Yield Monitor

Yield monitors combine three primary sensors. A mass-flow sensor — typically an impact plate on the clean grain elevator or an optical flow sensor — measures grain throughput in kilograms per second. A capacitive or NIR moisture sensor corrects mass to a standard moisture basis (15.5% for corn, 13% for soybean). A GPS or RTK receiver logs position at 1–5 Hz. Harvest-logger software combines these streams, corrects for header width and grain-flow lag through the combine (typically 12–18 seconds), and writes a point per second. At 5 km/h with a 9-meter header, the result is one yield observation per ~4 square meters.

Raw yield data requires cleaning before analysis. Common errors include start-pass and end-pass lag artifacts, overlap from adjacent passes, speed variations during turns, and header-width underfills at field edges. Open-source tools and commercial platforms (SMS, Climate FieldView, Trimble Ag, John Deere Operations Center) apply filters to remove these artifacts, producing a clean map suitable for zone delineation. Properly processed maps typically retain 85–95% of raw points.

Yield maps unlock three management workflows. Variable-rate prescriptions: multi-year average yield maps reveal stable high- and low-performing zones that justify differential seeding, fertility, and drainage investments — variable-rate application guided by yield history often pays back in 1–3 seasons. Root-cause diagnosis: overlaying yield maps with soil-test maps, elevation, NDVI, and drainage layers in GIS reveals why certain zones underperform, pointing to compaction, fertility, or water limitations. Economic accounting: multiplying yield by price and subtracting zone-specific input costs generates profit-per-hectare maps that sometimes show 30–40% of a field's area is unprofitable even when the whole-field margin is positive. Iowa State and Purdue Extension resources document this workflow. WiseYield does not import yield-monitor maps yet; logged harvests join soil profiles, satellite canopy trends and financial records to calibrate per-field yield predictions and profitability — not zone-level prescriptions.