Precision Agriculture &
GPS
Ag Science
Fall 2000
Introduction
• Precision farming:
• managing each crop
production input on a site
specific basis.
• Example inputs:
–fertilizer
–pesticides
--lime
-- seed
Objectives of Precision
Farming
• Reduce waste
• Increase profit
• Maintain environment
Comparison
• Pre-mechanization:
• Farmers dealt with each seed
& plant
• Post-mechanization:
• Farmers dealt with entire
fields
Variable Rate Application
• Applying different amounts
of input while going across
field
Variable Rate Technology
• Tools and equipment that
allows for variable rate
application
Variability in the Field
• Soil fertility
• Moisture content
• Soil texture
• Topography
• Pest population
• pH
Fast changers:
• nitrate level
• moisture
content
• pest population
Slow changers:
• topography
• texture
• pH
Fertilizers
• 97% of corn acres applied
with N
• ~25% cash production costs
• Consider environmental
impact
Pesticides
• $7 billion spent annually
• 98% of corn & soybean acres
• Environment is concern
Seed
• 1900 -- 1 farmer fed 8 people
• 1990 -- 1 farmer feeds >100
people
• We can change plant
population as we plant
Components of Precision
Farming
• Tillage - depth & residue
• Planting - seed rate & depth
• Spraying - certain area
• Crop scouting - problem area
• Harvesting - yield monitor
Where on Earth are We?
• Dead reckoning
• Land-based positioning
• Satellite-based positioning
Dead Reckoning
• Uses starting point
• Speed
• Travel time
• Number of passes to
determine location
Land-Based Positioning
• Uses radio towers
• Must have three towers
Satellite-Based Positioning
• AKA
• Global Positioning System
• GPS for short
GPS
• Constellation of satellites
• Developed by Department of
Defense
• Used 24 hrs./day anywhere
on Earth
Uses
• Military
• Industrial
•Commercial
•Civilian
Segments of GPS
• Space
• User
• Control
Space
• 24 satellites
• 12,000 miles above Earth
• Orbit twice daily
• Always have at least 4
satellites in view
• “In view” = above horizon
• Each satellite sends &
receives radio signals
• Radio signals travel
~183,000 miles per second
• Satellites equipped with
atomic clock for accuracy
User Segment
• GPS Units & Receivers
• Free of charge usage of
signals
Control Segment
• Track & monitor satellites
• Master Control Station AFB in Colorado Springs