Agriculture Reference
In-Depth Information
pesticides (Stone, 2008). Today, these agricultural chemicals or pesticides play an
important role in world food production. About 500 million lb of pesticides (active
ingredient) valued at $11.8 billion in 2006 and $12.5 billion in 2007 were applied
to cropland in the United States (Birchfield et al., 2006). In about two decades,
total pesticide use on a mass basis went down by about 40% (compared to 845 lb in
1988), but at the same time, the total dollars spent (compared to $4.6 billion in 1988)
went up almost three times (USEPA, 1991; Pimentel et al., 1992; U.S. Bureau of the
Census, 1993). Hence, pesticides are relied on heavily for effective pest control to
minimize yield loss in crop production.
Farming practices have changed significantly over the past 50 years since pesticides
were introduced, and the majority of producers now rely on chemicals to control a wide
range of quality-reducing or yield-inhibiting pests. Pests targeted by pesticide applica-
tions include insects, fungus (molds), competing plants, microbes, rodents, diseases, and
weeds. Applying pesticides to broadcast, row, horticultural, and nursery crops as well as
vegetables has been both an effective and efficient method to protect crops and reduce
yield losses from agricultural infestations caused by these pests.
Various chemical application systems have been developed and used in the past to
control pests in production agriculture. Pesticides are commonly applied by ground-
driven sprayers or aerial platforms, but the fundamental technologies and needs for
automation are similar to both ground and aerial applications. Ground-driven spray-
ers are more prevalent, and the automation techniques applied to ground sprayers
will be the focus of this chapter. These units can be self-propelled vehicles designed
specifically for the application of chemicals including pesticides (Figure 10.1, left),
or they can be sprayer units mounted on or towed by other power units such as trac-
tors (Figure 10.1).
Chemicals are typically applied in a liquid form onto the crop canopy by the use
of various atomization devices such as spray nozzles, which produce a mist made
up of small droplets that can be easily deposited on target surfaces. Nozzles are
arranged on different types of support structures based on the targeted crop canopy
architecture (e.g., boom sprayer for row crops, and a tower sprayer for horticultural
crops; Figure 10.1). Multiple tanks are used to carry the concentrated chemicals and
carrier depending on the fluid delivery mechanism (premixed or direct injection with
online mixing) and carrier media. The carriers, which can be water, air, or fertil-
izer solution, are used to dilute concentrated chemicals. The chemicals and carri-
ers are drawn out of the tank and pumped to the nozzles through a fluid conduit
(Figure 10.2). In a premix system, chemical and carriers are mixed in a tank, and a
single pump is used to deliver the mixture to nozzles. In the direct injection systems,
chemical is injected into the carrier at a desired rate during the field application. In a
typical situation, these chemical applicators pass through the agricultural fields sev-
eral times a year to apply different types of pesticides at different stages of growth
and production. Therefore, good machine performance of these vehicles is critical to
achieve effective crop protection.
Until the early 1970s, ground-driven pesticide applicators did not utilize electronic
control systems. These conventional systems were designed to broadcast chemicals
without any mechanism to vary application rate on the go to optimize chemical
use. In such systems, the nozzle delivery rate was fixed through the adjustment of
