Estimation of Leaf Area Index for Cotton Canopies Using the LI‐COR LAI‐2000 Plant Canopy Analyzer

Abstract

Measurement of leaf area index (LAI) is useful for understanding cotton (Gossypium hirsutum L.) growth, water use, and canopy light interception. Destructive measurement is time consuming and labor intensive. Our objective was to evaluate sampling procedures using the Li‐Cor (Lincoln, NE) LAI 2000 plant canopy analyzer (PCA) for nondestructive estimation of cotton LAI on the southern High Plains of Texas. We evaluated shading as a way to allow PCA measurements in direct sunlight and the influence of solar direction when using this procedure. We also evaluated a test of canopy homogeneity (information required for setting PCA field of view), determined the number of belowcanopy measurements required, examined the influence of leaf wilting on PCA LAI determinations, and tested an alternative method (masking the sensor's two outer rings) for calculating LAI from PCA measurements. The best agreement between PCA and destructively measured LAI values was obtained when PCA observations were made either during uniformly overcast conditions or around solar noon using the shading method. Heterogeneous canopies with large gaps between rows required both a restricted (45°) azimuthal field of view and averaging the LAI values for two transects, made with the field of view parallel and then perpendicular to the row direction. This method agreed well (r2 = 0.84) with destructively measured LAI in the range of 0.5 to 3.5 and did not deviate from a 1:1 relationship. The PCA underestimated LAI by ≥ 20% when measurements were made on canopies wilted due to water stress. Masking the PCA sensor's outer rings did not improve the relationship between estimated and measured LAI in the range of LAI sampled.

Parameterization of leaf growth in rice (Oryza sativa L.) utilizing a plant canopy analyzer

“…Researchers have reported indirect measurements of LAI obtained with the LAI-2000 in common bean (Phaseolus vulgaris L.), cotton (Gossypium hirsutum L.), maize (Zea mays L.), rice (Oryza sativa L.) and soybean [Glycine max (L.) Merr.] (Hicks and Lascano, 1995;Dingkuhn et al, 1999;Wilhelm et al, 2000;de Jesus et al, 2001;http://dx.doi.org/10.1016/j.fcr.2015.002 0378-4290/© 2015 Elsevier B.V. All rights reserved.…”

Optical Instruments for Measuring Leaf Area Index in Low Vegetation: Application in Arctic Ecosystems

“…By measuring below-and above-canopy radiation, the fraction of transmitted radiation that passes through a plant canopy can be quantified, which is then used to estimate LAI. The technique is applied in a whole range of (agro-)ecosystems ranging from coniferous and deciduous forests to agricultural crops (e.g., Gower and Norman 1991, Deblonde et al 1994, Dufrene and Breda 1995, Hicks and Lascano 1995, Cutini et al 1998, Le Dantec et al 2000. The main problems with using this fast and easy-to-apply LAI-2000 tool for low-stature vegetation are that the sensor either cannot get totally underneath the plant canopy, thereby missing part of the leaf area present, or that the sensor is too close to the individual leaves of the canopy, which leads to a large distortion of the LAI estimate (LI-COR 1992).…”

Canopy Volume and Root Length Influence Greenshoulder and Internal Greening in Carrot

“…This instrument has been widely used since 1986 (Hicks and Lascano, 1995). The LAI E has been modified as an estimated value (LAI).…”

“…The LAI E has been modified as an estimated value (LAI). One measurement was made above the canopy followed by five measurements below the canopy to determine canopy light interception at five different angles from which LAI E is computed using a model of radiative transfer in vegetative canopies (Hicks and Lascano, 1995). Five readings below the crop canopy with the fish-eye field-of-view assured that LAI E calculations are based on an appropriate sample of the foliage canopy.…”