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Spectral estimation of absorbed photosynthetically active radiation in corn zea mays canopies






Remote Sensing of Environment 17(3): 221-232

Spectral estimation of absorbed photosynthetically active radiation in corn zea mays canopies

Most models of crop growth and yield require an estimate of canopy leaf area index [LAI] or absorption of radiation; however, direct measurement of LAI or light absorption can be tedious and time-consuming. Relationships between photosynthetically active radiation (PAR) absorbed by corn (Z. mays L.) canopies and the spectral reflectance of the canopies. Absorption of PAR was measured near solar noon in corn canopies planted in north-south rows at densities of 50,000 and 100,000 plants/ha. Reflectance factor data were acquired with a radiometer with spectral bands similar to the Landsat MSS. Three spectral vegetation indices (ratio of near IR to red reflectance, normalized difference and greenness) were associated with > 95% of the variability in absorbed PAR from planting to silking. The relationships developed between adsorbed PAR and the 3 indices were tested with reflectance factor data acquired from corn canopies planted in 1979-1982 that excluded those canopies from which the equations were developed. Treatments included in these data were 2 hybrids, 4 planting densities (25, 50, 75 and 100 thousand plants/ha), 3 soil types (Typic Argiaquoll, Udollic Ochraqualf, and Aeric Ochraqualf) and several planting dates. Seasonal cumulations of measured LAI and each of the 3 indices were associated with > 50% of the variation in final grain yields from the test years. Seasonal cumulations of daily adsorbed PAR, estimated indirectly from the multispectral reflectance of the canopies, were associated with up to 73% of the variation in final grain yields. Adsorbed PAR, cumulated through the growing season, is a better indicator of yield than cumulated leaf area index.


Accession: 006459666



Related references

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