From Laboratory to Proximal Sensing Spectroscopy for Soil Organic Carbon Estimation—A Review

Theodora Angelopoulou,Athanasios Balafoutis,Dionysis Bochtis,George Zalidis

doi:10.3390/su12020443

Abstract

Rapid and cost-effective soil properties estimations are considered imperative for the monitoring and recording of agricultural soil condition for the implementation of site-specific management practices. Conventional laboratory measurements are costly and time-consuming, and, therefore, cannot be considered appropriate for large datasets. This article reviews laboratory and proximal sensing spectroscopy in the visible and near infrared (VNIR)–short wave infrared (SWIR) wavelength region for soil organic carbon and soil organic matter estimation as an alternative to analytical chemistry measurements. The aim of this work is to report the progress made in the last decade on data preprocessing, calibration approaches, and system configurations used for VNIR-SWIR spectroscopy of soil organic carbon and soil organic matter estimation. We present and compare the results of over fifty selective studies and discuss the factors that affect the accuracy of spectroscopic measurements for both laboratory and in situ applications.

Highlights

Food production requires fertile soils that can be deteriorated by intensive agricultural practices [1]
The objective of this review was to summarize the progress made during the last decade using laboratory and proximal soil sensing in the visible and near infrared (VNIR)-short wave infrared (SWIR) region for Soil organic carbon (SOC) estimations
Laboratory measurements are considered to be a well-established method for soil properties estimations, but there is not yet a commonly accepted universal model with broad application

Summary

Introduction

Food production requires fertile soils that can be deteriorated by intensive agricultural practices [1]. In order to have sustainable agricultural systems, economic viability for both farmers and society should be considered, but environmental costs need to be taken into account, avoiding the implementation of practices that could lead to irreversible soil degradation [2]. The Sustainable Development Goals, adopted by the United Nations on September 2015, identified the importance of preserving soil resources from degradation in order to achieve such goals [7,8]. A key indicator of soil fertility, and soil quality, is soil organic matter (SOM) content [9]. Soil organic carbon (SOC) as a component of SOM affects soil fertility, and has an impact on climate change, as soil represents one of the largest terrestrial carbon pools [10]. There are still challenges that need to be addressed concerning data harmonization between different sources due to diversions in spatial and temporal data resolution, as well as a lack of the necessary information about soil sampling design and, in numerous cases, an absence of important auxiliary variable measurements for SOC stock estimation (i.e., bulk density) [15]

Objectives

Methods

Findings

Discussion

Conclusion