Precision Agriculture
in Crop Production
As discussed elsewhere on the Precision
Farming pages, site-specific crop management
(SSM) uses a variety of technologies to manage
different parts of a field separately. Natural,
inherent variability within fields means
that mechanized farming could traditionally
apply only crop treatments for “average” soil,
nutrient, moisture, weed, and growth conditions.
Necessarily, this has led to over- and under-applications
of herbicides, pesticides, irrigation, and
fertilizers––except on those
rare sites that are truly average. Chemical
excesses from blanket applications, then,
end up running off or leaching from fields
into ground water and surface waters. Most
current SSM practices use precise global
positioning combined with location-specific
measurements—either in-field data collection
(such as soil variables or pest occurrence)
or remotely sensed data (such as from aircraft
or satellites)—to quantify spatially
variable field conditions.
Within-field operations, then, adjust treatments
based on spatially referenced management
decisions recorded on maps of management
zones. Now precision technologies are being
developed that can sense microsite specific
conditions in real time “on the go” and
can automatically adjust treatments to meet
each site's unique needs (variable
rate nitrogen application). These latter
types of technologies require no a priori spatial
information, but rely, instead, on the ability
to simultaneously measure soil or plant conditions
and to effect treatments.
In fact, SSM is more akin to traditional
agricultural practices, wherein small-scale,
non-mechanized farming permitted spatially
variable treatments. Farmers, at that time,
possessed intimate knowledge of each small
corner of each field and, because agronomic
practices were primarily manual, could readily
translate that knowledge into location-specific
cultural practices.
Later, agricultural mechanization reduced
labor costs (the primary input cost) and
permitted massive increases in production
while wasting other, cheaper inputs (fertilizer,
herbicides). Because these other costs have
increased in recent decades—and environmental
costs are now being accounted for—producers
are looking to variable-rate technologies
to minimize input costs and mitigate environmental
concerns.
An excellent scientific review of site-specific
management research is provided by R. Plant, Computers
and Electronics in Agriculture 30:
9-29. Many of the RESOURCES links on the
Precision Farming page contain a wealth of
both applied and scientific information.
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