Agriculture Reference
In-Depth Information
and the fertilizer amount applied increased by almost 3%. The average fertilizer
utilization ratio is less than that in developed countries by more than 10%. The uti-
lization ratio of nitrogen is 30%, that of phosphorus is from 10% to 25%, and that
of potassium is from 40% to 50%. The increasing fertilizer consumption with low
utilization ratio leads to decreasing fertilizer returns, serious soil and groundwater
pollution, and food contamination. Hence, variable-rate fertilization technology and
applicators are quite important to nutrition management in precision agriculture.
The precision variable-fertilizing technology determines the amounts of different
kinds of fertilizers to be used according to soil fertility conditions and crop needs.
Nutrition management is mainly about the automatic operation systems such as the
variable rate fertilization applicator used for soil and crop nutrition. Variable-rate
fertilizer application allows crop producers to apply different rates of fertilizer at
different locations across fields. The technology needed to accomplish variable-rate
fertilization includes an in-cab computer and software with a field zone applica-
tion map, fertilizer equipment capable of changing rates during operation, and GP.
The fertilizer rate at specific locations within fields is based on the georeferenced
field zone map on the in-cab computer. The system includes a vehicle-mounted GPS
unit to monitor field locations, allowing the computer to change the application rate
between zones. Electronic communication between the in-cab computer and the rate
controller on the application machine performs to change the fertilizer rate across
the field. The normal applicator is based on Differential Global Positioning System
satellite positioning principle. It combines data from GPS, GIS, and Digital Display
Generator (DDG) to make fertilization decisions and to output the application rate of
fertilization into an integrated circuit (IC) card. When the applicator operates in the
field, the position data received by GPS, which is equipped on the applicator, stimu-
lates the fertilization decision command in the IC card. The command then controls
the rotational velocity of the fertilizer shaft through a single chip computer to realize
the variable rate fertilization.
Chemical fertilizers, which are used to increase production yield, account for
a large percentage of the total operational costs in agriculture. The first variable
rate fertilization application was realized in the farm owned by the University of
Minnesota in 1993-1994. The precision agriculture experiment applied GPS tech-
nology and variable-rate fertilization; results showed that the yield results using
variable rate fertilization was increased by 30% compared with the traditional bal-
ance of fertilizer. Most of the current variable rate of fertilization is based on the
electronic map of the variable rate fertilizer applicator, in which GPS signals and
fertilizes according to the amount of signal to the driver module controlling com-
mands sent from the console, is the core of the entire variable fertilization system.
European RDS companies, Hrdro Agri companies, and the Americas Agtron com-
panies, Agleader Company, Micro-Trak Inc., Mid-Tech Inc., and Trimble companies,
already have a generic product in the market; its interface can adapt to liquid fertil-
izer, granular fertilizer, and other operating machinery controls. America Ag-Chem
Equipment Company designed the SOILECTION fertilization system. This fertil-
ization system can be applied to solid and liquid fertilizers, and can regulate the
amounts of seeds and fertilizers to be used via air seeder and no-tillage seeder, and
can even change the proportion of three kinds of fertilizers or seeds (Zhao et al.,
