The authors gratefully acknowledge the financial support provided by the Canadian Foundation for Innovation (John Evans Leadership Fund) in the acquisition of the hydraulic property analyser instrument.

1. Soil sampling and sample preparation
NOTE: A schematic diagram of the workflow of this method can be found in Figure 1.
<ol>
	<li>Sample collection
	<ol>
		<li>Excavate the top few centimeters above the desired sampling depth to remove unwanted debris, particularly loose organic litter and soil surface crusting.</li>
		<li>Place the metal sampling core level on the surface of the exposed soil, with the sharp edge side facing the soil surface; then, place the hammering holder on top of the ring.</li>
		<li>Hit the top of the hammering holder repeatedly using a rubber mallet until the top of the metal sampling core aligns with the soil surface.</li>
		<li>Dig around the metal sampling core; then, dig underneath the core to remove it from the soil.</li>
		<li>Level both sides of the metal sampling core with a trowel or knife once it is removed from the soil; then, place plastic covers on either side of the core.</li>
		<li>Add a sample label to the metal core.</li>
	</ol>
	</li>
	<li>Sample storage and use
	<ol>
		<li>Store samples in a refrigerator of approximately 4 oC prior to analysis.</li>
		<li>Saturate samples at least 24 h before analysis by placing the sample cores in a large plastic container with degassed deionized water. First, remove the plastic cover that is on the flat edge side of the metal sampling core and place a paper coffee filter on top, followed by a saturation plate. Then, invert the core and saturation plate into the container and fill it with degassed deionized water within 1 cm of the top of the soil sample. Refill the container with degassed deionized water as needed until the soil has reached saturation. 
		NOTE: Saturation occurs when water is visible on the exposed surface of the soil.</li>
	</ol>
	</li>
</ol>
2. Sensor unit and tensiometer establishment
<ol>
	<li>Tensiometer preparation
	<ol>
		<li>Soak the tensiometers for 24 h in degassed deionized water: one tall (50 mm length) and one short (25 mm) tensiometer for each sensor unit that will be used in the analysis campaign.</li>
		<li>Seal the container holding the tensiometers to limit atmosphere diffusion into the water.</li>
	</ol>
	</li>
	<li>Sensor unit degassing by vacuum pump method 
	NOTE: Complete the following steps for each sensor unit that will be used in the campaign.
	<ol>
		<li>Fill both tensiometer shaft ports with degassed deionized water to the top of the port using a 20 mL syringe and fine-tip needle. Ensure the pressure transducer is clean by shining a light into the port and assessing if there are debris present.</li>
		<li>Place the acrylic top on the sensor unit and fasten the metal clips. Insert the syringe containing degassed deionized water into the opening of the acrylic top and fill to just below the top of the acrylic head.</li>
		<li>Attach the acrylic top to the degassing unit by inserting the &#39;T&#39; tube on the degassing unit to the top of the acrylic head. 
		NOTE: Two sensor units with acrylic tops can be attached to each degassing unit.</li>
	</ol>
	</li>
	<li>Tensiometer refilling
	<ol>
		<li>Place a stage-mounted cup into both available positions on the degassing unit, then fill &#190; of the cup with degassed deionized water.</li>
		<li>Screw the tensiometers into the threaded acrylic holders; then, move the black O-ring to meet the top of the acrylic holder. Place into the degassed deionized water held within the stage-mounted cups.</li>
	</ol>
	</li>
	<li>Begin vacuum degassing
	<ol>
		<li>Ensure all connections are attached tightly to prevent leakage.</li>
		<li>Turn on the vacuum pump until -0.4 Bar is reached; then, turn off the vacuum pump and let the system equalize. Turn on the vacuum pump again until -0.8 bar is reached.</li>
		<li>Tap the bottom of the sensor unit assembly on a thick towel to remove air bubbles from the tensiometer ports in the sensor unit.</li>
		<li>Keep the system under vacuum for at least 24 h. Check for leaks by turning off the vacuum and ensuring it remains at pressure. Turn on the vacuum pump at regular intervals to bring the vacuum to pressure, since it will slowly lose pressure as the system equalizes.</li>
		<li>After 24 h, remove the tubing from the acrylic top, and remove all tensiometers from the acrylic holders. Place the short and tall tensiometers into separate beakers of degassed deionized water.</li>
	</ol>
	</li>
</ol>
3. Initiating a campaign
<ol>
	<li>Preparation of sensor units
	<ol>
		<li>Plug the sensor unit assembly into the system connection cords.</li>
		<li>Place an absorbent material such as a towel under the connected sensor unit and remove the acrylic top by releasing the metal clips.</li>
		<li>Repeat Steps 3.1.1 and 3.1.2 for each sensor unit assembly for a multi-sensor setup, or continue to 3.A.iv for a single sensor setup.</li>
		<li>Click the data measurement software to open the program and click the Show Devices icon.</li>
		<li>Ensure that all the sensor units that are connected appear in the sidebar of the software.</li>
	</ol>
	</li>
	<li>Tensiometer installation
	<ol>
		<li>Click the Refilling Wizard icon at the top of the software to open the user interface. From the dropdown menu, navigate to the appropriate sensor unit. 
		NOTE: Transducers are in good working order if their initial readings are 0 hPa (&#177; 5 hPa).</li>
		<li>Select a tensiometer from the beaker. Ensure that there are no visible air bubbles in the shaft, and that there is water forming over the top of the tensiometer shaft in a convex meniscus. Add more degassed deionized water with a syringe to the top of the tensiometer if there is no convex meniscus.</li>
		<li>Move the black O-ring on the tensiometer to the center of the threads.</li>
		<li>Invert the tensiometer into the standing water present on the sensor unit while keeping the convex meniscus intact.</li>
		<li>Install the short tensiometer in the tensiometer port that is indicated with a short line. Install the tall tensiometer in the tensiometer port that is indicated with a long line.</li>
		<li>Carefully screw the tensiometer into the tensiometer port while watching the pressure readings on the Current Readings tab. Obtain a tight seal by doing a half-to-full turn of the tensiometer. 
		&#8203;NOTE: After being installed on the tensiometer port, ensure that tensiometer readings are 0 hPa (&#177; 5 hPa).</li>
		<li>Place a silicon bulb filled with degassed deionized water on the top of the tensiometer to prevent desiccation of the tip while other tensiometers are being installed.</li>
		<li>Repeat steps 3.2.1 to 3.2.7 for each tensiometer and sensor unit used in the campaign.</li>
	</ol>
	</li>
	<li>Sample placement on sensor units
	<ol>
		<li>Remove a saturated sample and the corresponding saturation plate from the container of degassed deionized water and place them on a working surface.</li>
		<li>Place the auger guide on top of the sample ring.</li>
		<li>Insert the tensiometer shaft auger into the hole of the auger guide and turn the tensiometer shaft auger in a complete rotation to remove soil. Repeat for the second hole. 
		NOTE: Keep track of the depth each hole makes in the soil sample as it corresponds to the height of the tensiometer.</li>
		<li>Remove the auger guide and ensure that the soil sample has not collapsed in the hole.</li>
		<li>Remove the silicon bulbs on each tensiometer and place the silicon disk on top of the sensor unit. 
		NOTE: Ensure that no air is trapped under the silicon disk, and that the temperature sensor is not covered.</li>
		<li>Align the holes in the sample core with the corresponding tensiometer height on the sensor unit.</li>
		<li>Invert the sample core and place it on top of the sensor unit, fitting the sample onto the tensiometers.</li>
		<li>Remove the coffee filter and saturation plate. Secure the soil core with metal clasps located on the side of the sensor unit.</li>
		<li>Repeat steps 3.3.1 to 3.3.8 for each of the samples.</li>
	</ol>
	</li>
	<li>System campaign initiation
	<ol>
		<li>Once each sensor unit has been set up, input the sample identification present on the metal core as it corresponds to each of the sensor unit serial numbers. Input a unique name for the field campaign, the click Browse to save the location of the file.</li>
		<li>Click Start.</li>
		<li>Take the initial weight reading after two tensiometer readings have been completed. First, unplug the connection cord from the sensor unit, wait for a dialog box to appear on the software, and place it on the weight scale. Remove the sensor unit once the software indicates the weight reading has been taken and plug it back into the connection cord. Repeat for all sensor units.</li>
		<li>Weigh samples 3x a day for the first 2 days of measurement, then 2x a day at regular intervals for the remainder of the campaign</li>
	</ol>
	</li>
</ol>
4. System campaign termination
<ol>
	<li>Software termination
	<ol>
		<li>Take a final weight measurement for each sensor unit once the sample has reached the air entry point.</li>
		<li>Click Stop and disconnect the connection cord from each sensor unit.</li>
	</ol>
	</li>
	<li>Campaign disassembly
	<ol>
		<li>Remove the sample core from the sensor unit. Place all soil material into a container, and oven-dry the soil sample. 
		NOTE: If working with fine-textured soils, wet each soil sample within an hour before removing it from the sensor unit.</li>
		<li>Remove the silicone disk and clean the top of the sensor unit with a wet towel if necessary.</li>
		<li>Carefully remove each tensiometer from slots. Clean the tips of the tensiometers with a soft bristled toothbrush and water if dirty.</li>
		<li>Clean the sensor unit surface by inverting the unit and spraying water from a safety wash bottle.</li>
		<li>Clean the tensiometer shaft port by inverting the sensor unit and squirting water with a syringe into the port.</li>
	</ol>
	</li>
</ol>
5. Data analysis
<ol>
	<li>Obtain the dry soil weight of each sample and the corresponding metal core.</li>
	<li>Click the data analysis software to open the program and click on a sample file to open the data in the software. Input the weight of the metal core in the Parameter section of the Information tab.</li>
	<li>Click the Measurements tab | Search Air Entry Point. To fine-tune the point of cavitation, move the dotted lines of the start and stop points in the tensiometer data range. Do the same for the air entry points if it needs to be specified for the software.</li>
	<li>Click on the Evaluation tab, and under Calculation of water contents, ensure that From dry soil weight (g) is selected. Input the weight of the dried soil.</li>
	<li>Click on the Fitting tab | apply the model that best suits the data.</li>
	<li>Click on the Export tab, choose a file path, and ensure the file is exported in .xlxs format.</li>
	<li>Repeat steps 5.1 to 5.7 for each soil sample.</li>
</ol>

Protocol for Soil Hydraulic Property Measurement via Evaporation

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G., Xing, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Equations+for+the+soil-water+characteristic+curve.">Equations for the soil-water characteristic curve.</a> Can Geotech J. 31 (4), 521-532 (1994).</li><li>van Genuchten, M. 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The authors have no conflicts of interest to disclose.

The simple evaporation experiment approach using the method that is described here is an efficient means to develop the SWRC and hydraulic conductivity curves. Simplicity and accuracy of data measurement make it a viable alternative to more traditional methods14. The method described here goes beyond the user manual and current literature to synthesize and expand on finer points of this intricate instrument. Particular attention needs to be paid to the soil sample collection, transport, and analys...

Soil water retention and hydraulic conductivity within natural and human-altered environments help us understand and observe changes in soil health and functionality. Quantifying hydraulic properties through the soil water retention curve (SWRC) and soil water conductivity curve offers insight into key drivers of soil physical behavior and water movement characterization1. The relationship between volumetric water content (&#952;) and matric head (h) is represented within an SWRC, and the ranges within the curve describe the saturation point, field capacity, and permanent wilting point2. Soil management practices, amendments, agroecosystem types, and environmental conditions can all have an impact on soil hydraulics3,4. These factors can in turn influence solute transport5 and plant available water6, soil respiration and microbial activity7, as well as wetting and drying cycles8. As an important piece in quantifying healthy and functioning soil, proper analysis of the SWRC is imperative for obtaining an informed understanding of soil hydraulic properties.
A variety of measurement techniques currently exist for developing a reliable SWRC, with the hanging-water column and pressure plate methods being common traditional approaches for determining the pore size distribution of soil2. Traditional methods can be time-consuming, usually taking weeks or months to analyze a small set of samples9. Moreover, once analysis is complete, these methods result in only a few data points that inform the SWRC9. Additionally, the accuracy of producing representative data using traditional methods such as pressure plates can become a concern at lower matric potentials, in particular, with fine-textured soils10,11. More modern techniques, which involve the simple evaporation experiment approach using tensiometers and the chilled-mirror dew point method, tend to deliver more reproducible data across a wide range of soil textures2. Initially developed by Wind in 1968, the simple evaporation experiment involved measuring water mass changes and tension changes through tensiometers in the soil sample over time12. As evaporation occurs, soil sample mass measurements are taken at specific time intervals to create an SWRC. Later refined by Schindler (1980), the method involved only two tensiometers placed at different pressure heads within the soil sample. The modified method was then tested and validated as capable of being used in scientific analysis13,14. A key benefit of the simple evaporation experiment is the potential to easily produce data across a large portion of the soil moisture curve (0 to -300 kPa), with more data points than with traditional methods. 
These modern methods involve automated instruments that take numerous data points throughout the sample analysis period and produce data using a software interface. The hydraulic property instrument is a contemporary instrument that creates water retention curves and conductivity curves from sample data15. By employing a simple evaporation experiment using the hydraulic property instrument, the relationship between water content and water potential in the soil can be evaluated1. In this experiment, water present within the tensiometer shaft exists in an equilibrium with water in the soil solution. As evaporation of soil water occurs and the soil sample dries, cavitation takes place in the tensiometer, and the experiment ends. There is a limitation of the hydraulic property instrument in the dry range of the SWRC, as the instrument is only capable of operating within matric potentials of 0 to -100 kPa. This can be remedied with the inclusion of data generated with a chilled-mirror dew point experiment using a soil water potential instrument16, which can extend the data range to -300,000 kPa or the permanent wilting point. All these data are brought together in the modeling software post processing to cohesively inform the SWRC from null tensions to higher tensions even beyond wilting point. The SWRC and hydraulic conductivity curves are then generated based on matric potential data points taken throughout the measurement period, allowing a complete curve projected from saturation to permanent wilting point to be generated. 
The method described here presents a succinct operating procedure for soil analysis with a hydraulic property instrument. This method has been conducted in a number of scientific settings, including quantification of soil health in a broad range of agroecosystems3,17,18,19, and efforts have been made to understand best practices beyond the instrument user manual20. Here, a standardized protocol is outlined for all steps of the procedure, including field sampling, sample preparation, software function, and data processing. Following this method will ensure a successful campaign that results in reliable data. Critical steps for ensuring quality data, common challenges, and best practices are presented to ensure proper implementation.

<table><tbody><tr><td>4 L Buchner Flasks (two)</td><td>Various</td><td>n/a</td><td>Containers for water degassing</td></tr><tr><td>20 mL Syringe, fine tip</td><td>BD</td><td>BD-302830</td><td></td></tr><tr><td>Coffee filter</td><td>Various</td><td>n/a</td><td>Prevents soil travel out of core while soaking</td></tr><tr><td>HYPROP Complete Set</td><td>Hoskin</td><td>110813/E240-M020210</td><td>tensiometer shaft auger, tube for vacuum syringe and refilling adapter, auger guide, HYPROP USB adapter, HYPROP sensor unit, tensiometer shafts (50 mm and 25 mm), saturation plate, refilling adapter, silicone gasket, set of o-rings, LABROS balance, software, cables</td></tr><tr><td>HYPROP Refill Unit</td><td>Hoskin</td><td>108899/ E240-M020258</td><td>vacuum pump, vacuum mount, beaker mount, refilling adapters</td></tr><tr><td>Large Plastic Tubs</td><td>Various</td><td>n/a</td><td>Holds water and soil cores during saturation</td></tr><tr><td>METER hammering holder</td><td>Hoskin</td><td>100255/E240-100201</td><td></td></tr><tr><td>Rubber Mallet</td><td>Home Depot</td><td>18CT1031</td><td>Sample collection tool used with hammering holder</td></tr><tr><td>Shovel</td><td>Home Depot</td><td>83200</td><td></td></tr><tr><td>Soil Sampling Ring incl. 2 caps</td><td>Hoskin</td><td>100254/E240-100101</td><td></td></tr><tr><td>Stir plate/ Stirring Bar</td><td>Various</td><td>n/a</td><td></td></tr><tr><td>Trowel</td><td>Home Depot</td><td>91365</td><td></td></tr></tbody></table>

measurements of soil water potential and conductivity based on a simple evaporation experiment using a hydraulic property analyzer

The measurement of soil hydraulic properties is critical in understanding the physical components of soil health as well as integrated knowledge of soil systems under various management practices. Collecting reliable data is imperative for informing decisions that affect agriculture and the environment. The simple evaporation experiment described here uses instrumentation in a laboratory setting to analyze soil samples collected in the field. The soil water tension of the sample is measured by the instrument, and tension data is modeled by software to return soil hydraulic properties. This method can be utilized to measure soil water retention and hydraulic conductivity and give insight into differences in treatments or environmental dynamics over time. Initial establishment requires a user, but data acquisition is automated with the instrument. Soil hydraulic properties are not easily measured with traditional experiments, and this protocol offers a simple and optimal alternative. Interpretation of results and options for extending the data range are discussed.

Upon completing a proper measurement campaign following the protocol above, it will be possible to view the data output of the experiment in the analysis software. Output curves originate from tensiometer readings that measure water tension (hPa) over time (t), and the initial curve of this data is generated immediately after termination of the campaign. Selected examples of tension curves of two soil samples can be examined to illustrate optimal and suboptimal results (Figure 2). Optimal re...

Author Spotlight: Advancing Agricultural Land Ecosystem Research with a Hydraulic Property Analyzer to Assess Soil Health

This article features a simple evaporation experiment using a hydraulic property instrument for a soil sample. Through efficient means, measurements can be taken over a series of days to generate high-quality data.

Measurements of Soil Water Potential and Conductivity based on a Simple Evaporation Experiment using a Hydraulic Property Analyzer

The measurement of soil hydraulic properties is critical in understanding the physical components of soil health as well as integrated knowledge of soil ...

measurements-soil-water-potential-conductivity-based-on-simple

Research

JoVE Journal

Environment

909 Views.  University of Alberta. In het Sustainable Land Ecosystems Lab richt ons onderzoek zich op het vinden van duurzame oplossingen voor problemen die van invloed zijn op landecosystemen, waaronder akkerland en grasland. Om dit complexe probleem op te lossen, moet onderzoek worden gedaan naar de gezondheid van de bodem, een belangrijk onderdeel van alle ecosystemen van landbouwgronden. Het verkrijgen van een bodemwaterretentiecurve die zich uitstrekt tot in het droge bereik is een uitdag...

Video: Auteur in de schijnwerpers: onderzoek naar landbouwgrondecosystemen bevorderen met een hydraulische eigenschapsanalysator om de gezondheid van de bodem te beoordel

Soil Sampling and Isolation of Entomopathogenic Nematodes (Steinernematidae, Heterorhabditidae)

Entomopathogenic nematodes (a.k.a. EPN) represent a group of soil-inhabiting nematodes that parasitize a wide range of insects. These nematodes belong to two families: Steinernematidae and Heterorhabditidae. Until now, more than 70 species have been described in the Steinernematidae and there are about 20 species in the Heterorhabditidae. The nematodes have a mutualistic partnership with Enterobacteriaceae bacteria and together they act as a potent insecticidal complex that kills a wide range of insect species.
Herein, we focus on the most common techniques considered for collecting EPN from soil. The second part of this presentation focuses on the insect-baiting technique, a widely used approach for the isolation of EPN from soil samples, and the modified White trap technique which is used for the recovery of these nematodes from infected insects. These methods and techniques are key steps for the successful establishment of EPN cultures in the laboratory and also form the basis for other bioassays that consider these nematodes as model organisms for research in other biological disciplines. The techniques shown in this presentation correspond to those performed and/or designed by members of S. P. Stock laboratory as well as those described by various authors.

Soil Sampling and Isolation of Entomopathogenic Nematodes Steinernematidae, Heterorhabditidae

Entomopathogenic nematodes are soil-inhabiting roundworms that parasitize a wide range of insects. We demonstrate sampling methods used for the isolation of these nematodes from the soil using two techniques: the insect baiting and the modified White trap, for the recovery of nematodes from soil samples and infected insect cadavers, respectively.

Entomopathogenic nematodes (a.k.a. EPN) represent a group of soil-inhabiting nematodes that parasitize a wide range of insects. These nematodes belong to ...

Exploring the Effects of Atmospheric Forcings on Evaporation: Experimental Integration of the Atmospheric Boundary Layer and Shallow Subsurface

Evaporation is directly influenced by the interactions between the atmosphere, land surface and soil subsurface. This work aims to experimentally study evaporation under various surface boundary conditions to improve our current understanding and characterization of this multiphase phenomenon as well as to validate numerical heat and mass transfer theories that couple Navier-Stokes flow in the atmosphere and Darcian flow in the porous media. Experimental data were collected using a unique soil tank apparatus interfaced with a small climate controlled wind tunnel. The experimental apparatus was instrumented with a suite of state of the art sensor technologies for the continuous and autonomous collection of soil moisture, soil thermal properties, soil and air temperature, relative humidity, and wind speed. This experimental apparatus can be used to generate data under well controlled boundary conditions, allowing for better control and gathering of accurate data at scales of interest not feasible in the field. Induced airflow at several distinct wind speeds over the soil surface resulted in unique behavior of heat and mass transfer during the different evaporative stages.

A protocol for the design and construction of a soil tank interfaced to a small climate controlled wind tunnel to study the effects of atmospheric forcings on evaporation is presented. Both the soil tank and wind tunnel are instrumented with sensor technologies for the continuous in situ measurement of environmental conditions.

Evaporation is directly influenced by the interactions between the atmosphere, land surface and soil subsurface. This work aims to experimentally study ...

A CO2 Concentration Gradient Facility for Testing CO2 Enrichment and Soil Effects on Grassland Ecosystem Function

Continuing increases in atmospheric carbon dioxide concentrations (CA) mandate techniques for examining impacts on terrestrial ecosystems. Most experiments examine only two or a few levels of CA concentration and a single soil type, but if CA can be varied as a gradient from subambient to superambient concentrations on multiple soils, we can discern whether past ecosystem responses may continue linearly in the future and whether responses may vary across the landscape. The Lysimeter Carbon Dioxide Gradient Facility applies a 250 to 500 &#181;l L-1 CA gradient to Blackland prairie plant communities established on lysimeters containing clay, silty clay, and sandy soils. The gradient is created as photosynthesis by vegetation enclosed in in temperature-controlled chambers progressively depletes carbon dioxide from air flowing directionally through the chambers. Maintaining proper air flow rate, adequate photosynthetic capacity, and temperature control are critical to overcome the main limitations of the system, which are declining photosynthetic rates and increased water stress during summer. The facility is an economical alternative to other techniques of CA enrichment, successfully discerns the shape of ecosystem responses to subambient to superambient CA enrichment, and can be adapted to test for interactions of carbon dioxide with other greenhouse gases such as methane or ozone.

A CO2 Concentration Gradient Facility for Testing CO2 Enrichment and Soil Effects on Grassland Ecosystem Function

The Lysimeter Carbon Dioxide Gradient Facility creates a 250 to 500 &#181;l L-1 linear carbon dioxide gradient in temperature-controlled chambers housing grassland plant communities on clay, silty clay, and sandy soil monoliths. The facility is used to determine how past and future carbon dioxide levels affect grassland carbon cycling.

Continuing increases in atmospheric carbon dioxide concentrations (CA) mandate techniques for examining impacts on terrestrial ecosystems. Most ...

Soil Lysimeter Excavation for Coupled Hydrological, Geochemical, and Microbiological Investigations

Studying co-evolution of hydrological and biogeochemical processes in the subsurface of natural landscapes can enhance the understanding of coupled Earth-system processes. Such knowledge is imperative in improving predictions of hydro-biogeochemical cycles, especially under climate change scenarios. We present an experimental method, designed to capture sub-surface heterogeneity of an initially homogeneous soil system. This method is based on destructive sampling of a soil lysimeter designed to simulate a small-scale hillslope. A weighing lysimeter of one cubic meter capacity was divided into sections (voxels) and was excavated layer-by-layer, with sub samples being collected from each voxel. The excavation procedure was aimed at detecting the incipient heterogeneity of the system by focusing on the spatial assessment of hydrological, geochemical, and microbiological properties of the soil. Representative results of a few physicochemical variables tested show the development of heterogeneity. Additional work to test interactions between hydrological, geochemical, and microbiological signatures is planned to interpret the observed patterns. Our study also demonstrates the possibility of carrying out similar excavations in order to observe and quantify different aspects of soil-development under varying environmental conditions and scale.

This study presents an excavation method for investigating subsurface hydrological, geochemical, and microbiological heterogeneity of a soil lysimeter. The lysimeter simulates an artificial hillslope which was initially under homogeneous condition and had been subjected to approximately 5,000 mm of water over eight cycles of irrigation in an 18-month period.

Studying co-evolution of hydrological and biogeochemical processes in the subsurface of natural landscapes can enhance the understanding of coupled ...

Wastewater Irrigation Impacts on Soil Hydraulic Conductivity: Coupled Field Sampling and Laboratory Determination of Saturated Hydraulic Conductivity

Since the early 1960s, an alternative wastewater discharge practice at The Pennsylvania State University has been researched and its impacts monitored. Rather than discharging treated wastewater to a stream, and thereby directly impacting the stream quality, the effluent is applied to forested and cropped land managed by the University. Concerns related to reductions in soil hydraulic conductivity occur when considering wastewater reuse. The methodology described in this manuscript, matching soil sample size with the size of the laboratory-based hydraulic conductivity measurement apparatus, provides the benefits of a relatively rapid collection of samples with the benefits of controlled laboratory boundary conditions. The results suggest that there may have been some impact of wastewater reuse on the soil&#39;s ability to transmit water at deeper depths in the depressional areas of the site. Most of the reductions in the soil hydraulic conductivity in the depressions appear to be related to the depth from which the sample was collected, and by inference, associated with the soil structural and textural differences.

Here we present a methodology which matches a soil sample size and a hydraulic conductivity measurement device to prevent the so-called wall flow along the inside of the soil container from being erroneously included in water flow measurements. Its use is demonstrated with samples collected from a wastewater irrigation site.

Since the early 1960s, an alternative wastewater discharge practice at The Pennsylvania State University has been researched and its impacts monitored. ...

Manufacturing Simple and Inexpensive Soil Surface Temperature and Gravimetric Water Content Sensors

Quantifying temperature and moisture at the soil surface is essential for understanding how soil surface biota respond to changes in the environment. However, at the soil surface these variables are highly dynamic and standard sensors do not explicitly measure temperature or moisture in the upper few millimeters of the soil profile. This paper describes methods for manufacturing simple, inexpensive sensors that simultaneously measure the temperature and moisture of the upper 5 mm of the soil surface. In addition to sensor construction, steps for quality control, as well as for calibration for various substrates, are explained. The sensors incorporate a Type E thermocouple to measure temperature and assess soil moisture by measuring the resistance between two gold-plated metal probes at the end of the sensor at a depth of 5 mm. The methods presented here can be altered to customize probes for different depths or substrates. These sensors have been effective in a variety of environments and have endured months of heavy rains in tropical forests as well as intense solar radiation in deserts of the southwestern U.S. Results demonstrate the effectiveness of these sensors for evaluating warming, drying, and freezing of the soil surface in a global change experiment.

Accurately measuring temperature and water content of the upper 5 mm of the soil surface can improve our understanding of environmental controls on biological, chemical, and physical processes. Here we describe a protocol for manufacturing, calibrating, and conducting measurements with soil surface temperature and moisture sensors.

Quantifying temperature and moisture at the soil surface is essential for understanding how soil surface biota respond to changes in the environment. ...

A Telemetric, Gravimetric Platform for Real-Time Physiological Phenotyping of Plant&ndash;Environment Interactions

Food security for the growing global population is a major concern. The data provided by genomic tools far exceeds the supply of phenotypic data, creating a knowledge gap. To meet the challenge of improving crops to feed the growing global population, this gap must be bridged.
Physiological traits are considered key functional traits in the context of responsiveness or sensitivity to environmental conditions. Many recently introduced high-throughput (HTP) phenotyping techniques are based on remote sensing or imaging and are capable of directly measuring morphological traits, but measure physiological parameters mainly indirectly.
This paper describes a method for direct physiological phenotyping that has several advantages for the functional phenotyping of plant&#8211;environment interactions. It helps users overcome the many challenges encountered in the use of load-cell gravimetric systems and pot experiments. The suggested techniques will enable users to distinguish between soil weight, plant weight and soil water content, providing a method for the continuous and simultaneous measurement of dynamic soil, plant and atmosphere conditions, alongside the measurement of key physiological traits. This method allows researchers to closely mimic field stress scenarios while taking into consideration the environment&#8217;s effects on the plants&#8217; physiology. This method also minimizes pot effects, which are one of the major problems in pre-field phenotyping. It includes a feed-back fertigation system that enables a truly randomized experimental design at a field-like plant density. This system detects the soil-water-content limiting threshold (&#952;) and allows for the translation of data into knowledge through the use of a real-time analytic tool and an online statistical resource. This method for the rapid and direct measurement of the physiological responses of multiple plants to a dynamic environment has great potential for use in screening for beneficial traits associated with responses to abiotic stress, in the context of pre-field breeding and crop improvement.

A Telemetric, Gravimetric Platform for Real-Time Physiological Phenotyping of Plant&#8211;Environment Interactions

This high-throughput, telemetric, whole-plant water relations gravimetric phenotyping method enables direct and simultaneous real-time measurements, as well as the analysis of multiple yield-related physiological traits involved in dynamic plant&#8211;environment interactions.

Food security for the growing global population is a major concern. The data provided by genomic tools far exceeds the supply of phenotypic data, creating ...

In Situ Soil Moisture Sensors in Undisturbed Soils

Soil moisture directly affects operational hydrology, food security, ecosystem services, and the climate system. However, the adoption of soil moisture data has been slow due to inconsistent data collection, poor standardization, and typically short record duration. Soil moisture, or quantitatively volumetric soil water content (SWC), is measured using buried, in situ sensors that infer SWC from an electromagnetic response. This signal can vary considerably with local site conditions such as clay content and mineralogy, soil salinity or bulk electrical conductivity, and soil temperature; each of these can have varying impacts depending on the sensor technology.
Furthermore, poor soil contact and sensor degradation can affect the quality of these readings over time. Unlike more traditional environmental sensors, there are no accepted standards, maintenance practices, or quality controls for SWC data. As such, SWC is a challenging measurement for many environmental monitoring networks to implement. Here, we attempt to establish a community-based standard of practice for in situ SWC sensors so that future research and applications have consistent guidance on site selection, sensor installation, data interpretation, and long-term maintenance of monitoring stations.
The videography focuses on a multi-agency consensus of best-practices and recommendations for the installation of in situ SWC sensors. This paper presents an overview of this protocol along with the various steps essential for high-quality and long-term SWC data collection. This protocol will be of use to scientists and engineers hoping to deploy a single station or an entire network.

In Situ Soil Moisture Sensors in Undisturbed Soils

The determination of soil water content is a critical mission requirement for many state and federal agencies. This protocol synthesizes multi-agency efforts to measure soil water content using buried in situ sensors.

Soil moisture directly affects operational hydrology, food security, ecosystem services, and the climate system. However, the adoption of soil moisture ...

Measurement of Leaf Hydraulic Conductance and Stomatal Conductance and Their Responses to Irradiance and Dehydration Using the Evaporative Flux Method (EFM)

Water is a key resource, and the plant water transport system sets limits on maximum growth and drought tolerance. When plants open their stomata to achieve a high stomatal conductance (gs) to capture CO2 for photosynthesis, water is lost by transpiration1,2. Water evaporating from the airspaces is replaced from cell walls, in turn drawing water from the xylem of leaf veins, in turn drawing from xylem in the stems and roots. As water is pulled through the system, it experiences hydraulic resistance, creating tension throughout the system and a low leaf water potential (&Psi;leaf). The leaf itself is a critical bottleneck in the whole plant system, accounting for on average 30% of the plant hydraulic resistance3. Leaf hydraulic conductance (Kleaf = 1/ leaf hydraulic resistance) is the ratio of the water flow rate to the water potential gradient across the leaf, and summarizes the behavior of a complex system: water moves through the petiole and through several orders of veins, exits into the bundle sheath and passes through or around mesophyll cells before evaporating into the airspace and being transpired from the stomata. Kleaf is of strong interest as an important physiological trait to compare species, quantifying the effectiveness of the leaf structure and physiology for water transport, and a key variable to investigate for its relationship to variation in structure (e.g., in leaf venation architecture) and its impacts on photosynthetic gas exchange. Further, Kleaf responds strongly to the internal and external leaf environment3. Kleaf can increase dramatically with irradiance apparently due to changes in the expression and activation of aquaporins, the proteins involved in water transport through membranes4, and Kleaf declines strongly during drought, due to cavitation and/or collapse of xylem conduits, and/or loss of permeability in the extra-xylem tissues due to mesophyll and bundle sheath cell shrinkage or aquaporin deactivation5-10. Because Kleaf can constrain gs and photosynthetic rate across species in well watered conditions and during drought, and thus limit whole-plant performance they may possibly determine species distributions especially as droughts increase in frequency and severity11-14.
We present a simple method for simultaneous determination of Kleaf and gs on excised leaves. A transpiring leaf is connected by its petiole to tubing running to a water source on a balance. The loss of water from the balance is recorded to calculate the flow rate through the leaf. When steady state transpiration (E, mmol &bull; m-2 &bull; s-1) is reached, gs is determined by dividing by vapor pressure deficit, and Kleaf by dividing by the water potential driving force determined using a pressure chamber (Kleaf= E /- &Delta;&psi;leaf, MPa)15.
This method can be used to assess Kleaf responses to different irradiances and the vulnerability of Kleaf to dehydration14,16,17.

Measurement of Leaf Hydraulic Conductance and Stomatal Conductance and Their Responses to Irradiance and Dehydration Using the Evaporative Flux Method EFM

We describe a relatively rapid (30 min) and realistic method for simultaneously measurement of leaf hydraulic conductance (Kleaf) and stomatal conductance (gs) for transpiring excised leaves. The method can be modified to measure the light and dehydration responses of Kleaf and gs.

Water is a key resource, and the plant water transport system sets limits on maximum growth and drought tolerance. When plants open their stomata to ...

Biology

Soil Core Sample Collection for Water Retention Property Analysis

This video demonstrates the technique for collecting a soil sample for hydraulic property analysis. The sampling area is cleared, and the top crust is evacuated. The sampling ring is then placed into the soil to collect the sample. The ring with the sample is then cleaned, labeled, packed, and transferred undisturbed for analysis.

This video demonstrates the technique for collecting a soil sample for hydraulic property analysis. The sampling area is cleared, and the top crust is ...

Measurements of Soil Water Potential and Conductivity based on a Simple Evaporation Experiment using a Hydraulic Property Analyzer

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