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The soil quality paradigm was originally developed in the temperate region with the overarching objective of approaching air quality and water quality standards. Although holistic and systems-oriented, soil quality focused principally on issues arising from large nutrient and energy inputs to agricultural lands. Soil quality in the tropics, however, focuses on three overarching concerns: food insecurity,...
There has been growing interest in the use of diffuse reflectance as a quick, inexpensive tool for soil characterization. Some studies, using techniques like Partial Least Squares (PLS) regression of 1st derivative spectra have reported predictive accuracies for soil Organic C (OC) and Inorganic C (IC) that approach the analytical limits of standard laboratory measures. We applied 1st derivative Visible...
There has been growing interest in the use of diffuse infrared reflectance as a quick, inexpensive tool for soil characterization. In studies reported to date, calibration and validation samples have been collected at either a local or regional scale. For this study, we selected 3768 samples from all 50 U.S. states and two tropical territories and an additional 416 samples from 36 different countries...
Research data on soil quality are scarce in Madagascar, despite the island's widely recognized problems of soil and environmental degradation. One of the major constraints to properly assessing current status, trends and processes of soil degradation is the high level of costs involved when using conventional soil analytical methods. Previous studies have demonstrated that visible-near-infrared (Vis-NIR)...
The impacts of human land use in the highlands of Madagascar are often equated with land degradation and decreasing soil fertility. The practice most often focused on is deforestation through slash-and-burn cultivation (tavy), and shifting cultivators are often portrayed as being ignorant, poverty-stricken peasants felling trees for fields and food. However, there is uncertainty whether soil degradation...
Diffuse reflectance spectroscopy (DRS) is attracting much interest in the soil science community because it has a number of advantages over conventional methods of soil analyses. The techniques are more rapid, timely, cheaper and hence more efficient at obtaining the data when a large number of samples and analysis are required. Moreover, a single spectrum may be used to assess various physical, chemical...
Combining global soil-spectral libraries with local calibration samples has the potential to provide improved visible and near-infrared (VNIR, 400–2500 nm) diffuse reflectance spectroscopy (DRS) soil characterization predictions than with either global or local calibrations alone. In this study, a geographically diverse “global” soil-spectral library with 4184 samples was augmented with up to 418...
In order to reduce costs and time in the analysis of soil properties, visible/near-infrared diffuse reflectance spectroscopy (VNIRS) has been proposed. Since various pre-processing transformations and calibration techniques are in use to analyze soil spectral data, much uncertainty still exists about predictive soil modeling. We investigated the feasibility of VNIRS to determine the concentration...
Local, field-scale, VisNIR-DRS soil calibrations generally yield the most accurate predictions but require a substantial number of local calibration samples at every application site. Global to regional calibrations are more economically efficient, but don't provide sufficient accuracy for many applications. In this study, we quantified the value of augmenting a large global spectral library with...
Proximal soil sensing (PSS) using portable visible–near infrared (vis–NIR: 400–2500 nm) spectrophotometers can be used to measure soil properties in situ. The objectives of this research were: (i) to compare field spectra collected in situ to spectra collected in the laboratory, (ii) to estimate soil colour and mineral composition from the spectra, and (iii) to make predictions of clay content using...
Visible and near-infrared (VisNIR, 400–2500 nm) diffuse reflectance spectroscopy (DRS) is a rapid, inexpensive sensing method that has shown promise for lab-based soil characterization. However, little has been reported on how DRS will work in a field setting on intact soil cores. Seventy-two soil cores, representing 21 soil series and four parent materials, were extracted from six fields in Central...
Mid-infrared diffuse reflectance spectroscopy (MIR-DRS, 2500 to 25000 nm) can provide rapid, cheap and relatively accurate predictions for a number of soil properties. This paper examines the ability of MIR-DRS to predict various soil chemical properties with emphasis on the elucidation of possible mechanisms of prediction. Three datasets from the states of Queensland, New South Wales, and Victoria,...
Goethite (Gt) is an important iron mineral in soils and sediments. Conventional measurements cannot effectively identify it at the low concentrations typical of soils and sediments. In this paper we demonstrate that diffuse reflectance spectroscopy (DRS) in conjunction with thermal treatment provides a definitive technique for identifying Gt in soil and sediments. The DRS pattern of Gt exhibits diagnostic...
For use as decision support for variable rate applications in precision agriculture, the commonly used sample point density of one sample per hectare is often not enough. However, increasing the sampling density using laboratory analyses is too expensive for farmers to implement. It is therefore important to find methods for rationalisation. To this end, farm-scale visible and near infrared reflection...
The aims of this paper are: to compare different data mining algorithms for modelling soil visible–near infrared (vis–NIR: 350–2500nm) diffuse reflectance spectra and to assess the interpretability of the results. We compared multiple linear regression (MLR), partial least squares regression (PLSR), multivariate adaptive regression splines (MARS), support vector machines (SVM), random forests (RF),...
The proportion of water stable aggregates larger than 0.25mm (WSA), mean weighted aggregate diameter (MWD) and water dispersible clay (WDC) are three good indicators of the risk of surface sealing, runoff generation and soil erosion by water. These aggregation indices are influenced by the contents in clay, iron oxides, calcium carbonate and organic matter, among other soil properties. Because these...
Oil spills occur across large landscapes in a variety of soils. Visible and near-infrared (VisNIR, 350–2500nm) diffuse reflectance spectroscopy (DRS) is a rapid, cost-effective sensing method that has shown potential for characterizing petroleum contaminated soils. This study used DRS to measure reflectance patterns of 68 samples made by mixing samples from two soils with different clay content, three...
Accurate assessment of total carbon (C t ) content is important for fertility and nutrient management of soils, as well as for carbon sequestration studies. The non-destructive analysis of soils by diffuse reflectance spectroscopy (DRS) is a potential supplement or alternative to the traditional time-consuming and costly combustion method of C t analysis, especially in spatial or temporal...
Visible and near-infrared diffuse reflectance spectroscopy (VNIR-DRS) provides a rapid and inexpensive tool for simultaneous prediction of a variety of different soil properties. Usually, some sophisticated multivariate mathematical or statistical methods are employed in order to extract the required information from the raw spectrum scan. For this purpose especially the partial least squares regression...
In the Brazilian Amazon patches of anthropogenic soils known as Amazonian Dark Earths (ADEs) occur. These soils are rich in carbon (C) and plant nutrients compared to the naturally occurring strongly weathered soils. In this paper we explore the potential of visible to near infrared (vis–NIR) and mid infrared (MIR) spectroscopy as an alternative to traditional soil analysis of ADE properties for predicting...
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