On spectral indices as a function of soil variability in safflower crop
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J. Indian Soc. Remote Sens. (September 2008) 36:267–272
RESEARCH ARTICLE
On Spectral Indices as a Function of Soil Variability in Safflower Crop T.N. Hajare . N.G. Patil . K.S. Verma
Received: 7 November 2007 / Accepted: 28 February 2008
Keywords Safflower . Spectral indices . NDVI . LAI . Radiometer
Abstract Spectral indices as an indicator of physiological traits affecting safflower yield in relation to soil variability were evaluated in a two year experiment (1997-1999). Reflectance, biometric and phonological data were collected. Two indices namely normalized differential vegetation index (NDVI) and ratio of spectral reflectance in infrared region to red region (1R/R) were derived from radiometric observation. Yield data indicated significant difference in different soils. Temporal NDVI behaviour as a function of soil type was not prominent especially in early stages of crop growth. However NDVI at 75 days after sowing (DAS) was found to be relatively better indicator of plant status
and yield. IR/R was relatively less effective in indicating the differential response of crop to soil types. Effect of soil and crop interaction on spectral indices was significant at 75 and 90 DAS, which was attributed to attainment of maximum leaf area and leaf area at these stages of growth. Regression analysis showed strong positive relationship between NDVI and leaf area, dry matter and yield. IR/R and leaf area had the strongest and consistent relationship (r = 0.96). A single regression equation accounted for yield variability in the dataset. Thus possible transformation of NDVI maps (satellite data) to LAI units and consequently applications like yield forecasting was indicated. Utility of spectra-temporal data as a pointer of plant development status and yield was also demonstrated.
T.N. Hajare () . N.G. Patil . K.S. Verma National Bureau of Soil Survey and Land Use Planning, Nagpur - 440 010, India
Introduction
e-mail: [email protected]
One of the major applications of remote sensing tools in agriculture pertains to studies on yield forecasting, irrigation requirement, pest management
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J. Indian Soc. Remote Sens. (September 2008) 36:267–272
etc. However, research reports on spectral changes in relation to crop management practices and soil related factors are scarce for oilseed crops in general and safflower crops in particular. Safflower (Carthamus tinctorius L.) is a major oilseed crop in India with 98 per cent of the total acreage spread in the states of Maharashtra, Karnataka and Andhra Pradesh (Anonymous, 1994). It is grown in heavy textured clay soils of Vidarbha region (Maharashtra) primarily due to its characteristics such as drought tolerance and ability of the tap root to penetrate into deep soil layers (Weiss, 1983). The objective of this study was to explore the potential of using spectral indices in indirect and accurate estimation of physiological traits affecting the yield of safflower as a function of soil variability. It was conducted during 1997–98 and 1998–99 at Futala
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