Soil Bulk Density Estimation Methods: A Review

. In this paper, we present and analyze a novel global database of
soil infiltration measurements, the Soil Water Infiltration Global (SWIG)
database. In total, 5023 infiltration curves were collected across all
continents in the SWIG database. These data were either provided and quality
checked by the scientists who performed the experiments or they were
digitized from published articles. Data from 54 different countries were
included in the database with major contributions from Iran, China, and the USA.
In addition to its extensive geographical coverage, the collected
infiltration curves cover research from 1976 to late 2017. Basic information
on measurement location and method, soil properties, and land use was
gathered along with the infiltration data, making the database valuable for
the development of pedotransfer functions (PTFs) for estimating soil hydraulic
properties, for the evaluation of infiltration measurement methods, and for
developing and validating infiltration models. Soil textural information
(clay, silt, and sand content) is available for 3842 out of 5023 infiltration
measurements ( ∼  76%) covering nearly all soil USDA textural classes
except for the sandy clay and silt classes. Information on land use is
available for 76 % of the experimental sites with agricultural land use as
the dominant type ( ∼  40%). We are convinced that the SWIG database
will allow for a better parameterization of the infiltration process in land
surface models and for testing infiltration models. All collected data and
related soil characteristics are provided online in
*.xlsx and *.csv formats for reference, and we add a disclaimer that the
database is for public domain use only and can be copied freely by
referencing it. Supplementary data are available at
 https://doi.org/10.1594/PANGAEA.885492 (Rahmati et al., 2018). Data
quality assessment is strongly advised prior to any use of this database.
Finally, we would like to encourage scientists to extend and update the SWIG database
by uploading new data to it.

/pdf/development-and-analysis-of-the-soil-water-infiltration-wy1ftn2tpp.pdf

Development and analysis of the Soil Water Infiltration Global database

Time domain reflectometry (TDR) is the most widely used non-destructive method to determine the water content of soils and other porous media. TDR equipment can be automated and multiplexed to acquire accurate and rapid waveforms (return signal) without safety concerns associated with radioactive methods (e.g., neutron probe and Gamma-ray probe). Two key steps are required for TDR applications: (1) Obtain and analyze TDR waveforms using travel-time and signal attenuation analysis to determine dielectric permittivity and electrical conductivity, respectively. (2) Calibrate to determine a new- or apply an existing (e.g., Topp et al. (1980) ) relationship between the derived soil dielectric permittivity and the volumetric water content of the porous medium of interest. A majority of researchers and practitioners focus on step two and additionally develop new mathematical models to get better estimates of water content. Although there are reviews of TDR principles and applications in soil science, there is a lack of information on how TDR can disclose critical information in porous media beyond average soil water content. Therefore, we present a newly expanded review of TDR applications in porous media including soils, plants, snow, food stuffs, and concrete. We begin by reviewing TDR basics, including principles, probe design, commercially available equipment, and graphical and numerical methods as well as available software for waveform analysis. Applications of TDR to estimate volumetric water content in various types of porous media, the latest techniques available to derive spatial variability of soil water distributions along a single TDR probe are included, followed by TDR waveform based analyses to estimate electrical conductivity (EC), wetting/drying and freezing/thawing fronts, and snow depth. The combination of TDR measurements coupled with other methods (e.g., gypsum/ceramics and heat pulse method) to determine a wide range of soil physical properties (e.g., soil water retention curve, thermal properties, and hydraulic conductivity) and fluxes (e.g., soil heat flux, liquid water flux, and vapor flux) are also included. The study concludes with a discussion of limitations and future perspectives on various TDR applications.

A review of time domain reflectometry (TDR) applications in porous media

Land use change has remarkable impact on hydrological processes. However, little is known on the land use dependent variation of soil water infiltration characteristics. This study aims to investigate the effects of land use type on the spatial variation of infiltration characteristics and to identify their scale-specific controls. A total of 132 in-situ infiltration measurements were conducted using a disc infiltrometer along four 96-m transects under different land use types (forestland, shrubland, cropland with tillage, and cropland without tillage) in a typical agricultural region in north China. Classical statistics and multivariate empirical mode decomposition (MEMD) were used to explore the features of the overall and scale-specific spatial variation of four infiltration characteristics, i.e., cumulative infiltration over 30 min (I 30 ), sorptivity (S), unsaturated hydraulic conductivity (K 0 , h 0  = –2 cm) and saturated hydraulic conductivity (K s ). Besides, the scale-specific correlations between the infiltration characteristics and selected environmental factors, i.e., bulk density (BD), soil organic matter (SOM), initial soil water content (IWC) and water temperature (T) were investigated. The results indicated that land use type significantly affected not only the values of the infiltration characteristics but also their overall and scale-specific spatial variability. Tillage was found to have great impact on these infiltration characteristics. Generally, cropland with tillage revealed significantly higher values and weaker overall spatial variation of I 30 and S; while its K 0 and K s were significantly lower. Four major common spatial scales, i.e., 8–9 m, 13–16 m, 28–34 m and 47–94 m, were identified for the infiltration characteristics under different land use types using MEMD. The spatial variation of infiltration characteristics in forestland and shrubland were decomposed into larger common scales than that in croplands. Furthermore, the dominating factors of infiltration characteristics were scale-specific and also varied with land use type. Generally, SOM and BD were considered as important controls in smaller scales in croplands and the impacts of IWC and T were more effective in larger scales in forestland and shrubland.

Land use dependent variation of soil water infiltration characteristics and their scale-specific controls

Beerkan Estimation of Soil Transfer parameters (BEST) across soils and scales

http://digital.csic.es/bitstream/10261/114663/1/MoretD_JHydrol_2015.pdf

Estimate of soil hydraulic properties from disc infiltrometer three-dimensional infiltration curve. Numerical analysis and field application

This paper describes a new method (NSQE) to estimate soil hydraulic properties (sorptivity, S, and hydraulic conductivity, K) from full-time cumulative infiltration curves. The technique relies on an inverse procedure involving the quasi-exact equation of Haverkamp et al. (1994). The numerical resolution is described and the sensitivity of the method is theoretically evaluated, showing that the accuracy of the estimates depends on the measured infiltration time. A new procedure to detect and remove the effect of the contact sand layer on the cumulative infiltration curve is also given. The method was subsequently compared to the differentiated linearization procedure (DL), which calculate K and S from the simplified Haverkamp et al. (1994) equation, valid only for short to medium times. A total of 264 infiltration measurements performed with a 10 cm diameter disc under different soil conditions were used. Compared to the DL procedure, field measurements showed that the NSQE method allowed better estimates of soil hydraulic properties, independently on the infiltration noise and the presence of contact sand layer. Overall, although comparable S values were estimated with both methods, the longer infiltration times allowed by the proposed method made this procedure more accurate estimations of K. In conclusion, the NSQE method have shown to be a significant advance to accurate estimate of the soil hydraulic properties form the transient water flow.

Estimate of Soil Hydraulic Properties from Disc Infiltrometer Three-dimensional Infiltration Curve: Theoretical Analysis and Field Applicability☆

Aggregate density (ρ) is defined as the relationship between the mass and the volume occupied by an aggregate. Previous studies have characterised ρ on large to medium-sized soil aggregates (>4 mm diameter); however, little information is available for smaller aggregates (  0.99, P < 0.0001) between the volumes estimated on rough stones with the PHM and Archimedes methods demonstrates that this technique can be satisfactorily used to estimate the volume and, consequently, the ρ of small soil aggregates. The results showed an increase in ρ with decreasing aggregate size. A general trend of increasing ρ with the degree of soil disturbance by tillage was also observed.

/pdf/applicability-of-the-photogrammetry-technique-to-determine-55uejcmyt5.pdf

Applicability of the photogrammetry technique to determine the volume and the bulk density of small soil aggregates

http://digital.csic.es/bitstream/10261/53191/1/MoretD_JHydrol_2012.pdf

A new TDR probe for measurements of soil solution electrical conductivity

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Estimate of soil hydraulic properties from disc infiltrometer three-dimensional infiltration curve. Numerical analysis and field application

Estimate of Soil Hydraulic Properties from Disc Infiltrometer Three-dimensional Infiltration Curve: Theoretical Analysis and Field Applicability☆

Applicability of the photogrammetry technique to determine the volume and the bulk density of small soil aggregates

A new TDR probe for measurements of soil solution electrical conductivity