Spectral response of gram varieties under variable soil conditions

The spectral response of gram (Cicer arietinum) varieties was studied in a crop sequence experiment conducted on three soils in Gondkhairi watershed, Nagpur district of Maharashtra state. A poor relationship between leaf area and Normalized Difference Vegetation Index (NDVI) (r= 0.17) and IR/R (r= 0 .11) was observed in ICCV-88202 and ICCC-37 varieties 66 days after sowing ( DAS). The hypothesis that short-duration varieties should show a signific ant positive correlation (due to these crops attaining high biomass at an e arly growth stage) did not hold good. Contrary to this, in ICCV-10 (a mediu m maturing variety) the leaf area showed a poor relation with NDVI (r= 0.39 ) and IR/ R (r= 0.45) at 84 DAS. As varieties ICCV-88202 (V-2) and ICCC-37 (V-3) in soil types S-1 and S-2 are high in biomass at 66 DAS (as is eviden t from the high values of leaf area) the possible reason for such a poor re lationship is masking the effect due to profuse violet and pink flowers at the top of the plant canopy. Analysis of variance ( ANOVA) results indicate that the influences due to soils and varieties yield a significant differe nce in IR/R ratio but a non-significant difference in NDVI both at 66 and 8 4 DAS. In gram with indeterminate growth habit, the biophysical parameters showed a more consistent relationship with IR/ R ratio than with NDVI. The yield prediction is expected to be more valid for ICCV-10 at 66 DAS (R-2 = 0.90**), whereas ICCV-88202 and ICCC-37 are similar for such a prediction b oth at 66 DAS ( V-2, R-2 = 0.66*; V-3, R-2 = 0.81**) and 84 DAS (V-2, R-2 = 0.66*; V-3, R-2 = 0.78**). Regression models encompassing varietal and soi l influences at different growth stages were simulated to predict yields.