Compatibility of North Dakota Soils for Irrigation
EB-68, October, 1996
Dave Franzen, NDSU Extension Soils Specialist
Tom Scherer, NDSU Extension Irrigation Specialist
Bruce Seelig, NDSU Extension Water Quality Specialist
How to Use This Information
Classification of Soils for Irrigation Suitability
Irrigation Suitability Groups
Irrigability Groups
Important Topographic and Soil Properties Affecting Irrigability
Other More Technical Information
How to Use This Information
Irrigation increases the productivity of soils, increases the effectiveness and
consistency of certain soil applied herbicides, and provides a more stable supply of farm
products to food and feed processors. However, irrigation can degrade the quality of soil
and cause crop yields to decline even to the point of field abandonment when soils and
water are not compatible. There are examples throughout history of soil degradation and
land abandonment due to improper irrigation. When irrigation acreage expands to new areas,
determining soil and water compatibility is critical to sustain yields at high levels.
This is intended as a first step to help present and prospective irrigators understand
the principles behind the irrigability of soils in North Dakota. This circular should
be used in combination with a soil survey of the land to be irrigated. Each soil
description may have different phases of slope and other properties which modify its
suitability for irrigation. Consultation with a qualified soil scientist is highly
recommended before making the decision to irrigate.
Classification of Soils for Irrigation Suitability
Soil series are classified for irrigation suitability. A soil series is based on
distinguishing characteristics including the kind of subsoil layers, or horizons, the
depth of each horizon, and the texture, color, carbonate content, sodium content,
structure, organic matter and other diagnostic characteristics of each horizon.
Soil series are grouped into three irrigation categories – Non-irrigable (N),
Conditional (C), and Irrigable (I). Non-irrigable soils should not be irrigated by any
water source and under any circumstance. The decision to classify a soil as non-irrigable
is based on the knowledge that irrigation will not benefit the irrigator economically and
may decrease the productivity of the soil.
A conditional soil can be irrigated under a high degree of management that will vary
according to the quality of water and soil properties. Specific recommendations for
conditional soil management are important for sustaining irrigation and soil health for
the future.
An irrigable soil can be irrigated with most irrigation water under most circumstances.
A high level of management is advised to increase the efficiency of the operation and
decrease possible nutrient or pesticide pollution due to excess water movement through the
soil.
Some fields will contain soils that fall into two or perhaps all three irrigation
categories. Assistance of a qualified soil professional is advised for fields with
conditional soils. An irrigation system should be set up to exclude areas that fall into
the non-irrigable category, but this may not always be possible. If most of the field
falls into the irrigable category, but significant areas are conditional and
non-irrigable, management decisions will be strongly influenced by the soils in these
catagories. Required management may include annual soil testing for nitrates, sodium and
salts, addition of calcium amendments, lower nitrogen fertilizer rates, drainage tile, or
other special activities. Special management methods will depend on the reason for
placement into conditional or non-irrigable classes.
The special requirements for irrigating small areas of conditional or nonirrigable
soils should be part of the estimate of total irrigation costs. From a practical point of
view, separate management of these small areas in irrigated fields is not likely to occur.
As site-specific farming techniques are developed, more practical methods of managing soil
inclusions will become available. Research is underway to develop an irrigation system
that will vary the amount of water given to an area under pivot irrigation on-the-go.
However, this technology may not be adopted commercially for some time.
Understanding the irrigability of an area begins with knowledge of local soil series
and the way they are represented on a soil survey map. When soil boundaries are drawn on
soil maps, the soil mapping unit is not purely one soil. The other soils present are of
minor extent and are called mapping unit inclusions. Mapping unit inclusions should be
considered when making an irrigation management decision. Soil series have been evaluated
and placed into groups called Irrigability Groups.
Finding and using a soil survey
Soil surveys for each county are available through the local NRCS office. Copies of the
soil survey for a North Dakota county may also be found in county extension offices, local
libraries, the NDSU library and the NDSU Soils Department. The soil survey contains maps
that show the different soils on each parcel of land in the county. Information regarding
these soils and their use, such as general irrigation suitability is also included in the
soil survey. NDSU
Extension Bulletin EB-60, Soil Survey: the Foundation for Productive Natural Resources
Management, provides details regarding the use of soil survey reports.
Determining the soils within a field is all that is necessary to use the information in
this circular. The irrigability classification system and recommendations are based on the
North Dakota Irrigation Guide. This document should be referred to for a more
comprehensive discussion of soils and irrigation compatibility, compared to the irrigation
suitability ratings found in the county soil survey report. Questions about how to use a
soil survey can be answered by the local NRCS office or the local county extension office.
Reviewing the irrigability ratings with a qualified soil scientist such as a registered
North Dakota Professional Soil Classifier is always a good idea before the decision to
irrigate is made.
Table 1a. Alphabetical list of soil series, irrigability group and irrigability. Soil type
names Aastad - Grassna.
--------------------------------------------------------------- ------
Soil Series Group Soil Series Group Soil Series Group
----------------------------------------------------------------------
Aastad C, 3D Brandenburg N,1A/I,10 Eckman I, 4A
Aberdeen N, 2A Brantford I, 6A Edgeley N, 3C
Absher N, 1B Breien C, 7A Egeland I, 7A
Acel C, 2B Brisbane I, 6B Ekalaka N, 1B
Alkabo N, 1B Bryant I, 4A Embden I, 7A
Amor N, 3C Buse N,1A/C,3D Emrick I, 4A
Antler C, 3B Cabba N, 1A Enloe C, 2C
Appam I, 8A Cabbart N, 1A Eramosh C, 2C
Aquents N, Cashel C, 3B Esmond N,1A/I,4A
Arikira N, 1A Cathay N, 2A Etheridge C, 2B
Arnegard I, 4A Cathro N, 1F Evridge N, 1B
Arveson C, 7B Cavour N, 1B Exline N, 1B
Arvilla I, 8A Chama N, 3C Fairdale I, 4A
Aylmer I, 9 Chanta I, 6B Falkirk C, 3D
Baahish I, 6A Cherry C, 3A Falsen I, 9
Badland N, 1A Chinook C, 7A Fargo C, 2C
Banks I, 8A Claire I, 9 Farland C, 3A
Bantry C, 8B Clontarf I, 8A Farnuf C, 3A
Barnes C, 3D Coe N,1A/I,10 Felor C, 3A
Bearden C, 3B Cohagen N, 1A Flasher C, 3A
Bearpaw C, 2B Colvin C, 3B Flaxton C, 5A
Beisigl C, 7A Cormant C, 3B Fleak N, 1A
Belfield N, 2A Cozberg I, 7A Foldahl C, 5A
Benoit C, 6C Cresbard N, 2A Fordville I, 6B
Benz C, 1C Daglum N, 1B Forman C, 3D
Beotia C, 3A Darnen I, 4A Fossum C, 3D
Bigsandy C, 3B Desart N, 1B Fram C, 4B
Binford I, 8A Dickey C, 5A Fulda C, 2C
Blanchard I, 8A Dilts N, 1E Galchutt C, 2C
Blown-Out Land N, 1A Dimmick C, 2C Gardena I, 4A
Bohnsack C, 4B Divide C, 6C Gilby C, 3B
Borup C, 4B Dogtooth N, 1B Glendive I, 7A
Bottineau C, 3D Dooley C, 3D Glyndon C, 4B
Bowbells C, 3D Doran C, 2C Golva I, 4A
Bowdle I, 6B Dovray C, 2C Grail C, 2B
Boxwell N, 3C Dupree N, 1E Grano C, 2C
Bowdoin N, 1D Easby N, 1C Grassna I, 4A
------------------------------------------------------ ---------------
For explanation of irrigability group, see pages - following.
N = nonirrigable, C = conditional, I = irrigable.
Table 1b. Alphabetical list of soil types, irrigabability group and irrigability. Soil
type names Great Bend-Oburn.
----------------------------------------------------------------------
Soil Series Group Soil Series Group Soil Type Group
----------------------------------------------------------------------
Great Bend I, 4A La Prairie I, 4A Makoti C, 3A
Grimstad C, 5B Ladelle I, 4A Maladay I, 7A
Gwinner C, 2B Ladner N, 1B Mandan I, 4A
Hamar C, 2B Lakoa N, 1A Manfred N, 1B
Hamerly C, 3B Lakota N, 1B Manning I, 8A
Hamlet C, 3D Lallie N, 1C Marias C,2B/N,1C
Hanly I, 8A Lambert I, 4A Markey N, 1F
Harriet N, 1B Lamoure C, 3B Marmarth N, 3C
Hattie C, 2B Langhei N,1A/C,3D Marysland C, 6C
Havre I, 4A Lankin C, 3D Maschetah I, 4A
Haverlon I, 4A Lanona C, 5A Mauvais C, 3B
Heda I, 8A Larson N, 1B Max C, 3D
Hegne C, 2C Lawther C, 2B McDonaldsville C, 2C
Heil N, 1B Lefor N, 3C McKeen C, 3B
Heimdal I, 4A Lehr I, 6A McKenzie N, 1B
Hidatsa I, 6B Lemert N, 1B Mekinock N, 1B
Hoffmanville C, 6B Letcher N, 1B Metigoshe I, 9
Inkster I, 7A Lihen I, 8A Minnewaukan C, 8B
Janesburg N, 1B Lindaas C, 2C Miranda N, 1B
Karlsruhe C, 8B Linton I, 4A Mondamin C, 2B
Kelvin C, 3D Lisam N, 1E Moreau N, 1D
Kensal I, 6A Lismore C, 3D Morton N, 3C
Kirby N,1A/I,10 Littlemo C, 6B Mott I, 7A
Kloten N, 1E Livona C, 5A Nahon N, 1B
Korchea I, 4A Lohler C, 2C Neche C, 3B
Korell I, 4A Lohnes I, 9 Niobell N, 2A
Krantzburg I, 4A Lonna I, 3A Nobe N, 1B
Kratka C, 5B Ludden C, 2C Noonan N, 1B
Krem C, 5A Maddock I, 8A Nutley C, 2B
Kremlin I, 4A Magnus C, 2B Oburn N, 1B
----------------------------------------------------------------------
For explanation of irrigability groups, see pages - following.
N = Nonirrigable, C = conditional, I = irrigability.
Table 1c. Alphabetical list of soil types, irrigability group and irrigability. Soil type
names Ojata-Zeona.
----------------------------------------------------------------------
Soil Series Group Soil Series Group Soil Series Group
----------------------------------------------------------------------
Ojata N, 1C Schaller I, 8A Vanda N, 1C
Oldham C, 2C Scorio C, 2C Vang I, 6B
Olga C, 2B Searing I, 6B Vebar I, 7A
Omio N, 3C Seelyeville N, 1F Velva I, 7A
Osakis I, 8A Sen N, 3C Venlo C, 8B
Overly C, 3A Serden N,1A/I,9 Venendrye C, 8B
Parnell C, 2C Seroco N,1A/I,9 Viborg C, 3D
Parshall I, 7A Sham N, 1D Viking C, 2C
Patent N, 1D Shambo I, 4A Virgelle C, 5A
Peever C, 2B Sinai C, 2B Wabek N,1A/I,10
Perella C, 3B Sinnigam N, 1E Wahpeton C, 3B
Playmoor N, 1C Sioux N,1A/I,10 Walsh C, 3D
Poppleton C, 2B Southam C, 2C Waham I, 8A
Portal N, 1B Spottswood I, 6B Wamchaska I, 9
Rauville C, 3B Stady I, 6B Wanagan I,6A or 6B
Reeder N, 3C Stirum N, 1B Warsing I, 6A
Regan C, 3B Straw I, 4A Watrous N, 3C
Regent C, 2B Suomi C, 2B Waukon C, 3D
Renshaw I, 6A Sutley I, 4A Wayden N, 1A
Rhame I, 7A Svea C, 3D Werner N, 1A
Rhoades N, 1B Swenoda C, 5A Wheatville C, 3B
Ridgelawn C, 6B Tally I, 7A Whitebird N, 1B
Rifle N, 1F Tansem I, 4A Wildrose C, 2B
Ringling N,1A/I,10 Telfer I, 4A Williams C, 3D
Rockwell C, 5B Temnick C, 3D Wilton C, 3D
Rollette C, 2B Tiffany C, 7B Wolf Point N, 1C
Rollis C, 3B Tinsley N,1A/I,10 Wyard C, 4B
Rolla C, 2B Toby I, 7A Wyndmere C, 7B
Rondell I, 4A Tolna C, 7B Wyrene C, 7B
Roseglen I, 4A Tonka C, 2C Yawdin N, 1A
Rosewood C, 8B Totten N, 1B Yegen C, 3A
Rusklyn I, 4A Towner C, 5A Yetull I, 9
Ruso I, 8A Trembles I, 7A Zahl N,1A/I,4A
Ryan N, 1B Tusler N, 1A Zeeland C, 2B
Sakakawea I, 4A Ulen C, 8B Zell N,1A/I,4A
Savage C, 2B Vallers C, 3B Zeona I, 9
----------------------------------------------------------------------
For explanation of irrigability groups, see pages - following.
N = nonirrigable, C = conditional, I = irrigable.
In the following text, "<" means less than and ">" means
greater than.
Non-Irrigable (NI)
These are soils with very severe limitations due to slope, sodicity, salinity,
excessively slow permeability and/or root restrictive subsoil layering. Irrigation is
strongly discouraged. Irrigation will cause soil quality to be degraded and reduce the
productivity of the soils for future generations of farm producers. Different phases of
each soil series will modify irrigation recommendations.
1A. Non-irrigable because of slope
----------------------------------------------
Arikara Langhei, slopes >5%
Badland Lakoa
Blow-out Land Ringling, slopes >5%
Brandenburg, slopes >5% Serden, slopes >5%
Buse, slopes, >5% Seroco, slopes >5%
Cabba Sioux, slopes >5%
Cabbart Tinsley, slopes >5%
Coe Tusler, slopes >5%
Cohagen Wabek, slopes >5%
Dumps Wayden, slopes >5%
Esmond, slopes >5% Werner
Flasher Yawdin
Fleak Zahl, slopes >5%
Kirby, slopes > 5% Zell, slopes >5%
1B. Non-irrigable because of sodicity
-------------------------------------------
Absher Exline Letcher Oburn
Alkabo Harriet Manfred Portal
Cavour Heil McKenzie Rhoades
Daglum Janesburg Mekinock Ryan
Desart Ladner Miranda Slickspots
Dogtooth Lakota Nahon Stirum
Ekalaka Larson Nobe Totten
Evridge Lemert Noonan Whitebird
1C. Non-irrigable because of salinity
------------------------------------------
Benz Lallie Ojata Vanda
Easby Lambeth Playmoor Wolf Point
1D. Non-irrigable because of extremely slow permeability
----------------------------------------------------
Bowdoin Moreau Patent Sham
1E. Non-irrigable because of restrictive subsoil layering
-----------------------------------------------------
Dilts Kloten Livona
Dupree Lisam Sinnigam
1F. Non-irrigable because of very poorly drained muck
and peat soils
-------------------------------------------------
Cathro Markey Rifle Seelyeville
2A. Non-irrigable because of high salts in the subsoil
--------------------------------------------------
Aberdeen Cathay Niobell
Belfield Cresbard
3C. Non-irrigable because of shallow depth to bedrock
and lateral seepage hazard
--------------------------------------------------
Amor Edgeley Morton Sen
Boxwell Lefor Omio Watrous
Chama Marmarth Reeder
Conditional Soils (C)
Conditional soils can be irrigated under a high level of management. Soil conditions
which contribute to conditional status are the presence of salts, poor drainage
properties, the presence of subsurface layering and the need for supplemental surface and
subsurface drainage. Irrigation without high levels of management may degrade soil quality
for future generations, but can be successfully irrigated if recommendations are followed.
Soil phases of each soil series may modify irrigation recommendations.
2B. Fine-textured, well and moderately drained with
moderately or slow permeability and high available
water capacity. Classified conditional because of
salinity hazard and poor internal drainage.
---------------------------------------------------
Acel Hattie Nutley Rolla
Bearpaw Lawther Olga Savage
Etheridge Magnus Peever Sinai
Frazer Marias Regent Wildrose
Grail Mondomin Rolette Zeeland
Gwinner
Irrigation water quality
Maximum allowable EC <1000 umhos/cm
Maximum allowable SAR <6
Irrigation management
See NDSU Extension Service Circular AE-792 (revised), Irrigation Scheduling by the
Checkbook Method, for irrigation scheduling information.
2C. Fine textured soils with poor and very poor drainage
and slow, very slow permeability and high available
water capacity
-----------------------------------------------------
Dimmick Fulda Lohler Quam
Doran Galchutt Ludden Southam
Dovray Grano McDonaldsville Scorio
Enloe Hegne Oldham Tonka
Eramosh Lindaas Parnell Viking
Fargo
Irrigation water quality
Maximum allowable EC <1000 umhos/cm
Maximum allowable SAR <6
Irrigation management
See NDSU Extension Bulletin AE-792 (revised) for irrigation scheduling information.
3A. Medium to moderately fine textured. Well drained
to moderately well drained with moderately slow
permeability and high available water holding
capacity. Conditional due to the hazard of salt buildup.
--------------------------------------------------------
Beotia Farland Feler Overly
Cherry Farnuff Makoti
Irrigation water quality
Maximum allowable EC <1500 umhos/cm
Maximum allowable SAR <6
Irrigation management
Salinity of the root zone should be monitored every three to five years. Extra water may
be required to leach out salts periodically if soil moisture conditions during the fall
through early spring do not provide for water movement through the soil. Leaching should
be done in the fall or early spring when crop requirements for water are low. The
application of 3/4 inches of water in excess of field capacity should pass through the
crop root zone.
3B. Medium, moderately fine and fine textured, moderately
well drained to poorly drained soils with slow to
moderately slow permeability and high water holding capacity.
Conditional because of the need for supplemental surface
and subsurface drainage.
-------------------------------------------------------------
Antler Flom McKeen Roliss
Bearden Gilby Neche Suomi
Big Sandy Hamerly Perella Vallers
Cashell LaMoure Rauville Wahpeton
Colvin Mauvais Regan Wheatville
Irrigation water quality
Maximum allowable EC <1500 umhos/cm
Maximum allowable SAR <6
Irrigation management
Monitor for salinity every 3-5 years. See NDSU Extension Service Circular AE-792 (revised)
for irrigation scheduling information.
3D. Medium and moderately fine textured soils, well drained with
soft bedrock at 20 to 40 inches, moderate and moderately slow
permeability, and high water holding capacity. These soils are
conditional due to slow internal drainage and the hazard of
salinity buildup.
--------------------------------------------------------------
Aastad Kelvin Temvik
Barnes Kittson Walsh
Bottineau Forman Waukon
Bowbells Hamlet Williams
Buse, slope
Irrigation water quality
Maximum allowable EC <1800 umhos/cm
Maximum allowable SAR <6
Irrigation management
Extra water may be required for leaching if fall through spring precipitation does not
provide at least 3/4 inches of water in excess of field capacity passing through the root
zone.
4B. Medium textured, somewhat poorly drained and poorly drained
with moderate permeability and high water holding capacity.
Conditional because of the need for supplemental surface and
subsurface drainage.
------------------------------------------------------------
Bohnsack Fram Wyard
Borup Glyndon
Irrigation water quality
Maximum allowable EC <2250 umhos/cm
Maximum allowable SAR <6
Irrigation management
See NDSU Extension Service Circular AE-792 (revised) for irrigation scheduling
information.
5A. Coarse and moderately coarse textured, well to moderately
drained soils with glacial till or lake sediments at 20 to
40 inches, moderately slow permeability and moderate water
holding capacity. Conditional due to restricted drainage
because of subsoil stratification. Salinity should be
monitored every 3 to 5 years. Drain-age systems may be
required for adequate drainage.
-------------------------------------------------------------
Dickey Krem Swenoda
Foldahl Lanona Towner
Flaxton Livona Virgelle
Irrigation water quality
Maximum allowable EC <1800 umhos/cm
Maximum allowable SAR <9
Irrigation management
See NDSU Extension Bulletin AE-792 for irrigation scheduling information.
5B. Moderately coarse textured, somewhat poorly drained and
poorly drained soils with glacial till or lake sediments
at 20 to 40 inches, moderately slow permeability and
moderate water holding capacity.
---------------------------------------------------------
Grimstad Kratka Rockwell
Irrigation water quality
Maximum allowable EC <1800 umhos/cm
Maximum allowable SAR <9
Irrigation management
Surface and subsurface drains required.
6C. Medium textured, somewhat poorly drained and poorly drained
soils with coarse sand and gravel at or just below the rooting
zone, moderate to moderately rapid permeability and moderate
to low water holding capacity. Conditional because of rapid
water movement and need for supplemental drainage.
--------------------------------------------------------------
Benoit Divide Marysland
Irrigation water quality
Maxiumum allowable EC <3000 umhos/cm
Maximum allowable SAR <6
Irrigation management
Surface and subsurface drains required.
7B. Medium and moderately coarse textured, somewhat poorly
drained and poorly drained soils with moderately rapid
permeability and low to moderate water holding capacity.
Conditional because of the need for supplemental drainage.
----------------------------------------------------------
Arveson Tolna Wyrene
Tiffany Wyndmere
Irrigation water quality
Maxiumum allowable EC <3000 umhos/cm
Maximum allowable SAR <12
Irrigation management
Surface and subsurface drained required.
8B. Coarse textured, somewhat poorly drained and poorly
drained soils with rapid permeability and low water
holding capacity. Conditional because of the requirement
for supplemental drainage.
--------------------------------------------------------
Bantry Hamar Poppleton Venlo
Cormant Karlsruhe Rosewood Verendrye
Fossum Minnewaukan Ulen
Irrigation water quality
Maximum allowable EC <3000 umhos/cm
Maximum allowable SAR <12
Irrigation management
Surface and subsurface drainage required.
Irrigable Soils (I)
Irrigable soils need generally less management than conditional soils. Even though the
soils are in an irrigable class, good irrigation management is essential. For example,
Arnegard, Grassna and LaDelle are in the 4A irrigable class. However, in times of soil
wetness, these sites may receive additional water due to surface and subsurface water
flow. This additional water may increase salinity and sodicity beyond what might be
expected with normal irrigation. Use of lower quality water than recommended can lower the
productivity of the soils from salts and sodium. Different phases of each soil series may
modify irrigation recommendations.
4A. Medium and moderately fine textured, well and moderately
well drained soils with moderate permeability and high
water holding capacity.
-----------------------------------------------------------
Arnegard Havre Mandan
Bryant Havrelon Randell
Darnen Heimdal Roseglen
Eckman Korchea Rusklyn
Emrick Korell Sakakawea
Esmond, slope
Irrigation water quality
Maximum allowable EC <2250 umhos/cm
Maximum allowable SAR <6
Irrigation management
See NDSU Extension Service Circular AE-792 (revised) for irrigation scheduling
information.
6A. Medium textured, well and moderately well drained soils
with coarse sand and gravel at 10 to 20 inches, moderate
or moderately rapid permeability, low water holding capacity.
-------------------------------------------------------------
Baahish Kensal Renshaw
Brantford Lehr Warsing
Irrigation water quality
Maximum allowable EC <3000 umhos/cm
Maximum allowable SAR <9
Irrigation management
See NDSU Extension Service Circular AE-792 (revised) for irrigation scheduling
information.
6B. Medium textured, well drained soils with coarse sand and
gravel at 20 to 40 inches, moderate or moderately rapid
permeability, and moderate or low water holding capacity.
-------------------------------------------------------------
Bowdle Fordville Littlemo Spottswood
Brisbane Hidatsa Ridgelawn Stady
Chanta Hoffmanville Searing Vang
Irrigation water quality
Maximum allowable EC <3000 umhos/cm
Maxiumum allowable SAR <9
Irrigation management
See NDSU Extension Service Circular AE-792 (revised) for irrigation scheduling
information.
7A. Moderately coarse textured, well and moderately
well drained soils with moderately rapid permeability,
moderate water holding capacity.
--------------------------------------------------------
Conditional due to under- Completely irrigable
lying weathered sandstone ----------------------
20 to 40 inches Chinook Mott
-------------------------- Egeland Parshall
Beisigl Malachy Embden Tally
Breien Rhame Glendive Toby
Cozberg Vebar Inkster Trembles
Velva
Irrigation water quality
Maximum allowable EC <3000 umhos/cm
Maximum allowable SAR <12
Irrigation management
See NDSU Extension Service Circular AE-792 (revised) for irrigation scheduling
information.
8A. Moderately coarse and coarse textured, somewhat excessively
to moderately well drained soils. Rapid permeability and
low water holding capacity. Some shallow to gravel.
------------------------------------------------------------
Depth to gravel in parentheses
------------------------------------------------------------
Appan Lihen
Arvilla (12-25 inches) Maddock
Banks Manning (20-40 inches)
Binford (12-25 inches) Osakis (12-25 inches)
Breien Ruso (20-40 inches)
Clontarf Shaller
Hanly Telfer
Hecla Walum (12-25 inches)
Irrigation water quality
Maximum allowable EC <3000 umhos/cm
Maxiumum allowable SAR <12
Irrigation management
See NDSU Extension Service Circular AE-792 (revised) for irrigation scheduling
information.
9A. Coarse textured soils with rapid permeability, low water
holding capacity.
----------------------------------------------------------
Alymer Falsen Seroco, slopes
Irrigation water quality
Maximum allowable EC <3000 umhos/cm
Maximum allowable SAR <12
Irrigation management
Frequent irrigations will be required.
10. Medium to coarse textured, excessively and well drained
soils with coarse sand and gravel or porcelainite (scoria)
at less than 10 inches, rapid permeability and very low
water holding capacity.
-----------------------------------------------------------
(The following soils will fall into group IA if slope is
greater than 5%.)
-----------------------------------------------------------
Brandenburg Kirby Sioux Wabek
Coe Ringling Tinsley
Irrigation water quality
Maximum allowable EC <3000 umhos/cm
Maximum allowable SAR <12
Irrigation management
Light, frequent irrigations will be required. These soils may be susceptible to drought
even under irrigation.
Important Topographic and Soil Properties Affecting
Irrigability
Soil depth
Soil depth depends on the potential rooting depth of plants to be grown and any
restrictions within the soil that may hinder rooting depth. The rooting depth of canola
may only be about 3 feet, while for alfalfa the rooting depth may be over 4 feet.
Discontinuities in the soil from layers of sand, gravel or bedrock may serve to physically
limit rooting depth.
Soil texture
The percentage of sand, silt and clay sized particles in the soil is the soil texture.
Texture influences other properties such as water holding capacity, infiltration rate and
internal drainage.
Soil structure
Soil particles are arranged into aggregates through the action of weather, organic
matter attraction, soil mineral composition, time and outside physical forces such as
compaction, root growth and animal activities. Soils containing aggregates unstable under
irrigation may require special management. Movement of water into and within soils is
partially dependent on soil structure.
Water holding capacity
Water holding capacity is defined as the soil water retained between a suction of
0.1-0.5 bars (field capacity) and 15 bars (permanent wilting point). Water held between
these two suction values is regarded as plant available water. A silt loam soil holds
about 2.25-2.5 inches of water per foot of soil, while a sandy loam can hold only about 1
inch of water per foot. Soils with higher organic matter generally hold more water than a
soil with lower organic matter.
Slope
Slope is important in determining the water runoff potential from a field. Water and
soil losses from runoff reduce both short-term and long-term economic returns. Generally,
more run-off will occur on fine textured soils compared to coarser textured soils on
similar slope.
Infiltration rate
Infiltration rate is the relative rate that water penetrates and moves into the soil. A
faster infiltration rate allows less runoff than soil with slower rates.
Internal drainage
Internal drainage describes the degree and persistence of soil wetness and is
influenced by slope, soil infiltration rate, soil texture (percent gravel,sand, silt and
clay), depth to water table and depth to impermeable layers. Excessively drained soils
often have crop production problems related to lack of water and nutrients due to rapid
movement of water through the soil profile. On the other hand, soils with poor internal
drainage that remain wet may increase disease potential to crops, cause denitrification
losses of nitrogen fertilizer or cause accumulation of salts. Soils with good internal
drainage respond well to irrigation. Irrigation water is retained for use by crops, while
allowing sufficient movement of water within the soil to minimize saturation of pore
space.
Salinity
High levels of soil salts usually result from a water table near the soil surface. High
salt levels may reduce crop yields and increase the water requirement of plants.
Irrigation may decrease the depth to water table over time in some soils, increasing the
risk of salinization. Irrigation water containing high salt levels may also increase the
risk of salinization. As salinity increases, crop productivity will decrease. Salinity is
a soil property that changes relatively quickly with time compared to other properties
such as texture. Soil testing for salts is necessary to not only follow possible increases
over time in irrigated fields, but also determine if irrigation should be attempted in the
first place.
Sodicity
Sodium (Na) affects the physical condition of the soil by dispersing aggregates. The
soil becomes pasty when wet and develops a condition called "puddling", where
water remains on the surface for an extended period. The soil becomes hard when dry, and
its permeability to water and air is reduced. If irrigation causes sodium salts to
accumulate near the soil surface, increased sodium levels may cause yield reduction.
Sodium buildup usually occurs slowly and may not be easily detected from one year to the
next. Regular soil testing is recommended to determine long-term trends in sodium
accumulation. Sodium buildup is one of the most serious long term dangers to productivity
decline due to irrigating some soils. Water management becomes difficult, seed germination
may be poor and roots cannot penetrate well into the soil.
Other More Technical Information
Important chemical characteristics of water affecting irigability of North Dakota
soils
Salinity—The salt content of irrigation water is important for the
long-term irrigability of many soils. The allowable salt content depends on permeability
of the soil, beginning soil salt content, depth to the water table, drainage and texture.
Salts are detected by measuring the flow of electrical current through a sample of soil
or water. The more salts in a sample, the less resistance to electrical current and
greater the electrical conductivity (EC). Most labs in North Dakota measure conductivity
on a 1:1 by weight soil to water slurry. Soils with electrical conductivity greater than 1
dS/cm in the slurry method can decrease the yield potential of some crop plants.
Modification of the water table may be neccessary before irrigation is performed. In
areas where salinity is increasing, fertilizer additions should be reduced. Salt problems
may be serious enough to discourage irrigation of some fields. See NDSU Extension
Service Circular SF-1087, Managing Saline Soils in North Dakota, and EB-57, Salinity
and Sodicity in North Dakota Soils, for more information regarding saline soil development
and management.
The United States Salinity Laboratory rates salinity in terms of a scale from C1-C4.
The definitions of the scale are described below.
Salinity designations of irrigation water:
C1 — (Low-salinity water) Little likelihood that soil salinity will develop. Some
leaching may be required, but not more than normal leaching from standard irrigation
practices unless the soils are extremely low in permeability.
C2 — (Medium-salinity water) Water can be used if a moderate amount of leaching is
used. Plants with moderate tolerance to salinity can be grown without special practices
for salinity control.
C3 — (High-salinity water) Cannot be used on soils with restricted drainage.
Special management is required even with good drainage. Plants with good salt tolerance
must be selected.
C4 — (Very high-salinity water) Not suitable for irrigation except under very
special conditions which include permeable soils, adequate drainage, excess water for
leaching and very salt-tolerant crops.
Sodicity—The sodium level in the soil in relation to calcium and magnesium,
as well as the sodium content of the irrigation water is important to the long-term
productivity and health of the soil. Sodium disperses clay particles, causing
randomization of clay sheets. Aggregation is poor, resulting in poor water infiltration
(ponding) and poor root penetration. Less water and nutrients are available for plant
growth.
The amount of sodium in the soil and in irrigation water are also factors which
influence sodification. The use of high sodium water depends on the level of salinity and
sodicity in the soil and water as described in Figure 1.
Figure 1. Classification of irrigation water (from Agriculture
Handbook No. 60, USDA Salinity Laboratory, Riverside, CA).
The influence of sodium on soil properties depends on the relative amount of sodium
with respect to calcium and magnesium. The most accepted method of comparing sodium to
calcium and magnesium is by calculating the sodium adsorption ratio (SAR). The SAR may be
determined on a soil extract or irrigation water. The calcium, magnesium and sodium
content of the sample must first be measured by a laboratory. After analysis, the SAR can
then be calculated using the following formula:
SAR = Na+ /( (( Ca (squared+) + Mg (squared+) )/2)
where:
Na+ is the concentration of sodium in milliequivalents per liter of soil extract or
meq/liter of irrigation water.
Ca2+ and Mg2+ are the concentrations of calcium and magnesium, respectively in meq/liter
of soil extract or irrigation water.
A soil extract from a saturated soil with an SAR of greater than 13 is usually an
indication of sodium problems and not generally recommended for irrigation.
The SAR, however, is not the only factor to be considered when managing sodicity. The
type of anion (chloride or sulfate) in the soil affects the amount of Ca2+ and Mg2+
effective in the soil. The free sulfate in soils high in sulfate may combine with Ca2+ so
that the Ca2+ is not available to replace sodium from the soil cation exchange complex.
Although an SAR in a sulfate system might suggest a relatively low sodium threat, the
effective SAR would be higher. The bicarbonate (HCO3-) or carbonate (CO32-) content of
irrigation water or soil may also cause precipitation of calcium and magnesium carbonates
and increase the SAR of the soil.
Texture also modifies the effect of SAR as a management guide. Although an SAR of 13
indicates significant clay dispersion in both a clay loam and sandy loam soil, the actual
effect of the dispersion on soil properties is less in the sandy loam. Soils with a
relatively low SAR may become dispersed depending on the amount of clay particles held
together in part by the attraction of calcium to other clay particles and the dispersing
action of sodium which counteracts the aggregation process. See NDSU Extension Service
Circulars EB-57 and SF-1087 for
more information on sodic soil development and management.
The U.S. Salinity Laboratory defines sodicity in terms of a scale from S1-S4. The
definitions of each class are described below.
Sodium designations of irrigation water:
S1 — (Low sodium water) Can be used on nearly all soils with little danger of
sodium buildup to the soil, although levels may still be high enough to injure sodium
sensitive plants.
S2 — (Medium sodium water) May present a potential sodium buildup on fine-textured
soils with low permeability especially if soil free calcium levels are low.
S3 — (high sodium water) May cause sodium buildup in most soils and requires
special management, including good drainage, excess water for leaching and organic matter
addition. Soils with very high levels of free calcium may not develop problems. Chemical
additions (calcium bearing minerals) may be required to replace soil sodium.
Chemical additions may not be practical if salinity of irrigation water is high.
S4 — (very high sodium water) Unsuitable for irrigation water except if the water
is low or medium salinity (C1 or C2). Under low irrigation salinity, addition of gypsum
or calcium chloride may make use of S4 water possible.
Boron—Accumulation of boron has not been documented as an irrigation
problem in North Dakota. In a few western states, boron can sometimes be a concern. High
levels of boron are toxic to crop plants. Irrigation water should be tested for boron when
the well source is originally tested. If the boron level is less than 2 ppm, then boron
should not be a problem. If higher than 2 ppm, periodic soil testing every four years
would be a good way to monitor boron levels. Water from most North Dakota aquifers is not
expected to have high boron levels.
Countering sodium buildup from the use of high SAR irrigation water
The laboratory derived SAR may not be a clear indicator of the actual dispersion of
clay particles due to increased sodium levels or decreased soluble calcium in a soil. A
quick field test of suspected problem areas may help direct the need for an amendment.
Place a one-half cup of surface soil in a clear glass quart jar, add one pint of distilled
water and shake well. Leave the jar undisturbed for 12 hours. If the water has not cleared
in that time, the clay has become dispersed and an amendment may be required to keep the
surface soil productive.
Sodium accumulation and clay dispersion may be countered by the addition of soluble
calcium compounds that replace more weakly held sodium on clay and organic matter surfaces
and increase flocculation. Free sodium can then be leached from the soil surface to below
the root zone where it will not interfere with plant growth. The hazard of sodium
accumulation from irrigation water is illustrated in Figure 1 (USDA, 1954).
The sodicity buildup hazard for irrigation water is dependent on both its SAR and its
salinity. As the salt content of the water increases sodicity hazard also increases. This
means that lower SARs may cause significant sodium buildup in the soil. The reason for an
increased sodicity hazard with greater salinity is simply the greater number of sodium
ions to replace calcium in the soil.
The effective use of calcium amendments is related to the salinity and SAR of the
irrigation water and the soil mineral content. Addition of calcium amendments to
irrigation water may be most helpful with irrigation water classes C1-S3, C1-S4, and
C2-S4. The sodicity hazard of irrigation water classes C1-S3 and C1-S4 may be reduced with
the addition of calcium amendments to irrigation water. Application of soluble calcium
amendments may be most useful with soils irrigated with water in classes C2-S3 and C3-S2.
Calcium amendments for soil and irrigation water
Gypsum, which is the common name for calcium sulfate (CaSO4), has been used
successfully as a reclamation amendment when the soil was not already saturated with
gypsum. In areas with low soil salt content, gypsum is the preferred method of reclaiming
high sodium soils. Gypsum dissolves in the soil and calcium ions replace sodium ions on
clay and organic matter surfaces. Water moving through the soil then leaches the sodium
out of the root zone. However, in many North Dakota soils, sodium and calcium levels are
high together. Addition of gypsum in soils already high in gypsum will not result in a
replacement of sodium, since greater amounts of gypsum will not increase the number of
free calcium ions in solution. Other amendments may be more useful.
In soils with high levels of calcium carbonate and low levels of gypsum, application of
elemental sulfur is sometimes used to produce gypsum. Sulfur is oxidized in soils by
sulfur bacteria. The resulting sulfuric acid reacts with calcium carbonate to produce
gypsum.
In some soils, subsurface gypsum layers can be incorporated into surface soils with
high sodium levels through deep tillage. Mixing gypsum into high sodium soils may be a
practical way to reclaim some soils. Before tillage, soil sampling surface and deep layers
with respect to sodium and gypsum levels will be necessary. If excess gypsum is not
present in the subsurface layers, deep tillage may not be helpful.
More soluble calcium amendments, such as calcium chloride, may be more useful in
replacing sodium ions in sulfatic systems. Calcium chloride is more soluble in sulfatic
systems than gypsum. The economics of reclamation and effectiveness of amendments in
reclaiming sodic soils or countering sodium accumulation should be evaluated before
deciding to use a soluble calcium amendment.
Acknowledgements
Thanks go to Dr. Jim Richardson, Professor of Soil Science, NDSU, and to Mike
Sweeney, Professor Emeritus, for advise. Thanks also to Mike Ulmer at the state USDA-NRCS
office in Bismarck for recent soil series updates.
References
Franzen, D., C. Fanning and T. Gregoire. 1994. Managing saline soils in North Dakota.
NDSU Ext. Bull. SF 1087.
Scherer, T.F., B. Seelig and D. Franzen. 1996. Soil, water and plant characteristics
important to irrigation. NDSU Ext. Bull. EB-66.
Seelig, B. 1993. Soil survey: the foundation for productive natural resource
management. NDSU Ext. Bull. 60.
Seelig, B.D. and J.L. Richardson. Salinity and sodicity in North Dakota soils. NDSU
Ext. Bull. EB-57.
Sylla, M. 1983. Greenhouse reclamation of salt-affected soils of ND. MS thesis. NDSU.
U.S. Salinity Laboratory Staff. 1954. Diagnosis and improvement of saline and alkali
soils. Agric. Hanb. No. 60, USDA. U.S. Gov. Print. Off., Washington, D.C.
EB-68, October, 1996
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