Soil bulk density is defined as the ratio of the mass of dry solids to the bulk volume of the soil occupied by those dry solids. Bulk density of the soil is an important site characterization parameter since it changes for a given soil. It varies with structural condition of the soil, particularly that related to packing.
The Soil Bulk Density Data Set contains bulk density of the soil based on dry weight at two depths, 0-10 cm and 10-20 cm. Samples were collected at 31 different locations within the FIFE study area during the growing season of 1987. Samples were collected primarily in the northwest quadrant of the study area but at least one sitegrid is located in each of the quadrants of the study area.
Soil Bulk Density Data (FIFE).
The Soil Bulk Density Data Set contains bulk density of the soil based on dry weight at two depths, 0-10 cm and 10-20 cm. Samples were collected at 31 different locations within the FIFE study area during the growing season of 1987.
Obtain and calculate measures of soil bulk density.
Soil density at a specific depth.
Bulk density of the soil based on dry weight is available in this data set at two depths, 0-10 cm and 10-20 cm. Samples were collected at 31 different locations within the FIFE study area during the growing season of 1987 (April - October). Samples were collected primarily in the northwest quadrant of the study area but at least one sitegrid is located in each of the quadrants of the study area. Bulk density of the soil is an important site characterization parameter since it changes for a given soil. It varies with structural condition of the soil, particularly that related to packing.
Staff Science Soils Data Acquisition Program.
Dr. Alan K. Nelson
NASA Goddard Sp. Fl. Ctr.
The Bulk Soil Density data were produced by the Evapotranspiration Laboratory, Kansas State University staff. The dedicated efforts of Dr. A.K. Nelson in preparing these data is particularly appreciated.
Soil bulk density is defined as the ratio of the mass of dry solids to the bulk volume of the soil occupied by those dry solids. The bulk volume includes the volume of the solids and the pore space. Bulk density is needed for converting water percentage by weight to content by volume, for calculating porosity and void ratio when the particle density is known, and for estimating the weight of a volume of soil too large to weigh conveniently.
Two different cylindrical metal samplers were used for collecting soil samples to determine soil moisture. The larger (4.86 cm diameter) volumetric sampler was deemed to sufficiently maintain the structure of its samples of soil that the volume of the sampler could be assumed to be the volume of the samples collected with that sampler. A smaller, circa 2-cm diameter sampler (used in rocky soils and when the soils were too dry to penetrate with the volumetric sampler) was deemed to be inappropriate for bulk density measurements because the structure of the collected sample was not maintained and the volume of the sampler was not necessarily the same as the volume of the collected sample.
At several stations, where the soils were very rocky or gravely, measurements specifically for bulk density were collected one, two, or three times during the FIFE study. Such sampling required a trowel, plastic bags to line the excavated hole, water to pour into the plastic bag, and a graduated cylinder to determine the volume of water in the bag.
Other apparatus include soil containers with tight-fitting lids, a drying oven with means for controlling the temperature from 100 to 110 degrees Celsius and a balance for weighing the samples.
Determination of soil bulk density.
Dry weight bulk density at two depths.
Soil bulk density is defined as the ratio of the dry wet weight of soil, to the volume of the soil.
Samples were obtained with a 4.86-cm diameter soil sampler.
2205 Lee Street
Evanston, IL 60202.
A cylindrical metal sampler was pressed or driven into the soil to the desired depth and carefully removed to preserve a known volume of sample as it existed in situ. Samples were taken from the 0-5 cm and 5-10 cm depths. The total sample (approximately 100-150 grams) was put into a tin sample can and sealed with plastic electrical tape. Each sample can was identified by the sample site ID code. After sampling, the cans were opened and weighed to obtain the wet weight. Open cans were placed in ovens at 105 degrees Celsius for a minimum of 24 hours for drying, then they were weighed again to obtain the dry weight.
Bulk density measurements were also made (in gravely soils) in the field using a fixed ring to establish a datum and a water displacement method. A plastic bag was inserted into the cavity of the ring. A graduated cylinder was filled with water and the volume recorded. Water was then poured into the plastic bag until the cavity of the ring was filled to level. The volume of water remaining in the graduated cylinder was recorded. The bag with the water in it was carefully removed, taking care not to spill the water or rip the bag. Soil was excavated from the ring cavity to a depth of 5 cm and placed into the sample can(s). All loose soil was removed from the cavity. The bag (with the initial volume of water) was replaced into the cavity and additional water was added until the cavity of the ring was again filled to level. The volume of water remaining in the graduated cylinder was again recorded. The difference between the two recorded graduated cylinder readings is the volume of the soil sample. The bag was again removed, soil excavated to a depth of 10 cm, the bag re-placed and re-filled, and a measure of the volume of the sample between the 5-cm and 10-cm depths calculated. The soil samples were then dried in an oven at 105 degrees C for 24 hours. The dried samples were then weighed and the weight of the can was subtracted to get the dry soil weight.
The FIFE study area, with areal extent of 15 km by 15 km, is located south of the Tuttle Reservoir and Kansas River, and about 10 km from Manhattan, Kansas, USA. The northwest corner of the area has UTM coordinates of 4,334,000 Northing and 705,000 Easting in UTM Zone 14.
Soil bulk density data were collected at the following locations within the FIFE study area:
SITEGRID STN_ID NORTHING EASTING LATITUDE LONGITUDE ELEV -------- ------ -------- ------- --------- --------- ----- 2731-SBD 1 4328625 711102 39 04 59 -96 33 34 446 1916-SBD 2 4330296 708270 39 05 56 -96 35 30 340 2428-SBD 3 4329265 710635 39 05 20 -96 33 53 415 2731-SBD 4 4328678 711110 39 05 01 -96 33 34 446 2123-SBD 5 4329866 709506 39 05 41 -96 34 39 405 2132-SBD 6 4329774 711336 39 05 36 -96 33 23 405 3221-SBD 7 4327682 709112 39 04 30 -96 34 58 410 3129-SBD 8 4327702 710711 39 04 30 -96 33 51 430 3921-SBD 9 4326116 709185 39 03 39 -96 34 57 415 3414-SBD 10 4327286 707854 39 04 19 -96 35 51 410 4439-SBD 11 4325219 712795 39 03 07 -96 32 27 445 2915-SBD 12 4328167 708028 39 04 47 -96 35 42 415 6735-SBD 13 4320652 712073 39 00 40 -96 33 03 385 2516-SBD 14 4328956 708102 39 05 12 -96 35 38 405 5926-SBD 15 4322227 710270 39 01 32 -96 34 16 370 4609-SBD 17 4324766 706700 39 02 58 -96 36 41 398 6912-SBD 19 4320178 707307 39 00 29 -96 36 21 385 6340-SBD 20 4321484 713000 39 01 06 -96 32 23 410 8639-SBD 21 4316771 712827 38 58 33 -96 32 36 440 6469-SBD 23 4321189 718752 39 00 51 -96 28 25 440 4168-SBD 25 4325704 718646 39 03 18 -96 28 24 438 1563-SBD 27 4331067 717658 39 06 12 -96 28 59 350 6943-SBD 28 4320147 713500 39 00 22 -96 32 04 415 0847-SBD 29 4332344 714439 39 06 57 -96 31 11 418 2139-SBD 31 4329843 712789 39 05 37 -96 32 23 385 3479-SBD 34 4327134 720890 39 04 02 -96 26 49 420 2655-SBD 36 4328787 716070 39 05 00 -96 30 07 367 1478-SBD 38 4331216 720603 39 06 15 -96 26 56 350 1246-SBD 40 4331666 714212 39 06 35 -96 31 21 365 1445-SBD 42 4331160 714090 39 06 19 -96 31 27 400 2043-SBD 44 4330003 713536 39 05 42 -96 31 51 415
These are averages for replicate measurements of 25 samples, 5 samples taken at each of 5 locations within a sitegrid. These samples were taken at the center of the station and at the North, South, East and West corners of each station, approximately 30 meters from the center. The horizontal resolution with this sampling regime is therefore about 60 meters. At one station (11) samples were taken anywhere from 60 - 150 meters from the center of the site giving a resolution of 120 to 300 meters.
Vertical resolution varied with depth. It was 5 cm from 0 - 10 of depth and 10 cm from 10 - 20 of depth.
Soil samples were collected from late spring through the fall of 1987, during the four Intensive Field Campaigns (IFC). The campaigns ran during the growing season (April - Oct.), each ran for approximately two weeks.
All soil-moisture samples with a dry weight of greater than 65 grams were used to calculate the bulk density for each location within the FIFE study area (see the Calculations Section).
The SQL definition for this table is found in the SOILDENS.TDF file located on the CD-ROM Volume 1.
Parameter/Variable Description Range Units Source
SITEGRID_ID This is a FIS grid location code. Site grid codes (SSEE-III) give the south (SS) and the east (EE) cell number in a 100 x 100 array of 200 m square cells. The last 3 characters (III) are an instrument identifier.
STATION_ID The station ID designating the location of the observations.
DEPTH The depth at which the [mm] measurements were taken.
NUM_OBS The number of observations used to calculate the SOIL_DENSITY and SOIL_DENSITY_SDEV at this depth.
SOIL_BULK_DENSITY The Soil Bulk Density at this [grams] depth. [cm^-3]
SOIL_BULK_DENSITY_SDEV The standard deviation of the [grams] Soil Bulk Density at this depth. [cm^-3]
FIFE_DATA_CRTFCN_CODE The FIFE Certification Code for * the data, in the following format: CPI (Certified by PI), CPI-??? (CPI - questionable data).
LAST_REVISION_DATE data, in the format (DD-MMM-YY).
The primary certification codes are: EXM Example or Test data (not for release). PRE Preliminary (unchecked, use at your own risk). CPI Checked by Principal Investigator (reviewed for quality) CGR Checked by a group and reconciled (data comparisons and cross-checks).
The certification code modifiers are: PRE-NFP Preliminary - Not for publication, at the request of investigator. CPI-MRG PAMS data that are "merged" from two separate receiving stations to eliminate transmission errors. CPI-??? Investigator thinks data item may be questionable.
SITEGRID_ID STATION_ID DEPTH NUM_OBS SOIL_BULK_DENSITY ----------- ---------- ----- ------- ----------------- 1563-SBD 27 25 5 1.27 1563-SBD 27 75 5 1.17 4168-SBD 25 25 145 1.04 4168-SBD 25 75 145 1.12 SOIL_BULK_DENSITY_SDEV FIFE_DATA_CRTFCN_CODE LAST_REVISION_DATE ---------------------- --------------------- ------------------ .25 CPI 05-NOV-93 .13 CPI 05-NOV-93 .14 CPI 05-NOV-93 .16 CPI 05-NOV-93
The horizontal resolution is about 60 meters. At one station the resolution was between 120 to 300 meters. Vertical resolution varied with depth. It was 5 cm from 0 - 10 of depth and 10 cm from 10 - 20 of depth. All soil-moisture samples with a dry weight of greater than 65 grams were used to calculate the bulk density for each location within the FIFE study area
A general description of data granularity as it applies to the IMS appears in the EOSDIS Glossary.
The CD-ROM file format consists of numerical and character fields of varying length separated by commas. The character fields are enclosed with a single apostrophe. There are no spaces between the fields. Each file begins with five header records. Header records contain the following information: Record 1 Name of this file, its table name, number of records in this file, path and name of the document that describes the data in this file, and name of principal investigator for these data. Record 2 Path and filename of the previous data set, and path and filename of the next data set. (Path and filenames for files that contain another set of data taken at the same site on the same day.) Record 3 Path and filename of the previous site, and path and filename of the next site. (Path and filenames for files of the same data set taken on the same day for the previous and next sites (sequentially numbered by SITEGRID_ID)). Record 4 Path and filename of the previous date, and path and filename of the next date. (Path and filenames for files of the same data set taken at the same site for the previous and next date.) Record 5 Column names for the data within the file, delimited by commas. Record 6 Data records begin.
Each field represents one of the attributes listed in the chart in the Data Characteristics Section and described in detail in the TDF file. These fields are in the same order as in the chart.
Bulk densities were calculated in the following manner: Any dry gravimetric soil samples collected during the summer of 1987, which weighed more than 65 grams, were assumed to have been collected with the volumetric sampler (i.e., volume = 92.92 cubic centimeters). The bulk density for each of these samples was calculated according to the following formula:
A mean of all bulk density determinations at a given site-depth was calculated. The number of determinations and the standard deviation of the mean bulk density are also reported.
See the Calculations Section.
The soil at Stations 7, 27, and 31 (Sitegrid IDs 3221, 1563 and 2139, respectively) proved too rocky to use the volumetric soil probe. These stations were sampled on two or three different occasions through the summer by hand. The volume of the sample was determined by lining the hole with a plastic bag and measuring the volume of water needed to fill the bag to the level of the surrounding surface. The bulk densities were then calculated using the following formula:
In general, the soil samples used for calculating bulk density were in fact collected for the purposes of gravimetric water content. Thus, there will be some errors due to a non-volumetric sample: if driven too deep, the corer would compact the soil giving a too-high estimate of bulk density; while if not driven to the hilt, the soil sample would not fill the corer giving a too-low estimate of the bulk density. Compression may occur in dry soils if they are very loose. In dry or hard soils, hammering the sampler into the soil often shatters the sample, and the structure of the soil in situ is destroyed during sampling. Ironically, those bulk density measurements calculated on only two or three samples would be most accurate in methodology (plastic-bag technique rather than soil corer) but were only undertaken at sites where the variability of the soils could lead to large errors in the estimate of a mean bulk density.
The use of soil-moisture samples in the calculation of bulk density allowed a much greater sample size than any study undertaken just for bulk density. The ravages of collecting 210 samples daily may have lead to some non-representative sampling. However, the soils crew was by-and-large a conscientious group and the large number of samples should dilute the errors introduced by problems encountered during sampling. The samples collected with the plastic-bag technique were meticulously carried out; variability in these small samples sizes is attributable to the variability in the soils.
No quantitative assessment was made, see the Confidence Level/Accuracy Judgment Section.
FIS staff applied a general Quality Assessment (QA) procedure to the data to identify inconsistencies and problems for potential users. As a general procedure, the FIS QA consisted of examining the maximum, minimum, average, and standard deviation for each numerical field in the data table. An attempt was made to find an explanation for unexpected high or low values, values outside of the normal physical range for a variable, or standard deviations that appeared inconsistent with the mean. In some cases, histograms were examined to determine whether outliers were consistent with the shape of the data distribution.
The discrepancies, which were identified, are reported as problems in the Known Problems with the Data Section.
The data verification performed by the ORNL DAAC deals with the quality of the data format, media, and readability. The ORNL DAAC does not make an assessment of the quality of the data itself except during the course of performing other QA procedures as described below.
The FIFE data were transferred to the ORNL DAAC via CD-ROM. These CD-ROMs are distributed by the ORNL DAAC unmodified as a set or in individual volumes, as requested. In addition, the DAAC has incorporated each of the 98 FIFE tabular datasets from the CD-ROMs into its online data holdings. Incorporation of these data involved the following steps:
Each distinct type of data (i.e. "data set" on the CD-ROM), is accompanied by a documentation file (i.e., .doc file) and a data format/structure definition file (i.e., .tdf file). The data format files on the CD-ROM are Oracle SQL commands (e.g., "create table") that can be used to set up a relational database table structure. This file provides column/variable names, character/numeric type, length, and format, and labels/comments. These SQL commands were converted to SAS code and were used to create SAS data sets and subsequently to input data files directly from the CD-ROM into a SAS dataset. During this process, file names and directory paths were captured and metadata was extracted to the extent possible electronically. No files were found to be corrupted or unreadable during the conversion process.
Additional Quality Assurance procedures were performed as follows:
As errors are discovered in the online tabular data by investigators, users, or DAAC staff, corrections are made in cooperation with the principal investigators. These corrections are then distributed to users. CD-ROM data are corrected when re-mastering occurs for replenishment of CD-ROM stock.
This data set could be used in conjunction with other soil moisture data to validate the soil moisture values predicted by the airborne remote sensing instruments during FIFE. It could be used with caution in similar prairie landscapes to compare remote sensing derived soil moisture and field measured soil moisture.
Bulk densities for Station 11 were provided by Sashi Verma, (402) 472-3679.
This data set could be used in conjunction with other soil moisture data to validate the soil moisture values predicted by the airborne remote sensing instruments during FIFE.
The FIFE field campaigns were held in 1987 and 1989 and there are no plans for new data collection. Field work continues near the FIFE site at the Long-Term Ecological Research (LTER) Network Konza research site (i.e., LTER continues to monitor the site). The FIFE investigators are continuing to analyze and model the data from the field campaigns to produce new data products.
Software to access the data set is available on the all volumes of the FIFE CD-ROM set. For a detailed description of the available software see the Software Description Document.
ORNL DAAC User Services
Oak Ridge National Laboratory
Telephone: (865) 241-3952
FAX: (865) 574-4665
ORNL Distributed Active Archive Center
Oak Ridge National Laboratory
Telephone: (865) 241-3952
FAX: (865) 574-4665
Users may place requests by telephone, electronic mail, or FAX. Data is also available via the World Wide Web at http://daac.ornl.gov.
FIFE data are available from the ORNL DAAC. Please contact the ORNL DAAC User Services Office for the most current information about these data.
The Soil Bulk Density data are available on FIFE CD-ROM Volume 1. The CD-ROM file name is as follows:
Gardner, W.H. 1986. Water content. p.635-662. In: A. Klute (ed.) Methods of Soil Analysis. Part 1. Physical and mineralogical methods, 2nd ed. Agronomy Monogr. 9. ASA and SSSA, Madison, WI.
Engman, E.T., W. Kustas, T.J. Schmugge, and J.R. Wang. 1987. Relationship among the remotely sensed soil moisture, streamflow, and evapotranspiration. AGU Fall Meeting, San Francisco.
Contact the EOS Distributed Active Archive Center (DAAC) at Oak Ridge National Laboratory (ORNL), Oak Ridge, Tennessee (see the Data Center Identification Section). Documentation about using the archive and/or online access to the data at the ORNL DAAC is not available at this revision.
A general glossary for the DAAC is located at Glossary.
A general list of acronyms for the DAAC is available at Acronyms.
April 26, 1994 (citation revised on October 15, 2002).
Warning: This document has not been checked by the FIFE Information Scientist for technical or editorial accuracy. There may be inconsistencies with other documents, technical or editorial errors that were inadvertently introduced when the document was compiled, or references to preliminary data that were not included on the final CD-ROM.
Previous versions of this document have been reviewed by the Principal Investigator, the person who transmitted the data to FIS, a FIS staff member, or a FIFE scientist generally familiar with the data.
June 26, 1996.
Nelson, A. K. 1994. Soil Bulk Density Data (FIFE). Data set. Available on-line [http://www.daac.ornl.gov] from Oak Ridge National Laboratory Distributed Active Archive Center, Oak Ridge, Tennessee, U.S.A. doi:10.3334/ORNLDAAC/104. Also published in D. E. Strebel, D. R. Landis, K. F. Huemmrich, and B. W. Meeson (eds.), Collected Data of the First ISLSCP Field Experiment, Vol. 1: Surface Observations and Non-Image Data Sets. CD-ROM. National Aeronautics and Space Administration, Goddard Space Flight Center, Greenbelt, Maryland, U.S.A. (available from http://www.daac.ornl.gov).