Name: soil sampling and isolation of entomopathogenic nematodes (steinernematidae, heterorhabditidae)
Uploaded: 2014-07-11T15:00:00
Description: Watch this Scientific Journal Video about Soil Sampling and Isolation of Entomopathogenic Nematodes Steinernematidae, Heterorhabditidae at JoVE.com

The authors wish to thank past members of the Stock lab: Sam-Kyu Kim, Kathryn Plichta and Victoria Miranda-Thompson for their contributions to the improvement of many of these protocols. We acknowledge the National Science Foundation support (grants IOS-0840932 and IOS-0724978) to S. P. Stock.

1. Soil Sample Collection
<ol>
	<li>Consider covering a minimum area of 2 - 4 m2 for each sampling site.</li>
	<li>Collect soil samples at a depth of at least 15 cm (Figure 4).</li>
	<li>Take at least 5 random samples within this area.</li>
	<li>Take 3 subsamples per sample. Depending on the objective of the study, either combine the subsamples or keep them separate.</li>
	<li>Place each sample in a plastic bag. Consider double-bagging to avoid leaking of samples (Figure 4)....

<ol>
	<li>Bedding, R. A., Akhurst, R. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+simple+technique+for+the+detection+of+insect+parasitic+rhabditid+nematodes+in+soil.">A simple technique for the detection of insect parasitic rhabditid nematodes in soil.</a> Nematologica. 21, 109-110 (1975).</li><li>Boemare, N. E., Akhurst, R. A., Dworkin, M., Falkow, S., Rosenberg, E., Schleifer, K. -. H., Stackebrandt, E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> The Genera Photorhabdus and Xenorhabdus. In The Prokaryotes. , 473-488 (2007).</li><li>Gaugler, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Entomopathogenic Nematology. , (2002).</li><li>Gaugler, R., Kaya, H. K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Entomopathogenic Nematode s in Biological Control. , (1990).</li><li>Hazir, S., Keskin, N., Stock, S. P., Kaya, H. K., &#214;zcan, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Diversity+and+distribution+of+entomopathogenic+nematodes+(Rhabditida:+Steinernematidae+and+Heterorhabditidae)+in+Turkey.">Diversity and distribution of entomopathogenic nematodes (Rhabditida: Steinernematidae and Heterorhabditidae) in Turkey.</a> Biodiversit., &amp; Conservation. 12, 375-386 (2003).</li><li>Kaya, H. K., Gaugler, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Entomopathogenic+nematodes.">Entomopathogenic nematodes.</a> Annual Review of Entomology. 38, 181-206 (1993).</li><li>Kaya, H. K., Stock, S. P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Techniques in insect nematology. In Manual of techniques in insect pathology. , 281-324 (1997).</li><li>Lacey, L. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Manual of techniques in invertebrate pathology. , (2012).</li><li>McCoy, C. W., Shapiro-Ilan, D., Duncan, L., Nguyen, K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Entomopathogenic+nematodes+and+other+natural+enemies+as+mortality+factors+for+larvae+of+Diaprepes+abbreviatus+(Coleoptera:+Curculionidae).">Entomopathogenic nematodes and other natural enemies as mortality factors for larvae of Diaprepes abbreviatus (Coleoptera: Curculionidae).</a> Biological Control. 19, 182-190 (2000).</li><li>Meyling, N. V., Eilenberg, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Occurrence+and+distribution+of+soil+borne+entomopathogenic+fungi+within+a+single+organic+agroecosystem.">Occurrence and distribution of soil borne entomopathogenic fungi within a single organic agroecosystem.</a> Agriculture, ecosystem., &amp; environment. 113, 336-341 (2006).</li><li>Poinar, G. O. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Taxonomy and biology of Steinernematidae and Heterorhabditidae. In: Entomopathogenic Nemtaodes in Biological. , 23-61 (1990).</li><li>Stock, S. P., Gress, J. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Diversity+and+phylogenetic+relationships+of+entomopathogenic+nematodes+(Steinernematidae+and+Heterorhabditidae)+from+the+Sky+Islands+of+southern+Arizona.">Diversity and phylogenetic relationships of entomopathogenic nematodes (Steinernematidae and Heterorhabditidae) from the Sky Islands of southern Arizona.</a> Journal of invertebrate pathology. 92, 66-72 (2006).</li><li>Stock, S. P., Hunt, D. J., Grewal, P. S., Ehlers, R. U., Shapiro-Ilan, D. I. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Nematode+morphology+and+systematics.">Nematode morphology and systematics.</a> Nematodes as biological control agents. CAB International Publishing. , 3-43 (2005).</li><li>Stock, S. P., Goodrich&#8211;Blair, H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Entomopathogenic+nematodes+and+their+bacterial+symbionts:+The+inside+out+of+a+mutualistic+association.">Entomopathogenic nematodes and their bacterial symbionts: The inside out of a mutualistic association.</a> Symbiosis. 46, 65-75 (2008).</li><li>Stuart, R. J., Gaugler, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Patchiness+in+populations+of+entomopathogenic+nematodes.">Patchiness in populations of entomopathogenic nematodes.</a> Journal of Invertebrate Pathology. 64, 39-45 (1994).</li><li>White, G. F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+method+for+obtaining+infective+nematode+larvae+from+cultures.">A method for obtaining infective nematode larvae from cultures.</a> Science. 66, 302-303 (1927).</li></ol>

This demonstration is the first of two presentations that describe a number of techniques that are commonly used for studying EPN and their symbiotic bacteria. These techniques represent key steps for the successful establishment of EPN cultures in the laboratory and also form the basis for other bioassays that employ EPN as model organisms for research.
Various soil surveys of EPN have shown that their abundance and distribution can vary across seasons, habitats and geographic regions4, ...

Many nematodes are associated with insects, and their host interactions range from beneficial to detrimental. Herein, we focus on a group of nematodes that are pathogens of insects, also known as entomopathogenic nematodes (or EPN). Two nematode families belong to this group of nematodes: Steinernematidae and Heterorhabditidae11,13. Their pathogenic effect is in fact conferred by their interaction with facultative anaerobic enteric bacteria (Xenorhabdus bacteria associate with steinernematids and Photorhabdus bacteria associate with heterorhabditids)2. The bacteria are vectored from one insect host to another by the only free living nematode stage, the third-stage infective juvenile (also known as dauer juvenile, infective juvenile or IJ), which lives in the soil. Once inside the insect, the nematodes release the bacteria into the insect&#8217;s hemolymph, which kill the insect host by massive septicemia. The bacteria also degrade the insect&#8217;s tissues and become the nematodes&#8217; food source, allowing them to mature and multiply. Usually, one or two generations of adult nematodes are produced within the insect cadaver. The progeny of the last adult generation reassociates with a few bacterial cells in a more specialize manner than their previous nutritional relationship, and nurture these cells in their intestines as they move out from the insect carcass into the soil where they will await another insect to parasitize6,11,14 (Figure 1).
Since their discovery in 1927, EPN have been considered valuable alternatives to chemical pesticides as they can parasitize a wide range of insects that are agricultural pests3,4,5. However, over the past two decades, these nematodes and their symbiotic bacteria have been recognized as a malleable model system for studying biological, ecological and evolutionary aspects of host-microbe interactions14.
The goal of this presentation is to show the methods and techniques most commonly used for soil sampling and isolation of EPN. A variety of tools is available and can be used for collecting soil samples including: soil corers, trowels, post-hole diggers, augers, sampling tubes, hand shovels, among others (Figure 2).
Depending on the purpose of the study, two sampling strategies can be considered: a) stratified, b) random sampling (Figure 3). The stratified sampling is usually used as part of an intensive study in a specific or demarked area over a given period of time. In general, a transect is demarked and soil samples are taken at stipulated intervals in the transect over a period of time (Figure 3A)15. The random sampling is generally employed when focusing on an extensive area. This sampling strategy has been used for studying the diversity of EPN from a large geographic area or region (Figure 3B)12. A number of factors can be considered depending on the focus of the study including a diverse range of elevations, soil textures and habitats (e.g., cultivated fields, forests, pastures, parks, seashores, riparian areas, etc.).
We show the insect-baiting technique, which was originally described by Bedding and Akhurst1 and represents a simple and selective alternative for recovering EPN from soil samples. This is a selective procedure that is based on the premise that the nematodes (IJ stage) will be attracted to an insect host and parasitize it. This technique can also be considered for isolation of other insect pathogens such as fungi, and bacteria8,10.
We also demonstrate the modified White trap technique which is used for retrieving nematode progeny from infected insect hosts7,14. This is an effortless method that offers the advantage of retrieving a &#8216;clean&#8217; nematode progeny free of debris from the degrading insect cadavers.
Finally, the techniques described and shown in this article correspond to those conceived and/or performed in our laboratory as well as those described by various colleagues and collaborators.

<table border="0" cellpadding="0" cellspacing="0" width="1119">
	<tbody>
		<tr height="21">
			<td height="21" style="height:21px;width:271px;">Name of Reagent/ Equipment</td>
			<td style="width:309px;">Company</td>
			<td style="width:241px;">Catalog Number</td>
			<td style="width:299px;">Comments/Description</td>
		</tr>
		<tr height="22">
			<td height="22" style="height:22px;width:271px;">Galleria mellonella</td>
			<td style="width:309px;">Timberline</td>
			<td style="width:241px;">http://www.timberlinefisheries.com/ProductDetails.asp?ProductCode=WAXLG</td>
			<td>for insect baiting technique</td>
		</tr>
		<tr height="25">
			<td height="25" style="height:25px;width:271px;">Filter Paper, 55mm Grade 1 Cellulose</td>
			<td style="width:309px;">Whatman/VWR</td>
			<td>28450-048</td>
			<td>infection chamber and White trap assembly</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:271px;">60 x 15 mm Petri Dishes</td>
			<td style="width:309px;">VWR</td>
			<td>25384-092</td>
			<td>infection chamber and White trap assembly</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:271px;">100 x 15 Petri Dishes</td>
			<td style="width:309px;">VWR</td>
			<td style="width:241px;">25384-088</td>
			<td>infection chamber and White trap assembly</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:271px;">ZIPloc Plastic Bags</td>
			<td style="width:309px;">Ace Hardware or local hardware store</td>
			<td style="width:241px;">N/A</td>
			<td>soil sampling</td>
		</tr>
		<tr height="19">
			<td height="19" style="height:19px;width:271px;">Mechanical Pipettor P1000, P200 ml</td>
			<td style="width:309px;">VWR</td>
			<td>89130-562; 89130-566&#160;</td>
			<td>infection chamber and White trap assembly</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:271px;">pippetor tips 1000ml, 200 ml</td>
			<td style="width:309px;">VWR</td>
			<td style="width:241px;">16466-004 ; 53510</td>
			<td>infection chamber and White trap assembly</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:271px;">Bleach</td>
			<td style="width:309px;">Ace Hardware or local hardware store</td>
			<td>N/A</td>
			<td>soil sampling , desisnfecting</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:271px;">Sodium Hypochlorite</td>
			<td style="width:309px;">Ace Hardware or local hardware store</td>
			<td>N/A</td>
			<td>soil sampling , desisnfecting</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:271px;">70% Ethyl alochol</td>
			<td style="width:309px;">AAPER</td>
			<td>17212945</td>
			<td>soil sampling , desisnfecting</td>
		</tr>
		<tr height="18">
			<td height="18" style="height:18px;width:271px;">Shovels</td>
			<td style="width:309px;">Ace Hardware or local hardware store</td>
			<td style="width:241px;">N/A</td>
			<td>soil sampling</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:271px;">Tubular soil sampler</td>
			<td>Accuproducts</td>
			<td style="width:241px;">N/A</td>
			<td>soil sampling</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:271px;">Soil Probe, long handle</td>
			<td>Nupla&#160;</td>
			<td style="width:241px;">PRB4T 69401 Classic</td>
			<td>soil sampling</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:271px;">Measuring tape</td>
			<td style="width:309px;">Ace Hardware or local hardware store</td>
			<td style="width:241px;">N/A</td>
			<td>soil sampling</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:271px;">Flagging tape, various colors</td>
			<td style="width:309px;">Ace Hardware or local hardware store</td>
			<td style="width:241px;">N/A</td>
			<td>soil sampling</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:271px;">tissue culture flasks</td>
			<td style="width:309px;">VWR</td>
			<td style="width:241px;">Falcon, 29185-304&#160;</td>
			<td>White trap, collection of EPN</td>
		</tr>
		<tr height="22">
			<td height="22" style="height:22px;width:271px;">wash bottles, Polyethylene, Wide Mouth</td>
			<td style="width:309px;">VWR</td>
			<td>16650-107</td>
			<td>White trap, collection of EPN</td>
		</tr>
	</tbody>
</table>

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 Sample Collection
Third-stage infective juveniles of EPN are the only free living stages in these nematodes&#8217; life cycle which reside in the soil (Figure 1). Therefore, collecting soil samples is a very efficient method to recover of these nematodes. Figure 4 shows a soil profile indicating the depth at which samples should be taken. Preserving the moisture of a sample is a key factor for survival of the nematodes. Consequently, it is important to ke...

Watch this Scientific Journal Video about Soil Sampling and Isolation of Entomopathogenic Nematodes Steinernematidae, Heterorhabditidae at JoVE.com

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.

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 ...

soil-sampling-isolation-entomopathogenic-nematodes-steinernematidae

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

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

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. ...

Isolation and Analysis of Microbial Communities in Soil, Rhizosphere, and Roots in Perennial Grass Experiments

Plant and soil microbiome studies are becoming increasingly important for understanding the roles microorganisms play in agricultural productivity. The purpose of this manuscript is to provide detail on how to rapidly sample soil, rhizosphere, and endosphere of replicated field trials and analyze changes that may occur in the microbial communities due to sample type, treatment, and plant genotype. The experiment used to demonstrate these methods consists of replicated field plots containing two, pure, warm-season grasses (Panicum virgatum and Andropogon gerardii) and a low-diversity grass mixture (A. gerardii, Sorghastrum nutans, and Bouteloua curtipendula). Briefly, plants are excavated, a variety of roots are cut and placed in phosphate buffer, and then shaken to collect the rhizosphere. Roots are brought to the laboratory on ice and surface sterilized with bleach and ethanol (EtOH). The rhizosphere is filtered and concentrated by centrifugation. Excavated soil from around the root ball is placed into plastic bags and brought to the lab where a small amount of soil is taken for DNA extractions. DNA is extracted from roots, soil, and rhizosphere and then amplified with primers for the V4 region of the 16S rRNA gene. Amplicons are sequenced, then analyzed with open access bioinformatics tools. These methods allow researchers to test how the microbial community diversity and composition varies due to sample type, treatment, and plant genotype. Using these methods along with statistical models, the representative results demonstrate there are significant differences in microbial communities of roots, rhizosphere, and soil. Methods presented here provide a complete set of steps for how to collect field samples, isolate, extract, quantify, amplify, and sequence DNA, and analyze microbial community diversity and composition in replicated field trials.

Excavation of plant roots from the field as well as processing of samples into endosphere, rhizosphere, and soil are described in detail, including DNA extraction and data analysis methods. This paper is designed to enable other laboratories to use these techniques for the study of soil, endosphere, and rhizosphere microbiomes.

Plant and soil microbiome studies are becoming increasingly important for understanding the roles microorganisms play in agricultural productivity. The ...

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 ...

Microplot Design and Plant and Soil Sample Preparation for 15Nitrogen Analysis

Many&#160;nitrogen fertilizer studies evaluate the overall effect of a treatment on end-of-season measurements such as grain yield or cumulative N losses. A stable isotope approach is necessary to follow and quantify the fate of fertilizer derived N (FDN) through the soil-crop system. The purpose of this paper is to describe a small-plot research&#160;design utilizing non-confined 15N enriched microplots for multiple soil and plant sampling events over two growing seasons and provide sample collection, handling, and processing protocols for total 15N analysis. The methods were demonstrated using a replicated study from south-central Minnesota planted to corn (Zea mays L.). Each treatment consisted of six corn rows (76 cm row-spacing) 15.2 m long with a microplot (2.4 m by 3.8 m) embedded at one end. Fertilizer-grade urea was applied at 135 kg N&#8729;ha-1 at planting, while the microplot received urea enriched to 5 atom % 15N. Soil and plant samples were taken several times throughout the growing season, taking care to minimize cross-contamination by using separate tools and physically separating unenriched and enriched samples during all procedures. Soil and plant samples were dried, ground to pass through a 2 mm screen, and then ground to a flour-like consistency using a roller jar mill. Tracer studies require additional planning, sample processing time and manual labor, and incur higher costs for 15N enriched materials and sample analysis than traditional N studies. However, using the mass balance approach, tracer studies with multiple in-season sampling events allow the researcher to estimate FDN distribution through the soil-crop system and estimate unaccounted-for FDN from the system.

Microplot Design and Plant and Soil Sample Preparation for 15Nitrogen Analysis

A microplot design for 15N tracer research is described to accommodate multiple in-season plant and soil sampling events. Soil and plant sample collection and processing procedures, including grinding and weighing protocols, for 15N analysis are put forth.

Many&#160;nitrogen fertilizer studies evaluate the overall effect of a treatment on end-of-season measurements such as grain yield or cumulative N losses. ...