Name: a protocol for collecting and constructing soil core lysimeters
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Description: Watch this Scientific Journal Video about A Protocol for Collecting and Constructing Soil Core Lysimeters at JoVE.com

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...

<ol>
	<li>Patterson, P. H., Lorenz, E. S., Weaver, W. D., Schwart, J. H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Litter+production+and+nutrients+from+commercial+broiler+chickens.">Litter production and nutrients from commercial broiler chickens.</a> J. Applied Poultry Res. 7 (3), 247-252 (1998).</li><li>Cullum, R. F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Macropore+flow+estimations+under+no-till+and+till+systems.">Macropore flow estimations under no-till and till systems.</a> Catena. 78, 87-91 (2009).</li><li>Kladivko, E. J., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Nitrate+leaching+to+subsurface+drains+as+affected+by+drain+spacing+and+changes+in+crop+production+systems.">Nitrate leaching to subsurface drains as affected by drain spacing and changes in crop production systems.</a> J. Environ. Qual. 33, 1803-1813 (2004).</li><li>Persson, L., Bergstrom, L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Drilling+method+for+collection+of+undisturbed+soil+monoliths).">Drilling method for collection of undisturbed soil monoliths).</a> Soil Sci. Soc. Am. J. 55 (1), 285-287 (1991).</li><li>Belford, R. K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Collection+and+evaluation+of+large+soil+monoliths+for+soil+and+crop+studies.">Collection and evaluation of large soil monoliths for soil and crop studies.</a> J. Soil Sci. 30 (2), 363-373 (1979).</li><li>Dell, C. J., Kleinman, P. J. A., Schmidt, J. P., Beegle, D. P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Low+disturbance+manure+incorporation+effects+on+ammonia+and+nitrate+loss.">Low disturbance manure incorporation effects on ammonia and nitrate loss.</a> J. Environ. Qual. 41, 928-937 (2012).</li><li>Owens, L. B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Nitrate-nitrogen+concentrations+in+percolate+from+lysimeters+planted+to+a+legume-grass+mixture.">Nitrate-nitrogen concentrations in percolate from lysimeters planted to a legume-grass mixture.</a> J. Environ. Qual. 19, 131-135 (1990).</li><li>Zhu, Y., Fox, R. H., Toth, J. D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Leachate+collection+efficiency+of+zero-tension+pan+and+passive+capillary+fiberglass+wick+lysimeters.">Leachate collection efficiency of zero-tension pan and passive capillary fiberglass wick lysimeters.</a> Soil Sci. Soc. Am. J. , (2002).</li><li>Jemison, J. M., Fox, R. H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Estimation+of+zero-tension+pan+lysimeter+collection+efficiency.">Estimation of zero-tension pan lysimeter collection efficiency.</a> Soil Sci. 154, 85-94 (1992).</li><li>Corwin, D. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Evaluation+of+a+simple+lysimeter-design+modification+to+minimize+sidewall+flow.">Evaluation of a simple lysimeter-design modification to minimize sidewall flow.</a> J. Contaminant Hydrology. 42 (1), 35-49 (2000).</li><li>Havis, R. N., Alberts, E. E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Nutrient+leaching+from+field+decomposed+corn+and+soybean+residue+under+simulated+rainfall.">Nutrient leaching from field decomposed corn and soybean residue under simulated rainfall.</a> Soil Sci. Soc. Am. J. 57, 211-218 (1993).</li><li>Bergstrom, L., Johanssson, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Leaching+of+nitrate+from+monolith+lysimeters+of+different+types+of+agricultural+soils.">Leaching of nitrate from monolith lysimeters of different types of agricultural soils.</a> J. Environ. Qual. 20, 801-807 (1991).</li><li>Lotter, D., Seidel, R., Liebhardt, W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+performance+of+organic+and+conventional+cropping+systems+in+an+extreme+climate+year.">The performance of organic and conventional cropping systems in an extreme climate year.</a> Am. J. Alternative Agriculture. 18 (3), 146-154 (2003).</li><li>Moyer, J., Saporito, L., Janke, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Design,+construction,+and+installation+of+an+intact+soil+core+lysimeter.">Design, construction, and installation of an intact soil core lysimeter.</a> Agronomy J. 88 (2), 253-256 (1996).</li><li>Stout, W. L., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Nitrate+leaching+from+cattle+urine+and+feces+in+northeast+US.">Nitrate leaching from cattle urine and feces in northeast US.</a> Soil Sci. Soc. Am. J. 61, 1787-1794 (1997).</li><li>Stout, W. L., Gburek, W. J., Schnabel, R. R., Folmar, G. J., Weaver, S. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Soil-climate+effects+on+nitrate+leaching+from+cattle+excreta.">Soil-climate effects on nitrate leaching from cattle excreta.</a> J. Environ. Qual. 27, 992-998 (1998).</li><li>Kleinman, P. J. A., Srinivasan, M. S., Sharpley, A. N., Gburek, W. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Phosphorus+leaching+through+intact+soil+columns+before+and+after+poultry+manure+applications.">Phosphorus leaching through intact soil columns before and after poultry manure applications.</a> Soil Sci. 170 (3), 153-166 (2005).</li><li>Kleinman, P. J. A., Sharpley, A. N., Saporito, L. S., Buda, A. R., Bryant, R. B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Application+of+manure+to+no-till+soils:+Phosphorus+losses+by+subsurface+and+surface+pathways.">Application of manure to no-till soils: Phosphorus losses by subsurface and surface pathways.</a> Nutr. Cycling Agroecosyst. 84, 215-227 (2009).</li><li>McDowell, R. W., Sharpley, A. N. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Approximating+phosphorus+release+to+surface+runoff+and+subsurface+drainage.">Approximating phosphorus release to surface runoff and subsurface drainage.</a> J. Environ. Qual. 30, 508-520 (2001).</li><li>McDowell, R. W., Sharpley, A. N. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Phosphorus+losses+in+subsurface+flow+before+and+after+manure+application.">Phosphorus losses in subsurface flow before and after manure application.</a> Sci. Total Environ. 278, 113-125 (2001).</li><li>Brock, E. H., Ketterings, Q. M., Kleinman, P. J. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Phosphorus+leaching+through+intact+soil+cores+as+influenced+by+type+and+duration+of+manure+application.">Phosphorus leaching through intact soil cores as influenced by type and duration of manure application.</a> Nutr. Cycl. Agroecosyst. 77, 269-281 (2007).</li><li>Svanback, A., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Influence+of+soil+phosphorus+and+manure+on+phosphorus+leaching+in+Swedish+topsoils.">Influence of soil phosphorus and manure on phosphorus leaching in Swedish topsoils.</a> Nutr. Cycling Agroecosyst. 96, 133-147 (2013).</li><li>Feyereisen, G. W., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Effect+of+direct+incorporation+of+poultry+litter+on+phosphorus+leaching+from+coastal+plain+soils.">Effect of direct incorporation of poultry litter on phosphorus leaching from coastal plain soils.</a> J. Soil Water Cons. 65 (4), 243-251 (2010).</li><li>Williams, M. R., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Manure+application+under+winter+conditions:+Nutrient+runoff+and+leachate+losses.">Manure application under winter conditions: Nutrient runoff and leachate losses.</a> Trans. ASABE. 54 (3), 891-899 (2011).</li><li>Liu, J., Aronsson, H., Ul&#233;n, B., Bergstr&#246;m, L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Potential+phosphorus+leaching+from+sandy+topsoils+with+different+fertilizer+histories+before+and+after+application+of+pig+slurry.">Potential phosphorus leaching from sandy topsoils with different fertilizer histories before and after application of pig slurry.</a> Soil Use Mgmt. 28, 457-467 (2012).</li><li>Kibet, L. C., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Transport+of+dissolved+trace+elements+in+surface+runoff+and+leachate+from+a+coastal+plain+soil+after+poultry+litter+application.">Transport of dissolved trace elements in surface runoff and leachate from a coastal plain soil after poultry litter application.</a> J. Soil Water Cons. 68 (3), 212-220 (2013).</li><li>Han, K., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Phosphorus+and+nitrogen+leaching+before+and+after+tillage+and+urea+application.">Phosphorus and nitrogen leaching before and after tillage and urea application.</a> J. Environ. Qual. 44, 560-571 (2014).</li><li>Day, P. R., Black, C. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=This+chapter+in+Methods+of+Soil+Analysis.+Part+1.+Physical+and+Mineralogical+Properties,+Including+Statistics+of+Measurement+and+Sampling.">This chapter in Methods of Soil Analysis. Part 1. Physical and Mineralogical Properties, Including Statistics of Measurement and Sampling.</a> American Society of Agronomy, Soil Science Society of America. , (1965).</li><li>Kleinman, P. J. A., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Phosphorus+leaching+from+agricultural+soils+of+the+Delmarva+Peninsula,+USA.">Phosphorus leaching from agricultural soils of the Delmarva Peninsula, USA.</a> J. Environ. Qual. 44 (2), 524-534 (2015).</li><li>. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Lachat+Instruments.+Determination+of+nitrate/nitrite+in+surface+and+wastewaters+by+flow+injection+analysis.">Lachat Instruments. Determination of nitrate/nitrite in surface and wastewaters by flow injection analysis.</a> QuickChem Method. , (2003).</li></ol>

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...

Watch this Scientific Journal Video about A Protocol for Collecting and Constructing Soil Core Lysimeters at JoVE.com

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 ...

The overall goal of this procedure is to demonstrate the collection, assembly, and irrigation of an intact soil core lysimeter to study nitrogen leaching through undisturbed agricultural soils. This method is designed to answer questions concerning nutrients and other chemicals that can leach below the root zone to shallow ground water. The main advantage of this technique is that it is quick and easy.We have found that we need four or five replicates to produce significant results. Although in this video we were looking at nitrate leaching, the method can be used to study many other compounds, such as phosphorus, pharmaceuticals, hormones, or metals such as arsenic. To begin, remove surface vegitation, rocks and other debris from the collection area.Position two lysimeter bodies on level ground where lysimeters are to be taken. Ensure that lysimeters are level, so that soil within the column is of a uniform depth. 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 the top of the lysimeter bodies. The outriggers also provide stability for the drop hammer. Partially hoist the steel plate weighing 1, 180 kilograms up a 3-meter tower with the aid of a mechanical winch.Release the steel plate to hammer to columns into the soil. Repeat this step several times, until the column rim is 2 cm above the soil surface. Check for soil compaction inside the lysimeter by measuring the depth of the soil inside and outside of the column.If the soil inside the column is more than 1 cm lower than the soil outside the column, soils are compacted, and are not suitable for research. Place a plywood disc inside the rim of the column to prevent contamination. Dig a trench beside the soil core and slightly deeper than the column bottom with a backhoe.Widen the hole with a shovel or pick, and expose as much of the outside of the cylinder as possible. 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 the outside column wall. Pry the digging bar back and forth until the soil interface at the bottom of the column is broken, and slide the column into the center of the trench.Frame the lifting scissors around the top of the lysimeter 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 a flat board.After flipping the soil core over so that the bottom side is up, gently level the soil even with the rim of the PVC with a straight edge. Remove stones protruding above the plane of the rim with a pen knife or a screwdriver. Also loosen the soil and expose the natural surface textures therein.Fill any voids with chemically inert play sand and gently pack it. Grade the sand even with the column bottom with a straight edge, and remove any excess sand. Next, extrude a continuous round bead of clear silicone caulk around the rim of the lysimeter.The caulk should be thick enough to seal the perforated disk bottom to the lysimeter's, and prevent leaking. Lay the perforated disk onto the rim, with the filter fabric facing the sand, and press down firmly to allow good contact of the plate and lysimeter. Then drill eight evenly spaced pilot holes around the edge of the plate, and fasten the perforated disk with 1-inch stainless steel screws and a drill driver.Slip the flexible pipe coupling onto the lysimeter base, so that about 2 cm of the coupling are projecting above the lysimeter rim. Fit the modified PVC cap into the flexible pipe coupling, and push the cap down until it makes contact with the lysimeter body. Then place the fastening bands in the grooves of the coupling and lightly secure without constricting the coupling.Tighten the metal bands with a handheld hex driver until the lysimeter cap is held firmly in place. The lysimeter is ready to be flipped, and transported to a climate controlled facility. To install moisture sensors, first 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. Drill a 1 cm diameter hole through the wall of the lysimeter at each end of the marked lines. Cut the remaining 3 cm of plastic between the drilled holes away with a rotary cutting tool.Next, chisel a 1-cm thick by 5-cm long slit into the soil to accommodate the casing of a moisture sensor. Push the moisture sensor into the hole, into the cleaned out slot, until the sensor prongs are firmly buried in the soil and only the wire is sticking out of the lysimeter. Clean the soil from the walls of the slot with a brush or rag.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. Seal gaps between the soil and the lysimeter wall with caulk to reduce the risk of preferential flow down the inside walls of the lysimeter.First, pierce and load a tube of clear silicone caulk into a standard caulk gun. Place the tip of the caulk tube between the void in the soil to be filled and the inside face of the lysimeter body. Then 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. After checking that the soil core is level as described in the text protocol, wrap Teflon tape around the threaded nylon tube fitting, and turn the fitting clockwise into the cap. Tighten the fitting with an adjustable wrench until none of the threads are visible.Push a 0.5-inch hose onto the barbed end of the nylon fitting, and cut the hose so that it passes approximately 4 cm into the mouth of the collection jug. Set the container under the lysimeter, and place the hose inside the collection jug. Cover the soil surface with cheesecloth, or another chemically inert mesh such as a window screen, to protect and preserve soil aggregates and surface residue.Measure 1, 450 ml of simulated rain water into a graduated cylinder, and pour it into a watering can equipped with a shower head. Gently and evenly sprinkle the water over the window screen at a rate that does not disturb the soil surface. After waiting a period of time for the water to infiltrate and percolate through the soil column into the cap and collection container, tip the lysimeter in toward the outlet hole until all water is drained from the lysimeter reservoir cap into the collection vessel.Measure the mass of leachate collected with a scale, and convert mass in grams to milliliters. Pour the leachate sample into a 350 ml sterile plastic sample bottle. Immediately filter 50 ml with a suction funnel equipped with 0.45 micron filter paper in preparation for nitrate analysis using color imagery via flow injection analysis.Representative results of the irrigation and leaching experiments are shown here. Average weekly leachate depths ranged from 1.12 to 1.95 cm for the four soils. Leachate recovery expresses percentage of irrigation water applied, followed a general trend related to soil texture, with recoveries from the sandy Evesboro and Sassafras soils being slightly more efficient than from the finer textured Bojac and Quindocqua soils.This figure shows that changes in soil water content at 5-cm and 25-cm depths, following irrigation, demonstrate differences in water transmission between coarser and finer textured soils. Moisture profiles indicate rapid movement of irrigation water through the coarser textured Evesboro sand and Sassafras sandy loam soils. This figure shows change in nitrate concentration before and after poultry litter application.Nitrate concentrations in leachate increased after litter application, but followed different temporal patterns between soils. Differences in leachate nitrate mass loss reflect not only trends in nitrate concentrations in leachate, but also differences in leachate depths. To assess the role of poultry litter application and leachate volume on nitrate flux, soil nitrate fluxes from before litter application were subtracted from subsequent weekly fluxes.While attempting this procedure, it is important to be safe. Always wear hearing protection while operating drills or the drop hammer. For safety, never work underneath the drop hammer.Be aware of other people in the area when you're operating the drop hammer, and maintain a safe distance from the drop hammer when operating. After watching this video you should have a good idea how to collect an intact soil core, construct a lysimeter, install soil moisture sensors, carry out irrigation, and collect leachate.

a-protocol-for-collecting-and-constructing-soil-core-lysimeters

Research

JoVE Journal

Environment

Design and Operation of a Continuous 13C and 15N Labeling Chamber for Uniform or Differential, Metabolic and Structural, Plant Isotope Labeling

Tracing rare stable isotopes from plant material through the ecosystem provides the most sensitive information about ecosystem processes; from CO2 fluxes and soil organic matter formation to small-scale stable-isotope biomarker probing. Coupling multiple stable isotopes such as 13C with 15N, 18O or&#160;2H has the potential to reveal even more information about complex stoichiometric relationships during biogeochemical transformations. Isotope labeled plant material has been used in various studies of litter decomposition and soil organic matter formation1-4. From these and other studies, however, it has become apparent that structural components of plant material behave differently than metabolic components (i.e. leachable low molecular weight compounds) in terms of microbial utilization and long-term carbon storage5-7. The ability to study structural and metabolic components separately provides a powerful new tool for advancing the forefront of ecosystem biogeochemical studies. Here we describe a method for producing 13C and 15N labeled plant material that is either uniformly labeled throughout the plant or differentially labeled in structural and metabolic plant components.
Here, we present the construction and operation of a continuous 13C and 15N labeling chamber that can be modified to meet various research needs. Uniformly labeled plant material is produced by continuous labeling from seedling to harvest, while differential labeling is achieved by removing the growing plants from the chamber weeks prior to harvest. Representative results from growing Andropogon gerardii Kaw demonstrate the system&#39;s ability to efficiently label plant material at the targeted levels. Through this method we have produced plant material with a 4.4 atom%13C and 6.7 atom%15N uniform plant label, or material that is differentially labeled by up to 1.29 atom%13C and 0.56 atom%15N in its metabolic and structural components (hot water extractable and hot water residual components, respectively). Challenges lie in maintaining proper temperature, humidity, CO2 concentration,&#160;and light levels in an airtight 13C-CO2 atmosphere for successful plant production. This chamber description represents a useful research tool to effectively produce uniformly or differentially multi-isotope labeled plant material for use in experiments on ecosystem biogeochemical cycling.

Design and Operation of a Continuous 13C and 15N Labeling Chamber for Uniform or Differential, Metabolic and Structural, Plant Isotope Labeling

This method explains how to build and operate a continuous 13C and 15N isotope labeling chamber for uniform or differential plant tissue labeling. Representative results from metabolic and structural labeling of Andropogon gerardii are discussed.

Tracing rare stable isotopes from plant material through the ecosystem provides the most sensitive information about ecosystem processes; from CO2 fluxes ...

Experimental Protocol for Manipulating Plant-induced Soil Heterogeneity

Coexistence theory has often treated environmental heterogeneity as being independent of the community composition; however biotic feedbacks such as plant-soil feedbacks (PSF) have large effects on plant performance, and create environmental heterogeneity that depends on the community composition. Understanding the importance of PSF for plant community assembly necessitates understanding of the role of heterogeneity in PSF, in addition to mean PSF effects. Here, we describe a protocol for manipulating plant-induced soil heterogeneity. Two example experiments are presented: (1) a field experiment with a 6-patch grid of soils to measure plant population responses and (2) a greenhouse experiment with 2-patch soils to measure individual plant responses. Soils can be collected from the zone of root influence (soils from the rhizosphere and directly adjacent to the rhizosphere) of plants in the field from conspecific and heterospecific plant species. Replicate collections are used to avoid pseudoreplicating soil samples. These soils are then placed into separate patches for heterogeneous treatments or mixed for a homogenized treatment. Care should be taken to ensure that heterogeneous and homogenized treatments experience the same degree of soil disturbance. Plants can then be placed in these soil treatments to determine the effect of plant-induced soil heterogeneity on plant performance. We demonstrate that plant-induced heterogeneity results in different outcomes than predicted by traditional coexistence models, perhaps because of the dynamic nature of these feedbacks. Theory that incorporates environmental heterogeneity influenced by the assembling community and additional empirical work is needed to determine when heterogeneity intrinsic to the assembling community will result in different assembly outcomes compared with heterogeneity extrinsic to the community composition.

Understanding the role of environmental heterogeneity in species coexistence has typically focused on types of heterogeneity that are extrinsic to the community&#8217;s species composition. We provide novel detailed methods for creating soil heterogeneity treatments using soils subject to plant-soil feedback conditioning, or heterogeneity intrinsic to the community composition.

Coexistence theory has often treated environmental heterogeneity as being independent of the community composition; however biotic feedbacks such as ...

A Protocol for Conducting Rainfall Simulation to Study Soil Runoff

Rainfall is a driving force for the transport of environmental contaminants from agricultural soils to surficial water bodies via surface runoff. The objective of this study was to characterize the effects of antecedent soil moisture content on the fate and transport of surface applied commercial urea, a common form of nitrogen (N) fertilizer, following a rainfall event that occurs within 24&#160;hr&#160;after fertilizer application. Although urea is assumed to be readily hydrolyzed to ammonium and therefore not often available for transport, recent studies suggest that urea can be transported from agricultural soils to coastal waters where it is implicated in harmful algal blooms. A rainfall simulator was used to apply a consistent rate of uniform rainfall across packed soil boxes that had been prewetted to different soil moisture contents. By controlling rainfall and soil physical characteristics, the effects of antecedent soil moisture on urea loss were isolated. Wetter soils exhibited shorter time from rainfall initiation to runoff initiation, greater total volume of runoff, higher urea concentrations in runoff, and greater mass loadings of urea in runoff. These results also demonstrate the importance of controlling for antecedent soil moisture content in studies designed to isolate other variables, such as soil physical or chemical characteristics, slope, soil cover, management, or rainfall characteristics. Because rainfall simulators are designed to deliver raindrops of similar size and velocity as natural rainfall, studies conducted under a standardized protocol can yield valuable data that, in turn, can be used to develop models for predicting the fate and transport of pollutants in runoff.

A rainfall simulator was used to apply a consistent rate of uniform rainfall to packed soil boxes in a study of the fate and transport of urea, a nonpoint source environmental contaminant. Under uniform soil and rainfall conditions, antecedent soil moisture content exerted strong control over urea loss in surface runoff.

Rainfall is a driving force for the transport of environmental contaminants from agricultural soils to surficial water bodies via surface runoff. The ...

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 ...

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 ...

A Gusseted Thermogradient Table to Control Soil Temperatures for Evaluating Plant Growth and Monitoring Soil Processes

Thermogradient tables were first developed in the 1950s primarily to test seed germination over a range of temperatures simultaneously without using a series of incubators. A temperature gradient is passively established across the surface of the table between the heated and cooled ends and is lost quickly at distances above the surface. Since temperature is only controlled on the table surface, experiments are restricted to shallow containers, such as Petri dishes, placed on the table. Welding continuous aluminum vertical strips or gussets perpendicular to the surface of a table enables temperature control in depth via convective heat flow. Soil in the channels between gussets was maintained across a gradient of temperatures allowing a greater diversity of experimentation. The gusseted design was evaluated by germinating oat, lettuce, tomato, and melon seeds. Soil temperatures were monitored using individual, battery-powered dataloggers positioned across the table. LED lights installed in the lids or along the sides of the gradient table create a controlled temperature chamber where seedlings can be grown over a range of temperatures. The gusseted design enabled accurate determination of optimum temperatures for fastest germination rate and the highest percentage germination for each species. Germination information from gradient table experiments can help predict seed germination and seedling growth under the adverse soil conditions often encountered during field crop production. Temperature effects on seed germination, seedling growth, and soil ecology can be tested under controlled conditions in a laboratory using a gusseted thermogradient table.

Traditional thermogradient tables create a range of temperatures across the surface. Welding gussets perpendicular to the surface of a thermogradient table will control temperature in depth increasing possible research applications.

Thermogradient tables were first developed in the 1950s primarily to test seed germination over a range of temperatures simultaneously without using a ...

A Lipid Extraction and Analysis Method for Characterizing Soil Microbes in Experiments with Many Samples

Microbial communities are important drivers and regulators of ecosystem processes. To understand how management of ecosystems may affect microbial communities, a relatively precise but effort-intensive technique to assay microbial community composition is phospholipid fatty acid (PLFA) analysis. PLFA was developed to analyze phospholipid biomarkers, which can be used as indicators of microbial biomass and the composition of broad functional groups of fungi and bacteria. It has commonly been used to compare soils under alternative plant communities, ecology, and management regimes. The PLFA method has been shown to be sensitive to detecting shifts in microbial community composition.
An alternative method, fatty acid methyl ester extraction and analysis (MIDI-FA) was developed for rapid extraction of total lipids, without separation of the phospholipid fraction, from pure cultures as a microbial identification technique. This method is rapid but is less suited for soil samples because it lacks an initial step separating soil particles and begins instead with a saponification reaction that likely produces artifacts from the background organic matter in the soil. 
This article describes a method that increases throughput while balancing effort and accuracy for extraction of lipids from the cell membranes of microorganisms for use in characterizing both total lipids and the relative abundance of indicator lipids to determine soil microbial community structure in studies with many samples. The method combines the accuracy achieved through PLFA profiling by extracting and concentrating soil lipids as a first step, and a reduction in effort by saponifying the organic material extracted and processing with the MIDI-FA method as a second step.

The article describes a method that increases throughput while balancing effort and accuracy for extraction of lipids from the cell membranes of microorganisms for use in characterizing both total lipids and the relative abundance of indicator lipids to determine soil microbial community structure in studies with many samples.

Microbial communities are important drivers and regulators of ecosystem processes. To understand how management of ecosystems may affect microbial ...

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 ...

Use of Principal Components for Scaling Up Topographic Models to Map Soil Redistribution and Soil Organic Carbon

Landscape topography is a critical factor affecting soil formation and plays an important role in determining soil properties on the earth surface, as it regulates the gravity-driven soil movement induced by runoff and tillage activities. The recent application of Light Detection and Ranging (LiDAR) data holds promise for generating high spatial resolution topographic metrics that can be used to investigate soil property variability. In this study, fifteen topographic metrics derived from LiDAR data were used to investigate topographic impacts on redistribution of soil and spatial distribution of soil organic carbon (SOC). Specifically, we explored the use of topographic principal components (TPCs) for characterizing topography metrics and stepwise principal component regression (SPCR) to develop topography-based soil erosion and SOC models at site and watershed scales. Performance of SPCR models was evaluated against stepwise ordinary least square regression (SOLSR) models. Results showed that SPCR models outperformed SOLSR models in predicting soil redistribution rates and SOC density at different spatial scales. Use of TPCs removes potential collinearity between individual input variables, and dimensionality reduction by principal component analysis (PCA) diminishes the risk of overfitting the prediction models. This study proposes a new approach for modeling soil redistribution across various spatial scales. For one application, access to private lands is often limited, and the need to extrapolate findings from representative study sites to larger settings that include private lands can be important.

Landscape processes are critical components of soil formation and play important roles in determining soil properties and spatial structure in landscapes. We propose a new approach using stepwise principal component regression to predict soil redistribution and soil organic carbon across various spatial scales.

Landscape topography is a critical factor affecting soil formation and plays an important role in determining soil properties on the earth surface, as it ...