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Estimating biophysical properties of coffee (Coffea canephora) plants with above-canopy field measurements, using CropSpec®

Putra, Bayu T. Widjaja, Soni, Peeyush, Morimoto, Eiji, Pujiyanto, Pujiyanto
International agrophysics 2018 v.32 no.2 pp. 183-191
Coffea canephora, chlorophyll, crops, field experimentation, light intensity, nitrogen, nitrogen content, remote sensing, trees, vegetation index
Remote sensing technologies have been applied to many crops, but tree crops like Robusta coffee (Coffea canephora) under shade conditions require additional attention while making above-canopy measurements. The objective of this study was to determine how well chlorophyll and nitrogen status of Robusta coffee plants can be estimated with the laser-based (CropSpec®) active sensor. This study also identified appropriate vegetation indices for estimating Nitrogen content by above-canopy measurement, using near-infra red and red-edge bands. Varying light intensity and different background of the plants were considered in developing the indices. Field experiments were conducted involving different non-destructive tools (CropSpec® and SPAD-502 chlorophyll meter). Subsequently, Kjeldahl laboratory analyses were performed to determine the actual Nitrogen content of the plants with different ages and field conditions used in the non-destructive previous stage. Measurements were undertaken for assessing the biophysical properties of tree plant. The usefulness of near-infrared and red-edge bands from these sensors in measuring critical nitrogen levels of coffee plants by above-canopy measurement are investigated in this study.