The Impact of Sampling Methodology on Soil Bulk Density Measurement by the Clod Method

Aldi Airori Author

08/03/2020 Added

133 Plays

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Bulk density is an important indicator of soil health and porosity. It is also important in the calculation of soil organic carbon. Therefore, the sampling methods are crucial in measuring soil bulk density.

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[00:00:01.632]Hello everyone
[00:00:02.372]my name is Aldi Airori
[00:00:03.766]I am a senior Environmental Science major
[00:00:05.956]and I am studying the impact of
[00:00:07.577]sampling methodology on soil bulk density
[00:00:09.607]measurement by the clod method
[00:00:11.407]under the guidance of Dr. Judith Turk
[00:00:13.187]from the School of Natural Resources
[00:00:14.987]and Trinity Baker,
[00:00:16.206]her graduate research assistant
[00:00:21.057]soil bulk density is the ratio
[00:00:23.096]of oven-dry mass to the volume
[00:00:25.017]of the soil sample
[00:00:26.509]it is an indicator of soil porosity
[00:00:28.729]and it tells you how fertile the soil is
[00:00:31.309]the high bulk density values
[00:00:32.932]indicates lower porosity
[00:00:34.635]which means the soil has higher compaction
[00:00:38.931]the picture on the left shows a truck
[00:00:41.045]with hydraulic probes that was
[00:00:42.685]used to collect soil sample
[00:00:45.728]why bulk density is very important
[00:00:47.928]especially for its ecological functions
[00:00:50.380]is because it serves as the indicator
[00:00:52.402]for the soil ability for
[00:00:54.122]structural support,
[00:00:55.077]movement of water absorption,
[00:00:56.817]and aeration
[00:00:58.023]the ideal bulk density for plant growth
[00:01:00.727]is less than 1.10 g/cm^3
[00:01:04.722]this low bulk density means
[00:01:06.432]less compaction in the soil
[00:01:07.961]and more aeration.
[00:01:09.117]thus, it is the ideal soil
[00:01:10.831]for plant growth.
[00:01:12.907]Bulk density is also used
[00:01:14.487]in the soil organic carbon stock
[00:01:16.147]calculation. Which plays important roles
[00:01:18.437]to carbon cycle or climate change research
[00:01:23.117]the formula used to calculate
[00:01:24.647]the bulk density is by dividing
[00:01:26.398]the oven-dry mass of the soil
[00:01:28.039]to the volumes
[00:01:31.693]the objective of this study
[00:01:33.233]was to test the hypothesis
[00:01:34.728]whether bulk density measurement
[00:01:36.396]using clods extracted from hydraulic
[00:01:38.255]prob cores can be comparable
[00:01:40.107]to those obtained using clod from soil pit
[00:01:44.117]we were also trying to determine
[00:01:46.027]how large the core needs to be
[00:01:47.716]to generate valid results
[00:01:49.107]and if the results from the
[00:01:50.822]different methods are comparable
[00:01:52.514]because this will provide
[00:01:54.249]greater flexibility in sampling methods
[00:01:58.509]the samples were collected from 2 sites
[00:02:00.762]that were a part of
[00:02:01.708]soil judging regional competitions
[00:02:03.355]south of Aurora, NE
[00:02:05.734]the soil sampled
[00:02:06.834]were all mollisols
[00:02:08.217]which has a very dark brown
[00:02:10.355]to black surface horizon.
[00:02:12.759]mollisols usually formed
[00:02:14.269]under grass in
[00:02:15.337]moderate climate.
[00:02:17.844]this picture is an example
[00:02:19.414]of a soil profile
[00:02:20.584]and it was taken
[00:02:21.484]on one of the sites.
[00:02:25.574]three types of sampling methods
[00:02:27.494]were utilized
[00:02:28.623]the first one by directly extracting
[00:02:30.563]soil clod from the pit
[00:02:32.544]the second one by using 5.1 cm core
[00:02:36.190]and the third one by using 8.9 cm core
[00:02:40.002]these are the computer-generated samples
[00:02:42.162]of the soil clods with
[00:02:43.278]their respective methods
[00:02:46.142]the three-dimensional laser scanner
[00:02:48.326]was used to scan the clods
[00:02:49.901]and accurately measure its volume
[00:02:52.095]it is a new alternative to
[00:02:53.685]traditional soil analysis method
[00:02:55.997]it is also a non-destructive method
[00:02:58.286]which preserves the samples
[00:03:00.023]for future use
[00:03:04.324]because the value of bulk density
[00:03:06.282]affects soil porosity
[00:03:07.760]these illustrations describes
[00:03:09.596]how it looks like
[00:03:10.648]under the surface
[00:03:12.655]porous soil will have
[00:03:14.084]lower bulk density that allows
[00:03:16.161]water and air movement
[00:03:18.506]while compacted soil with
[00:03:20.117]high bulk density will block
[00:03:22.088]the movement of air and water
[00:03:24.285]in the soil because of its compaction
[00:03:28.389]the core sampling utilizes hydraulic probe
[00:03:31.105]to collect soil and these also includes
[00:03:34.921]the interaggregate pores inside
[00:03:37.607]although it created compactions
[00:03:39.543]around the edges of the clod
[00:03:42.633]the clod from the pit method utilizes
[00:03:44.837]an open pit of soil profile
[00:03:46.710]and the clod sample was directly collected
[00:03:50.580]from the soil pit
[00:03:52.168]leaving out the interaggregate pores
[00:03:57.801]62% of our terrestrial carbon pools
[00:04:00.917]are stored in our soil,
[00:04:02.354]21% on the atmosphere
[00:04:04.494]and 17% in the plants
[00:04:07.641]we will need bulk density values
[00:04:09.662]to measure this 62%
[00:04:11.446]of the carbon pool
[00:04:13.196]therefore, the methods used to measure
[00:04:15.176]bulk density are critical to the accuracy
[00:04:17.216]of carbon stock calculation
[00:04:19.074]because the core sampler size used on
[00:04:21.324]bulk density might affect
[00:04:22.824]the mass estimates of soil organic carbon
[00:04:29.086]the data were analyzed using
[00:04:30.776]PROC GLIMMIX in SAS
[00:04:32.276]and graphed using R studios
[00:04:34.838]it was found that there was
[00:04:36.188]no significant effect of method
[00:04:38.289]on the bulk density values calculated
[00:04:40.539]for both dry and moist samples
[00:04:42.400]in the different horizon level
[00:04:44.139]this means the different methods
[00:04:45.789]apply in this study will give
[00:04:47.249]similar values for the bulk densities
[00:04:49.062]for both dry and moist samples
[00:04:52.993]In conclusion,
[00:04:54.263]there is no significant difference
[00:04:55.937]between bulk density measured using
[00:04:57.821]clod extracted from hydraulic probed cores
[00:05:00.479]compared to those obtained using
[00:05:02.209]clods from the soil pits
[00:05:04.643]However,
[00:05:05.573]the core size used in this study
[00:05:07.481]to extract the clod were limited
[00:05:09.351]between 5.1 cm and 8.9 cm cores
[00:05:14.254]and the soil sampled were
[00:05:15.714]all non-gravel mollisols
[00:05:17.665]so different soils and core size
[00:05:19.555]might yield different results.
[00:05:22.850]Thank You!

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The Impact of Sampling Methodology on Soil Bulk Density Measurement by the Clod Method

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