Winter Oilseed-Rape Yield Estimates from Hyperspectral Radiometer Measurements

Abstract

Abstract. Spectral reflectance data can be used for estimation of plant biophysical parameters such as seed yield, related to the use of solar energy. A field experiment was conducted to investigate relationships between canopy reflectance and seed yield of winter oilseed rape sown on four different dates. Ground hyperspectral reflectance measurements were made using a hand-held radiometer and multispectral images were taken with a VIS-NIR camera. The different sowing dates generated a wide range of difference in crop spectral response and seed yields. The strongest relationships (R 2 =0.87) between the yield and spectral data recorded by both sensors occurred at early flowering stages. Later, the presence of flowers caused a decline in the relationship between yield and spectral data especially in the visible (VIS) range. In the full flowering stage the strongest correlation (R 2 =0.72) with the yield showed vegetation indices of the near-infrared (NIR) bands.

Spectral considerations for modeling yield of canola

“…For both study sites, our results demonstrate that the NDVI-yield relationship weakens as bloom intensifies in agreement with Piekarczyk (2011). The Oregon and North Dakota study sites show the same patterns/trends regardless of growing environment and sensor resolution.…”

“…Prior remote sensing research on canola has demonstrated the importance of timing for image acquisition if estimating relationships with grain yield. It has already been established that flowers in a canola canopy are problematic for relating NDVI to yield (Basnyat et al, 2004;Piekarczyk, 2011). An important temporal finding is that the relationship between NDVI and yield declines as flowering increases (Piekarczyk, 2011); however, no spectral solution to this problem has been offered to-date.…”

“…It has already been established that flowers in a canola canopy are problematic for relating NDVI to yield (Basnyat et al, 2004;Piekarczyk, 2011). An important temporal finding is that the relationship between NDVI and yield declines as flowering increases (Piekarczyk, 2011); however, no spectral solution to this problem has been offered to-date. Holzapfel et al (2009) found that NDVI data acquired between the six-leaf stage and the beginning of flowering were correlated to canola seed yield (R 2 = 0.35; p < 0.001).…”

“…During the flowering stage there is reduced interception of photosynthetically active radiation (Yates & Steven, 1987). Yellow flowers contribute red light (yellow = green+red) to a canopy-level signal and this added radiation reduces NDVI values (Behrens et al, 2006;Piekarczyk, 2011;Shen et al, 2009), which adversely affects the performance of NDVI to map variability in biomass (Shen et al, 2010;Sulik & Long, 2015) or yield potential. For instance, if there is a field of flowering radish, turnip, mustard, or other Brassica crop-any flower where there is a substantial red light component (i.e., white, red, yellow), then the red channel's value will be a combination of foliar (what NDVI is supposed to index) and floral reflectance.…”

Remote Sensing of Yields: Application of UAV Imagery-Derived NDVI for Estimating Maize Vigor and Yields in Complex Farming Systems in Sub-Saharan Africa

“…Using a hand-held radiometer to measure hyperspectral reflectance data and a VIS-NIR camera to capture multispectral images, Piekarczyk et al [29] found the strongest relationship (R 2 = 0.87) between the spectral indices and yields from oilseed crops at early flowering stages on experimental plots in Poland. The authors also found that while the increasing presence of flowers weakened this relationship, especially in the visible range, a strong relationship (R 2 = 0.72) was obtained at full flowering from VIs in the NIR bands.…”