Precision Agriculture & GPS

Introduction Precision farming: managing each crop production input on a site specific basis. Example inputs: fertilizer --lime pesticides -- 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