Full text: Resource and environmental monitoring (A)

   
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IAPRS & SIS, Vol.34, Part 7, "Resource and Environmental Monitoring", Hyderabad, India,2002 
  
Badhwar model (Equation 1) was fitted to the mean NDVI 
temporal set to develop district-wise wheat spectral profiles. 
Badhwar (1980) described wheat growth profile by the 
following functional form: 
G(t) = GO * (/T0)** exp [-B (t-T0?)] for t» TO: DH 
G(t) = GO for t < TO 
where G(t) = wheat NDVI at time t 
G0 = soil NDVI at TO 
TO = spectral emergence day 
a, B 7 crop specific constants (070 and B>0). 
By analysing the image, a value of 0.1 NDVI was found for GO 
in this study. Using the profile parameters a and p, the day of 
peak NDVI, Tmax is estimated as: 
Tmax = (0/2)? (2) 
The profile parameters (Alpha (a) and Beta (ß)) and phenology 
indicators (TO and Tmax) were computed for all the 16 districts. 
In order to save on the computation time spent in iterative 
running of CGMS with dates of sowing varying by one day 
interval, the CGMS was run for five dates of sowing (310, 320, 
330, 340 and 350 Julian day) only. A constant N fertilizer 
application rate of 120 kg/ha applied in. three splits and four 
irrigations each of 60mm to all the districts were specified. For 
each date of sowing, the district-wise daily average LAI profile 
was computed from grid simulated daily LAI profile belonging 
to that district. The two consecutive dates of sowing DOSI and 
DOS2 which had a lower date of peak LAI (DLL) and a higher 
date of peak LAI (DHL) with respect to Tmax were identified. 
The district-wise date of sowing (DOS) was computed by linear 
interpolation as given below: 
DOS=DOS1+(Tmax-DLL)*(DOS2 -DOS1)/(DHL-DLL) (3) 
2.3 CGMS Performance Evaluation 
The CGMS performance in terms of district level yield 
prediction was evaluated under three scenarios of specification 
of management inputs. Scenario-1: a constant date of sowing 
(330 Julian day), constant fertilizer application rate (120 N 
kg/ha) and constant number of irrigations (4 each of 60 mm) for 
all the grids. Scenario-2: district-wise RS-derived date of 
sowing and constant fertilizer and irrigation application. 
Scenario-3: district-wise spectral growth profile derived date of 
sowing, district-wise estimated fertilizer application rate 
computed from consumption statistics (Anonymous, 2001) and 
a constant irrigation application. For CGMS evaluation, district 
level observed wheat yields were obtained from the State 
Department of Agriculture of Haryana. 
3. RESULTS 
Haryana was covered in 708 grid cells of 5"X5' and the area of 
grid cells varied between 73.54 and 75.94 km”. The soil texture 
classes were dominated by loamy class (338 grid cells), 
followed by sandy (192 cells) and coarse loamy (156 cells) 
classes. In the case of average organic Carbon, 493 grid cells 
had values between 0.2 — 0.4 percent, 162 between 0.4 — 0.6 
percent while 24 grid cells had above 0.6 and 29 below 0.2 
percent. The classified image generated from multi-date WiFS 
data indicated that 35 percent of grid cells had wheat area 
fraction of less than 0.25, 21 percent between 0.25 — 0.50, 24 
percent between 0.50 — 0.75, and 20 percent above 0.75. 
The spectral growth profile parameters fitted to district-wise 
mean NDVI were found to be statistically significant. The 
values of profile parameters Alpha, Beta, TO and Tmax ranged 
from 30.2 to 79.8, 9.074E-5 to 2.300E-4, 320.6 to 359.8 Julian 
days, and 41.8 to 53.8 Julian days, respectively (Table 1). The 
TO showed a variation of 40 days whereas Tmax showed a 
variation of only 12 days. 
  
  
DISTRICT ALPHA BETA TO Tmax 
(*1.0E-4) (Julian (Julian 
day) day) 
Ambala 47.006 1.40 335.4 43.7 
Bhiwani 69.508 2.01 353.7 49.7 
Faridabad 79.410 2.30 356.2 49.4 
Gurgaon 71.790 2.12 350.3 45.1 
Hissar 79.826 2:27 359.8 53.8 
Jind 75.680 2.7 355.5 51.6 
Kaithal 63.537 1.86 345.9 47.5 
Karnal 56.335 1.68 339.0 43.8 
Kurukshetra 48.789 1.47 333.3 41.8 
Mahendragarh 53.605 1.60 339.7 43.8 
Panipat 63.979 1.88 346.1 46.6 
Rewari 60.219 1.80 343.0 43.4 
Rohtak 73171 2.1 355.1 50.3 
Sirsa 77.910 222 357.3 52.4 
Sonipat 69.561 2.02 351.6 48.5 
Yamunanagar 30.223 0.91 320.6 42.1 
  
TO is days from 1-Jan-2000; Tmax is days from 1-Jan-2001 
Table 1. District-wise Badhwar crop growth profile parameters 
and phenology indicators (TO and Tmax) obtained 
from multi-date WiFS data for Haryana. 
Determining the date of sowing (DOS) from NDVI profiles and 
its use in CGMS were investigated in this study. As explained 
in methodology section, this involved analysis of dates of peak 
simulated LAI from a series of possible sowing dates with date 
of estimated NDVI peak from Badhwar model fit. This is 
illustrated in Figure 2 for the district of Karnal. The estimated 
NDVI peak date (Tmax) was 43.8 while the dates of peak LAI 
for DOS of 320 and 330 were 37 and 45, respectively. Using 
linear interpolation (Equation 3), DOS of 329 was estimated. 
The district-wise DOS computed by CGMS iterations varied 
from 329 Julian day (26-Nov-00) to 344 Julian day (11-Dec-00) 
showing a variation of 15 days across the State at district level 
with a median value of 339 Julian day (5-Dec-00). The 
comparison of TO and computed DOS showed a significant 
positive correlation of 0.81. This comparison also showed 
anomaly for the two northern districts of Ambala and 
Yamunanagar where the TO values were earlier than the 
computed DOS by 1 and 10 days, respectively. This could be 
due to the error in the spectral NDVI profile of wheat for these 
   
  
    
     
   
    
     
   
    
   
  
    
   
    
    
   
     
    
  
  
    
    
    
    
   
    
   
    
  
    
    
   
    
    
  
   
  
  
    
	        
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