Premium
Soil Analysis Based on Samples Withdrawn from Different Volumes: Correlation versus Calibration
Author(s) -
Wielopolski Lucian,
Johnsen Kurt,
Zhang Yuen
Publication year - 2010
Publication title -
soil science society of america journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.836
H-Index - 168
eISSN - 1435-0661
pISSN - 0361-5995
DOI - 10.2136/sssaj2009.0205
Subject(s) - laser induced breakdown spectroscopy , near infrared spectroscopy , calibration , soil test , environmental science , spectroscopy , soil science , sampling (signal processing) , analytical chemistry (journal) , materials science , computer science , chemistry , soil water , mathematics , environmental chemistry , statistics , physics , optics , filter (signal processing) , quantum mechanics , computer vision
Soil, particularly in forests, is replete with spatial variation with respect to soil C. The present standard chemical method for soil analysis by dry combustion (DC) is destructive, and comprehensive sampling is labor intensive and time consuming. These, among other factors, are contributing to the development of new methods for soil analysis. These include a near‐ and mid‐infrared (NIR and MIR) spectroscopy, laser‐induced breakdown spectroscopy (LIBS), and inelastic neutron scattering (INS). These technologies overcome many of the state‐of‐the‐art DC method's shortcomings and offer advances that it cannot. While NIR and MIR measure C bonds, the other two new methods, like DC, are more specific in measuring C and other elements based on chemical, atomic, and nuclear reactions. In addition to their fundamentally different physical principles, these approaches vastly differ in the volumes they typically sample: LIBS, 10 −9 m 3 ; DC, 10 −7 m 3 ; NIR and MIR, 10 −6 m 3 ; and INS, about 0.3 m 3 Thus, extra care is needed when comparing the findings from any two of these methods. Also, the high heterogeneity of the soil matrix, the nonuniformity of C distribution, and the presence of coarse fragments, particularly in forested ecosystems, further compound the difficulties in making direct comparisons. We investigated the implications of these differences when correlating any two of these methods and reviewed the processes of comparing a volumetric measurement against a point measurement. We also conducted a detailed comparison of the INS method with the standard DC test. We found that the total (soil organic matter and roots) measured by the INS correlated better than its components with the DC analyses( r 2 = 0.97, P = 10 −7 ). The samples for DC analysis were taken from excavations of 40‐ by 40‐ by 40‐cm plots, in 5‐ and 10‐cm layers.