A combine yield monitor is a measurement system that estimates how much grain is being harvested at each location in a field. It matters because yield is not uniform, even within the same field, due to soil, water, nutrients, pests, and machine settings. By combining sensor readings with GPS position, the monitor turns harvesting into a data collection process.
Farmers use this information to make better decisions about planting, fertilizer, irrigation, and field management.
Key Facts
- Mass flow rate measures grain moving through the combine per unit time: flow rate = mass / time.
- Dry yield corrects measured grain mass for moisture content so different field areas can be compared fairly.
- Yield can be estimated by yield = grain mass / harvested area.
- Harvested area during a time interval can be estimated by area = header width x distance traveled.
- Distance traveled can be calculated from speed and time: distance = speed x time.
- Accurate yield maps require calibration, clean sensors, correct header width, GPS data, and moisture correction.
Vocabulary
- Yield monitor
- A yield monitor is a combine system that estimates crop yield using grain flow, moisture, speed, header width, and position data.
- Mass flow sensor
- A mass flow sensor measures the rate at which harvested grain moves through the combine, often near the clean grain elevator.
- Moisture sensor
- A moisture sensor measures the water content of grain so the monitor can adjust yield to a standard moisture level.
- GPS receiver
- A GPS receiver records the combine's location so each yield measurement can be placed on a field map.
- Yield map
- A yield map is a color-coded field map showing how crop production changes from one area to another.
Common Mistakes to Avoid
- Ignoring calibration, which is wrong because an uncalibrated flow sensor can make the whole yield map too high or too low.
- Using wet grain mass as final yield, which is wrong because moisture differences can make two areas look different even if they contain the same amount of dry grain.
- Entering the wrong header width, which is wrong because harvested area depends on width and directly affects the calculated yield.
- Treating every color change on a yield map as a soil problem, which is wrong because sensor delay, speed changes, plugged equipment, or GPS errors can also create patterns.
Practice Questions
- 1 A combine harvests with a 9.0 m header and travels 120 m in 60 s. What area is harvested during that time?
- 2 A yield monitor records 540 kg of grain from a harvested area of 0.060 ha. What is the yield in kg/ha?
- 3 A yield map shows a narrow low-yield stripe exactly where the combine slowed and turned near the field edge. Explain why this pattern might be caused by machine operation rather than crop growth.