Classification, properties, and managementof Aridisols

C. B. Mack,* O. A. Chadwick, and H. Eswaran

ABSTRACT Slide 10 (Fig. 1). Soil moisture regimes characterize the presence or absence of groundwater or water held at a Arid andsemiarid regions makeup almost one-third of the tension in the soil at whichit is available to mostplants. Earth’s surface. Soils in these areas comprisean important This graph depicts the soil water balance in an aridic soil global resourcethat mustbe carefully managedfor sustained moisture regime. agriculturalproduction. An educational slide set has beende- Slide 28 (Fig. 2). Duripans are soil horizons cemented velopedto illustratethe entirerange of soils foundin aridregions by secondary silica. Like petrocalcic and petrogypsic andintegrate information on physicaland chemical soil proper- horizons, duripans present major constraints for agricul- ties, soil classification, andrelated soil managementconsider- ture because they limit root growth and water movement. ations for agriculturaldevelopment. Slide 31 (Fig. 3). Durargids are Argids that have a duripan whose upper boundary is within 1 m of the sur- face. Duripans restrict root growth and water movement A sLio~ set that illustrates the classification, proper- through the soil. Whenfound at shallow depths, they ties, and managementof arid soils has been pro- present formidable constraints for agricultural de- duced by the University of Arizona, Office of Arid Land velopment. Studies in cooperation with the USDA,Soil Management Slide 49 (Fig. 4). Vertic Haplargids differ from Typic Support Services. This slide set is designed to be used as Haplargids by having cracks that remain open for 8 mo a teaching aid illustrating the taxonomyof arid soils and or more in most years. These soils have high clay con- how soil taxonomic data can be used for management tents and are an intergrade to the Vertisol soil Order. Ver- decisions. The target audience includes students, as well tic Haplargids can be agriculturally productive but, as technicians and professionals whocharacterize and uti- because of their high clay contents, they require special lize soils in developing countries of the world. managementpractices. The program consists of 96 color slides, divided into Slide 74 (Fig. 5). One of the most extensive problems three basic parts: facing irrigated agriculture in arid regions is the presence 1. The first 28 slides provide an introduction to Soil of soluble salts in the soil in amountsthat inhibit plant Taxonomyand define technical aspects important growth. This aerial photograph shows salt accumulation in the classification of Aridisols, such as the aridic in fields and its effect on crop growth. Approximately soil moisture regime and diagnostic soil horizons one-third of developed agricultural lands in arid regions (e.g., calcic, gypsic, salic, duripan). reflect some degree of salt accumulation. 2. The next 24 slides examine the taxonomic structure Slide 79 (Fig. 6). Seed placement is also important in of the Aridisol Order with examples of arid soils the managementof saline soils. Under furrow irrigation, classified to the Subgrouplevel. soluble salts are concentrated towardsthe crest of the bed. 3. The final 34 slides illustrate the need for sensitive Therefore, optimumseed placement is on the lower side managementof Aridisols for agricultural produc- of the bed, as seen here. tion. Included are definitions and examples of The slide program provides a means of effectively in- saline, sodic and saline-sodic soils, seed placement, troducing the wide range of properties found in arid soils and land leveling and irrigation techniques. of the world, howthese soil properties affect classifica- tion in Soil Taxonomy, and the management practices The narrative for six selected slides is presented below. used to make these soils agriculturally productive. A A photo of the corresponding slide for each narrative is 30-minaudio cassette narrative is part of the slide set that given in Fig. 1-6. also includes a 10-page program guide. C.B. Mack,Office of Arid LandsStudies, Univ.of Arizona,845 N. The program is available in the USAand developed ParkAve., Tucson,AZ 85719; O.A. Chadwick, Jet PropulsionLab., countries for $90.00 from: Office of Arid Lands Studies, California Inst. of Technology,4800 Oak Grove Dr., Pasadena,CA Publications, University of Arizona, 845 N. Park Ave., 91109;and H. Eswaran,USDA-SCS, Soil ManagementSupport Serv., Tucson, AZ 85719; telephone 602/621-1955. P.O. Box2890, Washington, DC 20013. Funding provided by the U.S. Agencyfor International Developmentunder PASA no. BST-1229-P- To obtain copies of the program in developing coun- AG-2178.Received 19 Apr. 1989. *Correspondingauthor. tries contact your local USAIDmission or write to: SMSS Program Leader, Soil Conservation Service, USDA,P.O. Publishedin J. Agron.Educ. 19:64-65 (1990). Box 2890, Washington, DC 20013.

64 J. Agron.Educ., Vol. 19, no. 1, 1990 Aridic Soil Moisture Regime 1 ... 200z -E C 150 .g .--m .-a 100 p a

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"n Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec H Soil moisture deficit - Precipitation 0 Soil moisture recharge --- Potential evapotranspiration Soil moisture utilization Temperature