Estimation of Soil Salinity Under Various Soil Moisture Conditions Using Laboratory Based Thermal Infrared Spectra
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RESEARCH ARTICLE
Estimation of Soil Salinity Under Various Soil Moisture Conditions Using Laboratory Based Thermal Infrared Spectra Lu Xu1,2
•
Zhichun Wang3 • Jinshan Hu1 • Shuguo Wang1 • John Maina Nyongesah4
Received: 12 June 2020 / Accepted: 12 November 2020 Ó Indian Society of Remote Sensing 2020
Abstract Soil salinization is a world-wide phenomenon that threatens ecological environment and agricultural production. Modeling soil salt content (SSC) is a big challenge because of its huge spatiotemporal variation and the interference of soil water content (SWC) and soil salt types. Prior studies showed more interest in the use of hyperspectral reflectance, while few studies focused on thermal infrared band domain. In this study, we arranged samples with three salt types and several levels of SWC and measured the soil emissivity for each sample at each level of SWC. We employed both original and derivate emissivity to figure out the relationship between SSC and soil thermal infrared spectra, then used partial least squares regression to estimate SSC. Finally, the optimal model was determined with the evaluation criteria, RPD (ratio of performance to deviation) for predictive ability and AICc (corrected Akaike Information Criterion) for simplicity. The models were applied to estimate SSC and coefficient of determination (R2) of 0.67, 0.71, 0.69 and 0.7, and root mean relative error of 4.03, 3.78, 3.92, 3.86 (g/100 g) was obtained, respectively, for NaCl, Na2SO4, Na2CO3 and all salt types. The study provided a comparison result of three salt types for soil salinity estimation and a criterion for modeling effectively and succinctly and should have potential applications in the future. Keywords Soil water content Soil salt content Thermal infrared spectra PLSR AICc
Introduction Soil salinity is a world-wide environmental and ecological threat in both irrigated lands within arid and semiarid regions. It influences crop yields and agricultural production greatly, which leads to land erosion and degradation (Corwin and Lesch 2003; Metternicht and Zinck 2003).
& Lu Xu [email protected] 1
School of Geography, Geomatics and Planning, Jiangsu Normal University, 101 Road Shanghai, Xuzhou 221116, Jiangsu, China
2
Xinjiang Institute of Ecology and Geography, Chinese Academy of Sciences, 818 Road Beijing, Urumqi 830011, China
3
Northeast Institute of Geography and Agroecology, Chinese Academy of Sciences, 4888 Shengbei Street, Changchun 130012, China
4
Jaramogi Oginga, Odinga University of Science and Technology, Bondo 210-40601, Kenya
Statistically about 60% of the world’s land area has been regarded as degraded land (Pimentel 2006). According to the statistics of United Nations Food and Agriculture Organization, saline soil covers approximately 397 million hectares in the world and causes enormous losses (Koohafkan and Stewart 2012). Thus, timely detection and evaluation of severity level and area of soil salinity are imperative for making decisions to improve the management methods or undertake r
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