Agriculture Reference
In-Depth Information
chemical product, per relevant unit. Formulation is the form in which a chemical is
supplied to the user, containing both active and inert ingredients. For area treatments
to surface of a field, the chemical formulation are prepared based on intended appli-
cation rates and are expressed in kg/ha or L/ha. For volumetric treatments such as
chemical application in tree fruits, the relevant unit will be volume resulting in appli-
cation rates with units such as kg/m
3
or L/m
3
. For individual organism applications,
the units are target specific, varying from kg/plant to kg/animal (ASAE Standards
327.3, American Association of Agricultural and Biological Engineers, 2007). In the
case of a boom sprayer, the formulation application rate is described by the equation:
QC
SW
R
=
t
t
600 000
,
(10.1)
p
where
R
p
= formulation application rate (kg/ha)
Q
t
= volume delivery rate to the spray boom (L/min)
C
t
= concentration of the formulation in the carrier (kg/L)
W
= boom width (m)
S
= ground speed of the sprayer (km/h)
The formulation application rate (
R
p
) derived from the above equation assumes
broadcast application across the full width of the boom width or spray swath. In
this equation, any change in the variables
Q
t
,
C
t
,
W
, or
S
will lead to a change in the
formulation application rate. The boom width,
W
, is a constant based on the number
of nozzles mounted on the spray boom and their spacing on the boom. If flow to a
boom section was turned off, the boom width would be reduced, and the volume
delivery rate would need to be reduced immediately to maintain a correct application
rate to the remaining boom sections that are applying. As the vehicle ground speed,
S
, changes, the volume delivery rate needs to be changed proportionally. In addition,
this equation is assuming that the forward speed of the vehicle is the forward speed
of the entire spray boom. However, when the sprayer vehicle is turning or yawing,
then the boom also will be yawing, subject to any inherent boom dynamics, and the
formulation application rate will not be uniform along the boom, but will vary in
magnitude along the boom width depending on the magnitude of the velocity vector
along the boom.
Likewise, the variation in the volume delivery rate,
Q
t
, will directly lead to varia-
tion in the formulation application rate. In a system without rate control, the volume
delivery rate is set by the dynamic interaction between pump, the fluid capacitance
and resistance in the plumbing connecting the pump to the boom, and the spray
nozzle characteristics. The pump will be driven by a prime mover and as long as
the prime mover's rotational speed is constant and there are no changes to the boom
characteristics (i.e., no change in the operational status of individual boom sections),
the volume delivery rate will be constant. However, any changes in spraying width,
ground speed, and intended application rate will lead to changes in the volume deliv-
ery rate. In cases where rate control is used, transient delays in the response of the
