Capability of Diffuse Reflectance Spectroscopy to Predict Soil Water Retention and Related Soil Properties in an Irrigated Lowland District of Southern Italy

Antonio Leone,Guido Leone,Nadia Orefice,Natalia Leone,Eleonora Grilli,Ciro Galeone,Valeria Ancona

doi:10.3390/w11081712

Abstract

In this study, we examined the potential of vis-NIR reflectance spectroscopy, coupled with partial least squares regression (PLSR) analysis, for the evaluation and prediction of soil water retention at field capacity (FC) and permanent wilting point (PWP) and related basic soil properties [organic carbon (OC), sand, silt, and clay contents] in an agricultural irrigated land of southern Italy. Soil properties were determined in the laboratory with reference to the Italian Official Methods for Soil Analysis. Vis-NIR reflectance spectra were measured in the laboratory, using a high-resolution spectroradiometer. All soil variables, with the exception of silt, evidently affected some specific spectral features. Multivariate calibrations were performed to predict the soil properties from reflectance spectra. PLSR was used to calibrate the spectral data using two-thirds of samples for calibration and one-third for validation. Spectroscopic data were pre-processed [multiplicative scatter correction (MSC), standard normal variance (SNV), wavelet detrending (WD), first and second derivative transformation, and filtering] prior to multivariate calibration. The results revealed very good models (2.0 < RPD < 2.5) for the prediction of FC, PWP and sand, and excellent (RPD > 2.5) models for the prediction of clay and OC, whereas a poor (RPD < 1.4) prediction model was obtained for silt.

Highlights

In Italy, there is a considerable number of irrigated agricultural lowlands, such as the Po valley, the “Maremma Toscana”, the “Tavoliere delle Puglie”, the Salento, Volturno and Sele plains, and others [1]
This paper aims to examine the potential of visible-near infrared (vis-NIR) spectroscopy, coupled with partial least squares regression (PLSR), for the
This study focused on the use of vis-NIR reflectance spectroscopy under controlled laboratory conditions for characterizing hydraulic and related, basic soil properties in the coastal area of the lower Volturno river basin, southern Italy

Summary

Introduction

In Italy, there is a considerable number of irrigated agricultural lowlands, such as the Po valley (to the North), the “Maremma Toscana” (to the Middle), the “Tavoliere delle Puglie”, the Salento, Volturno and Sele plains (to the South), and others [1]. In these areas, rivers and groundwater represent the primary sources of water for irrigation. The competing demands of water, combined with the effects of global warming, have caused persistent and often serious water scarcity [2]. Efforts must be made to improve the management of irrigation water to reduce its consumption while maintaining crop productivity [3].

Objectives

Methods

Conclusion