🌱 A look back at a ground-based field campaign from Cascavel, Brazil (2015–16), where two crops — common bean and soybean — were tracked survey by survey with terrestrial sensors: a hyperspectral spectroradiometer, an active NDVI sensor, LAI, chlorophyll (SPAD-type index), plant height, intercepted PAR, and a photo of every visit.

Common bean

Sown on 2016-03-03 and surveyed at DAS 0, 10, 25, 43, 55, 70 (13 monitored points), tracking chlorophyll index, height, LAI, PAR interception, and NDVI (ground sensor + field spectrometer) from emergence through pod fill.

Each variable has its own units and scale, so the curves below are indexed to that variable’s own season peak (=100%) to compare growth shapes — height and LAI plateau by flowering (DAS43), while NDVI keeps climbing into pod fill (DAS55) before the frost cuts every curve short at DAS70.

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DAS 0 · 2016-03-03 — sowing
DAS 10 · 2016-03-14 — emergence
DAS 25 · 2016-03-29 — vegetative growth
DAS 43 · 2016-04-16 — flowering
DAS 55 · 2016-04-29 — pod fill
DAS 70 · 2016-05-14

The canopy reflectance spectrum itself shifts with growth stage: the DAS43 peak-canopy curve shows a much deeper red chlorophyll absorption dip (~680 nm) and higher near-infrared plateau (750–1300 nm) than the sparse DAS10 canopy — and the frost-killed DAS70 curve partly recovers toward the bare-soil shape of DAS10.

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Soybean

Sown ahead of a 2015-11-10 first survey and tracked at DAS 34, 45, 81, 86, 110 (24 monitored points) through a full summer cycle, from canopy closure to senescence.

Same indexing as the bean chart: chlorophyll peaks earliest (DAS45), height and LAI plateau by DAS86, and every variable drops together at DAS110 as the crop matures toward harvest — a senescence signature rather than the bean’s abrupt frost cutoff.

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DAS 34 · 2015-11-10 — canopy closure
DAS 81 · 2015-12-17 — full bloom
DAS 86 · 2015-12-22 — pod fill
DAS 110 · 2016-01-25 — senescence

The soybean spectrum rises to a far higher near-infrared plateau at peak canopy (DAS86, ~0.6 reflectance) than bean ever reaches — denser, taller canopy — then collapses toward the senescent DAS110 curve as leaves yellow and dry down.

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This dataset — spectra, biophysics, and 499 geotagged field photos — supported several publications on estimating crop biophysical parameters from terrestrial remote sensing:

The full ground-truth dataset backs the original MSc dissertation: