3 THEORY SRS Sensors
correlate well with green LAI, although the relationship is specific
for each crop or natural canopy. For example, Aparicio et al. (2002)
studied NDVI versus LAI in more than twenty different durum wheat
genotypes in seven experiments over two years and found the rela-
tionship shown in Figure 4. Nguy-Robinson (2012) also studied the
behavior of NDVI versus LAI in maize and soybean. Their data sug-
gest a similar relationship between the two crops, but not identical.
These relationships have been developed for a wide range of crop
and natural canopies and we encourage our customers to seek out
the best relationship for their application.
Figure 4: Relationship between leaf area index and NDVI for 20-25
durum wheat genotypes studied over two years in seven different
experiments by Aparicio et al. (2002). Values shown were taken at
anthesis and milk-grain stage. Used with permission from author.
3.2 Fractional Interception of Photosynthetically Ac-
tive Radiation
The use of NDVI for determination of leaf area index has limita-
tions. Like many nondestructive techniques (e.g., fisheye and cep-
tometer techniques), the measurement of NDVI becomes less and less
sensitive as LAI increases above a certain point (Figure 3). Nguy-
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