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IAPRS & SIS, Vol.34, Part 7, “Resource and Environmental Monitoring”, Hyderabad, India, 2002
EFFECT OF NITROGEN LEVELS ON SPECTRAL INDICES IN RELATION TO
CHLOROPHYLL, WAX CONTENT, GRAINS AND YIELD OF WHEAT GENOTYPE IN
DIFFERENT SOWING ENVIRONMENTS
Mahender Singh*, Ram Niwas*, Manoj Yadav" and O. P. Bishnoi*
*Dept. of Agricultural Meteorology, CCS HAU, Hisar 125 004 India
"Haryana State Remote Sensing Application Centre, Hisar — 125 004 India
Scientists @harsac.com
ABSTRACT :
KEY WORDS: Remote sensing, spectral indices, chlorophyll, leaf area index, dry matter.
Field experiment was conducted during 1998-1999 and 1999-2000 in winter season with three dates of sowing, four nitrogen levels
and five wheat varieties with three replications in split plot design to understand various components/factors affecting wheat yield
and to create database on yield parameters using remote sensing data at Research Farm of CCS Haryana Agricultural University,
Hisar (India). Various spectral indices were computed using spectral reflectance of crop. Amongst spectral indices Perpendicular
Vegetative Index (PVI), Greenness Index (Gn), Simple Subtraction (SSb), and Simple Ratio (SR) increased with the advancement of
the crop upto 90 days after sowing and after that decreased with the crop age. The maximum values of PVI, Gn, SSb and SR were
obtained when the crop was sown on 25" November as compared to 10" and 25" December sown crop. In case of nitrogen
applications the indices increased with the increase of nitrogen levels and maximum was observed with 180-kg/ha nitrogen
application. Among varieties PBW343 showed maximum value of these indices and minimum was observed in Sonak. The
chlorophyll was also found higher in variety PBW343 and lower in Sonak as compared to UP2338, WH542, RAJ3765 and PBW343.
The chlorophyll and wax content differed significantly with dates of sowing, nitrogen levels and varieties. The correlation
coefficients of PVI, Gn, SSb and SR were 0.93, 0.88, 0.86, and 0.88 with yield at maximum LAI stage respectively. The spectral
indices explained 89, 95, 90 and 93 per cent variability in LAI, DM, Chlorophyll and yield, respectively.
INTRODUCTION
The remote sensing technique is being used extensively in
natural/physical resource inventorying, mapping and
monitoring. The major applications related to agro-
meteorology are in the management of land and water resource,
crop production forecasting and to assess the ravages brought
about by disaster such as flood, drought, crop epidemics etc.,
which seriously affect the agriculture. Effective crop
management and yield prediction over a large area would be
possible by remote sensing techniques, through operational
models on crop growth and development. The operational
models are based on the fact that each crop has a unique
spectral signature. The general spectral response of a crop
canopy in the visible and near infrared band of electromagnetic
spectrum is characterized by absorption in the 0.35 to 0.50 um
and 0.60 to 0.70 um regions due to chlorophyll pigments, high
reflectance in the green region around 0.54 um, a steep
decrease in the reflectance in the 0.70 to 0.74 um and very high
reflectance in 0.74 to 1.30 um region, due to leaf water content
(Knipling, 1970). Spectral response of a crop canopy is
influenced by leaf area index and percent ground cover, growth
stages, and difference in cultural practices, stress conditions.
Some of the reflectance properties are utilized in crop
identification, yield forecasting and crop condition assessment
(Bauer, 1985). Das and Kalra (1990) and Das (1992) have
reviewed researches on the use of spectral measurements in
various aspects of crop studies and many environmental and
cultural factors that affect canopy spectral and thermal
responses. Attempts have been made to study the predictability
of wheat yield grown under different dates of sowing through
dynamic wheat growth spectral indices. The indices derived
from remotely sensed data are not only useful in crop
production forecasting, but also in detecting and quantifying
large area of crop stresses viz. stress due to moisture, nutrients
and insect-pest and diseases. The assessment of stresses due to
nitrogen deficiencies and environmental stresses through the
measurements of spectral and thermal characters have been
well documented by Sahai and Dadhwal (1989): Navalgund
(1991); Das (1992) and Singh et al (1992). Therefore, the
prediction models need to be generated and tested by
correlating remote sensing variables, so.as to improve upon the
forecasting network on temporal and spatial scale. Hence,
keeping in view of the importance of above facts, this study
entitled "Effect of nitrogen levels on spectral indices in relation
to chlorophyll, wax content grain yield of wheat genotypes in
different sowing environments" using remote sensing technique
has been undertaken.
MATERIALS AND METHODS
Field experiments were carried out on wheat at Research area
of Department of Agricultural Meteorology, CCS Haryana
Agricultural University, Hisar which is situated at 29? 10 N
latitude, 75? 46 E longitude and altitude of 215.2 meters above
mean sea level during two consecutive winter (Rabi) seasons of
1998-99 and 1999-2000. The treatments consisted of three
1 #Corresponding Author - Manoj Yadav, Haryana State Remote Sensing Application Centre (HARSAC), Hisar — 125 004 India
Scientists 9 harsac.com