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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