Performance Evaluation of a Portable Laser-Induced Fluorescence Spectroscopy System for the Assessment of the Humification Degree of the Soil Organic Matter

Cleber H Dos Santos,Gustavo Nicolodelli,Adolpho J Melfi,Renan A Romano,Célia R Montes,Camila M Carvalho,Ladislau Martin-Neto,Paulino R Villas-Boas,Débora M B P Milori

doi:10.5935/0103-5053.20150039

Abstract

Laser-induced fluorescence spectroscopy (LIFS) has shown advantages for analyses of whole soil, providing results about chemical structure of soil organic matter (SOM) without the need for a chemical fractionating process; thus, allowing direct analysis of soils. Moreover, another advantage is the potential for the development of portable systems, which could be usable in field analyses. The aim of this paper is to evaluate the performance of a portable LIFS system to assess the humification degree (HD) of SOM. A good correlation (R > 0.8) was obtained for results (HD) achieved using the proposed portable system and a conventional fluorescence spectrometric method for humic acid. In addition, the results obtained using the portable LIFS system statistically agreed with the ones achieved using a benchtop LIFS system already described in the literature for such application (R = 0.953). Thus, the portable LIFS system constitutes an affordable option for the in situ characterization of SOM.

Highlights

Nowadays, the concern about soil quality has increased considerably due to environmental problems related to land degradation and sustainable agricultural production
From the data of carbon obtained by Total organic carbon (TOC) (Table 1) and the fluorescence spectrum area, the humification degree (HD) was determined for the diferent methods mentioned above
The correlation between HD determined using a portable system and that determined by conventional fluorescence spectroscopy methods for humic acid were high (R = 0.85 for A465, R = 0.83 for A4/A1 and R = 0.80 for I468/I374), suggesting that whole soil fluorescence with excitation at 405 nm is strongly related to humified structures of soil organic matter (SOM)

Summary

Introduction

The concern about soil quality has increased considerably due to environmental problems related to land degradation and sustainable agricultural production. The definition of soil quality and the development of techniques for such evaluation is an important challenge for science. The impact of agriculture on soil quality may be assessed indirectly through the measurement of soil characteristics (indicator of quality), which may allow comparisons with soils under native vegetation or among different soil managements.[1]. Soil organic matter (SOM) represents one of the main pools of the carbon on earth and has a key role on the carbon cycling.[2,3,4] SOM comprises humic substances (HS) and non-humic substances. An important information, often disregarded when studying SOM, is the soil humification degree (HD)

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Conclusion