The authors are grateful to the staff of USDA-ARS Pasture Systems and Watershed Management Unit. David Otto was important to both the design and construction of the custom made drop hammer (aka 'The Intimidator'). Michael Reiner and Terry Troutman assisted in the collection and construction of the lysimeters reported in this study. Sarah Fishel, Charles Montgomery and Paul Spock performed all of the nutrient analyses reported in this manuscript.

1. Preparing the Materials
<ol>
	<li>Cut the main body of the lysimeter from 30.5 cm (12 inch) diameter (ID; nominal) schedule 80 PVC; this has a wall thickness of 1.9 cm (0.75 inch) (Figure 1a). Cut the length of the lysimeter body depending on the thickness of the soil layer(s) to be studied; here, use a 53 cm (21 inch) long body. Rout a 0.63 cm deep by 45&#176; bevel around the bottom end of the lysimeter to form a sharp leading edge on the inside wall of the lysimeter body to aid in cutting through the soil.</li>
	<li>Modify a 34.5 cm ID, flat bottom PVC cap by gluing a 15.3 cm tall 30.5 cm ID ring of schedule 80 PVC into the cap to allow for free drainage of water and provide storage capacity for leachate prior to collection (Figure 1b). Cut the ring from the same stock as the main body to serve as a coupling to join the cap to the body. The cap will be joined to the body with a flexible coupling and hose clamps (Figure 1c and 1d). Install a port for sample collection by drilling a 1.27 cm hole and tapping it with a 1.27 cm 14 NPT pipe tap and turn a 1.27 cm nylon barbed male adapter (Figure 1e) into the outer edge of the cap where the sidewall and bottom meet.</li>
	<li>Cut a 34 cm diameter disk from 1.27 cm thick flat stock PVC that will be used to cover the bottom of the lysimeters (Figure 1g). Drill 180, evenly spaced, 0.32 cm. diameter holes into the disk to allow drainage from the bottom of the soil-filled lysimeter to enter the cap. Glue ground cloth or other filter fabric to one side of the disk to prevent soil from passing through the bottom disk during leachate drainage.</li>
	<li>Build lifting scissors from 2.5 cm flat iron and 2.5 cm water pipe (Figure 2). Cut two of the 2.5 cm bands of flat iron to 50.0 cm lengths and bend into a semi-circle using the outside of the lysimeter body as a guide. Weld a 5 cm band to each end of each semi-circle band. Join each of the bands with a hinge pin. Weld the water pipe on the outer ring of the bands opposite of each other.</li>
</ol>
2. Driving Lysimeter Casing into Soil with the Drop Hammer
<ol>
	<li>Remove surface vegetation, rocks and other debris from collection area. Position 2 lysimeter bodies on level ground where lysimeters are to be taken (Figure 3a). Ensure that lysimeters are level so that soil within the column is of a uniform depth.</li>
	<li>Drive a specially designed, trailer-mounted, drop hammer into place over the lysimeter bodies. When the drop hammer is in place, deploy hydraulically powered outriggers to level the steel plate with the ground and top of the lysimeter bodies. The outriggers also provide stability for the drop hammer (Figure 3b).</li>
	<li>Partially hoist the 10.2 cm thick, 1.52 m by 1.52 m square steel plate weighing 1,180 kg up a 3 m tower with the aid of a mechanical winch (Figure 3b). Release the steel plate to hammer the columns into the soil.</li>
	<li>Repeat step 2.3 several times until the column rim is 2 cm above the soil surface (Figure 3c).</li>
	<li>Check for soil compaction inside the lysimeter by measuring the depth of soil inside and outside of the column. If the soil inside the column is more than 1 cm lower than soil outside the column, soils are compacted and are not suitable for research.</li>
</ol>
3. Removing the Soil Core
<ol>
	<li>Place a perforated PVC disk (Figure 1c) and flexible pipe coupling (Figure 1d) over the column to prevent contamination by soil and other debris during the excavation process.</li>
	<li>Dig a trench beside the soil core and slightly deeper than the column bottom with a backhoe (Figure 4a).</li>
	<li>Widen the hole with a shovel or pick (Figure 4b) and expose as much of the outside of cylinder as possible.</li>
	<li>Push a heavy metal digging bar down along the entire length of the side of the column so that it is between the soil and outside column wall (Figure 4c).</li>
	<li>Pry the digging bar back and forth until the soil interface at the bottom of the column is broken.</li>
	<li>Frame the lifting scissors around the top of the lysimeter (shown in Figure 2) in preparation for soil core removal. With a person holding each bar, pull up until the scissors close tightly around the column and lift the lysimeter out of the hole. Place the lysimeter on a flat working surface such as piece of plywood.</li>
</ol>
4. Preparing the Soil Core for Lysimeter Assembly
<ol>
	<li>Flip the soil core over so that the bottom side is up. The wooden plywood disk installed in step 3.1 will hold the soil in place.</li>
	<li>Gently, level the soil even with the rim of the PVC (Figure 5a) with a straight edge. Remove stones protruding above the plane of the rim with a pen knife or screwdriver.</li>
	<li>Fill any voids with chemically inert play sand and gently pack it (Figure 5b).</li>
	<li>Grade the sand even with the column bottom with a straight edge and remove any excess sand (Figure 5c and d).</li>
	<li>Clean any soil from the rim and the outer side walls of the lysimeters with a brush or lightly blow it off the edge and ensure that the rim is clean for adhesives to stick and for a snug fitting of the cap.</li>
</ol>
5. Assembling the Lysimeter
<ol>
	<li>Extrude a continuous round bead of clear silicon caulk around the rim of the lysimeter (Figure 6a). The caulk should be thick enough to seal the perforated disk bottom to the lysimeters and prevent leaking.</li>
	<li>Lay the perforated disk (Figure 1c) onto the rim with the filter fabric facing the sand and press down firmly to allow good contact of the plate and lysimeter.</li>
	<li>Drill eight evenly spaced pilot holes around the edge of the plate and fasten the perforated disk with 1.0 inch stainless steel screws with a drill driver (Figure 6b).</li>
	<li>Slip the flexible pipe coupling on to the lysimeter base so that about 2 cm of the coupling is projecting above the lysimeter rim (Figure 5c).</li>
	<li>Fit the modified PVC cap into the flexible pipe coupling (Figure 6c), and push the cap down until it makes contact with the lysimeter body. With a block of wood on top of the cap use a mallet to gently tap the cap in place.</li>
	<li>Place the fastening bands in the grooves of the coupling and secure lightly without constricting the coupling. Tighten the metal around the coupling with a hand held 1/4 inch hex driver until the lysimeter cap is firmly held in place. The lysimeter is ready to be flipped and transported to a climate controlled facility.</li>
</ol>
6. Installing Moisture Sensors
<ol>
	<li>Scribe a 5 cm long, horizontal line on the lysimeter wall at 5 and 25 cm depths. Measure from the soil surface and not the rim of the lysimeter.</li>
	<li>Drill a 1.0 cm diameter hole through the wall of the lysimeter at each end of the marked lines.</li>
	<li>Cut the remaining 3 cm of plastic between the drilled holes away with a rotary cutting tool.</li>
	<li>Chisel a 1 cm thick by 5 cm long slit into the soil to accommodate the casing of a moisture sensor (e.g., Decagon).</li>
	<li>Push the moisture sensor into the hole into the cleaned out slot until the sensor prongs are firmly buried in the soil and that only the wire is sticking out of the lysimeter.</li>
	<li>Clean soil from the walls of the slot with a brush or rag.</li>
	<li>Apply a thick bead of silicone caulk into the slot to prevent water from leaking out. After the caulk has dried, apply a second cycle of silicone to ensure that all gaps in the hole surrounding the sensor are sealed.</li>
</ol>
7. Preparing Lysimeters for Leachate Collection
<ol>
	<li>Seal gaps between the soil and lysimeter wall with caulk to reduce the risk of preferential flow down the inside walls of the lysimeter.
	<ol>
		<li>Pierce and load a tube of clear silicone caulk into a standard caulk gun.</li>
		<li>Place tip of caulk tube between void in the soil to be filled and the inside face of the lysimeter body. Push the tip of the caulk gun below the soil about 2 cm. Squeeze the caulk out of the tube until it fills the void and oozes above the soil surface.</li>
	</ol>
	</li>
	<li>Set lysimeters on top of a bench or flat surface and sturdy enough to handle the weight of several lysimeters and high enough to allow free drainage of water into a 4.0 L jug (Figure 7).</li>
	<li>Check that soil core lysimeters are leveled in all directions with a small (15 cm) spirit level. If necessary place shims underneath lysimeters until the soil surface is completely leveled.</li>
	<li>Wrap Teflon tape around the threaded nylon tube fitting (0.5 in NPT) and turn the fitting clockwise into the cap. Tighten the fitting with an adjustable wrench until none of the threads are visible.</li>
	<li>Push a 0.5 inch hose onto the barbed end of the nylon fitting and cut the hose so that it passes approximately 4.0 cm into the mouth of the collection jug.</li>
	<li>Set the container under the lysimeter and place the hose inside the collection jug.</li>
</ol>
8. Irrigating Lysimeters and Collecting Leachate
<ol>
	<li>Cover the soil surface with cheese cloth or other permeable, chemically inert fabric to protect and preserve soil aggregates and surface residue.</li>
	<li>Measure 1,450 ml of deionized water into a graduated cylinder and pour it into watering can, equipped with shower head. Gently and evenly sprinkle the water over the fabric at a rate that does not disturb the soil surface.</li>
	<li>Wait a period of time for water to infiltrate an percolate through the soil column into the cap and collection container.</li>
	<li>Tip lysimeter in the toward the outlet hole until all water is drained from the lysimeter reservoir cap into the collection vessel.</li>
	<li>Measure the mass of leachate collected with a scale and convert mass in grams to ml (assume that 1.0 g of water is equivalent to 1.0 ml). Pour the leachate sample into 350 ml sterile plastic sample bottle. Immediately filter 50 ml with a suction funnel equipped with 0.45 &#181;m filter paper in preparation for nitrate analysis using colorimetry via flow injection analysis31.</li>
	<li>Store filtered and unfiltered portions of the samples in a refrigerator and 4 &#176;C until analysis.</li>
</ol>

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The authors declare no competing financial interests.

Important steps of lysimeter Collection
Leaching studies illustrate the influence of soil properties and manure management on nitrogen losses to shallow groundwater. Soil physical properties such as soil texture, aggregate structure and bulk density mediate the percolation of water and solutes. Accurately determining leachate volume and solute concentrations is dependent upon retaining the integrity of these soil physical properties during lysimeter collection by following these critical steps...

The Delmarva Peninsula borders the eastern shore of the Chesapeake Bay, and is the home to one of largest poultry production regions in the US. Roughly 600 million chickens and an estimated 750,000 tons of manure are generated from the production of these birds each year1. Most of the manure is used locally as a fertilizer amendment on agricultural fields. Because of historically high rates of manure application, nutrients such as nitrogen and phosphorus have accumulated in the soil and are now susceptible to off-site losses via subsurface leaching2. Much of the groundwater flow is directed toward an extensive network of ditches that ultimately drain to the Chesapeake Bay3. The nutrients carried to the Bay are linked to the decline in the Bay&#39;s health due to eutrophication4.
Connecting nutrient management with off-site losses of nutrients requires specialized tools to monitor hydrologic flows and associated nutrient transfers. Lysimeters represent a major category of instruments used to characterize and quantify the movement of nutrients through soils. Lysimeters have a long history of use in monitoring nutrient flow in percolating water5-7, from tension lysimeters that can be adjusted to counter soil matrix potential so that they better estimate plant available water, to zero-tension lysimeters that are more representative of processes occurring during free drainage. All approaches to lysimetery present inherent biases. For instance, some lysimeters are too small to fully represent spatially complex processes in natural soils, or are too large and expensive to provide good statistical replication of heterogeneous soils8. Further, pan lysimeters require soils above them to be saturated to collect leachate and are inefficient compared to tension lysimeters at measuring matrix flow9.
Closed lysimeter systems, such as zero-tension soil core lysimeters (also known as soil monolith lysimeters), greatly improve the confidence with which water budgets and associated pollutant budgets (e.g., nutrient budgets) are carried out10. These lysimeters are most representative when they contain intact cores of soil; lysimeters filled with repacked soils do not maintain the original structure, horizons and macropore connections that influence the transport of solutes and particulate compounds alike11,12. From an experimental stand point, approaches that facilitate greater replication of undisturbed soil conditions are advantageous, given the inherent spatial variability that exists in soil physical and chemical properties13.
Two preferred methods have been used for collecting intact soil core lysimeters: drop hammer and cutting head. The former has been more commonly performed, as it can be achieved with devices as simple as a sledge hammer (smaller lysimeters). When performed properly, soil core collection with a drop hammer has been shown to be relatively cost effective, especially when compared with other coring techniques. However, the sheer forces imposed by driving a lysimeter casing into the ground can cause smearing and compaction, producing conditions inside the lysimeter that are not representative of native soil and may even favor certain types of water movement (e.g., bypass flow, or flow along the soil core edge). As a result, some researchers have preferred the use of corers that cut away an intact soil with a drilling apparatus or other excavation device5.
Various materials have been used as casings for soil core lysimeters. Steel pipes and boxes are comparatively low cost, durable and readily available and can be used to collect larger lysimeters due to their strength14-17. However, while steel is satisfactory for evaluating the leaching of relatively unreactive compounds such as nitrate, the iron in steel reacts with phosphate and must therefore be coated or otherwise treated for the study of phosphorus leaching. Commonly, plastic casings are used to study phosphorus leaching, such as thick walled (Schedule 80) PVC pipe that can withstand the impact of a drop hammer (if used) and retain its structure when larger diameter soil cores are obtained (e.g., &#8805;30 cm)18-22.
In general, soil core lysimeters are analyzed ex situ. Once collected, soil core lysimeters may be installed in outdoor &#34;lysimeter farms&#34; where surrounding soil and above ground climates represent natural field conditions. For instance, in Sweden, the Swedish Agricultural University has maintained three separate lysimeter farms over the past three decades, analyzing pesticide fate-and-transport, long-term soil fertility trials, and management practices that can be scaled to 30 cm diameter intact cores23. Soil core lysimeters have also been subjected to indoor leaching experiments where there is greater control of climatic conditions24,25. Liu et al. used a rainfall simulator to regularly irrigate soil core lysimeters under an array of catch crops26. Kibet and Kun all employed hand irrigation techniques to study arsenic and nutrient leaching through soil cores27,28.
A variety of edaphic and hydrologic processes can be inferred from soil core lysimeters. Kun et al. (2015) used 30 cm diameter PVC column lysimeters to investigate nitrogen leaching after urea application28. By collecting leachate at different time intervals following an irrigation event, they were able to differentiate between rapid and gradual flows, with the former assumed to be dominated by macropore flow, and the later assumed to be dominated by matrix flow. Since urea is readily hydrolyzed when in contact with soil, they interpreted the presence of elevated urea concentrations in leachate collected shortly after urea application as evidence of macropore transport that bypassed the soil matrix. Over time, they detected elevated concentrations of different forms of nitrogen in leachate, tracking the transformation of applied urea to ammonium after initial hydrolysis, then the transformation of ammonium to nitrate with nitrification.
To illustrate considerations in designing, conducting and interpreting soil core lysimeter experiments, we carried out an investigation of four different soils found in the mid-Atlantic coastal plain of USA. The study measured leaching concentration and loss of nitrate before and after application of dry poultry manure (i.e., poultry &#34;litter&#34;)28. Nutrient losses from the application of poultry litter to soils are a key concern to the health of the Chesapeake Bay, and understanding the interaction of applied poultry litter and agricultural soil properties is needed to improve nutrient management recommendations. We present here a detailed method for extracting intact soil core lysimeters, tracking soil moisture, and interpreting differential nitrate leaching losses from these soils.
This experiment is part of a larger study conducted to assess nutrient leaching from agricultural soils of the Delmarva Peninsula, USA27,28. Soil core lysimeters were collected from sites in Delaware, Maryland and Virginia in 2010. Here we present unpublished results from these studies. Although initial experiments were conducted to assess phosphorus leaching, nitrate leaching from theses soils was also monitored.

Four common agricultural soils from the Atlantic coastal plain of the Chesapeake Bay Watershed were sampled: Bojac (coarse-loamy, mixed, semiactive, thermic Typic Hapludult); Evesboro (mesic, coated Lamellic Quartzipsamment); Quindocqua (fine-loamy, mixed, active, mesic Typic Endoaquult); Sassafras (fine-loamy, siliceous, semiactive, mesic Typic Hapludult). For each soil, horizon morphology was described from the profiles exposed by the excavation of the columns (Table 1). Surface textures of the soils ranged from sand (Evesboro) to loamy fine sand/sandy loam (Bojac and Sassafras) to silt loam (Quindocqua). Although all soils had been historically fertilized with poultry litter, none had been applied in the 10 months prior to the study. All soils had been in no-till corn production for at least one season prior to soil core lysimeter collection.

Following collection, soil core lysimeters were transported to the USDA-ARS simulatorium facility in State College, PA. There they were subject to indoor irrigation experiments (22-26 &#176;C) to assess nutrient leaching related to poultry litter application. Specifically, lysimeters were irrigated with 2 cm of water weekly for 8 weeks until nitrate in percolate was equilibrated between the soils. Poultry litter (dry poultry manure) was then applied to the surface of all soils at the rate of 162 kg ha-1 of total N. Irrigation was continued for 5 more weeks. Moisture sensors recorded volumetric moisture content at 5 minute intervals continuously, throughout the irrigation and leaching cycle. Leachate was collected after 24 hr and again 7 days later immediately prior to irrigation.
Leachate data from the soil core lysimeters were analyzed using simple descriptive statistics to illustrate differences in leachate quantity and quality between soils, as well as differences before and after litter application. Because soil moisture sensors were placed in only two of the replicate soil core lysimeters for each soil (Evesboro, Bojac, Sassafras, Quindocqua), statistics for soil moisture content were based on N = 2, whereas statistics for leachate depth, nitrate-N concentration and nitrate-N flux were derived from 10 soil core lysimeters for Evesboro, Bojac and Sassafras and 5 soil core lysimeters for Quindocqua. To assess the importance of replication within soils, coefficients of variation (CV) for leachate depth were calculated for different replicate numbers. A Monte Carlo simulation approach was used to repeatedly sample a subset of soil core lysimeters (N = 3) from the total number of replicates within each soil group (10 for Evesboro, Bojac, Sassafras; 5 for the Quindocqua).

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a protocol for collecting and constructing soil core lysimeters

Leaching of nutrients from land applied fertilizers and manure used in agriculture can lead to accelerated eutrophication of surface water. Because the landscape has complex and varied soil morphology, an accompanying disparity in flow paths for leachate through the soil macropore and matrix structure is present. The rate of flow through these paths is further affected by antecedent soil moisture. Lysimeters are used to quantify flow rate, volume of water and concentration of nutrients leaching downward through soils. While many lysimeter designs exist, accurately determining the volume of water and mass balance of nutrients is best accomplished with bounded lysimeters that leave the natural soil structure intact. 
Here we present a detailed method for the extraction and construction of soil core lysimeters equipped with soil moisture sensors at 5 cm and 25 cm depths. Lysimeters from four different Coastal Plain soils (Bojac, Evesboro, Quindocqua and Sassafras) were collected on the Delmarva Peninsula and moved to an indoor climate controlled facility. Soils were irrigated once weekly with the equivalent of 2 cm of rainfall to draw down soil nitrate-N concentrations. At the end of the draw down period, poultry litter was applied (162 kg TN ha-1) and leaching was resumed for an additional five weeks. Total recovery of applied irrigation water varied from 71% to 85%. Nitrate-N concentration varied over the course of the study from an average of 27.1 mg L-1 before litter application to 40.3 mg L-1 following litter application. While greatest flux of nutrients was measured in soils dominated by coarse sand (Sassafras) the greatest immediate flux occurred from the finest textured soil with pronounced macropore development (Quindocqua).

Soil moisture, leachate depth and leachate chemistry all illustrate variability across soils, revealing differences as a function of soil properties despite internal variability between replicate soil core lysimeters of a particular soil. The later point warrants particular note from the standpoint of experimental design, as inherent variability in soil moisture and leaching processes requires considerable replication to minimize type 2 statistical error. In the current study, coefficient...

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A Protocol for Collecting and Constructing Soil Core Lysimeters

A detailed method for extraction and assembly of intact soil core lysimeters and their use for study of leachate and associated loss of nutrients from surface applied poultry litter is demonstrated.

Leaching of nutrients from land applied fertilizers and manure used in agriculture can lead to accelerated eutrophication of surface water. Because the ...

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JoVE Journal

Environment

11.6K Views.  USDA - Agricultural Research Service. A detailed method for extraction and assembly of intact soil core lysimeters and their use for study of leachate and associated loss of nutrients from surface applied poultry litter is demonstrated.

Video: A Protocol for Collecting and Constructing Soil Core Lysimeters

Laboratory-determined Phosphorus Flux from Lake Sediments as a Measure of Internal Phosphorus Loading

Eutrophication is a water quality issue in lakes worldwide, and there is a critical need to identify and control nutrient sources. Internal phosphorus (P) loading from lake sediments can account for a substantial portion of the total P load in eutrophic, and some mesotrophic, lakes. Laboratory determination of P release rates from sediment cores is one approach for determining the role of internal P loading and guiding management decisions. Two principal alternatives to experimental determination of sediment P release exist for estimating internal load: in situ measurements of changes in hypolimnetic P over time and P mass balance. The experimental approach using laboratory-based sediment incubations to quantify internal P load is a direct method, making it a valuable tool for lake management and restoration.
Laboratory incubations of sediment cores can help determine the relative importance of internal vs. external P loads, as well as be used to answer a variety of lake management and research questions. We illustrate the use of sediment core incubations to assess the effectiveness of an aluminum sulfate (alum) treatment for reducing sediment P release. Other research questions that can be investigated using this approach include the effects of sediment resuspension and bioturbation on P release.
The approach also has limitations. Assumptions must be made with respect to: extrapolating results from sediment cores to the entire lake; deciding over what time periods to measure nutrient release; and addressing possible core tube artifacts. A comprehensive dissolved oxygen monitoring strategy to assess temporal and spatial redox status in the lake provides greater confidence in annual P loads estimated from sediment core incubations.

Lake eutrophication is a water quality issue worldwide, making the need to identify and control nutrient sources critical. Laboratory determination of phosphorus release rates from sediment cores is a valuable approach for determining the role of internal phosphorus loading and guiding management decisions.

Eutrophication is a water quality issue in lakes worldwide, and there is a critical need to identify and control nutrient sources. Internal phosphorus (P) ...

Integrated Field Lysimetry and Porewater Sampling for Evaluation of Chemical Mobility in Soils and Established Vegetation

Potentially toxic chemicals are routinely applied to land to meet growing demands on waste management and food production, but the fate of these chemicals is often not well understood. Here we demonstrate an integrated field lysimetry and porewater sampling method for evaluating the mobility of chemicals applied to soils and established vegetation. Lysimeters, open columns made of metal or plastic, are driven into bareground or vegetated soils. Porewater samplers, which are commercially available and use vacuum to collect percolating soil water, are installed at predetermined depths within the lysimeters. At prearranged times following chemical application to experimental plots, porewater is collected, and lysimeters, containing soil and vegetation, are exhumed. By analyzing chemical concentrations in the lysimeter soil, vegetation, and porewater, downward leaching rates, soil retention capacities, and plant uptake for the chemical of interest may be quantified. Because field lysimetry and porewater sampling are conducted under natural environmental conditions and with minimal soil disturbance, derived results project real-case scenarios and provide valuable information for chemical management. As chemicals are increasingly applied to land worldwide, the described techniques may be utilized to determine whether applied chemicals pose adverse effects to human health or the environment.

Field lysimetry and porewater sampling allow researchers to evaluate the fate of chemicals applied to soils and established vegetation. The goal of this protocol is to demonstrate how to install required instrumentation and collect samples for chemical analysis during integrated field lysimetry and porewater sampling experiments.

Potentially toxic chemicals are routinely applied to land to meet growing demands on waste management and food production, but the fate of these chemicals ...

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 ...

Measuring and Mapping Patterns of Soil Erosion and Deposition Related to Soil Carbonate Concentrations Under Agricultural Management

Spatial patterns of soil erosion and deposition can be inferred from differences in ground elevation mapped at appropriate time increments. Such changes in elevation are related to changes in near-surface soil carbonate (CaCO3) profiles. The objective is to describe a simple conceptual model and detailed protocol for repeatable field and laboratory measurements of these quantities. Here, accurate elevation is measured using a ground-based differential global positioning system (GPS); other data acquisition methods could be applied to the same basic method. Soil samples are collected from prescribed depth intervals and analyzed in the lab using an efficient and precise modified pressure-calcimeter method for quantitative analysis of inorganic carbon concentration. Standard statistical methods are applied to point data, and representative results show significant correlations between changes in soil surface layer CaCO3 and changes in elevation consistent with the conceptual model; CaCO3 generally decreased in depositional areas and increased in erosional areas. Maps are derived from point measurements of elevation and soil CaCO3 to aid analyses. A map of erosional and depositional patterns at the study site, a rain-fed winter wheat field cropped in alternating wheat-fallow strips, shows the interacting effects of water and wind erosion affected by management and topography. Alternative sampling methods and depth intervals are discussed and recommended for future work relating soil erosion and deposition to soil CaCO3.

Spatial patterns of soil erosion and deposition can be inferred from differences in ground elevation mapped at appropriate time increments. Such changes in elevation are related to changes in near-surface soil carbonates. Repeatable methods for field and laboratory measurements of these quantities and data analysis methods are described here.

Spatial patterns of soil erosion and deposition can be inferred from differences in ground elevation mapped at appropriate time increments. Such changes ...

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. ...

Sampling Soils in a Heterogeneous Research Plot

Soils are highly heterogeneous. In general, the number of soil samples required for soil research has always been determined arbitrarily and the associated accuracy is unknown. Here, we present a detailed protocol for efficient and clustered soil sampling in a research plot and, relying on a pilot sampling using this design, for demonstrating soil spatial heterogeneity and informing reasonable sample sizes and associated accuracy for future study. The protocol mainly comprises four steps: sampling design, field collection, soil analysis, and geostatistical analysis. The step-by-step procedure is modified according to former publications. Two examples will be presented to demonstrate contrasting spatial distributions of soil organic carbon (SOC) and soil microbial biomass carbon (MBC) under different management practices. In addition, we present a strategy to determine the sample size requirement (SSR) given a certain level of accuracy based on the plot-level coefficient of variation (CV). The field sampling protocol and the quantitative determination of the sample size will assist researchers in seeking feasible sampling strategies to meet research needs and resources' availability.

The traditional soil-sampling procedure determines the number of soil samples arbitrarily. Here, we provide a simple yet efficient clustered soil-sampling design to demonstrate soil spatial heterogeneity and quantitatively determine the number of soil samples required and the associated sampling accuracy.

Soils are highly heterogeneous. In general, the number of soil samples required for soil research has always been determined arbitrarily and the ...

Monitoring Pedogenic Inorganic Carbon Accumulation Due to Weathering of Amended Silicate Minerals in Agricultural Soils.

The present study aims to demonstrate a systematic procedure for monitoring inorganic carbon induced by enhanced weathering of comminuted rocks in agricultural soils. To this end, the core soil samples taken at different depth (including 0-15 cm, 15-30 cm, and 30-60 cm profiles) are collected from an agriculture field, the topsoil of which has already been enriched with an alkaline earth metal silicate containing mineral (such as wollastonite). After transporting to the laboratory, the soil samples are air-dried and sieved. Then, the inorganic carbon content of the samples is determined by a volumetric method called calcimetry. The representative results presented herein showed five folded increments of inorganic carbon content in the soils amended with the Ca-silicate compared to control soils. This compositional change was accompanied by more than 1 unit of pH increase in the amended soils, implying high dissolution of the silicate. Mineralogical and morphological analyses, as well as elemental composition, further corroborate the increase in the inorganic carbon content of silicate-amended soils. The sampling and analysis methods presented in this study can be adopted by researchers and professionals looking to trace pedogenic inorganic carbon changes in soils and subsoils, including those amended with other suitable silicate rocks such as basalt and olivine. These methods can also be exploited as tools for verifying soil inorganic carbon sequestration by private and governmental entities to certify and award carbon credits.

The verification method described here is adaptable for monitoring pedogenic inorganic carbon sequestration in various agricultural soils amended with alkaline earth metal silicate-containing rocks, such as wollastonite, basalt, and olivine. This type of validation is essential for carbon credit programs, which can benefit farmers that sequester carbon in their fields.

The present study aims to demonstrate a systematic procedure for monitoring inorganic carbon induced by enhanced weathering of comminuted rocks in ...

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 ...

JenaTron - An Experimental Approach to Study the Effects of Plant History and Soil History on Grassland Ecosystem Functioning

The global loss of biodiversity has motivated many studies that experimentally vary plant species richness and examine the consequences for ecosystem functioning. Such experiments generally show a positive relationship between above- and below-ground biodiversity and the functioning of terrestrial ecosystems. Moreover, this relationship tends to strengthen over time, seen as enhanced functioning of diverse plant communities and reduced functioning of low-diversity plant communities. Differences in multitrophic community assembly and biotic interactions in high- versus low-diversity plant communities are hypothesized to affect plant performance by altering consumer community structure and function and driving plastic or micro-evolutionary responses of plant species in the plant communities. To resolve this complex interplay of community history, we separated these effects into plant and soil history. Plant history refers to all plant-level responses to past abiotic and biotic selection pressures experienced in their communities, while soil history relates to all abiotic and biotic soil properties developed as a legacy of plant-soil interactions under variable plant diversity. We set up a biodiversity experiment in an Ecotron, a terrestrial mesocosm facility that allows controlling environmental conditions above- and below-ground, to test whether the strengthening biodiversity-ecosystem functioning relationship is due to soil history, plant history, or a combination of both. We established a plant diversity gradient consisting of 1, 2, 3, and 6 grassland plant species and factorially nested with soil history and plant history treatments for each level of plant species richness. Representative results demonstrate the successful establishment of target treatments in the Ecotron experiment, observing the effects of plant and soil history on initial plant development and final plant growth. Additionally, we provide a case study for data analysis of individual response variables. We outline research objectives and methods to comprehensively assess the multifunctional responses to the experimental treatments necessary to ultimately address the overarching hypothesis.

Here we present a study established in the iDiv Ecotron, terrestrial mesocosm chambers with controlled environmental conditions above- and below-ground, to study the independent and interactive effects of plant history and soil history on ecosystem functioning of grassland communities along a plant diversity gradient.

The global loss of biodiversity has motivated many studies that experimentally vary plant species richness and examine the consequences for ecosystem ...

Enhancing CO2 Sequestration: A Soil Biota Approach to Boost Mineral Weathering

Design and Construction of an Experimental Setup to Enhance Mineral Weathering through the Activity of Soil Organisms

Enhanced weathering (EW) is an emerging carbon dioxide (CO2) removal technology that can contribute to climate change mitigation. This technology relies on accelerating the natural process of mineral weathering in soils by manipulating the abiotic variables that govern this process, in particular mineral grain size and exposure to acids dissolved in water. EW mainly aims at reducing atmospheric CO2 concentrations by enhancing inorganic carbon sequestration. Until now, knowledge of EW has been mainly gained through experiments that focused on the abiotic variables known for stimulating mineral weathering, thereby neglecting the potential influence of biotic components. While bacteria, fungi, and earthworms are known to increase mineral weathering rates, the use of soil organisms in the context of EW remains underexplored. 
 This protocol describes the design and construction of an experimental setup developed to enhance mineral weathering rates through soil organisms while concurrently controlling abiotic conditions. The setup is designed to maximize weathering rates while maintaining soil organisms' activity. It consists of a large number of columns filled with rock powder and organic material, located in a climate chamber and with water applied via a downflow irrigation system. Columns are placed above a fridge containing jerrycans to collect the leachate. Representative results demonstrate that this setup is suitable to ensure the activity of soil organisms and quantify their effect on inorganic carbon sequestration. Challenges remain in minimizing leachate losses, ensuring homogeneous ventilation through the climate chamber, and avoiding flooding of the columns. With this setup, an innovative and promising approach is proposed to enhance mineral weathering rates through the activity of soil biota and disentangle the effect of biotic and abiotic factors as drivers of EW.

Author Spotlight: Unraveling the Role of Earthworms in Enhancing Mineral Weathering for CO2 Removal 

Here we present the construction and operation of an experimental setup to enhance mineral weathering through the activity of soil organisms while concurrently manipulating abiotic variables known to stimulate weathering. Representative results from the functioning of the setup and sample analyses are discussed together with points for improvement.

Enhanced weathering (EW) is an emerging carbon dioxide (CO2) removal technology that can contribute to climate change mitigation. This technology relies ...

A Protocol for Collecting and Constructing Soil Core Lysimeters

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