Yield mapping is a precision agriculture method that shows how crop yield changes across a field. A combine harvester measures crop flow while GPS records the machine location, creating a map of high, medium, and low production zones. This matters because two areas of the same field can produce very different amounts of grain.
Farmers use yield maps to make better decisions about seed, fertilizer, irrigation, drainage, and soil care.
As the combine moves, sensors estimate how much grain is being harvested each second or minute. Software combines the grain flow data with position data and often converts it into yield per area, such as bushels per acre or tonnes per hectare. The result is a colored grid or contour map, where green often represents high yield and red represents low yield.
Over several seasons, yield maps can reveal stable patterns that help separate real field problems from one-year effects like weather or equipment error.
Key Facts
- Yield = harvested crop mass / harvested area.
- Area covered = header width x distance traveled.
- Mass flow rate can be estimated as mass per time, so mass = flow rate x time.
- GPS location links each yield measurement to a specific place in the field.
- High-yield zones often indicate favorable soil, water, nutrients, or management.
- Multiple years of yield maps are more reliable than a single season map.
Vocabulary
- Yield map
- A yield map is a field map that shows how much crop was harvested from different locations.
- GPS
- GPS is a satellite-based system that gives the position of the combine as it moves through the field.
- Mass flow sensor
- A mass flow sensor estimates the amount of grain passing through the combine over time.
- Grid cell
- A grid cell is a small mapped section of the field assigned a yield value or color.
- Precision agriculture
- Precision agriculture is the use of data and technology to manage field conditions more accurately.
Common Mistakes to Avoid
- Treating every red zone as poor soil, which is wrong because low yield can also come from pests, flooding, weeds, compaction, or sensor errors.
- Ignoring combine calibration, which is wrong because an uncalibrated flow sensor can make the entire yield map inaccurate.
- Comparing areas without considering header width and travel speed, which is wrong because yield depends on crop mass divided by the actual area harvested.
- Basing major management decisions on one year of data, which is wrong because weather and unusual events can create patterns that do not repeat.
Practice Questions
- 1 A combine harvests a strip 9 m wide and 400 m long. If it collects 2880 kg of grain, what is the yield in kg per square meter?
- 2 A yield monitor records a grain flow rate of 12 kg/s for 30 s. During that time, the combine covers 270 square meters. What is the yield in kg per square meter?
- 3 A field has the same low-yield area in the same corner for three years, while another low-yield patch appears only after a very dry season. Explain which pattern is more likely to need a long-term management change and why.