /
acre. Instead, it works from the bottom-up by recommending the ideal volume
of carrier required to give dilute coverage to one cubic metre of full apple
foliage from an axial airblast sprayer. After an extensive literature
review, I’ve determined the rate to be 0.08 litres per cubic metre (0.0006
US gallons per (cubic foot). With this coverage constant in hand, the model
then determines the volume of canopy based on height, width and depth, the
average tree shape and the density of the average tree. The ideal carrier
volume should be no lower than 500 litres per hectare (53.5 US Gallons per
acre) because there are physical limitations to what an air blasted droplet
can achieve in terms of coverage.
In a 1997 survey, apple canopies in New Zealand ranged from 10,000 to 40,000
m3/ha (142,913 to 571,653 cubic feet per acre) and increased by 30% between
bud break and harvest. Therefore our new method proposes calibrating the
sprayer and determining the
