A.G.T. Schut : Imaging spectroscopy for characterisation of grass swards

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11 Jun 2003 16:00
Unit: Wageningen University
Location: Aula (gebouw 362), Gen. Foulkesweg 1, Wageningen
Promotor: prof.dr.ir. J. Goudriaan (Plant Production Systems)
Co Promotor: dr.ir. J.J.M.H. Ketelaars (Plant Research International)

 With a novel experimental system the potential of imaging spectroscopy for the characterisation of grass swards was explored. The system measures reflection between 405-1659 nm from 1.3 m above the soil surface, with a spatial resolution of 0.3-1.5 mm2. Grass sward images were taken during growth experiments with mini swards of perennial ryegrass, with and without white clover. From these images were estimated: ground cover, reflection intensity, image texture, spatial heterogeneity and patterns, and spectral characteristics of green leaves. Differences in image parameters appeared to be strongly related to growth, nitrogen deficiency, dry matter yield, feeding value and nutrient contents of the grass. Drought stress could be detected at an early stage. Image texture robustly differentiated clover from grass. Spatial heterogeneity quantified grass sward damage. Dry matter yield assessment was more accurate with imaging spectroscopy than with the disk plate meter or Cropscan. An outline is given for a mobile system for use in experimental or farm fields in order to validate the results of this study.
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