Agriculture Reference
In-Depth Information
measure red and NIR light reflectance from a crop canopy. The canopy reflectance
can be related to crop status and the need for nitrogen fertilizer. The sensing system
is integrated with a spraying system that can produce a variable rate application of
liquid nitrogen fertilizer. Although sensor-based variable rate systems do not require
a positioning system, the data from the sensors can be used for creating variable rate
maps for other map-based field operations if a GPS receiver is equipped.
4.5 ECONOMIC AND ENVIRONMENTAL BENEFITS
Variable rate application of production inputs has the potential to increase farm prof-
its and reduce adverse environmental impacts. Economic and environmental benefits
of variable rate chemical application are important for both producers and the general
public and will affect the pace of adoption of precision agriculture. Numerous short-
term studies of economic and environmental impacts of variable rate application
have been reported, but more research is needed to document its long-term impacts.
This information will facilitate the adoption of precision agriculture technologies.
4.5.1 P
ROFITABILITY
For a new practice to be widely adopted in production agriculture, the practice must
yield an economic profit except for regulatory requirements. Variable rate applica-
tion requires additional costs associated with soil sampling, data analysis, and new
equipment. Economic benefits from variable rate application can only be derived
from increased yields and/or savings in reduced inputs or a combination of both. If
the initial investment for equipment is high, actual economic returns of variable rate
application will be low or even negative for the first few years. Some costs associated
with soil sampling for a field can be accurately determined, whereas other costs for
new equipment and data analysis are difficult to estimate for each field. Nevertheless,
it is certain that these costs will go down if the same equipment and data analysis
software are used for more fields over more years.
Many studies have shown that variable rate applications of fertilizers are supe-
rior to uniform rate application in terms of economic benefits, but evidence of prof-
itability has been mixed based on nine published field research studies (Swinton
and Lowenberg-DeBoer, 1998). Numerous recent studies present more evidence
of profitability for variable rate application of fertilizers, pesticides, and seeds.
Mohammadzamani et al. (2009) conducted a study to develop a precision application
of a preemergence herbicide and reported a savings of 13% compared to a uniform
herbicide application. Robertson et al. (2011) described the extent of variable rate
adoption in Australia using a survey, and reported that the adoption rate increased to
20% of grain growers from less than 5% six years earlier, and this figure is expected
to increase. However, they also described technical issues with equipment, software
access, and the incompatibility of equipment remains as constraints for adoption.
Bullock et al. (1998) conducted a study to estimate the economic value of variable
rate seeding (VRS) with data consisting of more than 42,000 individual experimen-
tal units from 170 fields in the Midwestern U.S. Corn Belt, and reported that VRS
will not be economically feasible unless detailed information for field characteristics,
