Development of Relationships between Spectral Reflectance Data and Selected Biotic-abiotic Stresses in Cotton Crop
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Date
2018
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Punjab Agricultural University, Ludhiana
Abstract
The present study was conducted to develop the relationships between spectral
reflectance data and biotic-abiotic stresses in cotton crop. Four levels of urea application with
rate of 225, 275, 325 and 375 kg ha-1 were applied in experimental plots. Row to row spacing
for cotton crop were kept as 67.5 and 80 cm for the experiment. All the plots for the
experimental field were georeferenced using GPS device. Data was collected at various
growth stages of cotton crop using drone mounted cameras and Green Seeker for computation
of variations in NDVI at different nitrogen levels. NDVI obtained from different sensors were
increasing from vegetative stage (Mean NDVI = 0.454) till bud formation stage (mean NDVI
= 0.7089) and decreased at boll opening stage (mean NDVI = 0.5232) till maturity stage
(mean NDVI = 0.1432) of cotton crop. It was evident from the regression analysis that NDVI
values obtained from NIR+R camera and Green Seeker had a good relationship having
R2 = 0.74. Study also revealed that when mean insect population varied from 7.18 to 23.027
mean NDVI values obtained from NIR+ R camera after image processing varied in the range
of 0.477 to 0.5441 and mean NDVI obtained from Green Seeker varied from 0.801 to 0.831.
It was also found from the spatial maps and drone imagery that part of crop having more
vigour, NDVI values in the vegetative stage was most affected by whitefly attack.
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