HomeMy WebLinkAbout20182994.tiff USDA United States A product of the National Custom S Resource
--ia Department of Cooperative Soil Survey,
Agriculture a joint effort of the United Report for
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Resources Agricultural Experiment Colorado5
Conservation Stations , and local
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Preface
Soil surveys contain information that affects land use planning in survey areas.
They highlight soil limitations that affect various land uses and provide information
about the properties of the soils in the survey areas . Soil surveys are designed for
many different users , including farmers , ranchers , foresters , agronomists , urban
planners , community officials , engineers , developers , builders , and home buyers .
Also, conservationists , teachers , students , and specialists in recreation , waste
disposal , and pollution control can use the surveys to help them understand ,
protect, or enhance the environment.
Various land use regulations of Federal , State , and local governments may impose
special restrictions on land use or land treatment. Soil surveys identify soil
properties that are used in making various land use or land treatment decisions .
The information is intended to help the land users identify and reduce the effects of
soil limitations on various land uses . The landowner or user is responsible for
identifying and complying with existing laws and regulations .
Although soil survey information can be used for general farm , local , and wider area
planning , onsite investigation is needed to supplement this information in some
cases . Examples include soil quality assessments (http://www. nres. usda .gavlwpsl
portal/n reslm ain/so i l sf health/) and certain conservation and engineering
applications . For more detailed information , contact your local USDA Service Center
(https ://offices .sc. egov. usda .govllacatorlapp?agency=arcs) or your N RCS State Soil
Scientist (http ://www. nres .0 sda.gov/wps/portal/nresfd etail/soils/contactu sl?
cid =nres142p2_053951 ).
Great differences in soil properties can occur within short distances . Some soils are
seasonally wet or subject to flooding . Some are too unstable to be used as a
foundation for buildings or roads . Clayey or wet soils are poorly suited to use as
septic tank absorption fields . A high water table makes a soil poorly suited to
basements or underground installations .
The National Cooperative Soil Survey is a joint effort of the United States
Department of Agriculture and other Federal agencies, State agencies including the
Agricultural Experiment Stations, and local agencies . The Natural Resources
Conservation Service (NRCS) has leadership for the Federal part of the National
Cooperative Soil Survey.
Information about soils is updated periodically. Updated information is available
through the N RCS Web Soil Survey, the site for official soil survey information .
The U . S. Department of Agriculture (USDA) prohibits discrimination in all its
programs and activities on the basis of race, color, national origin , age, disability,
and where applicable , sex, marital status , familial status , parental status , religion ,
sexual orientation , genetic information , political beliefs , reprisal , or because all or a
part of an individual's income is derived from any public assistance program . (Not
all prohibited bases apply to all programs . ) Persons with disabilities who require
2
alternative means for communication of program information (Braille, large print,
audiotape, etc.) should contact USDA's TARGET Center at (202) 720-2600 (voice
and TDD ) . To file a complaint of discrimination , write to USDA, Director, Office of
Civil Rights , 1400 Independence Avenue , S .W. , Washington , D . C . 20250-9410 or
call (800) 795-3272 (voice) or (202) 720-6382 (TDD). USDA is an equal opportunity
provider and employer.
3
Contents
Preface 2
How Soil Surveys Are Made 5
Soil Map 8
Soil Map 9
Legend 10
Map Unit Legend 11
Map Unit Descriptions 11
Weld County, Colorado, Southern Part 13
1 —Altvan loam , 0 to 1 percent slopes 13
Soil Information for All Uses 15
Soil Reports 15
Soil Chemical Properties 15
Chemical Soil Properties 15
Soil Health 18
Soil Health - Aggregate Stability (West US) 18
Soil Health - Bulk Density and Texture 21
Soil Health - Organic Matter 23
Soil Physical Properties 27
Engineering Properties 27
Fragments on the Soil Surface 31
Particle Size and Coarse Fragments 33
Physical Soil Properties 35
Soil Qualities and Features 39
Soil Features 39
Water Management 42
Irrigation - Surface 42
References 45
4
■
How Soil Surveys
Soil surveys are made to provide information about the soils and miscellaneous
areas in a specific area . They include a description of the soils and miscellaneous
areas and their location on the landscape and tables that show soil properties and
limitations affecting various uses . Soil scientists observed the steepness , length ,
and shape of the slopes ; the general pattern of drainage; the kinds of crops and
native plants ; and the kinds of bedrock . They observed and described many soil
profiles . A soil profile is the sequence of natural layers , or horizons , in a soil . The
profile extends from the surface down into the unconsolidated material in which the
soil formed or from the surface down to bedrock. The unconsolidated material is
devoid of roots and other living organisms and has not been changed by other
biological activity.
Currently, soils are mapped according to the boundaries of major land resource
areas ( MLRAs). MLRAs are geographically associated land resource units that
share common characteristics related to physiography, geology, climate , water
resources , soils , biological resources , and land uses (USDA, 2006). Soil survey
areas typically consist of parts of one or more MLRA.
The soils and miscellaneous areas in a survey area occur in an orderly pattern that
is related to the geology, landforms, relief, climate , and natural vegetation of the
area . Each kind of soil and miscellaneous area is associated with a particular kind
of landform or with a segment of the landform . By observing the soils and
miscellaneous areas in the survey area and relating their position to specific
segments of the landform , a soil scientist develops a concept, or model , of how they
were formed . Thus , during mapping , this model enables the soil scientist to predict
with a considerable degree of accuracy the kind of soil or miscellaneous area at a
specific location on the landscape .
Commonly, individual soils on the landscape merge into one another as their
characteristics gradually change. To construct an accurate soil map, however, soil
scientists must determine the boundaries between the soils. They can observe only
a limited number of soil profiles . Nevertheless , these observations , supplemented
by an understanding of the soil-vegetation-landscape relationship , are sufficient to
verify predictions of the kinds of soil in an area and to determine the boundaries .
Soil scientists recorded the characteristics of the soil profiles that they studied . They
noted soil color, texture , size and shape of soil aggregates , kind and amount of rock
fragments , distribution of plant roots , reaction , and other features that enable them
to identify soils. After describing the soils in the survey area and determining their
properties , the soil scientists assigned the soils to taxonomic classes (units).
Taxonomic classes are concepts . Each taxonomic class has a set of soil
characteristics with precisely defined limits . The classes are used as a basis for
comparison to classify soils systematically. Soil taxonomy, the system of taxonomic
classification used in the United States , is based mainly on the kind and character
of soil properties and the arrangement of horizons within the profile . After the soil
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Custom Soil Resource Report
scientists classified and named the soils in the survey area, they compared the
individual soils with similar soils in the same taxonomic class in other areas so that
they could confirm data and assemble additional data based on experience and
research .
The objective of soil mapping is not to delineate pure map unit components; the
objective is to separate the landscape into landforms or landform segments that
have similar use and management requirements . Each map unit is defined by a
unique combination of soil components and/or miscellaneous areas in predictable
proportions . Some components may be highly contrasting to the other components
of the map unit. The presence of minor components in a map unit in no way
diminishes the usefulness or accuracy of the data . The delineation of such
landforms and landform segments on the map provides sufficient information for the
development of resource plans . If intensive use of small areas is planned , onsite
investigation is needed to define and locate the soils and miscellaneous areas .
Soil scientists make many field observations in the process of producing a soil map.
The frequency of observation is dependent upon several factors , including scale of
mapping , intensity of mapping , design of map units , complexity of the landscape,
and experience of the soil scientist. Observations are made to test and refine the
soil-landscape model and predictions and to verify the classification of the soils at
specific locations . Once the soil-landscape model is refined , a significantly smaller
number of measurements of individual soil properties are made and recorded .
These measurements may include field measurements , such as those for color,
depth to bedrock, and texture , and laboratory measurements , such as those for
content of sand , silt, clay, salt, and other components. Properties of each soil
typically vary from one point to another across the landscape.
Observations for map unit components are aggregated to develop ranges of
characteristics for the components. The aggregated values are presented . Direct
measurements do not exist for every property presented for every map unit
component. Values for some properties are estimated from combinations of other
properties .
While a soil survey is in progress , samples of some of the soils in the area generally
are collected for laboratory analyses and for engineering tests . Soil scientists
interpret the data from these analyses and tests as well as the field-observed
characteristics and the soil properties to determine the expected behavior of the
soils under different uses . Interpretations for all of the soils are field tested through
observation of the soils in different uses and under different levels of management.
Some interpretations are modified to fit local conditions , and some new
interpretations are developed to meet local needs . Data are assembled from other
sources, such as research information , production records , and field experience of
specialists . For example, data on crop yields under defined levels of management
are assembled from farm records and from field or plot experiments on the same
kinds of soil .
Predictions about soil behavior are based not only on soil properties but also on
such variables as climate and biological activity. Soil conditions are predictable over
long periods of time , but they are not predictable from year to year. For example ,
soil scientists can predict with a fairly high degree of accuracy that a given soil will
have a high water table within certain depths in most years, but they cannot predict
that a high water table will always be at a specific level in the soil on a specific date.
After soil scientists located and identified the significant natural bodies of soil in the
survey area, they drew the boundaries of these bodies on aerial photographs and
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Custom Soil Resource Report
identified each as a specific map unit. Aerial photographs show trees, buildings ,
fields , roads , and rivers , all of which help in locating boundaries accurately.
7
Soil Map
The soil map section includes the soil map for the defined area of interest, a list of
soil map units on the map and extent of each map unit, and cartographic symbols
displayed on the map. Also presented are various metadata about data used to
produce the map , and a description of each soil map unit.
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Custom Soil Resource Report
Soil Map
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Map projection: Web Mercator Corner coordinates: WG584 Edge tics: UTM Zone 13N WGS84
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Custom Soil Resource Report
MAP LEGEND MAP INFORMATION
Area of Interest (AOl) IN Spoil Area The soil surveys that comprise your AOI were mapped at
Area of Interest (AOI) 1 :24,000.
Stony Spot
Soils Very Stony Spot
Soil Map Unit Polygons Warning : Soil Map may not be valid at this scale..
V. Wet Spot
Lj Soil Map Unit Lines
Other Enlargement of maps beyond the scale of mapping can cause
Soil Map Unit Points misunderstanding of the detail of mapping and accuracy of soil
Special Line Features line placement. The maps do not show the small areas of
Special Point Features contrasting soils that could have been shown at a more detailed
lull Blowout Water Features scale.
Streams and Canals
r4 Borrow Pit
Transportation Please rely on the bar scale on each map sheet for map
Clay Spot
Rails measurements .
Closed Depression
Interstate Highways
Source of Map: Natural Resources Conservation Service
FX Gravel Pit US Routes Web Soil Survey URL:
Gravelly Spot Coordinate System : Web Mercator (EPSG :3857)
Major Roads
Landfill Local Roads Maps from the Web Soil Survey are based on the Web Mercator
ss. Lava Flow projection, which preserves direction and shape but distorts
Background distance and area. A projection that preserves area, such as the
Marsh or swamp 1 Aerial Photography Albers equal-area conic projection , should be used if more
* Mine or Quarry accurate calculations of distance or area are required .
Miscellaneous Water This product is generated from the USDA-NRCS certified data as
Perennial Water of the version date(s) listed below.
Rock Outcrop Soil Survey Area: Weld County, Colorado, Southern Part
Saline Spot Survey Area Data: Version 16, Oct 10, 2017
. 4.0 Sandy Spot
9 0 Soil map units are labeled (as space allows) for map scales
,e Severely Eroded Spot 1 :50,000 or larger.
Sinkhole Date(s) aerial images were photographed : Sep 20, 2015—Oct
31, Slide or Slip 15, 2016
Sodic Spot The orthophoto or other base map on which the soil lines were
compiled and digitized probably differs from the background
imagery displayed on these maps . As a result, some minor
shifting of map unit boundaries may be evident.
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Custom Soil Resource Report
Map Unit Legend
Map Unit Symbol Map Unit Name Acres in Aol Percent of AOI
1 Altman loam, 0 to 1 percent 123 100 .0%
slopes
Totals for Area of Interest 12.3 100 .0%
Map Unit Descriptions
The map units delineated on the detailed soil maps in a soil survey represent the
soils or miscellaneous areas in the survey area . The map unit descriptions , along
with the maps , can be used to determine the composition and properties of a unit.
A map unit delineation on a soil map represents an area dominated by one or more
major kinds of soil or miscellaneous areas . A map unit is identified and named
according to the taxonomic classification of the dominant soils . Within a taxonomic
class there are precisely defined limits for the properties of the soils . On the
landscape , however, the soils are natural phenomena, and they have the
characteristic variability of all natural phenomena . Thus , the range of some
observed properties may extend beyond the limits defined for a taxonomic class .
Areas of soils of a single taxonomic class rarely, if ever, can be mapped without
including areas of other taxonomic classes . Consequently, every map unit is made
u p of the soils or miscellaneous areas for which it is named and some minor
components that belong to taxonomic classes other than those of the major soils .
Most minor soils have properties similar to those of the dominant soil or soils in the
map unit, and thus they do not affect use and management. These are called
n on contrasting , or similar, components . They may or may not be mentioned in a
particular map unit description . Other minor components, however, have properties
and behavioral characteristics divergent enough to affect use or to require different
management. These are called contrasting , or dissimilar, components. They
generally are in small areas and could not be mapped separately because of the
scale used . Some small areas of strongly contrasting soils or miscellaneous areas
are identified by a special symbol on the maps . If included in the database for a
given area , the contrasting minor components are identified in the map unit
descriptions along with some characteristics of each . A few areas of minor
components may not have been observed , and consequently they are not
mentioned in the descriptions, especially where the pattern was so complex that it
was impractical to make enough observations to identify all the soils and
miscellaneous areas on the landscape .
The presence of minor components in a map unit in no way diminishes the
u sefulness or accuracy of the data. The objective of mapping is not to delineate
pure taxonomic classes but rather to separate the landscape into landforms or
landform segments that have similar use and management requirements. The
delineation of such segments on the map provides sufficient information for the
development of resource plans . If intensive use of small areas is planned , however,
onsite investigation is needed to define and locate the soils and miscellaneous
areas .
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Custom Soil Resource Report
An identifying symbol precedes the map unit name in the map unit descriptions .
Each description includes general facts about the unit and gives important soil
properties and qualities.
Soils that have profiles that are almost alike make up a soil series. Except for
differences in texture of the surface layer, all the soils of a series have major
horizons that are similar in composition , thickness , and arrangement.
Soils of one series can differ in texture of the surface layer, slope , stoniness ,
salinity, degree of erosion , and other characteristics that affect their use. On the
basis of such differences, a soil series is divided into soil phases. Most of the areas
shown on the detailed soil maps are phases of soil series . The name of a soil phase
commonly indicates a feature that affects use or management. For example, Alpha
silt loam , 0 to 2 percent slopes, is a phase of the Alpha series .
Some map units are made up of two or more major soils or miscellaneous areas .
These map units are complexes , associations , or undifferentiated groups .
A complex consists of two or more soils or miscellaneous areas in such an intricate
pattern or in such small areas that they cannot be shown separately on the maps .
The pattern and proportion of the soils or miscellaneous areas are somewhat similar
in all areas . Alpha-Beta complex, 0 to 6 percent slopes , is an example .
An association is made up of two or more geographically associated soils or
miscellaneous areas that are shown as one unit on the maps . Because of present
or anticipated uses of the map units in the survey area, it was not considered
practical or necessary to map the soils or miscellaneous areas separately. The
pattern and relative proportion of the soils or miscellaneous areas are somewhat
similar. Alpha- Beta association , 0 to 2 percent slopes , is an example .
An undifferentiated group is made up of two or more soils or miscellaneous areas
that could be mapped individually► but are mapped as one unit because similar
interpretations can be made for use and management. The pattern and proportion
of the soils or miscellaneous areas in a mapped area are not uniform . An area can
be made up of only one of the major soils or miscellaneous areas , or it can be made
up of all of them . Alpha and Beta soils , 0 to 2 percent slopes , is an example .
Some surveys include miscellaneous areas. Such areas have little or no soil
material and support little or no vegetation . Rock outcrop is an example .
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Custom Soil Resource Report
Weld County, Colorado , Southern Part
.1 ---Altvan loam, 0 to 1 percent slopes
Map Unit Setting
National map unit symbol: 361j
Elevation: 4,500 to 4,900 feet
Mean annual precipitation: 14 to 16 inches
Mean annual air temperature: 46 to 48 degrees F
Frost-free period: 130 to 150 days
Farmland classification: Not prime farmland
Map Unit Composition
Altvan and similar soils: 90 percent
Minor components: 10 percent
Estimates are based on observations, descriptions, and transects of the mapunit.
Description of Itvan
Setting
Landform: Terraces
Down-slope shape: Linear
Across-slope shape: Linear
Parent material: Old alluvium
Typical profile
H1 - 0 to 10 inches: loam
H2 - 10 to 25 inches: clay loam
H - 25 to 60 inches: gravelly sand
Properties and qualities
Slope: 0 to 1 percent
Depth to restrictive feature: More than 80 inches
Natural drainage class: Well drained
Runoff class: Low
Capacity of the most limiting layer to transmit water 'Ksat).: Moderately high to
high (0 .20 to 2 . 00 inlhr)
Depth to water table: More than 80 inches
Frequency of flooding: None
Frequency of ponding: None
Calcium carbonate, maximum in profile: 5 percent
Available water storage in profile: Low (about 5 . 7 inches )
Interpretive groups
Land capability classification ('irrigated): 3s
Land capability classification ('nonirrigated): 4e
Hydrologic Soil Group: B
Ecological site: Loamy Plains ( R067BY002CO)
Hydric soil rating: No
Minor Components
Cascajo
Percent of map unit: 9 percent
Hydric soil rating: No
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Custom Soil Resource Report
Aquic haplustolls
Percent of map unit 1 percent
Landform: Swales
1-1 ydric soil rating: Yes
14
Soil Information for All Uses
Soil Reports
The Soil Reports section includes various formatted tabular and narrative reports
(tables) containing data for each selected soil map unit and each component of
each unit. No aggregation of data has occurred as is done in reports in the Soil
Properties and Qualities and Suitabilities and Limitations sections .
The reports contain soil interpretive information as well as basic soil properties and
qualities . A description of each report (table) is included .
Soil Chemical Properties
This folder contains a collection of tabular reports that present soil chemical
properties . The reports (tables) include all selected map units and components for
each map unit. Soil chemical properties are measured or inferred from direct
observations in the field or laboratory. Examples of soil chemical properties include
pH , cation exchange capacity, calcium carbonate , gypsum , and electrical
conductivity.
Chemical Soil Properties
This table shows estimates of some chemical characteristics and features that
affect soil behavior. These estimates are given for the layers of each soil in the
survey area. The estimates are based on field observations and on test data for
these and similar soils.
Depth to the upper and lower boundaries of each layer is indicated .
Cation-exchange capacity is the total amount of extractable cations that can be held
by the soil , expressed in terms of milliequivalents per 100 grams of soil at neutrality
(pH 7. 0) or at some other stated pH value. Soils having a low cation-exchange
capacity hold fewer cations and may require more frequent applications of fertilizer
than soils having a high cation-exchange capacity. The ability to retain cations
reduces the hazard of ground-water pollution .
Effective cation-exchange capacity refers to the sum of extractable cations plus
aluminum expressed in terms of milliequivalents per 100 grams of soil . It is
determined for soils that have pH of less than 5 .5 .
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Custom Soil Resource Report
Soil reaction is a measure of acidity or alkalinity. It is important in selecting crops
and other plants, in evaluating soil amendments for fertility and stabilization , and in
determining the risk of corrosion .
Calcium carbonate equivalent is the percent of carbonates , by weight, in the fraction
of the soil less than 2 millimeters in size. The availability of plant nutrients is
influenced by the amount of carbonates in the soil .
Gypsum is expressed as a percent, by weight, of hydrated calcium sulfates in the
fraction of the soil less than 20 millimeters in size . Gypsum is partially soluble in
water. Soils that have a high content of gypsum may collapse if the gypsum is
removed by percolating water.
Salinity is a measure of soluble salts in the soil at saturation . It is expressed as the
electrical conductivity of the saturation extract, in millimhos per centimeter at 25
degrees C . Estimates are based on field and laboratory► measurements at
representative sites of nonirrigated soils . The salinity of irrigated soils is affected by
the quality of the irrigation water and by the frequency of water application . Hence ,
the salinity of soils in individual fields can differ greatly from the value given in the
table. Salinity affects the suitability of a soil for crop production , the stability of soil if
used as construction material , and the potential of the soil to corrode metal and
concrete .
Sodium adsorption ratio (SAR) is a measure of the amount of sodium (Na) relative
to calcium (Ca) and magnesium (Mg) in the water extract from saturated soil paste.
It is the ratio of the Na concentration divided by the square root of one-half of the
Ca +- Mg concentration . Soils that have SAR values of 13 or more may be
characterized by an increased dispersion of organic matter and clay particles ,
reduced saturated hydraulic conductivity and aeration , and a general degradation of
soil structure .
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Custom Soil Resource Report
Chemical Soil Properties—Weld County, Colorado, Southern Part
Map symbol and soil name Depth Cation- Effective Soil reaction Calcium Gypsum Salinity Sodium
exchange cation- carbonate adsorption
capacity exchange ratio
capacity
In meq/100g meq/100g pH Pa Pct. mmhrs/cm
1—Altvan loam, 0 to 1 percent
slopes
Altvan 0-10 10-20 — 6.6-7.8 0 0 0 0
10-25 10-25 — 6.6-7.8 0 0 0 0
25-60 0.0-5 .0 — 7.4-8.4 1 -5 0 0 0
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Custom Soil Resource Report
Soil Health
Soil health , also referred to as soil quality►, is defined as the continued capacity of
soil to function as a vital living ecosystem that sustains plants , animals , and
humans . This folder contains the tabular reports that provide the information specific
to the education and importance of managing soils so they► are sustainable for future
generations .
Soil Health - Aggregate Stability (West US)
Definition of that is Estimated
Aggregate stability is defined as the stability► of macroaggregates ( 1 -2 mm in size)
against flowing water and is expressed as percent stable aggregates of the less
than 2mm fraction . It is estimated from the organic matter content, total clay, and
sodium adsorption ratio . Aggregate stability values are provided for horizons within
the upper 6 inches , but not for sandy and organic surface layers.
Significance
Soil aggregate stability is an important soil property affecting soil health and crop
production . It is important for stabilizing soil structure, increasing water infiltration ,
and reducing erosion .
Soil aggregates are the smallest unit of soil structure . They are composed of
decaying particulate organic matter, clay particles , microbial products , and fine
roots . Aggregates are generally divided into macroaggregates (greater than 250
pm) and microaggregates (less than 250 pm) . The size, strength , and stability of
aggregates depend upon the stabilizing agents involved . They can be classified as
temporary, transient, or persistent. Improved aggregate stability leads to increased
water infiltration and storage in the profile, reduced erosion , and soil structure that is
resistant to compaction . Increases in soil organic carbon improves aggregation and
aggregate stability, which protect carbon compounds enmeshed in the aggregates
from decomposition , leading to carbon sequestration .
Factors Affecting Soil Aggregation and Aggregate Stability
Inherent Factors - Microaggregation is generally considered to be an inherent
property of the soil . Persistent binding agents include highly decomposed , high
molecular weight organic materials (e.g . , humic compounds), polymers , and
polyvalent cations (e.g . , calcium , aluminum , iron ) that have a heterogeneous , non-
specific structure . These agents are associated with microaggregation as well as
soil organic carbon (SOC ) sequestration . These persistent compounds are found in
the interior of aggregates , forming organo-mineral complexes via the polyvalent
cations . These agents are long-lasting , and the degree of aggregation formed by
them is considered part of the inherent soil properties . Generally, management does
not impact soil microaggregation . Soils naturally high in clay and polyvalent cations
are likely to form more microaggregates .
Dynamic Factors - Transient binding agents consist mainly of complex
carbohydrates , or polysaccharides , and organic mucilages . As plant residues and
compounds extruded by plant roots decompose, bacteria release mucilages that are
complex carbon-rich carbohydrates . These carbohydrates serve as binding agents,
or "glues ," to which clay particles can be adsorbed and bound together. The
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Custom Soil Resource Report
polysaccharides are non-humic compounds of high molecular weight and comprise
about 20 to 25% of the soil humus . They are critical for binding microaggregates
together, via polymer and polyvalent cation bridges , to form larger
macroaggregates . Although binding with clay particles does provide some
protection against decomposition , these binding agents generally decompose within
a few weeks and need to be continually renewed through actively growing plants ,
decaying residues , or organic amendments .
Temporary binding agents consist of plant roots , especially fine roots and root hairs ,
fungal hyphae , and bacterial and algal cells . These agents develop along with plant
roots , forming a network that entangles mineral particles , through adsorption, to
form macroaggregates . As roots cease to grow, the amount of these temporary
agents is reduced . Planting cover crops or perennial plants maintains living roots
longer in the soil , thus maintaining and strengthening the aggregates . Tillage
reduces the amount of roots and the microbial biomass, especially in the surface
horizon .
Consequences of Weak Aggregates
The first step in erosion is the breakdown of surface aggregates . Aggregates at the
soil surface are weakened if the binding agents degrade at rates exceeding
replenishment rates . These aggregates can be broken apart by outside forces , of
which raindrops , wind , and tillage are among the most important. Changes in soil
chemistry, such as increased sod i city of the soil , can also contribute to aggregate
breakdown . As aggregates are broken down , the component particles clog the
surface pores and surface sealing and crusting follow. This process results in.
reduced water infiltration , ponding , increased runoff and erosion , and sediment
transport on and off site . Its occurrence can be minimized by strengthening
aggregates .
Additionally, reducing the size and strength of the aggregates throughout the profile
weakens soil structure so that it is more easily compacted by► field operations ,
especially if the soil is too wet. Poor structure can lead to ponding after rainstorms ,
which can result in increased evaporation and less water in the profile that might
otherwise have been available for crop growth .
Maintaining and increasing aggregation and aggregate strength can be
accomplished through the implementation of soil health management systems.
These systems may include reduced tillage operations (or preferably no tillage
operations) and the incorporation of cover crops or a cash crop (such as winter
wheat) into the rotation . Having crops and cover crops with varied rooting structures
improves soil structure, as does maintaining living roots in the soil as long as
possible. Studies have shown that plants will push into the rhizosphere , via the root
system , about 20% of the carbon dioxide is fixed through photosynthesis . Those
carbon compounds can support the soil microbial population , which is critical to soil
structure, water infiltration , and nutrient cycling . Any management system that leads
to increased soil organic carbon is likely to improve aggregate stability.
Measuring Aggregate Stability
Aggregate stability is determined by a wet sieving technique preceded by vacuum
saturation of the 1 -2 mm size aggregates as described in USDA-ARS ( 1966). Stable
aggregates are corrected for sand greater than 0.25 mm as follows : Aggregate
stability (% ) = ((wt. of stable aggregates and sand ) — (wt. of sand )}l((wt. of sample)
— (wt. of sand)).
References
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Custom Soil Resource Report
Blanco-Canqui, H . , and R. Lai . 2004 . 1 Mechanisms of carbon sequestration in soil
aggregates . Criti . Rev. Plant Sci . 23:481 -504 . dot 10 . 1080/07352680490886842
Cambardella , C .A. , and E.T. Elliott . 1993. Carbon and nitrogen distribution in
aggregates from cultivated and native grassland soils . Soil Sci . Soc . Am . J .
57: 1071 - 1076 . doi : 10 . 2136/sssaj 1993 .03615995005700040032x
Denef, K. , J . Six, H . Bossuyt, S. D . Frey, E .T. Elliott, R . Merckx, and K. Paustian .
2001 . Influence of dry-wet cycles on the interrelationship between aggregate,
particulate organic matter, and microbial community dynamics . Soil Biol . Biochem .
33: 1599- 1611 . dot 10 . 1016/50038- 0717(01 )00076- 1
Gale , W.J . , and C . A. Cambardella. 2000 . Carbon dynamics of surface residue- and
root-derived organic mater under simulated no-till . Soil Sci . Soc. Am . J .
64: 190- 195 . doi : 10 .2136/sssaj2000 . 641190x
Gale , W.J . , C . A. Cambardella, and T. B . Bailey. 2000a . Root-derived carbon and the
formation and stabilization of aggregates. Soil Sci . Soc . Am . J . 64 :201 -207 . doi :
10.2136/sssaj2000.641201 x
Gale , W.J . , C . A. Cambardella, and T. B . Bailey. 2000b. Surface residue- and root-
derived carbon in stable and unstable aggregates . Soil Sci . Soc . Am . J . 64 : 196-201 .
doi : 10 .2136/sssaj2000 . 641196x
s aj2 000 . 64119 6x
Martin , J . P. 1971 . Decomposition and binding action of polysaccharides in soil . Soil
Biol . Biochem . 3 : 33-41 .
Six, J . , E . T. Elliott, and K. Paustian . 1999 . Aggregate and soil organic matter
dynamics under conventional and no-tillage systems . Soil Sci . Soc. Am . J .
63: 1350- 1358 .
Six, J . , K. Paustian, E.T. Elliott, and C . Combrink . 2000. Soil structure and organic
matter: I . Distribution of aggregate-size classes and aggregate-associated carbon .
Soil Sci . Soc . Am . J . 64 : 681 -689 .
Tisdall , J . M . , and J . M . Oades . 1982 . Organic matter and water-stable aggregates in
soil . J . Soil Sci . 33 : 141 - 163.
USDA-ARS . 1966. Aggregate stability of soils from western United States and
Canada . Tech . Bull . No . 1355 . Agricultural Research Service , United States
Department of Agriculture in cooperation with Colorado Agricultural Experiment
Station . U . S. Govn't Printing Office . Washington , D . C .
Report—Soil Health - Aggregate Stability (West US )
Soil Health - Aggregate Stability (West US)-Weld County, Colorado, Southern Part
Map symbol and soil Pct. of map Horizon Depth Aggregate Aggregate Aggregate
name unit Name (inches) Stability low Stability RV ( Pct) Stability high
(Pct) (Pct)
1 —Altvan loam, 0 to 1
percent slopes
Altvan 90 H1 0-10 58 66 72
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Soil Health - Bulk Density and Texture
Bulk density is a physical soil property measured by the ratio of dry weight of soil to
its volume.
Significance
Bulk density is one of several soil properties frequently used as a measure of soil
health (Volchko,ko, et al . , 2014) and is an indicator for soil compaction and root
restriction . Even though bulk density varies with soil texture, it is a dynamic soil
property that changes based on soil management with different soil cover, amount
of organic matter, soil structure, and porosity ( USDA, 2008). It influences water
movement in the soil , root growth and penetration and seed germination . Some of
the practices that can improve bulk density include increasing organic matter
content, reducing soil disturbance when the soil is wet, and maintaining soil surface
protection with a cover crop , especially multi-species that can provide a wide range
of root penetration .
Bulk density influences plant growth and engineering applications . Within a family
level particle-size class , bulk density is an indicator of how well plant roots are able
to extend into the soil . Bulk density is used to calculate porosity. Bulk density at a
water tension of 1 /3 bar (33 kPa) is used for soil classification in the required
characteristics for andic soil properties and in the criteria for Andic, Aquandic, and
Vitrandic is subgroups .
Factors Affecting Bulk Density
Inherent - Bulk density is dependent on soil texture and the densities of soil mineral
(sand , silt, and clay) and organic matter particles , as well as their packing
arrangement. Generally, loose , porous soils and those rich in organic matter have
lower bulk density. Sandy soils have relatively high bulk density since total pore
space in sands is less than that of silt or clay soils . Finer-textured soils that have
good structure , such as silt loams and clay loams, have higher pore space and
lower bulk density compared to sandy soils .
General relationship of soil bulk density to root growth based on soil texture
Soil Texture Ideal bulk densities for plant growth (g/ Bulk densities that restrict root growth
cm3) (g/cm3)
Sandy Less than 1 .60 More than 1 .80
Loamy Less than 1 .40 More than 1 .65
Clayey Less than 1 . 10 More than 1 .47
Dynamic - Bulk density is changed by crop and land management practices that
affect soil cover, organic matter, soil structure , and/or porosity. Cultivation can result
in compacted soil layers with increased bulk density. Livestock as well as the use of
agricultural and construction equipment exert pressure that compacts the soil and
reduces porosity, especially on wet soils . Freeze-thaw action in the soil can lead to
lowered bulk density.
Database Entries
Methods: In general , there are two broad groupings of bulk density methods . One
group is for soil materials coherent enough that a field sample can be removed , and
the other group is for soils that are too fragile to remove a sample and therefore an
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excavation operation must be performed . In the former group, there are clod
methods in which the sample has an undefined volume and is coated and then the
volume is determined by submergence. Also under the former there are various
methods in which a cylinder of known volume is obtained of soil sufficiently coherent
that it remains in the cylinder. The detailed procedures are outlined in Soil Survey
Investigations Report No. 42 , Soil Survey Laboratory Methods Manual , Version 5. 0 ,
November 2014 , USDA, NRCS .
Bulk density, one-third bar is the oven-dried weight of the less than 2 millimeter soil
material per unit volume of soil at a water tension of 1 /3 bar (33 kPa) . The bulk
density of each soil horizon is expressed in grams per cubic centimeter of soil
material . Three columns represent the low, representative value (RV), and high
values expected in the soil horizon .
Bulk density is used to convert the results of other soil measurements from a weight
to a volume basis .
Texture is given in the standard terms used by the U . S . Department of Agriculture .
These terms are defined according to percentages of sand , silt, and clay in the
fraction of the soil that is less than 2 millimeters in diameter. " Loam ," for example, is
soil that is 7 to 27 percent clay, 28 to 50 percent silt, and less than 52 percent sand .
If the content of particles coarser than sand is 15 percent or more, an appropriate
modifier is added , for example, "gravelly." The representative texture of each
horizon is displayed .
References:
Soil Survey Staff. 2014 . Kellogg Soil Survey Laboratory Methods Manual . Soil
Survey Investigations Report No . 42 , Version 5 . 0. R. Burt and Soil Survey Staff
(ed . ). U . S. Department of Agriculture, Natural Resources Conservation Service .
United State Department of Agriculture, Natural Resources Conservation Service.
2008 . Soil Quality Indicators — Bulk Density.
Volchko Y, Norrman J , Rosen , and Norberg T. 2014 . A minimum data set for
evaluation the ecological soil functions in remediation projects . J Soils Sediments
14: 1850- 1860 .
Report oil Health Bulk Density and Texture
Soil Health - Bulk Density and Texture—Weld County, Colorado, Southern Part
Map symbol and Pct. of Horizon Depth USDA texture - RV Bulk density Bulk density Bulk density
soil name map unit name (inches) 1 /3 bar low 1 /3 bar RV 1 /3 bar high
(glc m3) (g/cm3) (g/cm3)
1—Altvan loam, 0 to
1 percent slopes
Altvan 90 H1 0-10 Loam 1 .25 1 .33 1 .40
H2 10-25 Clay loam 1 .25 1 .33 1 .40
H3 25-60 Gravelly sand 1 .45 1 .53 1 .60
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Soil Health - Organic Matter
Organic matter percent is the weight of decomposed plant, animal , and microbial
residues exclusive of non-decomposed plant and animal residues . It is expressed
as a percentage, by weight, of the soil material that is less than 2 mm in diameter.
Significance
Soil organic matter (SOM) influences the physical , chemical , and biological
properties of soils far more than suggested by its relatively small proportion in most
soils . The organic fraction influences plant growth through its influence on these soil
properties . It encourages soil aggregation , especially macroaggregation , increases
porosity, and lowers bulk density. Because the soil structure is improved , water
infiltration rates increase. SOM has a high capacity to adsorb and exchange cations
and is important to pesticide binding . It furnishes energy to microorganisms in the
soil . As SOM is decomposed by soil microbes , it releases nitrogen , phosphorous ,
sulfur, and many micronutrients , which become available for plant growth . SOM is a
heterogeneous , dynamic substance that varies in particle size, carbon content,
decomposition rate , and turnover time. In general , the content of SOM is highest at
the surface where plant, animal , and microbial residue inputs are greatest and
decreases with depth .
Total organic carbon (TOC) is the carbon (C) stored in SOM . Total organic carbon is
also referred to as soil organic carbon (SOC) in the scientific literature. Organic
carbon enters the soil through the decomposition of plant and animal residues , root
exudates , and living and dead microorganisms . Inorganic carbon is common in
calcareous soils in the form of calcium and magnesium carbonates . In calcareous
soils , the content of inorganic carbon can exceed TOC .
Factors Affecting Content of SOM and SOC
Inherent factors - Soil texture , parent material , drainage, climate , and time affect
accumulation of SOM . Soils that are rich in clay have greater capacity to protect
SOM from decomposition by stabilizing substances that bind to clay surfaces . The
formation of soil aggregates enabled by the presence of clay, aluminum and iron
oxides , fungal hyphae, bacterial exudates (carbohydrates) , and fine roots protects
SOM from microbial decomposition . Extractable aluminum and allophanes , which
are present in volcanic soils, can react with SOM to form compounds that are stable
and resist microbial decomposition . Warm temperatures increase decomposition
rates of SOM . High mean annual precipitation increases accumulation rates of SOM
by stimulating the production of plant biomass .
Loss of SOM through erosion results in SOM variations along slope gradients .
Areas of level topography tend to have much more SOM than areas with other
slope classes . Both elevation and topographic gradients affect local climate,
vegetation distribution, and soil properties . They also affect associated
biogeochemical processes , including SOM dynamics. Analysis of factors affecting C
in the conterminous United States indicates that the effects of land use, topography
(elevation and slope ), and mean annual precipitation on SOM are more obvious
than the effects of mean annual temperature. However, when other variables are
highly restricted , SOM content clearly declines with increasing temperature .
Dynamic factors - Dynamic gains and losses in SOM are due primarily to
management decisions in combination with climate and microbial influences .
Accumulation of SOM is controlled by the rate of C mineralization , the amount and
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stage of decomposition of plant residues, and the addition of organic amendments
to soil .
Soil organic carbon comprises approximately 52 to 58% of the SOM and is the main
source of energy for soil microorganisms . The C within plant residues , particulate
organic matter, and soil microbial biomass is generally considered to be within the
active pool of SOM (table 1 ) . The emergent view of SOM focuses on microbial
access to SOM and includes an emphasis on the need to manage C flows rather
than discrete C pools . During decomposition of SOM , energy and nutrients are
released and utilized by plant roots and soil biota . Recognizing that SOM is a
continuum of decomposition products is a first step in designing management
strategies for renewing SOM sources throughout the year.
Table 1-Soil Organic Matter Pools
soil organic matter fraction Particle size Description
Soil microbial biomass Variable The living pool of soil organic matter,
particularly bacteria and fungi
Plant residues >= 2.0 mm Recognizable plant shoots and roots
Particulate organic matter 0 .06 to 2 mm Partially decomposed plant material,
hyphae, seeds, etc.
Biochemically stable organic matter The ultimate stage of decomposition,
dominated by stable compounds
Soil aggregates of various sizes and stabilities can act as sites at which SOM is
physically protected from decomposition and C mineralization . Soil disturbance and
aggregate destruction increase biodegradation of SOM . Aggregates are readily
broken apart by tillage operations .
Crop residues incorporated into or left on the soil surface reduce erosion and the
losses of SOM associated with sediment. In acidic soils, applications of lime
increase plant productivity, microbial activity, organic matter decomposition , and
CO2 release.
The diversity of the soil microbial population affects SOM . For example , while soil
bacteria and some fungi participate in SOM loss by mineralizing C compounds ,
other fungi , such as mycorrhizae , facilitate stabilization and physical protection by
aggregating SOM with clay and minerals . SOM is better protected from degradation
within aggregates than in free-form .
Relationship to Soil Function
SOM is one of the most important soil constituents . It affects plant growth by
improving aggregate stability, soil structure , water availability, and nutrient cycling .
SOM fractions in the active pool , described above , are the main source of energy
and nutrients for soil microorganisms , which mediate nutrient cycling in the soil .
Biochemically stable SOM participates in aggregate stability and in holding capacity
for nutrients and water.
Microaggregates are formed by mineral interactions with iron and aluminum oxides
and are generally considered an inherent soil characteristic. They are , however,
impacted by current and past management. Fine roots , fungal hyphae, and organic
carbon compounds, such as complex sugars (carbohydrates) and proteins (also
referred to as glues), bind mineral particles and microaggregates together to form
macroaggregates that are still porous enough to allow air, water, and plant roots to
move through the soil .
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An increase in SOM leads to greater biological diversity and activity in the soil , thus
increasing biological control of plant diseases and pests .
Problems Associated with Low Organic Matter Levels
Low levels of SOM result in energy-source shortages and thereby lowered levels of
microbial biomass, activity, and nutrient mineralization . In noncalcareous soils ,
aggregate stability, infiltration , drainage, and airflow are also reduced . Scarcity of
SOM results in less diversity in soil biota and a risk of disruption to the food chain
equilibrium . This disruption can cause disturbance in the soil environment (e.g . ,
increased plant pests and diseases and accumulation of toxic substances) .
Improving SOM Levels
An estimated 4 .4x109 tons of C have been lost from soils of the United States due
to traditional farming practices . Most of this carbon was SOC . Nearly half of the
SOM has been lost from many agricultural soils . Other farming practices , such as
no-till and cover cropping (especially when used together), can stop losses of SOM
and even lead to increases . Continuous application of manure and compost can
increase SOM . Burning , harvesting , or otherwise removing plant residues
decreases SOM .
Measurement
SOM is measured in the laboratory by determining total carbon (TC) content using
either dry or wet-dry combustion . Current analytical methods do not distinguish
between decomposed and nondecomposed residues , so soil is first sieved to 2 mm
to remove as much of the recognizable plant material as possible. If no carbonates
are present, TO is considered to be the same as TOC (or SOC ). For calcareous
soils , soil inorganic carbon in the form carbonates must also be measured and then
subtracted from the TC to determine TOC content. Results are given as the percent
TOC in dry soil . To convert percent TOC to percent SOM , multiply the TOC
percentage by 1 . 724. To convert percent SOM to percent TOC , divide the SOM
percentage by 1 . 724. Note that this value continues to be debated by researchers
with possible values ranging from 1 .4 to 2 . 5 (Pribyl , 2010). A conversion factor of 2
has been suggested for this database but has not yet been adopted . Detailed
procedures for measurement of SOM are outlined in "Soil Survey Investigations
Report No . 42 , Kellogg Soil Survey Laboratory Methods Manual , version 5. 0," (Soil
Survey Staff, 2014) .
Many soil testing laboratories use a "loss on ignition" method to estimate soil
organic matter. The estimate produced by this method must be correlated to
analytical TOC measurements for each area to improve accuracy. The loss on
ignition method can provide a good indication of the trend in SOM content within a
field . It is important to note that temperature and timing used for the loss on ignition
approach vary across labs and can influence results. Thus , comparisons should be
made using only results from within a given lab.
Many soil testing laboratories use a "loss on ignition" method to estimate soil
organic matter. The estimate produced by this method must be correlated to
analytical TOC measurements for each area to improve accuracy. The loss on
ignition method can provide a good indication of the trend in SOM content within a
field . It is important to note that temperature and timing used for the loss on ignition
approach vary across labs and can influence results. Thus , comparisons should be
made using only results from within a given lab.
Currently, no standard method exists to measure TOC in the field . Attempts have
been made to develop charts that match color to TOC content, but the correlation is
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better within soil landscapes and only for limited soils . Near-infrared spectroscopy
has been tested for measuring C directly in the field , but it is expensive and
sensitive to moisture content.
Estimates
Color and feel are soil characteristics that can be used to estimate SOM content.
Color comparisons in areas of similar parent materials and textures can be
correlated with laboratory data and thereby enable a soil scientist to make field
estimates . In general , darker colors or black indicate the presence of higher
amounts of organic matter. The contrast of color between the A horizon and
subsurface horizons is also a good indicator. Sandy soils tend to look darker with a
lower content of SOM . In general , lower numbers for hue, value , and chroma (in the
Munsell soil color system) tend to be associated with darker soil colors that are
attributed to higher content of SOM , soil moisture , or both .
References
United States Department of Agriculture, Natural Resources Conservation Service.
National soil survey handbook, title 430-VI . (http://soils .usda .gov)
Edwards , J . H . , C .W. Wood , D . L. Thurlow, and M . E . Ruf. 1999 . Tillage and crop
rotation effects on fertility status of a Hapludalf soil . Soil Science Society of America
Journal 56 : 1577- 1582 .
Sikora, L .J . , and D . E . Stott. 1996 . Soil organic carbon and nitrogen . In : J .W. Doran
and A.J . Jones , editors , Methods for assessing soil quality. Madison , WI . p. 157-
167 .
Schulze, D .O . , J . L. Nagel , O . E. Van Scoyoc, T. L . Henderson , M . F. Baumgardner,
and D . E . Stott. 1993. Significance of organic matter in determining soil colors . In :
J . M . Bigham and E .J . Ciolkosz, editors , Soil color. Soil Science Society of America,
Madison , WI . p. 71 -90.
Soil Survey Staff. 2014. Kellogg Soil Survey Laboratory methods manual . Soil
Survey Investigations Report No . 42 , Version 5. 0. R. Burt and Soil Survey Staff
(ed . ). U . S. Department of Agriculture, Natural Resources Conservation Service.
Report Soil Health - Organic Matter
Soil Health - Organic Matter-Weld County, Colorado, Southern Part
Map symbol and soil Pct. of map Horizon Depth Organic matter Organic matter Organic matter
name unit Name (inches) low (Pct) RV (Pct) high (Pct)
1—Altvan loam, 0 to 1
percent slopes
Altvan 90 H 1 0-10 1 .0 1 .5 2.0
H2 10-25 0.5 0.8 1 .0
H3 25-60 0.0 0 .3 0.5
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Soil Physical Properties
This folder contains a collection of tabular reports that present soil physical
properties . The reports (tables) include all selected map units and components for
each map unit. Soil physical properties are measured or inferred from direct
observations in the field or laboratory. Examples of soil physical properties include
percent clay, organic matter, saturated hydraulic conductivity, available water
capacity, and bulk density.
Engineering Properties
This table gives the engineering classifications and the range of engineering
properties for the layers of each soil in the survey area .
Hydrologic soil group is a group of soils having similar runoff potential under similar
storm and cover conditions . The criteria for determining Hydrologic soil group is
found in the National Engineering Handbook, Chapter 7 issued May 2007(http://
directives .sc. egov. usda .gov/Open NonWebContent. aspx?content= 17757.wba).
Listing HSGs by soil map unit component and not by soil series is a new concept for
the engineers . Past engineering references contained lists of HSGs by soil series .
Soil series are continually being defined and redefined , and the list of soil series
names changes so frequently as to make the task of maintaining a single national
list virtually impossible. Therefore , the criteria is now used to calculate the HSG
using the component soil properties and no such national series lists will be
maintained . All such references are obsolete and their use should be discontinued .
Soil properties that influence runoff potential are those that influence the minimum
rate of infiltration for a bare soil after prolonged welling and when not frozen . These
properties are depth to a seasonal high water table , saturated hydraulic conductivity
after prolonged wetting , and depth to a layer with a very slow water transmission
rate. Changes in soil properties caused by land management or climate changes
also cause the hydrologic soil group to change . The influence of ground cover is
treated independently. There are four hydrologic soil groups , A, B, C , and D , and
three dual groups, AID , BID , and C/D . In the dual groups , the first letter is for
drained areas and the second letter is for undrained areas .
The four hydrologic soil groups are described in the following paragraphs :
Group A. Soils having a high infiltration rate (low runoff potential) when thoroughly
wet. These consist mainly of deep , well drained to excessively► drained sands or
gravelly sands . These soils have a high rate of water transmission .
Group B. Soils having a moderate infiltration rate when thoroughly wet. These
consist chiefly of moderately deep or deep , moderately well drained or well drained
soils that have moderately fine texture to moderately coarse texture . These soils
have a moderate rate of water transmission .
Group G. Soils having a slow infiltration rate when thoroughly wet. These consist
chiefly of soils having a layer that impedes the downward movement of water or
soils of moderately fine texture or fine texture. These soils have a slow rate of water
transmission .
Group D. Soils having a very slow infiltration rate (high runoff potential ) when
thoroughly wet. These consist chiefly of clays that have a high shrink-swell
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potential , soils that have a high water table, soils that have a claypan or clay layer at
or near the surface, and soils that are shallow over nearly impervious material .
These soils have a very slow rate of water transmission .
Depth to the upper and lower boundaries of each layer is indicated .
Texture is given in the standard terms used by the U . S . Department of Agriculture .
These terms are defined according to percentages of sand , silt, and clay in the
fraction of the soil that is less than 2 millimeters in diameter. " Loam ," for example, is
soil that is 7 to 27 percent clay, 28 to 50 percent silt, and less than 52 percent sand .
If the content of particles coarser than sand is 15 percent or more, an appropriate
modifier is added , for example, "gravelly. "
Classification of the soils is determined according to the Unified soil classification
system (ASTM , 2005) and the system adopted by the American Association of
State Highway and Transportation Officials (AASHTO , 2004).
The Unified system classifies soils according to properties that affect their use as
construction material . Soils are classified according to particle-size distribution of
the fraction less than 3 inches in diameter and according to plasticity index, liquid
limit, and organic matter content. Sandy and gravelly soils are identified as GW, GP,
GM , GC , SW, SP, SM , and SC ; silty and clayey soils as ML, CL, OL , MH , CH , and
OH ; and highly organic soils as PT. Soils exhibiting engineering properties of two
groups can have a dual classification , for example , CL-ML.
The AASHTO system classifies soils according to those properties that affect
roadway construction and maintenance. In this system , the fraction of a mineral soil
that is less than 3 inches in diameter is classified in one of seven groups from A- 1
through A-7 on the basis of particle-size distribution , liquid limit, and plasticity index.
Soils in group A- 1 are coarse grained and low in content of fines (silt and clay). At
the other extreme , soils in group A-7 are fine grained . Highly organic soils are
classified in group A-8 on the basis of visual inspection .
If laboratory data are available , the A- 1 , A-2 , and A-7 groups are further classified
as A- 1 -a, A- 1 -b , A-2-4 , A-2-5, A-2-6 , A-2-7, A-7-5, or A-7-6. As an additional
refinement, the suitability of a soil as subgrade material can be indicated by a group
index number. Group index numbers range from 0 for the best subgrade material to
20 or higher for the poorest.
Percentage of rock fragments larger than 10 inches in diameter and 3 to 10 inches
in diameter are indicated as a percentage of the total soil on a dry►-weight basis . The
percentages are estimates determined mainly by converting volume percentage in
the field to weight percentage. Three values are provided to identify the expected
Low (L), Representative Value (R), and High ( H ).
Percentage (of soil particles) passing designated sieves is the percentage of the soil
fraction less than 3 inches in diameter based on an ovendry weight. The sieves ,
numbers 4, 10 , 40, and 200 (USA Standard Series), have openings of 4. 76, 2 . 00,
0 .420 , and 0 .074 millimeters , respectively. Estimates are based on laboratory tests
of soils sampled in the survey area and in nearby areas and on estimates made in
the field . Three values are provided to identify the expected Low ( L), Representative
Value (R), and High (H ).
Liquid limit and plasticity index (Atterberg limits) indicate the plasticity
characteristics of a soil . The estimates are based on test data from the survey area
or from nearby areas and on field examination . Three values are provided to identify
the expected Low (L) , Representative Value ( R), and High (H ) .
References :
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American Association of State Highway and Transportation Officials (AASHTO).
2004. Standard specifications for transportation materials and methods of sampling
and testing . 24th edition.
American Society for Testing and Materials (ASTM). 2005. Standard classification of
soils for engineering purposes . ASTM Standard x2487-00 .
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Absence of an entry indicates that the data were not estimated . The asterisk '*' denotes the representative texture; other
possible textures follow the dash . The criteria for determining the hydrologic soil group for individual soil components is
found in the National Engineering Handbook, Chapter 7 issued May 2007(http : //directives. sc. egov. usda . gov/
OpenNonWebContent. aspx?content= 17757.wba). Three values are provided to identify the expected Low ( L),
Representative Value ( R), and High (H ).
Engineering Properties—Weld County, Colorado, Southern Part
Map unit symbol and Pct. of Hydrolo Depth USDA texture Classification Pct Fragments Percentage passing sieve number— Liquid Plasticit
soil name map gic limit y index
unit group Unified AASHTO >10 3-10 4 10 40 200
inches inches
In L -R-H L-R-H L-R-H L-R-H L-R-H L-R-H L-R-H L-R-I-
1 —Altvan loam, 0 to 1
percent slopes
Altvan 90 B 0-10 Loam CL, CL- A-4 0- 0- 0 0- 0- 0 100-100 100- 100 85-90- 60-68- 25-28 5-8 -10
ML -100 - 100 95 75 -30
10-25 Sandy clay loam, SC-SM, A-4, A-6 0- 0- 0 0- 0- 0 100-100 100- 100 80-90-1 35-58- 25-30 5-10-15
clay loam CL, CL- -100 - 100 00 80 -35
ML, SC
25-60 Gravelly coarse SP, SP- A- 1 0- 5- 10 0- 8- 15 60-70- 55-65- 25-38- 0- 5- 10 — NP
sand , gravelly SM 80 75 50
sand
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Fragments on the soil surface
This table provides information about fragments on the soil surface . Surface
fragments are unattached , cemented pieces of bedrock , bedrock-like material ,
durinodes , concretions , nodules, or pedogenic horizons (e .g ., petrocalcic fragments)
2 mm or larger in diameter and woody material 20 mm or larger in diameter that are
exposed at the surface of the soil . Surface fragments can be rock fragments,
pararock fragments, or wood fragments . Vegetal material other than wood
fragments, whether live or dead , is not included .
Pct. of map unit is the percent of the map unit comprised by the component.
Surface fragment cover percent is the percent of the soil surface covered by
fragments 2 mm or larger in diameter (20 mm or larger in diameter for wood
fragments).
Distance between fragments is the average distance between surface fragments,
measured between edges .
Fragment size is the size based on the multiaxial dimensions of the surface
fragment .
Flat fragment class Length of fragment (mm)
Channers 2 - 150
Flagstones 150 - 380
Stones 380 - 600
Boulders >= 600
Nonflat fragment class Diameter (mm)
Gravel 2 - 75
Cobbles 75 - 250
Stones 250 - 600
Boulders >= 600
Fragment kind is the litho logy or composition of the surface fragments 2 mm or
larger (20 mm or larger for wood fragments).
Fragment shape is a description of the overall shape of the surface fragment.
Fragment roundness is an expression of the sharpness of edges and corners of
surface fragments.
Fragment hardness is the hardness of the fragment . It is equivalent to the rupture
resistance cemented of a surface fragment that has been air-dried and then
submerged in water.
Reference :
United States Department of Agriculture, Natural Resources Conservation Service .
National soil survey handbook, title 430-VI . (https ://www. nres . usda . govlwpslportall
n resls itelso i l s/home!}
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Three values are provided to identify the expected Low (L) , Representative Value ( RV), and High (H ).
Fragments on the Soil Surface—Weld County, Colorado, Southern Part
Map symbol and soil Pct. of surface fragment Distance Fragment size Fragment kind Fragment Fragment Fragment
name map cover percent between shape roundness hardness
unit fragments
L-RV-H Meters (L-RV-H)j) Millimeters 'L -RV-!-I)
1—Altvan loam, 0 to "1
percent slopes
Altvan 90 — — — — — — —
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Custom Soil Resource Report
Particle Size and Coarse Fragments
This table shows estimates of particle size distribution and coarse fragment content
of each soil in the survey area. The estimates are based on field observations and
on test data for these and similar soils.
Depth to the upper and lower boundaries of each layer is indicated .
Particle size is the effective diameter of a soil particle as measured by
sedimentation , sieving , or micrometric methods . Particle sizes are expressed as
classes with specific effective diameter class limits . The broad classes are sand ,
silt, and clay, ranging from the larger to the smaller.
Sand as a soil separate consists of mineral soil particles that are 0 . 05 millimeter to 2
millimeters in diameter. In this table, the estimated sand content of each soil layer is
given as a percentage , by weight, of the soil material that is less than 2 millimeters
in diameter.
Silt as a soil separate consists of mineral soil particles that are 0 .002 to 0 .05
millimeter in diameter. In this table, the estimated silt content of each soil layer is
given as a percentage , by weight, of the soil material that is less than 2 millimeters
in diameter.
Clay as a soil separate consists of mineral soil particles that are less than 0. 002
millimeter in diameter. In this table, the estimated clay content of each soil layer is
given as a percentage , by weight, of the soil material that is less than 2 millimeters
in diameter.
The content of sand , silt, and clay affects the physical behavior of a soil . Particle
size is important for engineering and agronomic interpretations , for determination of
soil hydrologic qualities , and for soil classification .
The amount and kind of clay affect the fertility and physical condition of the soil and
the ability of the soil to adsorb cations and to retain moisture . They influence shrink-
swell potential , saturated hydraulic conductivity ( Ksat), plasticity, the ease of soil
dispersion , and other soil properties . The amount and kind of clay in a soil also
affect tillage and earthmoving operations .
Total fragments is the content of fragments of rock and other materials larger than 2
millimeters in diameter on volumetric basis of the whole soil .
Fragments 2-74 mm refers to the content of coarse fragments in the 2 to 74
millimeter size fraction .
Fragments 75-249 mm refers to the content of coarse fragments in teh 75 to 249
millimeter size fraction .
Fragments 250-599 mm refers to the content of coarse fragments in the 250 to 599
millimeter size fraction .
Fragments >=600 mm refers to the content of coarse fragments in the greater than
or equal to 600 millimeter size fraction .
Reference:
United States Department of Agriculture, Natural ResourcesConservation Service.
National soil survey handbook, title 430-VI . (http://soils . usda .gov)
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Custom Soil Resource Report
Particle Size and Coarse Fragments—Weld County, Colorado, Southern Part
Map symbol and Horizon Depth Sand Silt Clay Total fragments Fragments 2-74 Fragments 75-249 Fragments Fragments
soil name mm mm 250-599 mm >=600 mm
In L-RV-H L-RV-H L-RV-H Pct RV Pct RV Pct RV Pct RV Pct RV Pct
Pct Pct
1—Altvan loam, 0 to
1 percent slopes
Altvan H1 0- 10 -42- -38- 15-20- 25 — — — — —
H2 10-25 -35- -38- 20-28- 35 — — — — —
H 3 25-60 -96- - 2- 0- 3- 5 31 23 5 — 3
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Custom Soil Resource Report
Physical Soil Properties
This table shows estimates of some physical characteristics and features that affect
soil behavior. These estimates are given for the layers of each soil in the survey
area . The estimates are based on field observations and on test data for these and
similar soils .
Depth to the upper and lower boundaries of each layer is indicated .
Particle size is the effective diameter of a soil particle as measured by
sedimentation , sieving , or micrometric methods . Particle sizes are expressed as
classes with specific effective diameter class limits . The broad classes are sand ,
silt, and clay, ranging from the larger to the smaller.
Sand as a soil separate consists of mineral soil particles that are 0 . 05 millimeter to 2
millimeters in diameter. In this table, the estimated sand content of each soil layer is
given as a percentage , by weight, of the soil material that is less than 2 millimeters
in diameter.
Silt as a soil separate consists of mineral soil particles that are 0 .002 to 0 .05
millimeter in diameter. In this table, the estimated silt content of each soil layer is
given as a percentage , by weight, of the soil material that is less than 2 millimeters
in diameter.
Clay as a soil separate consists of mineral soil particles that are less than 0. 002
millimeter in diameter. In this table, the estimated clay content of each soil layer is
given as a percentage , by weight, of the soil material that is less than 2 millimeters
in diameter.
The content of sand , silt, and clay affects the physical behavior of a soil . Particle
size is important for engineering and agronomic interpretations , for determination of
soil hydrologic qualities , and for soil classification .
The amount and kind of clay affect the fertility and physical condition of the soil and
the ability of the soil to adsorb cations and to retain moisture . They influence shrink-
swell potential , saturated hydraulic conductivity ( Ksat), plasticity, the ease of soil
dispersion , and other soil properties . The amount and kind of clay in a soil also
affect tillage and earthmoving operations .
Moist bulk density is the weight of soil (ovendry) per unit volume. Volume is
measured when the soil is at field moisture capacity, that is , the moisture content at
1 /3- or 1 /10-bar (33kPa or 10kPa) moisture tension . Weight is determined after the
soil is dried at 105 degrees C . In the table , the estimated moist bulk density of each
soil horizon is expressed in grams per cubic centimeter of soil material that is less
than 2 millimeters in diameter. Bulk density data are used to compute linear
extensibility, shrink-swell potential , available water capacity, total pore space, and
other soil properties . The moist bulk density of a soil indicates the pore space
available for water and roots . Depending on soil texture , a bulk density of more than
1 .4 can restrict water storage and root penetration . Moist bulk density is influenced
by texture, kind of clay, content of organic matter, and soil structure .
Saturated hydraulic conductivity (Ksat) refers to the ease with which pores in a
saturated soil transmit water. The estimates in the table are expressed in terms of
micrometers per second . They are based on soil characteristics observed in the
field , particularly structure , porosity, and texture . Saturated hydraulic conductivity
(Ksat) is considered in the design of soil drainage systems and septic tank
absorption fields.
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Custom Soil Resource Report
Available water capacity refers to the quantity of water that the soil is capable of
storing for use by plants. The capacity for water storage is given in inches of water
per inch of soil for each soil layer. The capacity varies , depending on soil properties
that affect retention of water. The most important properties are the content of
organic matter, soil texture, bulk density, and soil structure. Available water capacity
is an important factor in the choice of plants or crops to be grown and in the design
and management of irrigation systems . Available water capacity is not an estimate
of the quantity of water actually available to plants at any given time .
Linear extensibility refers to the change in length of an unconfined clod as moisture
content is decreased from a moist to a dry state. It is an expression of the volume
change between the water content of the clod at 113- or 1 / 10-bar tension (33kPa or
10kPa tension) and oven dryness. The volume change is reported in the table as
percent change for the whole soil . The amount and type of clay minerals in the soil
influence volume change.
Linear extensibility is used to determine the shrink-swell potential of soils . The
shrink-swell potential is low if the soil has a linear extensibility of less than 3
percent; moderate if 3 to 6 percent; high if 6 to 9 percent; and very high if more than
9 percent. If the linear extensibility is more than 3 , shrinking and swelling can cause
damage to buildings , roads , and other structures and to plant roots . Special design
commonly is needed .
Organic matter is the plant and animal residue in the soil at various stages of
decomposition . In this table , the estimated content of organic matter is expressed
as a percentage, by weight, of the soil material that is less than 2 millimeters in
diameter. The content of organic matter in a soil can be maintained by returning
crop residue to the soil .
Organic matter has a positive effect on available water capacity, water infiltration ,
soil organism activity, and tilth . It is a source of nitrogen and other nutrients for
crops and soil organisms.
Erosion factors are shown in the table as the K factor (Kw and KU and the T factor.
Erosion factor K indicates the susceptibility of a soil to sheet and rill erosion by
water. Factor K is one of six factors used in the Universal Soil Loss Equation
(LISLE) and the Revised Universal Soil Loss Equation (RUSLE) to predict the
average annual rate of soil loss by sheet and rill erosion in tons per acre per year.
The estimates are based primarily on percentage of silt, sand , and organic matter
and on soil structure and Ksat. Values of K range from 0. 02 to 0. 69 . Other factors
being equal , the higher the value, the more susceptible the soil is to sheet and rill
erosion by water.
Erosion factor kw indicates the erodibility of the whole soil . The estimates are
modified by the presence of rock fragments .
Erosion factor Kf indicates the erodibility of the fine-earth fraction , or the material
less than 2 millimeters in size.
Erosion factor T is an estimate of the maximum average annual rate of soil erosion
by wind and/or water that can occur without affecting crop productivity over a
sustained period . The rate is in tons per acre per year.
Wind erodibility groups are made up of soils that have similar properties affecting
their susceptibility to wind erosion in cultivated areas . The soils assigned to group 1
are the most susceptible to wind erosion , and those assigned to group 8 are the
least susceptible . The groups are described in the " National Soil Survey Handbook. "
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Custom Soil Resource Report
Wind erod'ibility index is a numerical value indicating the susceptibility of soil to wind
erosion , or the tons per acre per year that can be expected to be lost to wind
erosion . There is a close correlation between wind erosion and the texture of the
surface layer, the size and durability of surface clods , rock fragments , organic
matter, and a calcareous reaction . Soil moisture and frozen soil layers also
influence wind erosion .
Reference:
United States Department of Agriculture, Natural Resources conservation Service.
National soil survey handbook, title 430-VI . (http://soils . usda .gov)
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Custom Soil Resource Report
Three values are provided to identify the expected Low (L) , Representative Value ( R) , and High (H ) .
Physical Soil Properties—Weld County, Colorado, Southern Part
Map symbol Depth Sand Silt Clay Moist Saturated Available Linear Organic Erosion Wind Wind
and soil name bulk hydraulic water extensibility matter factors erodibility erodibility
density conductivity capacity group index
Kw Kf T
In Pct Pct Pot glcc micro m/sec In/'In Pct Pct
1—Altvan loam,
0 to 1 percent
slopes
Altvan 0-10 -42- -38- 15-20- 25 1 .25- 1 .33- 4 .00-23 .00-42 .0 0. 14-0 . 16-0. 1 0 .0- 1 . 5- 2 .9 1 . 0- 1 .5- .28 .28 3 6 48
1 .40 oi 7 2 .0
10-25 -35- -38- 20-28- 35 1 .25- 1 .33- 1 .41 -8.00- 14 . 11 0 . 14-0 . 18-0. 2 0.0- 1 . 5- 2 .9 0. 5- 0 .3- .32 . 32
1 .40 1 1 .0
25-60 -96- - 2- 0- 3- 5 1 .45-1 .53- 141 . 00- 141 .00- 0 .02-0 .04-0. 0 0 .0- 1 . 5- 2 .9 0. 0- 0.3- .02 .05
1 .60 141 .00 6 0 .5
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Custom Soil Resource Report
Soil Qualities and Features
This folder contains tabular reports that present various soil qualities and features .
The reports (tables) include all selected map units and components for each map
u nit. Soil qualities are behavior and performance attributes that are not directly
measured , but are inferred from observations of dynamic conditions and from soil
properties . Example soil qualities include natural drainage, and frost action . Soil
features are attributes that are not directly part of the soil . Example soil features
include slope and depth to restrictive layer. These features can greatly impact the
u se and management of the soil .
Soil Features
This table gives estimates of various soil features . The estimates are used in land
u se planning that involves engineering considerations.
A restrictive layer is a nearly continuous layer that has one or more physical ,
chemical , or thermal properties that significantly impede the movement of water and
air through the soil or that restrict roots or otherwise provide an unfavorable root
environment. Examples are bedrock, cemented layers , dense layers , and frozen
layers . The table indicates the hardness and thickness of the restrictive layer, both
of which significantly affect the ease of excavation . Depth to top is the vertical
distance from the soil surface to the upper boundary of the restrictive layer.
Subsidence is the settlement of organic soils or of saturated mineral soils of very
low density. Subsidence generally results from either desiccation and shrinkage, or
oxidation of organic material , or both , following drainage . Subsidence takes place
gradually, usually over a period of several years . The table shows the expected
initial subsidence , which usually is a result of drainage , and total subsidence , which
results from a combination of factors .
Potential for frost action is the likelihood of upward or lateral expansion of the soil
caused by the formation of segregated ice lenses (frost heave) and the subsequent
collapse of the soil and loss of strength on thawing . Frost action occurs when.
moisture moves into the freezing zone of the soil . Temperature , texture , density,
saturated hydraulic conductivity ( Ks at) , content of organic matter, and depth to the
water table are the most important factors considered in evaluating the potential for
frost action . It is assumed that the soil is not insulated by vegetation or snow and is
not artificially drained . Silty and highly structured , clayey soils that have a high water
table in winter are the most susceptible to frost action . Well drained , very gravelly,
or very sandy soils are the least susceptible. Frost heave and low soil strength
during thawing cause damage to pavements and other rigid structures .
Risk of corrosion pertains to potential soil-induced electrochemical or chemical
action that corrodes or weakens uncoated steel or concrete. The rate of corrosion of
u ncoated steel is related to such factors as soil moisture, particle-size distribution ,
acidity, and electrical conductivity of the soil . The rate of corrosion of concrete is
based mainly on the sulfate and sodium content, texture , moisture content, and
acidity of the soil . Special site examination and design may be needed if the
combination of factors results in a severe hazard of corrosion . The steel or concrete
in installations that intersect soil boundaries or soil layers is more susceptible to
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Custom Soil Resource Report
corrosion than the steel or concrete in installations that are entirely within one kind
of soil or within one soil layer.
For uncoated steel, the risk of corrosion, expressed as low, moderate , or high, is
based on soil drainage class , total acidity, electrical resistivity near field capacity,
and electrical conductivity of the saturation extract.
For concrete , the risk of corrosion also is expressed as low, moderate , or high. It is
based on soil texture , acidity, and amount of sulfates in the saturation extract .
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Custom Soil Resource Report
Soil Features-Weld County, Colorado , Southern Part
Map symbol and Restrictive Layer Subsidence Potential for frost Risk of corrosion
soil name action
Kind Depth to Thickness Hardness Initial Total Uncoated steel concrete
top
Low-RV- Range Low- Low-
High High High
In In In In
1 —Altvan loam, 0
to 1 percent
slopes
Altvan — — 0 — Moderate Moderate Low
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Custom Soil Resource Report
Water Management
This folder contains a collection of tabular reports that present soil interpretations
related to water management. The reports (tables) include all selected map units
and components for each map unit, limiting features and interpretive ratings . Water
management interpretations are tools for evaluating the potential of the soil in the
application of various water management practices. Example interpretations include
pond reservoir area, embankments , dikes , levees , and excavated ponds.
Irrigation - surface
This table shows the degree and kind of soil limitations that affect irrigation systems
on mineral soils . The ratings are both verbal and numerical . Rating class terms
indicate the extent to which the soils are limited by all of the soil features that affect
these uses . Not limited indicates that the soil has features that are very favorable for
the specified use . Good performance and very low maintenance can be expected .
Somewhat limited indicates that the soil has features that are moderately favorable
for the specified use . The limitations can be overcome or minimized by special
planning , design , or installation . Fair performance and moderate maintenance can
be expected . Very limited indicates that the soil has one or more features that are
unfavorable for the specified use . The limitations generally cannot be overcome
without major soil reclamation , special design , or expensive installation procedures .
Poor performance and high maintenance can be expected .
Numerical ratings in the table indicate the severity of individual limitations . The
ratings are shown as decimal fractions ranging from 0. 01 to 1 . 00 . They indicate
gradations between the point at which a soil feature has the greatest negative
impact on the use ( 1 . 00 ) and the point at which the soil feature is not a limitation
(0 . 00).
Irrigation systems are used to provide supplemental water to crops, orchards ,
vineyards, and vegetables in area where natural precipitation will not support
desired production of crops being grown .
Irrigation, surface (graded) evaluates a soil for graded flood or furrow irrigation
systems . The ratings are for soils in their natural condition and do not consider
present land use . .
Graded surface irrigation systems include graded border and graded furrow
irrigation systems . Graded border irrigation systems allow irrigation water to flow
across the soil surface while being confined by borders . Graded furrow irrigation
systems are systems that allow irrigation water to flow down furrow valleys while the
crop being irrigated is planted on the furrow ridge . Generally, graded border
systems are suitable for small grains while graded furrow systems are suitable for
row crops .
The soil properties and qualities important in the design and management of graded
surface irrigation systems are depth , available water holding capacity, sodium
adsorption ratio , surface rocks , permeability, salinity, slope, wetness , and flooding .
Features that affect system performance and plant growth are salinity, sodium
adsorption ratio , wetness , calcium carbonate content, and available water holding
capacity. .
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Custom Soil Resource Report
Irrigation, surface (level) evaluates a soil for basin , paddy, level furrow, or level
border irrigation systems . The ratings are for soils in their natural condition and do
not consider present land use .
Level surface irrigation systems are irrigation systems that use flood irrigation
techniques to spread irrigation water at a specified depth across the application
area . Basin , paddy, and borders generally use external ridges or borders to confine
the irrigation application while level furrow systems use furrow valleys and end
blocks or border ridges to confine the irrigation application during irrigation . With
furrow irrigation the crop is usually planted on the furrow ridge . Generally, basin ,
paddy and level border irrigation systems are suitable for rice , small grain , pasture,
and forage production . Level furrow systems are generally suited for row crops .
The soil properties and qualities important in the design and management of level
surface irrigation systems are depth , available water holding capacity, sodium
adsorption ratio , permeability, salinity, slope , and flooding . The soil properties and
qualities that influence installation are depth , flooding , and ponding . The features
that affect performance of the system and plant growth are salinity, sodium
adsorption ratio , and available water holding capacity.
Information in this table is intended for land use planning , for evaluating land use
alternatives , and for planning site investigations prior to design and construction .
The information , however, has limitations . For example, estimates and other data
generally apply only to that part of the soil between the surface and a depth of 5 to 7
feet. Because of the map scale , small areas of different soils may be included within
the mapped areas of a specific soil .
The information is not site specific and does not eliminate the need for onsite
investigation of the soils or for testing and analysis by personnel experienced in the
design and construction of engineering works .
Government ordinances and regulations that restrict certain land uses or impose
specific design criteria were not considered in preparing the information in this table.
Local ordinances and regulations should be considered in planning , in site
selection , and in design . The irrigation interpretations are not designed or intended
to be used in a regulatory manner.
Report—Irrigation - Surface
[The information in this table provides irrigation interpretations for mineral soils .
Onsite investigation may be needed to validate the interpretations and to confirm
the identity of the soil on a given site. The numbers in the value columns range from
0 .01 to 1 . 00. The larger the value, the greater the potential limitation . The table
shows only the top five limitations for any given soil . The soil may have additional
limitations]
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Custom Soil Resource Report
Irrigation - Surface—Weld County, Colorado, Southern Part
Map symbol and soil name Pct. of Irrigation , Surface (graded) Irrigation, Surface ( level)
map unit
Rating class and limiting Value Rating class and limiting Value
features features
1—Altvan loam, 0 to 1 percent
slopes
Altvan 90 Very limited Very limited
Seepage 1 .00 Seepage 1 .00
Rapid water movement 0.55 Rapid water movement 0 .55
Low water holding capacity 0.23 Low water holding capacity 0 .23
44
References
American Association of State Highway and Transportation Officials (AASHTO) .
2004. Standard specifications for transportation materials and methods of sampling
and testing . 24th edition .
American Society for Testing and Materials (ASTM). 2005. Standard classification of
soils for engineering purposes . ASTM Standard D2487-00 .
Cowardin , L. M . , V. Carter, F. C . Golet, and E.T. LaRoe. 1979 . Classification of
wetlands and deep-water habitats of the United States . U .S . Fish and Wildlife
Service FWS/OBS-79/31 .
Federal Register. July 13, 1994 . Changes in hydric soils of the United States .
Federal Register. September 18 , 2002. Hydric soils of the United States .
Hurt, G .W. , and L . M . Vasilas , editors. Version 6 .0 , 2006. Field indicators of hydric
soils in the United States .
National Research Council . 1995. Wetlands : Characteristics and boundaries .
Soil Survey Division Staff. 1993. Soil survey manual . Soil Conservation Service .
U . S . Department of Agriculture Handbook 18. http://www. nres . usda.gov/wps/portal!
nres/detail/national/soils/?cid =nres142p2_054262
Soil Survey Staff. 1999. Soil taxonomy: A basic system of soil classification for
making and interpreting soil surveys . 2nd edition . Natural Resources Conservation
Service , U . S . Department of Agriculture Handbook 436 . http ://
www. arcs . usd a.gov/wps/portal/nres/detail/national/soils/?cid=n res 142p2_053577
Soil Survey Staff. 2010. Keys to soil taxonomy. 11th edition . U . S . Department of
Agriculture, Natural Resources Conservation Service. http://
www. arcs . usd a.gov/wps/portal/nres/detail/national/soils/?cid=n res 142p2_O5358O
Tiner, R .W. , Jr. 1985 . Wetlands of Delaware. U . S. Fish and Wildlife Service and
Delaware Department of Natural Resources and Environmental Control , Wetlands
Section .
United States Army Corps of Engineers , Environmental Laboratory. 1987 . Corps of
Engineers wetlands delineation manual . Waterways Experiment Station Technical
Report Y-87- 1 .
United States Department of Agriculture, Natural Resources Conservation Service.
National forestry manual . http://www. nres . usda.gov/wps/portal/nres/detail/soils/
home/?cid= arcs 142p2_O53374
United States Department of Agriculture, Natural Resources Conservation Service.
National range and pasture handbook. http ://www.nres . usda .gov/wps/portal/arcs/
detail/national/land u s e/rang ep astu re/?cid =stel p rd b 10430 84
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Custom Soil Resource Report
UnitedStates Department of Agriculture, Natural Resources Conservation Service .
National soil survey handbook, title 430-VI . http ://www.nrcs. usda .goviwpsiportali
arcs/d etai I/soils/scientists/?cid = nres l 42 p2_054242
United States Department of Agriculture, Natural Resources Conservation Service.
2006. Land resource regions and major land resource areas of the United States,
the Caribbean , and the Pacific Basin . U .S. Department of Agriculture Handbook
296 . http : //www. nres . usda . goviwpslportal/nres/detailinationallsoils/?
cid =nrcs142p2_053624
res 142 p2_6 63624
United States Department of Agriculture, Soil Conservation Service . 1961 . Land
capability classification. U .S . Department of Agriculture Handbook 210. http://
www. nrcs . usda.gov/InternetiFSE_DOCUMENTS/nrcs142p2_052290. pdf
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