Classification,
properties,
and managementof Aridisols
C. B. Mack,* O. A. Chadwick,
ABSTRACT
Aridandsemiaridregions makeup almost one-thirdof the
Earth’s surface. Soils in these areas comprisean important
global resourcethat mustbe carefully managed
for sustained
agriculturalproduction.Aneducationalslide set has beendevelopedto illustratethe entirerangeof soils foundin aridregions
andintegrateinformation
on physicalandchemicalsoil properties, soil classification, andrelatedsoil management
considerations for agriculturaldevelopment.
A
sLio~ set that illustrates the classification, properties, and managementof arid soils has been produced by the University of Arizona, Office of Arid Land
Studies in cooperation with the USDA,Soil Management
Support Services. This slide set is designed to be used as
a teaching aid illustrating the taxonomyof arid soils and
how soil taxonomic data can be used for management
decisions. The target audience includes students, as well
as technicians and professionals whocharacterize and utilize soils in developing countries of the world.
The programconsists of 96 color slides, divided into
three basic parts:
1. The first 28 slides provide an introduction to Soil
Taxonomyand define technical aspects important
in the classification of Aridisols, such as the aridic
soil moisture regime and diagnostic soil horizons
(e.g., calcic, gypsic, salic, duripan).
2. The next 24 slides examinethe taxonomic structure
of the Aridisol Order with examples of arid soils
classified to the Subgrouplevel.
3. The final 34 slides illustrate the need for sensitive
managementof Aridisols for agricultural production. Included are definitions and examples of
saline, sodic and saline-sodic soils, seed placement,
and land leveling and irrigation techniques.
The narrative for six selected slides is presented below.
A photo of the corresponding slide for each narrative is
given in Fig. 1-6.
C.B. Mack,Officeof Arid LandsStudies, Univ.of Arizona,845N.
ParkAve., Tucson,AZ85719;O.A.Chadwick,
Jet PropulsionLab.,
California Inst. of Technology,
4800OakGroveDr., Pasadena,CA
91109;and H. Eswaran,USDA-SCS,
Soil Management
SupportServ.,
P.O. Box2890,Washington,
DC20013.Fundingprovidedby the U.S.
Agencyfor International Development
underPASA
no. BST-1229-PAG-2178.
Received19 Apr. 1989. *Corresponding
author.
Publishedin J. Agron.Educ.19:64-65(1990).
64
J. Agron.Educ., Vol. 19, no. 1, 1990
and H. Eswaran
Slide 10 (Fig. 1). Soil moisture regimes characterize the
presence or absence of groundwater or water held at a
tension in the soil at whichit is available to mostplants.
This graph depicts the soil water balance in an aridic soil
moisture regime.
Slide 28 (Fig. 2). Duripans are soil horizons cemented
by secondary silica. Like petrocalcic and petrogypsic
horizons, duripans present major constraints for agriculture because they limit root growth and water movement.
Slide 31 (Fig. 3). Durargids are Argids that have a
duripan whose upper boundary is within 1 m of the surface. Duripans restrict root growth and water movement
through the soil. Whenfound at shallow depths, they
present formidable constraints for agricultural development.
Slide 49 (Fig. 4). Vertic Haplargids differ from Typic
Haplargids by having cracks that remain open for 8 mo
or more in most years. These soils have high clay contents and are an intergrade to the Vertisol soil Order. Vertic Haplargids can be agriculturally productive but,
because of their high clay contents, they require special
managementpractices.
Slide 74 (Fig. 5). One of the most extensive problems
facing irrigated agriculture in arid regions is the presence
of soluble salts in the soil in amountsthat inhibit plant
growth. This aerial photograph shows salt accumulation
in fields and its effect on crop growth. Approximately
one-third of developed agricultural lands in arid regions
reflect some degree of salt accumulation.
Slide 79 (Fig. 6). Seed placement is also important in
the managementof saline soils. Underfurrow irrigation,
soluble salts are concentrated towardsthe crest of the bed.
Therefore, optimumseed placement is on the lower side
of the bed, as seen here.
The slide program provides a means of effectively introducing the wide range of properties found in arid soils
of the world, howthese soil properties affect classification in Soil Taxonomy, and the management practices
used to make these soils agriculturally productive. A
30-minaudio cassette narrative is part of the slide set that
also includes a 10-page program guide.
The program is available in the USAand developed
countries for $90.00 from: Office of Arid Lands Studies,
Publications, University of Arizona, 845 N. Park Ave.,
Tucson, AZ 85719; telephone 602/621-1955.
To obtain copies of the program in developing countries contact your local USAIDmission or write to: SMSS
Program Leader, Soil Conservation Service, USDA,P.O.
Box 2890, Washington, DC 20013.
1
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Aridic Soil Moisture Regime
200z
E
150
100
50
n"
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
H Soil moisture deficit
0 Soil moisture recharge
Soil moisture utilization
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Precipitation
Potential evapotranspiration
Temperature
C
.g
-
.-m
.-a
p
a