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IAPRS & SIS, Vol.34, Part 7, “Resource and Environmental Monitoring”, Hyderabad, India, 2002 
  
to higher air temperatures experienced at reproductive phase by 
wheat crop in delayed sowings which resulted ultimately in 
forced maturity. Tiwari and Singh (1993) reported that delayed 
sowing significantly reduced the grain yield. Nitrogen 
application had significantly influenced the grain yield Yield is 
significantly increased with increases of nitrogen doses .The 
maximum yield was found when the crop was fertilized with 
150 kg/ha nitrogen and minimum in case of when no nitrogen 
applied. The yield was significant higher in N3 with respect to 
N2.Among the wheat cultivars PBW343 produced significantly 
higher yield as compared to the other wheat cultivars (Table3). 
The grain yields were 38.51, 37.88, 35.03,33.85 and 31.99 
kg/ha in PBW343, UP2338, WH542, Raj3765andSonak, 
respectively. Randhawa et al. (1992) reported that when crop 
was sown late, its flowering period was shortened because by 
that time it comes to flowering and the atmospheric temperature 
was high. The yield of var. PBW343 is significant wit respect 
to var. UP2338. 
Chlorophyll and wax content 
Chlorophyll and Wax content of wheat leaves at anthesis under 
various treatments are presented in Table 3. The table shows 
that chlorophyll a, chlorophyll b, total chlorophyll and Wax 
contents differed significantly in different dates of sowing 
except chlorophyll b. Chlorophyll a, chlorophyll b, total 
chlorophyll, and wax contents were highest in D, followed by 
D, and lowest in D3; sowing date. Among different nitrogen 
levels chlorophyll a, chlorophyll b and total chlorophyll 
differed significantly, and increased with increasing doses of 
nitrogen fertilizer wax content were decreased with increased 
dose of fertilizer. However, Optenhofel et al., (1997) found that 
nitrate deficiency had no effect on epicular wax in wheat. The 
highest chlorophyll content was observed in N3 and lowest in 
Nj level; however, wax contents were highest in No treatment 
followed by N;, N; and N; treatments as shown in Table 3. 
Rathore and Manohar (1989) found that chlorophyll a and b 
content increased with nitrogen application in mustard crop. In 
cultivars also the total chlorophyll and wax content differed 
significantly except chlorophyll b. The chlorophyll contents 
were highest in PBW343 followed by UP2338, WH542, Sonak 
and Raj 3765 while and wax content were highest in Sonak 
followed by UP2338, WHS542, Raj 3765 and PBW 343. 
Anderson and Boardman (1964) quantified the chlorophyll a, b 
and carotenoids in wheat crops. 
Spectral Indices 
The data on different spectral indices at three main stages were 
presented in table 4. The values of all spectral indices were 
effected by different dates of sowing. The maximum values of 
SSb, PVI, Gn. and ND were 52.92,10.39, 28.01and 0.87 
respectively at maximum LAI stage when crop was sown on 
25"November and it decreased with delay in sowing and the 
minimum values of SSb, PVI, Gn and ND were 
44.30,8.83,23.42 and 0.76 respectively at maximum LAI stage 
when crop was sown on 25" December. 
In case of nitrogen application the vegetative indices increased 
with increasing doses of nitrogenous fertilizer. The maximum 
value of vegetative indices was found when the crop fertilized 
with 150-kg/ha nitrogen. This was due to higher LAI observed 
in this treatment (Table2). 
Among varieties the spectral indices were higher in PBW343 
followed by UP2338, WH542, Raj3765 and Sonak.. Among the 
spectral indices PVI was most important indices for yield 
prediction. The values of PVI were 10.62, 9.90, 9.77, 8.87 and 
8.68 in variety PBW343, UP2338, WH542, Raj3765 and Sonak 
at maximum LAI stage. 
Relationships between crop parameters and spectral indices 
The correlation coefficients between crop parameters and 
spectral indices at three different phenophases are presented in 
Table 5. Spectral indices recorded at maximum LAI stage were 
better correlated with crop parameters as compared to other 
phenophases. However, the correlation coefficients on other 
phenophases are also significant at P<0.05. Among the spectral 
indices recorded at maximum LAI stage, perpendicular 
vegetation index showed highest correlation with crop 
parameters except chlorophyll content, which showed 
maximum association with simple subtraction index. On the 
basis of 'r' values best spectral indices were selected for 
development of regression equations with crop parameters. The 
multiple regression equations for estimation of crop variables 
on the basis of spectral indices measured at maximum LAI 
stage are of forms: 
Leaf area index = 0.0712 + 0.1712 PVI, + 0.1264 Gn, 
(3.740) (3.113) 
R? - 0.89, SE=0.137, F=96.87 
Chlorophyll = 4.5164 - 0.0631 SSb, + 0.147 Gn, + 0.0926 Gn, 
(mg/g leaf f.wt.) (-4.238) (4.298) (1.666) 
R°=0.90, SE = 0.179, F = 70.64 
Dry Matter (g/m?) = 
-890.153+63.9426 PVI, + 4.969 GN, +1156.60 TVI, 
(6.417) (1.652) (3.680) 
R?=0.95, SE = 24.87, F = 126.236 
Yield = -28.129 + 1.715 Gn, + 4.438 PVI, 
(-4.628) (7.295) 
R? = 0.93, SE = 2.031, F = 155.25 
Where, 
PVI, = Perpendicular vegetation index at jointing stage 
PVI, =Perpendicular vegetation index at maximum LAI stage 
GN, =Greenness index at jointing stage 
GN, =Greenness index at maximum LAI stage 
SSb, = Simple subtractions index at maximum LAI stage 
ND, =Normalized difference at maximum LAI stage 
The spectral indices Gn, SR and PVI collectively explained 
variation in leaf area index, dry matter and yield upto 89, 95 
and 93 per cent, respectively. Whereas, simple ratio, simple 
subtractions and greenness index collectively explained 
variation in chlorophyll content upto 90 per cent. 
Similar spectral models were developed by Ram Niwas and 
Sastri (1995) for pearl millet. Mishra (1989) regressed the 
spectral indices with chlorophyll content of wheat leaves. 
REFERENCES 
Anderson, J.M. and Boardman, N.K.,1964. Studies on the 
greening of dark grown bean plants. II. Development of 
photochemical activity. Aust. J. Biol. Sci. 17,pp. 93-101. 
Bauer, M.E., 1985. Spectral inputs to crop identification and 
condition assessment. Proc. IEEE. 73(6):pp. 1071-1085. 
Das, D.K. (1992). Education and training in agricultural