Last reviewed 1 Oct 2026 · 6 min read
Concept
Precision agriculture (site-specific farming) means managing each part of a field according to its actual need, using information technology — the right input, at the right place, in the right amount, at the right time. It addresses spatial and temporal variability in soil and crop within a field.
Aims: raise yield and quality, cut input cost (seed, fertilizer, water, chemicals), reduce environmental damage, and improve record keeping and decisions.
The precision-farming cycle
- Collect data — grid soil sampling, yield maps, remote sensing, sensors, scouting.
- Analyse — GIS maps, statistics, crop models; define management zones.
- Decide — prescription maps (how much input where).
- Apply — variable-rate machines guided by GPS.
- Evaluate — yield monitor and economics; repeat each season.
Key technologies
GPS / GNSS (positioning)
- GNSS (Global Navigation Satellite Systems) include GPS (USA), GLONASS (Russia), Galileo (Europe), BeiDou (China), and India's NavIC (IRNSS) (regional).
- Position is found by trilateration from at least four satellites (three for position and one for the receiver clock error).
- Accuracy:
| System | Typical accuracy |
|---|---|
| Standalone GPS | about 3–10 m |
| DGPS (differential GPS) — correction from a base station or satellite-based augmentation (SBAS such as India's GAGAN) | about 0.3–3 m (sub-metre to metre) |
| RTK (Real-Time Kinematic) — carrier-phase with a base station/network | centimetre level (about 2 cm) |
Applications: guidance and auto-steer, yield mapping, soil sampling, boundary mapping, variable-rate application.
GIS (Geographic Information System)
A computer system that stores, overlays, analyses and displays spatial data (layers of soil, yield, elevation, moisture, nutrient, imagery), producing maps and prescriptions.
Remote sensing
- Satellite, aircraft and drone (UAV) images give crop condition over the whole field at various resolutions (spatial, spectral, temporal).
- Vegetation indices use red and near-infrared (NIR) reflectance: healthy leaves absorb red and reflect NIR strongly.
Values range from to : bare soil, water, cloud give low or negative values; dense healthy vegetation about 0.6–0.9.
A pixel reflects 0.50 of incoming NIR and 0.08 of red.
— healthy, dense vegetation. A stressed patch with NIR 0.30 and red 0.15 gives , flagging a problem area to be inspected.
Other indices: NDRE (red-edge), EVI, SAVI (soil-adjusted). Thermal imaging shows water stress; hyperspectral data show nutrient and disease signatures.
Sensors
| Sensor | Measures |
|---|---|
| Soil sensors | Electrical conductivity (EC) (salinity, texture), pH, moisture (capacitance/TDR), organic matter, compaction (cone penetrometer) |
| Crop sensors (active optical, e.g., GreenSeeker) | NDVI on the move → nitrogen need |
| Chlorophyll meter (SPAD) | Leaf greenness → N status |
| Weather and leaf-wetness sensors | Irrigation and disease decisions |
| Machine sensors | Flow, speed, grain flow, pressure |
Yield monitoring and mapping
- A combine yield monitor has a grain-flow sensor (impact or optical), a moisture sensor, a speed and header-position sensor and GPS; it records yield at each location (t/ha) and produces a yield map showing high- and low-yield zones.
- Correction for moisture is applied: yield is reported at a standard moisture content.
- Yield maps from several years reveal stable patterns that define management zones (drainage, compaction, fertility problems).
A combine with a 6 m header travels at 4 km/h while the flow sensor reads 7,200 kg/h of wet grain at 18 % moisture. The area rate is ha/h, so the wet yield kg/ha. Converted to 14 % standard moisture: .
Variable-rate technology (VRT)
- Map-based VRT: a prescription map and GPS instruct a controller that changes the rate of the applicator (fertilizer spreader, seed drill, sprayer, irrigation) as the machine moves.
- Sensor-based VRT (real time): a sensor (e.g., NDVI) measures the crop and adjusts the rate instantly, without a map.
- Applications: variable-rate fertilizer (N, P, K, lime), seeding rate, herbicide/pesticide (patch spraying), irrigation (VRI).
- Components: GPS receiver, controller, rate actuator (hydraulic or electric motor), flow sensor, display.
Guidance and auto-steer
- Lightbar guidance — shows the driver the deviation from the line; auto-steer — the system steers the tractor with RTK or DGPS accuracy.
- Benefits: less overlap and skips (3–10 % savings of inputs), reduced operator fatigue, night operation, controlled traffic (the same wheel tracks every year, so compaction is limited to the tramlines).
- Section control automatically switches off the sprayer or drill sections over already-treated areas.
Drones (UAVs) in agriculture
- Monitoring (multispectral cameras, NDVI maps), spraying (liquid pesticide and fertilizer from a tank; typical 10–30 L payload), seeding, crop-damage assessment.
- Advantages: fast, low water use, no soil compaction, safer for operators.
- Limits: battery life (15–30 minutes), payload, wind drift, regulation — India has drone rules (the Drone Rules 2021 and later amendments) and subsidy/training schemes for farmers and groups; check the current regulations and schemes.
IoT, decision support and big data
- Wireless sensors, cloud platforms, mobile apps, AI-based advisories for irrigation, pests, diseases, and market; digital agriculture initiatives (Digital Agriculture Mission, AgriStack — check the current status).
- Decision-support systems (DSS) and crop simulation models convert data into recommendations.