Measurement of radiant interception of crop canopies with the LAI-2000 plant canopy analyzer
作者:
N.Z. Jovanovic,
J.G. Annandale,
期刊:
South African Journal of Plant and Soil
(Taylor Available online 1998)
卷期:
Volume 15,
issue 1
页码: 6-13
ISSN:0257-1862
年代: 1998
DOI:10.1080/02571862.1998.10635107
出版商: Taylor & Francis Group
关键词: Canopy extinction coefficient;leaf area index;plant canopy analyzer;radiant interception;sunfleck ceptometer.
数据来源: Taylor
摘要:
The performance of the plant canopy analyzer (PCA), model LAI-2000 (LI-COR, Lincoln, NE, USA), has been tested in two separate field trials for 18 annual crop and pasture species. The objective was to recommend appropriate techniques for reliable estimates of fractional interception of radiation (Fl), leaf area index (LAI) and canopy extinction coefficients. At least six below-canopy measurements and the use of 180° view restriction masks are recommended for row crops. Measurements should preferably be carried out before 8:00. Alternatively, shading of the sensor and sampling area is recommended during sunshine hours. The PCA's fisheye sensor proved to be more suitable than the sunfleck ceptometer (Decagon Devices, Pullman, WA, USA) for a daily estimation of canopy cover. The ceptometer would be preferable for the estimation of hourly Fl which is affected by solar orientation. The PCA's indirect, non-destructive and time saving measurement can accurately estimate LAI of soybean, sorghum, pearl millet and small canopies of wheat and milkvetch (LAI < 1.5). LAI of maize, cow- peas, rye, oats, triticele, ryegrass and perennial grasses obtained with the PCA should be corrected using the derived empirical functions. Potential users should investigate specific measurement techniques for other crops to determine whether the PCA provides reliable data. Fl and LAI measurements with the PCA were used to generate a database of extinction coefficients for photosynthetically active and global solar radiation.
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