Mapping peak flowering phenology of rapeseed (Brassica napus) in North Dakota using Landsat 8 and Sentinel-2.
Rahimi E, Jung C
Phenology
Canola fields turning bright yellow in midsummer are one of the most dramatic agricultural spectacles in the northern plains — and the timing of that bloom, now trackable from space, directly determines how well bees can be moved in to pollinate it before the flowers drop.
Rapeseed — the plant that gives us canola oil — produces brilliant yellow flowers for a short window each summer, and catching that window is crucial for good harvests and healthy bee activity. Researchers used satellite cameras orbiting Earth to watch thousands of fields across North Dakota and map exactly when each field hit peak bloom, year after year. The newer European satellite gave sharper, more reliable answers than the older American one, mainly because it passes overhead more often and takes finer-detail photos.
Key Findings
Peak rapeseed flowering in North Dakota clusters around Julian day 200 (mid-July), with Sentinel-2 detecting it slightly later (days 203–230) than Landsat (days 196–213).
Sentinel-2's 5–7 day revisit cycle and 10 m resolution produced more temporally consistent flowering maps than Landsat's 16-day cycle and 30 m resolution.
The Normalized Difference Yellow Index (NDYI) successfully captured both year-to-year variability and field-level differences in flowering timing across a full decade of imagery.
chevron_right Technical Summary
Satellites can now pinpoint exactly when rapeseed fields burst into yellow bloom across North Dakota, helping farmers time pollination and harvest more precisely. The European Sentinel-2 satellite outperformed the older Landsat in accuracy, catching peak flowering around mid-July each year.
Abstract Preview
Detecting the peak flowering time of rapeseed (Brassica napus) is essential for optimizing crop management, improving yield forecasts, and enhancing pollination services. This study aimed to map an...
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Rapeseed, also known as rape and oilseed rape and canola, is a yellow-flowered member of the Brassicaceae family.