Dependency measures for assessing the covariation of spectrally active and inactive soil properties in diffuse reflectance spectroscopy

Sarathjith, M C and Das, B S and Wani, S P and Sahrawat, K L (2014) Dependency measures for assessing the covariation of spectrally active and inactive soil properties in diffuse reflectance spectroscopy. Soil Science Society of America Journal, 78. pp. 1522-1530. ISSN 1435-0661 (In Press)

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Diffuse reflectance spectroscopy (DRS) is a rapid and noninvasive assessment technique for several spectrally active soil properties (chromophores) such as sand, clay, organic C, and Fe contents. The approach is also used for estimating many spectrally inactive constituents (non-chromophores) based on the assumption of covariation between non-chromophores and chromophores. The linkage between covariation and the ability of DRS to estimate a non-chromophore has not been reported in the literature. In this study, we evaluated the covariation assumption using three dependency measures (Pearson correlation coefficient, r; biweight midcorrelation, bicor; and mutual information based adjacency, AMI), five chromophores (organic C, Fe, clay, and sand contents, and geometric mean diameter), and seven non-chromophores (pH, electrical conductivity, P, K, B, Zn, and Al contents) measured in 247 Alfisol and 249 Vertisol samples. An average dependency index (ADI) was developed for each of the three measures (ADIr, ADIbicor, and ADIAMI). The first derivative of the reflectance in conjunction with partial least squares regression was used for data modeling. Model accuracy was evaluated using residual prediction deviation (RPD). The relationships between RPD values of non-chromophores and the ADI values were examined for different chromophore groups (physical, chemical, and combined). The performance of ADIAMI was found to be superior to ADIr and ADIbicor. The ADIAMI computed using chemical chromophores gave strong linear relationships (R2 = 0.93) between ADIAMI and the RPD of chemical non-chromophores, suggesting that the AMI may be used as a robust dependency measure to assess the covariation of non-chromophores with chromophores in DRS.

Item Type: Article
Divisions: RP-Dryland Cereals
CRP: CGIAR Research Program on Dryland Cereals
Subjects: Others > Soil Science
Depositing User: Ms K Syamalamba
Date Deposited: 04 Sep 2014 05:56
Last Modified: 02 Jan 2015 04:22
Official URL:
Acknowledgement: UNSPECIFIED
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