Estimating biophysical properties of coffee (Coffea canephora) plants with above-canopy field measurements, using CropSpec®
 
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1
Agricultural Systems and Engineering, School of Environment, Resources and Development (SERD), Asian Institute of Technology, Pathum Thani 12120, Thailand
2
Faculty of Agricultural Technology, Jember University, Jember 68121, East Java, Indonesia
3
Laboratory of Bioproduction System Engineering, Faculty of Agriculture, Tottori University, 4-101 Koyama Tottori, 680-8553, Japan
4
Indonesian Coffee and Cocoa Research Institute (ICCRI), Jember, East Java, Indonesia
Publish date: 2018-04-17
 
Int. Agrophys. 2018, 32(2): 183–191
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ABSTRACT
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.
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