Introduction
Modern farming is high-tech. GNSS guides tractors within centimetres, tells farmers exactly where to apply fertilizer, and maps yields across fields. This is precision agriculture.
The Evolution of Farming
| Era | Method | Efficiency |
|---|---|---|
| Pre-1990s | Visual guidance | Overlap, skip rows common |
| 1990s | Lightbar guidance | Reduced overlap |
| 2000s | Auto-steer | Consistent rows |
| 2010s+ | RTK auto-steer | Centimetre precision |
Auto-Steer: The Tractor That Drives Itself
A GNSS receiver on the tractor receives RTK corrections, a steering controller follows pre-programmed A-B lines, and the tractor drives itself with centimetre precision. Accuracy levels range from sub-metre (lightbar guidance) to 10 cm (WAAS auto-steer) to 2–3 cm (RTK auto-steer).
Benefits
- Reduce overlap, save fuel, seed, and time
- Work longer hours with less operator fatigue
- Precise rows that align with later operations
- Automatic documentation of what was done
Variable Rate Technology (VRT)
The concept: apply different amounts of inputs in different places based on need.
- Create a prescription map (based on soil samples, yield history)
- Load it into the tractor display
- GNSS tells the applicator where it is
- Controller adjusts rate in real-time
Applications: fertilizer (more where soil needs it), seed (higher population in better soil), pesticide (spot treatment only), irrigation (vary water across field).
Yield Monitoring
A yield sensor on the combine harvester records crop flow while GNSS records position every second, creating a yield map at harvest. This reveals high and low producing areas, effect of drainage and soil type, and response to different treatments, invaluable for the following season's decisions.
GNSS Requirements by Operation
| Operation | Accuracy Needed | Technology |
|---|---|---|
| Scouting | 1–5 m | Smartphone / tablet |
| Soil sampling | 30–50 cm | DGPS |
| Spraying | 20–30 cm | WAAS / DGPS |
| Strip-till | 5–10 cm | DGPS / RTK |
| Planting | 2–5 cm | RTK |
| Harvest | 10–30 cm | DGPS |
Economics of Precision Agriculture
Costs include auto-steer systems ($2,000–$10,000), RTK subscriptions ($500–$1,500/year), and VRT equipment ($5,000–$20,000). Typical savings: 5–10% fuel, 5–15% input reduction, and 10–20% yield increase in some cases. Payback typically 1–3 years.
Challenges
- RTK coverage: Need reliable corrections, radio or cellular required; some areas have poor coverage
- Data management: Multiple data layers require GIS skills and compatible software
- Initial investment: Significant upfront cost with a learning curve
The Future
Autonomous equipment, fully driverless tractors, swarm operations with multiple small units, 24/7 operation, is already arriving. Integration with weather data, satellite imagery, soil sensors, and AI decision support is making precision agriculture smarter every season.
Vital Points
- Precision agriculture uses GNSS to optimise every field operation
- Auto-steer reduces overlap and operator fatigue
- Variable rate technology applies inputs exactly where needed
- Yield monitoring creates maps that guide future decisions
- RTK accuracy (2–3 cm) needed for planting
- Economic benefits typically pay back within years
- Future is autonomous and fully integrated