scholarly journals SHORT TDR PROBES TO MEASURE WATER AND FERTILIZER ION GRADIENTS IN CONTAINER MEDIA

HortScience ◽  
1994 ◽  
Vol 29 (7) ◽  
pp. 742c-742
Author(s):  
Shaun F. Kelly ◽  
J.L Green ◽  
John S. Selker
Keyword(s):  
Porous Media ◽  
Soil Moisture ◽  
Moisture Content ◽  
Soil Moisture Content ◽  
Steel Wire ◽  
Field Measurements ◽  
Time Domain Reflectometry ◽  
Ion Concentrations ◽  
High Bandwidth ◽  
High Concentrations

Time Domain Reflectometry (TDR) is used to measure in situ soil moisture content and salinity of porous media. Commercially available TDR systems used for field measurements have limited use in laboratory scale experiments where short high resolution probes are needed. A short TDR probe was designed for use with high bandwidth TDR instruments currently available. The probes are designed from SMA bulkhead connectors using gold-plated stainless steel wire 0.035 inches in diameter. A 20.GHz digital sampling oscilloscope (11801; Tektronix, Beaverton, Ore.) with an SD-24 TDR sampling head is used with the probes to determine water content and ion concentrations in porous media. The 7.5- and 3.0-cm-long probes were used to measure soil moisture content and ion concentrations in laboratory columns. Fertilizer and water gradients were observed by using bromide salts brought into contact with the top of laboratory columns, 7.6 cm in diameter and 18 cm long, packed with container media [1 peat: 1 vermiculite v/v)]. Soil moisture measurements in the presence of high concentrations of salts were made by insulating the probes with Teflon heat-shrinkable tubing to minimize conductivity losses.

scholarly journals Field Calibration of TDR to Assess the Soil Moisture of Drained Peatland Surface Layers

Water ◽  
2018 ◽  
Vol 10 (12) ◽  
pp. 1842 ◽  
Author(s):  
Tomasz Gnatowski ◽  
Jan Szatyłowicz ◽  
Bogumiła Pawluśkiewicz ◽  
Ryszard Oleszczuk ◽  
Maria Janicka ◽  
...  
Keyword(s):  
Dielectric Constant ◽  
Soil Moisture ◽  
Moisture Content ◽  
Soil Moisture Content ◽  
Mean Squared Error ◽  
Time Domain Reflectometry ◽  
Calibration Model ◽  
Surface Layers ◽  
Calibration Equation ◽  
North East

The proper monitoring of soil moisture content is important to understand water-related processes in peatland ecosystems. Time domain reflectometry (TDR) is a popular method used for soil moisture content measurements, the applicability of which is still challenging in field studies due to requirements regarding the calibration curve which converts the dielectric constant into the soil moisture content. The main objective of this study was to develop a general calibration equation for the TDR method based on simultaneous field measurements of the dielectric constant and gravimetric water content in the surface layers of degraded peatlands. Data were collected during field campaigns conducted temporarily between the years 2006 and 2016 at the drained peatland Kuwasy located in the north-east area of Poland. Based on the data analysis, a two-slopes linear calibration equation was developed as a general broken-line model (GBLM). A site-specific calibration model (SSM-D) for the TDR method was obtained in the form of a two-slopes equation describing the relationship between the soil moisture content and the dielectric constant and introducing the bioindices as covariates relating to plant species biodiversity and the state of the habitats. The root mean squared error for the GBLM and SSM-D models were equal, respectively, at 0.04 and 0.035 cm3 cm−3.

Thermal properties of Antarctic soils: wetting controls subsurface thermal state

2016 ◽  
Vol 28 (5) ◽  
pp. 361-370 ◽  
Author(s):  
Joseph S. Levy ◽  
Logan M. Schmidt
Keyword(s):  
Soil Moisture ◽  
Thermal Diffusivity ◽  
Moisture Content ◽  
Soil Moisture Content ◽  
Thermal State ◽  
Thermal Characteristics ◽  
Field Measurements ◽  
Dry Valleys ◽  
Ground Ice ◽  
Mineral Soils

AbstractMineral soils in the McMurdo Dry Valleys (MDV), Antarctica, are commonly considered to be dry, and therefore to be good insulators with low thermal diffusivity values (~0.2 mm2s-1). However, field measurements of soil moisture profiles with depth, coupled with observations of rapid ground ice melt, suggest that the thermal characteristics of MDV soils, and thus their resistance to thaw, may be spatially variable and strongly controlled by soil moisture content. The thermal conductivity, heat capacity and thermal diffusivity of 17 MDV soils were measured over a range of soil moisture conditions from dry to saturated. We found that thermal diffusivity varied by a factor of eight for these soils, despite the fact that they consist of members of only two soil groups. The thermal diffusivity of the soils increased in all cases with increasing soil moisture content, suggesting that permafrost and ground ice thaw in mineral soils may generate a positive thawing feedback in which wet soils conduct additional heat to depth, enhancing rates of permafrost thaw and thermokarst formation.

scholarly journals EFFECTS OF HYDROPHILIC POLYMERS AND ORGANIC AMENDMENTS ON ESTABLISHMENT OF KENTUCKY BLUEGRASS.

HortScience ◽  
1992 ◽  
Vol 27 (6) ◽  
pp. 588a-588
Author(s):  
A. James Downer ◽  
Ben Faber ◽  
Richard White
Keyword(s):  
Soil Moisture ◽  
Moisture Content ◽  
Water Content ◽  
Soil Moisture Content ◽  
Organic Amendments ◽  
Kentucky Bluegrass ◽  
Soil Bulk Density ◽  
Time Domain Reflectometry ◽  
Peat Moss ◽  
Turf Quality

Three polymers (a polyacrylamide, polyacrylate and a propenoate-propenamide copolymer) and three organic amendments (peat moss, wood shavings, and composted yardwaste) were incorporated at five rates in a sandy soil to 15cm depth. Soil moisture content was determined by time domain reflectometry and gravimetrically. Only the highest polymer rates (2928kg/ha [60#/1000sq.ft.]) produced significant increases in soil moisture content and reductions of soil bulk density. Peat moss and yardwaste increased soil water content while shavings decreased water content. Turf quality scores were not affected by polymers but were initially reduced by yardwaste and shavings.

scholarly journals Irrigation Levels Affect Plant Growth and Fruit Yield of Drip-Irrigated Bell Pepper

HortScience ◽  
2004 ◽  
Vol 39 (4) ◽  
pp. 748B-748 ◽  
Author(s):  
Juan C. Diaz-Perez* ◽  
Darbie Granberry ◽  
Kenneth Seebold ◽  
David Giddings ◽  
Denne Bertrand
Keyword(s):  
Soil Moisture ◽  
Plant Growth ◽  
Moisture Content ◽  
Soil Moisture Content ◽  
Time Domain Reflectometry ◽  
Fruit Yield ◽  
Bell Pepper ◽  
Plastic Mulch ◽  
Irrigation Rate ◽  
Stage Of Development

Bell pepper (Capsicum annum L.) plants have a high demand for water and nutrients and are sensitive to water stress during the establishment period and fruit setting. High levels of irrigation are often applied in order to maximize yields. However, field observations suggest that excessive irrigations may negatively affect bell pepper plants. The objective was to evaluate the effects of irrigation rate on plant growth and fruit yield. The trial was conducted in Spring 2003 at the Coastal Plain Experiment Station, Tifton, Ga. Drip-irrigated bell pepper (`Stiletto') plants were grown on black plastic mulch in 1-m wide beds (1.8-m centers). Plants were irrigated with an amount of water that ranged from 33% to 167% the rate of evapotranspiration (ET), adjusted by crop stage of development. Soil moisture content (% by volume) over the season was continuously monitored with time domain reflectometry sensors connected to a datalogger. The results showed that the average soil moisture content for the season increased with increasing rates of irrigation. Vegetative top fresh wt. and marketable fruit yield were reduced at both, low (33% ET) and high (166% ET) rates of water application. However, irrigation rate had a stronger effect on fruit yield than on top fresh wt. Plants supplied with high irrigation rates appeared to be more chlorotic compared to plants irrigated at medium rates (100% ET). There was a tendency for higher incidences of soil borne diseases (Pythium sp., Phytophtora capsici) in plants receiving higher rates of irrigation. The conclusion is high irrigation rates (>166% ET) are not recommended since they waste water and may result in both, higher incidences of soil-borne diseases and reduced bell pepper yields.

Estimating extractable soil moisture content for Australian soils from field measurements

Soil Research ◽  
2006 ◽  
Vol 44 (5) ◽  
pp. 531 ◽  
Author(s):  
A. R. Ladson ◽  
J. R. Lander ◽  
A. W. Western ◽  
R. B. Grayson ◽  
Lu Zhang
Keyword(s):  
Soil Moisture ◽  
Moisture Content ◽  
Soil Moisture Content ◽  
Transfer Functions ◽  
Vegetation Type ◽  
Field Measurements ◽  
Pasture Production ◽  
Soil Moisture Storage ◽  
Moisture Storage ◽  
Extractable Soil

The amount of water that can be stored in soil and evaporated or actively used by plants is a key parameter in hydrologic models and is important for crop and pasture production. Often, the active soil moisture store is estimated from laboratory measurements of soil properties. An alternative approach, described in this paper, is to estimate the extractable soil moisture capacity from direct measurements of soil moisture content in the field. A time series of soil moisture values, over the depth of the soil, shows the actual changes in water content. The difference between the wettest and driest profiles is an estimate of the extractable soil moisture storage. We have gathered data on extractable soil water capacity for 180 locations over Australia and have compared our values with published results from the Atlas of Australian Soils (AAS), derived from profile descriptions and pedo-transfer functions. Our results show that data from the AAS provide a useful lower bound for measured extractable soil moisture storage, but of the sites examined, 42% had values >2 times those in the AAS. In part, this was because total soil depths were underestimated in the AAS results compared with the active depths from the measured data. Active depths are strongly related to vegetation type.

Numerical Simulation of Terrestrial Radiation over a Snow Cover

2015 ◽  
Vol 32 (8) ◽  
pp. 1478-1485 ◽  
Author(s):  
P. Ducharme ◽  
A. Houdayer ◽  
Y. Choquette ◽  
B. Kapfer ◽  
J. P. Martin
Keyword(s):  
Soil Moisture ◽  
Moisture Content ◽  
Soil Moisture Content ◽  
Snow Water Equivalent ◽  
Field Measurements ◽  
Radioactive Material ◽  
Gamma Detector ◽  
Content Type ◽  
Basic Assumptions ◽  
Snow Water

AbstractThe intensity of terrestrial gamma radiation is a function of a number of parameters: emissivity and spatial distribution of the radioactive material in the soil, snow/water cover above ground, soil moisture content, type, and height above ground of the detector. Thus, the conversion of gamma measurements into reliable information must be based on a solid knowledge of the behavior of the gamma detector under different conditions. Such a detector, using a cylindrical NaI(Tl) crystal, was developed to remotely and automatically provide information on snow water equivalent (SWE) and soil moisture content (M). It became rapidly obvious that the behavior of the detector [gamma monitor (GMON)] over an infinite source could not be exactly reproduced in a laboratory. Therefore, a relatively simple model to simulate the behavior of GMON and to establish the relevant data analysis algorithms was conceived. This paper presents the basic assumptions for developing the model, the resulting algorithms, a comparison with field measurements, and some useful information on how GMON reacts to various field conditions.

Determining Moisture Content of Soil Layers with Time Domain Reflectometry and Micromechanics

2008 ◽  
Vol 2053 (1) ◽  
pp. 30-38 ◽  
Author(s):  
Sang Ick Lee ◽  
Dan G. Zollinger ◽  
Robert L. Lytton
Keyword(s):  
Dielectric Constant ◽  
Soil Moisture ◽  
Moisture Content ◽  
Water Content ◽  
Time Domain ◽  
Soil Moisture Content ◽  
Time Domain Reflectometry ◽  
Volumetric Water Content ◽  
Dry Density

Although the moisture condition of pavement sublayers can significantly affect pavement performance, accurate interpretation of in situ soil moisture measurements has been difficult to achieve because of the limitations of existing methods. Time domain reflectometry (TDR), originally developed to detect breaks or shorts in electrical conductors, has been used for measuring parameters related to the in situ soil moisture content. However, the apparent length method currently used to determine dielectric constant ignores other electrical properties of the conducting medium that may affect the interpretation of TDR trace to determine soil moisture. Furthermore, the existing methods for computing volumetric water content ignore the variations of dry density and determine the model parameters with assumption or regression analysis. These deficiencies can, in many cases, create a significant systematic error in the final determination of volumetric water content. To minimize these errors and improve the accuracy of moisture content estimate, a new three-step approach was proposed. The approach uses the transmission line equation to calculate the dielectric constant, conductivity, and reflectivity of a soil mixture. A micromechanics and self-consistent scheme was used to determine the volumetric moisture content and dry density on the basis of calibrated values of the solid and water dielectric constants. The system identification method was used iteratively to solve for dielectric parameters, soil moisture content, and dry density values. The validation of the new approach with ground-truth data indicated that the calculated errors were significantly less than those of existing method.

scholarly journals Evaluation of DualEM-II sensor for soil moisture content estimation in the potato fields of Atlantic Canada

2019 ◽  
Vol 65 (No. 6) ◽  
pp. 290-297 ◽  
Author(s):  
Aitazaz Farooque ◽  
Mahnaz Zare ◽  
Qamar Zaman ◽  
Farhat Abbas ◽  
Melanie Bos ◽  
...  
Keyword(s):  
Soil Moisture ◽  
Moisture Content ◽  
Precision Agriculture ◽  
Prince Edward Island ◽  
Soil Moisture Content ◽  
Root Zone ◽  
Time Domain Reflectometry ◽  
Atlantic Canada ◽  
Significant Difference ◽  
Non Destructive

The conventional gravimetric methods of estimating soil moisture content (θ) are laborious, time-consuming, and destructive to agricultural fields. We evaluated the performance of DualEM-II sensor in non-destructive way of θ prediction and for predicting θ variations within potato fields in Atlantic Canada. Values of θ were measured from four potato fields in New Brunswick and Prince Edward Island using a pre-calibrated (R<sup>2</sup> = 0.98) time domain reflectometry (TDR) from root zone of potato tubers under grid sampling arrangements. Horizontal co-planar (HCP) and perpendicular co-planar (PRP) readings were taken using DualEM-II sensor from the same locations of θ measurements. There was a better correlation between PRP and θ (r: 0.64–0.83) was calculated than between HCP and θ<br /> (r: 0.41–0.79). There was no significant difference (R<sup>2</sup>: 0.60–0.69; RMSE (root mean square error): 2.32–4.02) between the θ values measured with TDR (θ<sub>M</sub>) and those predicted with DualEM-II (θ<sub>P</sub>) confirming that the use of electromagnetic induction technique, evaluated during this study, is labor saving, quick, non-destructive, and accurate and can be considered a precision agriculture tool for efficiently managing soil water in potato fields.

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