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 imports cleaned yield maps and joins them with soil profiles, NDVI time series, and financial records to produce zone-level profitability and variable-rate prescriptions.