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Methodology for measuring fAPAR in crops using a combination of active optical and linear irradiance sensors: a case study in Triticale (X Triticosecale Wittmack)

journal contribution
posted on 30.08.2018, 00:00 by MM Rahman, JN Stanley, DW Lamb, Mark TrotterMark Trotter
The amount of photosynthetically active radiation (PAR, 0.4–0.7 μm) absorbed by plants for photosynthesis relative to incident radiation is defined as the fraction of absorbed photosynthetically active radiation (fAPAR). This is an important variable in both plant biomass production and plant growth modeling. This study investigates the application of a newly developed, linear irradiance sensor (LightScout Quantum Bar Sensor, LightScout, Spectrum Technologies, Inc. USA), to quantify fAPAR for a demonstrator crop, Triticale (X Triticosecale Wittmack). A protocol was devised for sensor placement to determine reflected PAR components of fAPAR and to determine the optimal time of day and sensor orientation for data collection. Coincident, top of canopy, normalized difference vegetation index (NDVI) measurements were also acquired with a CropCircle™ ACS-210 sensor and measurements correlated with derived fAPAR values. The optimum height of the linear irradiance sensor above soil or plant canopy was found to be 0.4 m while measuring reflected PAR. Measurement of fAPAR was found to be stable when conducted within 1 h of local solar noon in order to avoid significant bidirectional effects resulting from diurnal changes of leaf orientation relative to the vertically-placed sensor. In the row crop studied, averaging fAPAR readings derived from the linear irradiance sensor orientated across and along the plant row provided an R2 = 0.81 correlation with above-canopy NDVI. Across row sensor orientation also gave a similar correlation of R2= 0.76 allowing the user to reduce sampling time. © Springer Science+Business Media New York 2014.

Funding

Category 4 - CRC Research Income

History

Volume

15

Issue

5

Start Page

532

End Page

542

Number of Pages

11

ISSN

1385-2256

Publisher

Springer New York LLC

Peer Reviewed

Yes

Open Access

No

External Author Affiliations

University of New England; Cooperative Research Centre for Spatial Information

Era Eligible

Yes

Journal

Precision Agriculture