GNAFOR Field Collector a mobile-first web application for systematic field data collection in tropical forage grass experiments

GNAFOR Field Collector is an open-source, mobile-first web application for systematic field data collection in tropical forage grass experiments. Implemented as a single self-contained HTML file (HTML5/CSS3/JavaScript) under the MIT licence, the application requires no installation, has no external runtime dependencies, and operates fully offline, synchronising data to a Google Sheets spreadsheet when connectivity is restored. It provides four purpose-built data entry modules — leaf morphogenesis, tillering counts, dry mass production, and canopy height — together with automatic GPS tagging every 30 s, an offline local-storage queue with automatic retry and a soft / hard occupancy gauge, client-side input validation with biologically meaningful sanity checks, a bilingual Portuguese / English interface with a runtime language selector, CSV export with UTF-8 BOM encoding, a high-contrast accessibility mode, an in-app configuration overlay for non-technical users, and an automated test suite executed in continuous integration. The application was developed and validated in the Dunamis Experiment (Urochloa decumbens cv. Basilisk, deferred grazing study, UEMG – Unidade Divinópolis, Brazil, 2026), and is configurable for use with any tropical forage species; it addresses a methodological gap in tropical pasture research by replacing paper-based records with a digital, GPS-tagged, real-time system adapted to low-connectivity field environments.