Gamma-ray beam attenuation as an auxiliary technique for the evaluation of the soil water retention curve

The soil water retention curve is fundamental for the hydraulic characterization of a soil and has many applications in agricultural research as well as in practical agriculture. A new procedure for soil moisture and soil bulk density evaluation inside closed pressure chambers through gamma-ray beam attenuation is presented. The proposed procedure presents several advantages in relation to the traditional process: avoids the need of continuous sample manipulation; minimizes the problem of hysteresis; allows a more precise evaluation of soil moisture by taking into account changes of soil bulk density due to swelling or shrinking on addition or removal of water; allows frequent evaluation of soil moisture without the need of opening the pressure chamber; allows a more precise judgement of equilibrium; reduces drastically the time of the determination of the retention curve and allows easy automation of data acquisition by a computer.

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Soil water retention curve determined by gamma-ray beam attenuation

Soil and Tillage Research ◽

10.1016/j.still.2004.06.003 ◽

2005 ◽

Vol 82 (1) ◽

pp. 89-97 ◽

Cited By ~ 33

Author(s):

Luiz F. Pires ◽

Osny O. S. Bacchi ◽

Klaus Reichardt

Keyword(s):

Soil Water ◽

Water Retention ◽

Gamma Ray ◽

Water Retention Curve ◽

Soil Water Retention Curve ◽

Soil Water Retention ◽

Retention Curve ◽

Beam Attenuation

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Relating soil structure and hydrophysical characteristics to aerobic and anaerobic soil respiration

10.5194/egusphere-egu2020-21234 ◽

2020 ◽

Author(s):

Teamrat Ghezzehei ◽

Jennifer Alvarez ◽

Yocelyn Villa ◽

Rebecca Ryals

Keyword(s):

Organic Matter ◽

Soil Moisture ◽

Soil Water ◽

Soil Structure ◽

Water Retention ◽

Water Retention Curve ◽

Soil Water Retention Curve ◽

Soil Water Retention ◽

Retention Curve ◽

Aerobic And Anaerobic

<p>The dynamics of soil organic matter is strongly controlled by the hydrophysical environmental factors, including motility, aqueous diffusivity of substrates, gaseous diffusivity, and energetic constraints on microbial physiology. The relationships among these physical factors depend on soil moisture and the architecture of the soil pores. In this regard, the soil water retention curve can serve as a macroscopic signature of pore-size distribution. Therefore, the sensitivity of aerobic and anaerobic microbial activity must be closely associated with the shape of the soil water retention curve. The soil water retention curve is, in turn, strongly dependent on soil texture and structure. Here, we present a physically-based model of aerobic and anaerobic microbial respiration rates. We also present a novel experimental technique for the characterization of the soil-moisture sensitivity of soil microbial activity. The proposed experimental and modeling approaches allow direct coupling of the fate soil organic matter with the nature of soil structure.</p>

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MINIMUM NUMBER OF POINTS FOR A RELIABLE SOIL WATER RETENTION CURVE USING RICHARDS’ PRESSURE CHAMBER

Revista Engenharia na Agricultura - REVENG ◽

10.13083/reveng.v29i1.7320 ◽

2020 ◽

Vol 28 ◽

pp. 477-487

Author(s):

Gilmar Batista Grigolon ◽

Adriano Valentim Diotto ◽

Carlos José Gonçalves de Souza Lima ◽

João Paulo Francisco ◽

Marcos Vinícius Folegatti

Keyword(s):

Soil Moisture ◽

Soil Water ◽

Water Retention ◽

Soil Water Potential ◽

Pressure Chamber ◽

Water Dynamics ◽

Water Retention Curve ◽

Soil Water Retention Curve ◽

Soil Water Retention ◽

Retention Curve

The soil hydro-physical characteristics are very important for studies about soil water dynamics. The soil water retention curve it is a soil characteristic sometimes expensive and time consuming to be done and could be a problem for farmers. The numbers of points and its tension evaluated are normally choose arbitrarily. This study aimed to define the fewest pairs of soil moisture and water soil potential points which result in a reliable water retention curve in two different soils (sandy and clay). Using different tensions by suction table and Richards’ pressure chamber, nine replications were adjusted by van Genuchten's equation. Curves with 4, 5, 7, 8, 9, 10 and 13 points were studied and the curve with 13 points was adopted as standard. The obtained parameters for different pairs of soil moisture and their corresponding soil water potential were compared to the equivalent standard curve and submitted to analysis of variance (F test), and their values were compared by the Scott-Knott test (5% of probability). The curve with 7 points, using the tensions of 0; 40; 100; 300; 1,000; 5,000 e 15,000 hPa, was the lower number of points that did not showed statistical difference in any parameters of the model and the point with 15,000 hPa shown to be important and should be used on the combination of points to obtain a good adjustment.

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Retrieving Soil Physical Properties via Assimilating SMAP Brightness Temperature Observations in the Community Land Model

10.5194/ismc2021-4 ◽

2021 ◽

Author(s):

Hong Zhao ◽

Yijian Zeng ◽

Xujun Han ◽

Bob Su

Keyword(s):

Soil Moisture ◽

Physical Properties ◽

Soil Properties ◽

Water Retention ◽

Soil Physical Properties ◽

Water Retention Curve ◽

Soil Water Retention Curve ◽

Soil Water Retention ◽

Retention Curve ◽

Community Land Model

<p>Basic soil physical properties (i.e., soil texture and organic matter) and associated soil hydraulic properties (i.e., soil water retention curve and hydraulic conductivity) play an essential role in land surface models (LSMs) for estimating soil moisture. With the physical link between soil properties, LSMs and Radiative Transfer Models (RTMs), the soil physical properties can be retrieved, using a LSM coupled with a microwave L-band emission observation model in a data assimilation framework. To this purpose, this paper couples an enhanced physically-based discrete scattering-emission model with the Community Land Model 4.5 (CLM), to retreive soil physical properties using the Local Ensemble Transform Kalman Filter (LETKF) algorithm, assimilating Soil Moisture Active and Passive (SMAP) Level-1C (L1C) brightness temperature at H and V polarization ( and ) separately, assisted with in situ measurements at the Maqu site on the eastern Tibetan Plateau. Results show the improved estimate of soil properties at the topmost layer via assimilating SMAP ( H, V), as well as at profile using the retrieved top-layer soil properties and a prior depth ratio. The use of &#160;and &#160;shows varied sensitivities to retrievals of different soil compositions (i.e., sand, clay, silt) and soil moisture estimates. However, analyses show that the retrieved soil properties with fine accuracy are not sensitive factors affecting soil moisture estimates. Instead, uncertainties of CLM model structures shall be considered, such as the fixed PTFs (pedotransfer functions), the hydraulic function describing soil water retention curve and the water stress function determining root water update.</p>

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