Name: electrostatic method to remove particulate organic matter from soil
Uploaded: 2021-02-10T13:30:00
Description: Watch this Scientific Journal Video about Electrostatic Method to Remove Particulate Organic Matter from Soil at JoVE.com

This work was supported solely by USDA-ARS base funding. The authors greatly appreciate Mikayla Kelly, Caroline J. Melle, Alex Lasher, Emmi Klarer, and Katherine Son for their technical help.

1. Soil preparation
<ol>
	<li>Collect soil samples to the desired depth. Thoroughly dry the soil at 40 &#176;C or following lab-specific standard protocols.</li>
	<li>Sieve the soil through appropriate-sized soil sieves to obtain approximately 10-25 g of sieved soil. Many studies use a 1- or 2-mm sieve. The amount of soil is based on the mass required for the downstream analyses and will impact the number of times the electrostatic removal step will need to be repeated.</li>
	<li>Place the soil in a clean, dry metal or...

<ol>
	<li>Gosling, P., Parsons, N., Bending, G. D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=What+are+the+primary+factors+controlling+the+light+fraction+and+particulate+soil+organic+matter+content+of+agricultural+soils.">What are the primary factors controlling the light fraction and particulate soil organic matter content of agricultural soils.</a> Biology and Fertility of Soils. 49 (8), 1001-1014 (2013).</li><li>Gollany, H. T., 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=Soil+organic+carbon+accretion+vs.+sequestration+using+physicochemical+fractionation+and+CQESTR+simulation.">Soil organic carbon accretion vs. sequestration using physicochemical fractionation and CQESTR simulation.</a> Soil Science Society of America Journal. 77 (2), 618-629 (2013).</li><li>Cambardella, C. A., Gajda, A. M., Doran, J. W., Wienhold, B. J., Kettler, T. A., Kimble, J. M., Lal, R., Follett, R. F., Stewart, B. 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> Assessment methods for soil carbon. , 349-359 (2001).</li><li>Wander, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Soil organic matter in sustainable agriculture. , 67-102 (2004).</li><li>Curtin, D., Beare, M. H., Qiu, W., Sharp, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Does+particulate+organic+matter+fraction+meet+the+criteria+for+a+model+soil+organic+matter+pool.">Does particulate organic matter fraction meet the criteria for a model soil organic matter pool.</a> Pedosphere. 29 (2), 195-203 (2019).</li><li>Kirkby, C. 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=Stable+soil+organic+matter:+A+comparison+of+C:N:P:S+ratios+in+Australian+and+other+world+soils.">Stable soil organic matter: A comparison of C:N:P:S ratios in Australian and other world soils.</a> Geoderma. 163 (3-4), 197-208 (2011).</li><li>Strickland, T. C., Sollins, P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Improved+method+for+separating+light-+and+heavy-fraction+organic+material+from+soil.">Improved method for separating light- and heavy-fraction organic material from soil.</a> Soil Science Society of America Journal. 51 (5), 1390-1393 (1987).</li><li>Golchin, A., Oades, J. M., Skjemstad, J. O., Clarke, P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Study+of+free+and+occluded+particulate+organic+matter+in+soils+by+solid+state+13C+Cp/MAS+NMR+spectroscopy+and+scanning+electron+microscopy.">Study of free and occluded particulate organic matter in soils by solid state 13C Cp/MAS NMR spectroscopy and scanning electron microscopy.</a> Soil Research. 32 (2), 285-309 (1994).</li><li>Theodorou, C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Nitrogen+transformations+in+particle+size+fractions+from+a+second+rotation+pine+forest+soil.">Nitrogen transformations in particle size fractions from a second rotation pine forest soil.</a> Communications in Soil Science and Plant Analysis. 21 (5-6), 407-413 (1990).</li><li>Kaiser, M., Ellerbrock, R. H., Sommer, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Separation+of+coarse+organic+particles+from+bulk+surface+soil+samples+by+electrostatic+attraction.">Separation of coarse organic particles from bulk surface soil samples by electrostatic attraction.</a> Soil Science Society of America Journal. 73 (6), 2118-2130 (2009).</li><li>Kuzyakov, Y., Biriukova, O., Turyabahika, F., Stahr, K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Electrostatic+method+to+separate+roots+from+soil.">Electrostatic method to separate roots from soil.</a> Journal of Plant Nutrition and Soil Science. 164 (5), 541 (2001).</li><li>Schneider, C. A., Rasband, W. S., Eliceiri, K. W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=NIH+Image+to+ImageJ:+25+years+of+image+analysis.">NIH Image to ImageJ: 25 years of image analysis.</a> Nature Methods. 9 (7), 671-675 (2012).</li></ol>

The electrostatic attraction method was effective in removing POM from the silt loam soils. The method described here is slightly different from Kaiser, et al.10 which used a combination of glass/cotton. We treated all but the finest soil fraction and used polystyrene rather than glass due to the triboelectric difference, which for polystyrene/nylon is 100 nC/J compared to glass/ cotton at 20 nC/J12. Glass and polystyrene foam have proven effective and convenient in more re...

Accurate estimates of soil organic carbon (SOC) are important in evaluating changes resulting from agricultural management or the environment. Particulate organic matter (POM) has important functions in the ecology and physics of a soil but it is often short lived and varies based on several factors including season, moisture conditions, aeration, sample collection techniques, recent soil management, vegetation life cycle, and others1. These temporally unstable sources can confound estimates of long-term trends in stable and truly sequestered soil organic carbon2.
Despite being well-defined, common, and important, POM is not easily separated from soil nor is it easy to measure quantitatively. Particulate organic matter has been measured as that which floats in liquids (light fraction, typically 1.4-2.2 g cm-3), or as that which can be separated by size (e.g., &#62; 53-250 &#181;m or &#62; 250 &#181;m), or a combination of the two3,4,5. Both size-based and density-based techniques can influence the quantitative and chemical outcomes of POM measurement4. A careful visual inspection of soil that has been size-fractionated using routine methods often reveals long, narrow structures like roots and slivers of leaf or stem that have passed through the screen. Simply removing these structures by hand has been shown to substantially reduce measurements of total SOC2,6 but the method is notably subject to the diligence and visual acuity of the operator. POM separation from a soil sample as the light fraction during flotation in a dense liquid7 does not capture all POM, and excessive shaking during the flotation process can actually reduce the amount of light fraction recovered from a sample8. Flotation requires many steps and exposes the soil to chemical solutions which can change the chemical characteristics or dissolve and remove constituents that may be of interest4.
Alternative methods for removing POM have been used to avoid or augment the use of dense aqueous solutions. Kirkby, et al.6 compared light fraction removal using two flotation procedures to a dry sieving/winnowing method9. Winnowing was performed by passing a light current of air across a thin layer of soil to gently lift away the light from the heavy fraction. The dry sieving/winnowing performed similarly to the two flotation methods with regard to C, N, P, and S content; however, the authors suggest that dry sieving/winnowing produced &#34;slightly cleaner&#34; soils6. POM has also been separated from soil using electrostatic attraction10,11 in which organic particles are isolated by passing an electrostatically charged surface above the soil. The electrostatic attraction method successfully recovered POM, referred to as course organic particles, from dried, sieved (&#62; 0.315 mm) soils with statistical repeatability comparable to other methods of size and density fractionation10.
Here we demonstrate how electrostatic attraction can be used to remove POM of sizes ranging from visible to microscopic. Unlike other reported methods, electrostatic attraction of fine soil also removes a small portion of mineral and aggregated soil which is visibly like the remaining soil. Given our results to date, it is reasonable to assume that the removal of a small portion of non-POM soil will have no substantial effect on the downstream analyses; however, this assumption should be verified for a specific soil if large proportions of the total soil sample are being removed electrostatically. The methods and examples provided here were performed on silt loam loess soils from a semi-arid environment.
This method may not be suitable for all soil types but has the advantages of being quick and efficient in removing particulate organic matter too small to remove manually or by an air current. Process speed is important in reducing fatigue, ensuring consistency, and encouraging greater replication for better accuracy of conclusions. Additionally, the ability to remove very small particulates is important in avoiding bias toward soils with larger rather than small particulate sizes.

<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
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			<td>brush, camel-hair</td>
			<td></td>
			<td></td>
<td></td>
		</tr>
		<tr>
			<td>petri dish, glass or plastic</td>
			<td></td>
<td></td>
<td></td>
		</tr>
		<tr>
			<td>polystyrene foam, cotton or nylon cloth</td>
<td></td>
<td></td>
<td></td>
		</tr>
		<tr>
			<td>soil</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>soil sieves</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
	</tbody>
</table>

electrostatic method to remove particulate organic matter from soil

Estimations of soil organic carbon are dependent on soil processing methods including removal of undecomposed plant material. Inadequate separation of roots and plant material from soil can result in highly variable carbon measurements. Methods to remove the plant material are often limited to the largest, most visible plant materials. In this manuscript we describe how electrostatic attraction can be used to remove plant material from a soil sample. An electrostatically charged surface passed close to dry soil naturally attracts both undecomposed and partially decomposed plant particles, along with a small quantity of mineral and aggregated soil. The soil sample is spread in a thin layer on a flat surface or a soil sieve. A plastic or glass Petri dish is electrostatically charged by rubbing with polystyrene foam or nylon or cotton cloth. The charged dish is passed repeatedly over the soil. The dish is then brushed clean and recharged. Re-spreading the soil and repeating the procedure eventually results in a diminishing yield of particulates. The process removes about 1 to 5% of the soil sample, and about 2 to 3 times that proportion in organic carbon. Like other particulate removal methods, the endpoint is arbitrary and not all free particulates are removed. The process takes approximately 5 min and does not require a chemical process as do density flotation methods. Electrostatic attraction consistently removes material with higher than average C concentration and C:N ratio, and much of the material can be visually identified as plant or faunal material under a microscope.

The results presented here are based on the analysis of silt loam soils from agricultural sites in the Pacific Northwest (Table 1). Soils were collected to depths of 0-20 cm or 0-30 cm, dried at 40 &#176;C, passed through a 2 mm sieve, and treated using a polystyrene surface charged with a nylon cloth.
The amount of soil electrostatically removed from a sample varied. About 1% to 6% of the total soil mass was re...

Watch this Scientific Journal Video about Electrostatic Method to Remove Particulate Organic Matter from Soil at JoVE.com

Electrostatic Method to Remove Particulate Organic Matter from Soil

Removing recently deposited and incompletely decomposed plant material from soil samples reduces the influence of temporary seasonal inputs on soil organic carbon measurements. Attraction to an electrostatically charged surface can be used to quickly remove a substantial amount of particulate organic matter.

Estimations of soil organic carbon are dependent on soil processing methods including removal of undecomposed plant material. Inadequate separation of ...

Electrostatic attraction is an efficient way to reduce particulate organic matter in a soil sample. The main advantage of this method is that requires minimal visual judgment and works on fine particles not visible to the eye. Removing undecomposed organic fragments improves accuracy and consistency in measuring long term soil carbon storage.After collecting soil samples to the desired depth, thoroughly dry them at 40 degrees Celsius. Sift the soil through appropriate sides soil sieves to obtain approximately 10 to 25 grams of sieved soil. Place the soil in a clean dry metal or a glass flat bottomed pan that is large enough for the soil to be spread thin.Gently shake the pain horizontally to distribute the soil in as thin a layer as possible. Hold a 100 mm diameter glass or a polystyrene Petri dish top or bottom in one hand and vigorously rub the outer surface with a clean piece of nylon cloth, cotton cloth or polystyrene foam several times. Perform the surface charging away from the sample.When finished, inspect the surface of the Petri dish to make sure that it is clean. Lower the charged surface to within 0.5 to 2 centimeters above the soil and move it horizontally to pick up as much particulate material as possible. Attraction to the surface can be noted visually and audibly.When the Petri dish no longer attracts additional particles, move the dish away from the sample. To clean the electrostatic surface, hold it over a collection dish and use a fine brush to transfer the electrostatically attracted material from the Petri dish surface into the collection dish. Repeat this process until the number of organic matter particles being picked up decreases.Redistribute the soil sample by horizontal shaking of the soil pan to expose new material at the surface and continue electrostatic collection. Determine the end point by visual inspection of the charged surface to determine whether a significant amount of organic particulates has been removed from the soil. This protocol was used for the analysis of silt loam soils from agricultural sites in the Pacific Northwest.About 1%to 6%of the total soil mass was removed. In all cases the proportion of total sample carbon removed was greater than the soil mass removed. The carbon concentration and carbon to nitrogen ratio of the electrostatically removed soil fraction was always greater than the remaining soil.The ambient conditions and the combination of materials used to produce the charged surface affected the results. The affects of treatment endpoints were examined by collecting a series of three electrostatic samples one after the other from the same soil sample. The first treatment collected the greatest amount of carbon.The following two treatments were still highly enriched in carbon compared to the remaining soil. Finally, the amount of particulate material that could be electrostatically removed from the fine silt-sized fraction that passed through a 53 micrometer screen was tested on five silt loan soils. The electrostatically removed fractions demonstrated very little enrichment of particulate organic matter.Microscopic inspection revealed that particulate organic matter does exist in the fine soil fraction of the soils but in very small quantities. The C to N ratio tends to stabilize as in completely decomposed organic matter is removed. This might lead to better models of long term soil organic matter.

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