Agriculture Reference
In-Depth Information
Automation controlled
actuators
Nozzle flow
regulating valve
Section control
Variable rate
Nozzle body/
solenoid valve
Droplet size
control
Rate control
Flow regulating
valve
Rate control
Pump speed
Rate control
Hydraulic lift cylinder
Auto boom height
control
FIGURE 10.3
Various actuators of an automated chemical application system. Note that
this is a conceptual system with four types of control mechanisms being used; a commercial
sprayer may not have all four mechanisms implemented.
increments, reducing overlapping. These control strateriges will be detailed in the
following subsections.
10.3.2 R
ATE
C
ONTROLLERS
Historically, studies have shown that a great deal of pesticide was applied at the
wrong rate when electronic rate controllers were not used in the chemical applica-
tion system. In 1979, a field survey conducted in Nebraska (Rider and Dickey, 1982)
showed that one out of four applicators surveyed were applying within 5% of the
recommended rate. A total of 152 private and commercial applicators were surveyed
and the application errors ranged from 90% overapplication to 60% underapplica-
tion. In 1986, 140 private and commercial applicators were surveyed in Nebraska
(Grisso et al., 1988). Only one out of every three applicators in this survey was apply-
ing pesticides within 5% of the intended application rate. However, it was noted that
of the applicators that used electronic application rate controllers and/or monitors,
91% were within 10% of the recommended application rate.
Rate controllers were one of the earliest forms of chemical application automa-
tion. Rate controllers specifically target the efficient application of chemicals by
maintaining a constant formulation application rate as vehicle speed varies. During
an in-field chemical application event, many factors contribute to a high degree
of sprayer speed variability. These factors include changing soil conditions, field
obstacles, field geometry, operator inconsistencies, and machine responsiveness. To
