Chapter 1. Present status of salt-affected and waterlogged soils in Dasht-e-Azadegan and management strategies for their sustainable utilization

S.A.M. Cheraghi1*, N. Heydari2, Y. Hasheminejad1, M. Qadir3, H. Farahani3, and T. Oweis3

1National Salinity Research Center (NSRC), Yazd, ; 2Iranian Agricultural Engineering Research Institute, Karaj, Iran; 3International Center for Agricultural Research in the Dry Areas (ICARDA), Aleppo, Syria *Corresponding author: [email protected]

1

Introduction southwest Iran is potentially one of the most suitable regions for agricultural Salt-prone land and water resources production. However, salinization of are major impediments to the optimal land and water resources has become a utilization of crop production systems serious threat to efficient use of these in many arid and semi-arid regions of invaluable resources. It is estimated the world, including Iran (Alizadeh et that out of the total 6.7 Mha of the al. 2004; Moghaddam and Koocheki province, 1.2-1.5 Mha (18-22% of total 2004). The salinization of land and water area) are faced with the dual problems resources has been the consequence of of soil salinization and water logging both anthropogenic activities (causing (Anonymous 2000). human-induced or secondary salinity and/or sodicity) and naturally occurring The basin (KRB) is one of phenomena (causing primary fossil the major river basins in the Khuzestan salinity and/or sodicity) (Ghassemi et al. province, consisting of two main sub- 1995). The main cropping systems in the basins namely Karkheh Olia (upstream) country are based on irrigated agriculture and Karkheh Sofla (downstream). The where at least 50% area (4.1 Mha) fall KRB is, most notably, the eastern flank under different types of salt-affected of the ‘cradle of civilization’ (ancient soils (Cheraghi 2004). Therefore, the Mesopotamia) and a boundary between dependency on irrigated agriculture is the Arab and Persian cultures. This at stake in areas where salt-prone land major river system of western Iran has and degradation of water resources has unique agricultural and hydrological increased over time. aspects; but also much in common with other catchments around the world, Human-induced salinization of land and e.g. rural poverty and land degradation, water resources has occurred mostly in low water and agricultural productivity, unique topographic conditions of semi- a dry climate, and growing upstream- closed or closed intermountain basins downstream competition for water. where irrigated agriculture has been Agriculture in the upstream basin is practiced for centuries. The slightly mainly rain fed, while the downstream and moderately salt-affected soils are basin is mostly irrigated. The drainage mostly formed on the piedmonts at the outlet of the KRB, which also is a basin foot of the Elburz (Alborz) Mountains in outlet, is the Hoor-Al-Azim swamp in the northern part of the country. The southwest Iran and on the Iran- soils with severe to extreme salinity are border (Fig. 1.1). At present, there mostly located in the Central plateau, the are very limited modern irrigation and Khuzestan and southern coastal plains, drainage networks under operation within and the Caspian coastal plain (Koocheki the KRB and agriculture is yet to be fully and Moghaddam 2004). The extent and developed. However, the government characteristics of salt-affected soils in has started constructing irrigation Iran has been investigated by several and drainage networks with the goal researchers (Dewan and Famouri 1964; of improving the traditional irrigation Mahjoory 1979; Abtahi et al. 1979; systems, e.g. in the Dasht-e-Azadegan Matsumoto and Cho 1985; Banie 2001). (DA) plain in southern parts of the lower KRB (LKRB). It is in this area where this Owing to abundant water resources, project was carried out. This chapter fertile lands and sufficient extraterrestrial describes this area (Dasht-e-Azadegan) energy, in in terms of its geology, soils, climate, and

3 Fig. 1.1. Karkheh River Basin (KRB) and Dasht-e-Azadegan (DA) region water resources. It also reviews salinity in thickness from zero at the foot of the and waterlogging problems based on mountains to 100 m in the west and previous studies carried out in the region. northern west of the plain in the vicinity Lastly, general recommendations for of Hoor-al-Azim. Information about the effective use of soil and water resources upper strata of plain reveals that there for crop production and environmental are many varieties and diverse features are given. as compared to the deeper part of plain. There, it can be seen that thin lens-like sand features in a clay-silty background Geology appear on a limited scale. These features are accompanied by transverse layers, Azadegan plain is a deep structural hole indicative of a different deltaic formation. covered by Quaternary sediments. The These events show that the river tributary deepest part of this cavern is in the west beds have undergone frequent changes and northwest of the region and around of position at times near the Holocene Hoor-Al-Azim. The outer edge of the plain epoch. Furthermore, fine sediments is in the east and northeast, where the such as silt and clay particles and to bedrocks have been uplifted to form the a lesser extent chemical sediments, Mishodagh and Allaoakbar mountains. organic matter, and vegetative material The deepest layers of the plain are provide evidence of vast Quaternary composed of the Kachsaran, Mishan, and marshes in the plain, particularly on the (Fars group) formation, from west side of the plain, where marshes deep to shallow. These formations were along the western border of Iran can overlain by conglomerate rocks (Bakhtiari be seen. Sedimentary deposits of the formation). The semi-deep portion of the Holocene epoch covering the surface hole was filled by recent sediment, which of the plain include alluvial, fluvial, and covers Bakhtiari conglomerates. aeolian sediments. The alluvial and fluvial sediments of plain are products of the The whole of sedimentary deposits in the geodynamic action of the Karkheh river Azadegan plain were laid down during tributaries. the Quaternary period. Sediment ranges

4 Soils precipitation of the region has enhanced accumulation of secondary lime minerals The soils of the area are alluvial soils in the soil mineralogy control section so formed originally by the floods of the that the carbonatic or mixed (calcareous) river. These alluvial areas are flat and soil mineralogy classes are common in the permeability is low, with little slope and region. Based on the USDA Soil Taxonomy poor natural drainage. Azadegan plain is (Soil Survey Staff 2003), soils are mainly a flood plain with very weak topography. classified as orders of the Entisols and The maximum elevation of 12 m a.s.l. is Aridisols. The young (recently formed) around Sosangerd and the Sosangerd- Entisols of the region belong to two Hoveizeh highway. The lowest elevation suborders. Fluvents are characterized is on the northwest side of the plain; by either 0.2% or more organic carbon adjacent to Hoor-Al-Azim (3-4 m a.s.l.). of the Holocene age at a depth of 125 Azadegan plain is the terminal basin and cm below the mineral soil surface or all of tributaries of the Karkheh river end an irregular decrease in content of in this plain. Therefore, the plain is the organic carbon from a depth of 25 cm scene of constant accumulation of the to a depth of 125 cm, or to a densic, river sediment. lithic, or paralithic contact if shallower. These soils have wide distribution in The low precipitation has developed the the region so that seven soil series aridic soil moisture regime throughout the belong to this suborder. The Kout soil region. The moisture control section, in series, which is classified as Salorthidic normal years, is dry in all parts for more Torrifluvents, is a typical Solonchak than half of the cumulative days per year, profile. Fluvaquents also are identified in when the soil temperature at a depth the lowland physiographic region of the of 50 cm from the soil surface is above plain. Redoximorphic features (brown 5°C; and it is moist in some or all parts mottling in a pale green soil matrix) in for less than 90 consecutive days when Fluvaquents (Sarhangiyeh, Shahatt-e- the soil temperature at a depth of 50 cm Abbas and Machriyeh series) represent is above 8°C. These conditions cause hydric conditions (seasonally saturated) low availability of water for cropping and in young, flood plain soils. The coarse- as a result, soils are classified only in textured soils are extended around rivers the Aridisol and Entisol orders based on in city so the Psaments can be development status of diagnostic horizons identified just in this region. Psaments, (Soil Survey Staff 2003). which occur only in the Susangerd soil series of the region, have good drainage As a result of the hot climate, the and have less than 35% (by volume) rock mean annual soil temperature is 22°C fragments and a texture of loamy fine or higher, and the difference between sand or coarser in all layers. mean summer and mean winter soil temperatures is more than 6°C, either at Medium- to coarse-textured soils exist a depth of 50 cm from the soil surface or in areas around the Karkheh river and at a densic, lithic, or paralithic contact, its tributaries, which have experienced whichever is shallower, so the soil frequent flooding in previous times. temperature regime is considered to be Soil series in this area show a distinct hyperthermic in all series. stratification, including sequences of different-size textured ranges from The carbonatic nature of the parent coarse to medium textured and in these material, in addition to the low areas the slope is gently perpendicular

5 to the river (natural levees). For Aridisols existent of 260 dry days in a year, Dasht- also just two suborders of cambids and e-Azadegan has not been classified as salids had been identified in the region. Accentuated Sub-Desertic Area. The Cambids, which are Aridisols with cambic total rainfall in Sosangerd and Bostan diagnostic horizons, formed under is 180 and 200 mm, respectively. There submerged conditions in this region and is a weather station in Bostan. The so they belong to the Aquicambids that agricultural services centers also are cover Fenikhi, Yazd-e-No and Luliyeh equipped with rain gauges. In Table 1.2 series. In this sub-order, the soil profile is some of the factors influential in climate either irrigated and has aquic conditions and evaporation of the Dasht-e-Azadegan for some time in normal years in one or region are presented (Mahab-e-Ghods, more layers within 100 cm of the soil 1992). surface; or is saturated with water in one or more layers within 100 cm of the soil surface for 1 month or more in normal Crops years. Aridisols with the Salic diagnostic horizon that have a upper boundary of Current crops in Dasht-e-Azadegan horizon within 100 cm of soil surface include cereals such as wheat, barley, are classified as Salids. These soils are rice, and ground cereals; vegetables such identified in Jarahyeh and Abohomayzeh as melon, watermelon, tomato, cucumber, soil series. Table 1.1 gives a classification eggplant, okra, lettuce, cabbage, carrot, of the main soil series in Dasht-e- radish, onion, etc; grains such as beans; Azadegan (Mahab-e-Ghods 1992). plants used as fodder for livestock such as alfalfa, barely, corn, and sudan grass. More than 78% of agricultural production Climate in Dasht-e-Azadegan region is dominated by grains (Table 1.3), mainly wheat and The existing statistics indicate that the barley (Mahab-e-Ghods, 1992). weather is hot in summer with a mild and short winter. Annual mean temperature of the region is 23.1ºC. The maximum Water resources daily temperature in the warmest months of the year (July and August) is 43.02ºC The only source of water for the Dasht- and the minimum daily temperature in e-Azadegan is the Karkheh river with the coldest month of the year (January) is its tributaries. The river originates from 5ºC. The average precipitation in the area Zagross mountain ranges and is fed is 175 mm according to statistics of the by snow melt. The average monthly past 10 years. The wettest month of the discharge of the river for the period year is October, with 44.1 mm and the of 1987 to 1998 is shown in Fig. 1.2 driest months are May to late September (Mahab-e-Ghods 1992). There is a when there is almost no precipitation. distinct flood period during winter and Annual mean evaporation in this area is early spring. As explained later these 2004.9 mm. The maximum evaporation floods are the main cause of salinity of 303.6 mm is in July and the minimum and waterlogging in the region, because of 42.7 mm occurs in January. Based on large quantities of salts are deposited the climate data for the last 10 years in the soils as pure water is evaporated at Sosangerd and Howeyzeh stations, during the hot summers. Since the as well as the bioclimatic map of the construction of the Karkheh reservoir Mediterranean region, and despite the dam, the adverse effects of these floods

6 Order fl uvents Entisols fl uvents Entisols fl uvents Entisols fl uvents Entisols Typic SolorcthidsTypic Aridisols Fluventic AquicambidsFluventic Aridisols TorripsammentsTypic Entisols fl uvents Torri Typic Entisols fl uvents Torri Typic Entisols FluvaquentsTypic Entisols fl uvents Torri Typic Entisols Sub group USDA soil taxonomy thermic thermic thermic thermic Family total Area 1290 1.4 (calcareous), hyperthermic Fine, mixed Salortidic Torri 1460 1.6 carbonatic, hyperthermic Coarse loamy, Torri Typic ha % of fi cation of the main soil series Dasht-e-Azadegan (Mahab-e-Ghods1992) Soil series

KaramiYazd-e-Now 15760Abu-Homayzeh 18.2 7990 8100 (calcareous), hyper- Ahmad-Abad mixed Fine loamy, 8.7 8.9Kout 17440 carbonatic, hyperthermic hyperthermic mixed, Fine loamy, 19.1 Fine loamy, (calcareous), hyperthermic Fine, mixed Karkheh Haplosalids Typic Torri Typic Golbahar Aquicambids Fluventic Hovayzeh Aridisols Aridisols 7730 810 8.5 3490 0.9 hyperthermic Fine, mixed, 3.8 hyperthermic mixed, Coarse, loamy, (calcareous), hyper- mixed Fine loamy Salorthids Typic Aridisols Fenikhi 10640 11.6 hyperthermic Fine, mixed, Sousangerd 170 0.2 hyperthermic Mixed, Sariyeh 2300 2.5 (calcareous), hyperthermic Fine mixed Torri Vertic JarrahiyehLouliyehKout 2890Sum 3.2 1620Miscellaneous hyperthermic mixed, Fine loamy, 1.8Total 2040 230 2.2 hyperthermic Fine, mixed, 89430 Haplosalids 97.8 Typic 0.2 91470 (calcareous), hyperthermic Fine, mixed Fluvaquents Aridisols 100 Typic hyperthermic Fine, mixed, Aquicambids Fluventic Entisols Aridisols Hofel SarhangiyehShat-e-Abbas 4100Machriyeh 380 4.5 0.4 (calcareous), hyperthermic Fine, mixed 1950 Fluvaquents Typic carbonatic, hyperthermic Coarse loamy, 2.1 Fluvaquents Typic (calcareous), hyper- mixed Entisols Fine loamy, Entisols 1080 1.2 (calcareous), hyper- mixed Fine loamy

River alluvial plain alluvial River Lowland raphy Physiog- Plateaux Table 1.1. Classi

7 Table 1.2. Metrological parameters of Dasht-e-Azadegan plain (Hamidiyeh station)

Temperature (°C) Precipitation ET Month Average Average Average (mm) (mm) Min. Max. January 5 16.4 10.7 41.3 42.7 February 6.9 19.7 13.3 24.1 62.5 March 11 24.8 17.9 23.3 105 April 15.2 30 22.6 17.7 150 May 19.6 36.6 28.1 6.5 234 June 22 41.8 31.9 0.0 299.2 July 23.7 43.2 33.5 0.2 303.6 August 22.8 43.2 33 0.0 279.8 September 19.2 41.2 30.2 0.7 235 October 14.8 35.1 25 4.2 155.5 November 10.1 26.6 18.3 11.5 88.1 December 6.7 19.1 12.9 45.5 49.5 Average 14.8 31.5 23.1 175 2004.9

Table 1.3. Agricultural production in Dasht-e-Azadegan plain (cropping season 2003-2004)

Planted area Crop Yield (kg/ha) ha % Cereal 67417 90.25 2682 Pulses 626 0.84 1856 Industrial crops 1149 1.54 757 Vegetable 1218 1.63 38266 Summer crops 2836 3.80 28812 Forages 1456 1.94 26540 Total 74702 100 -

Table 1.4. Karkheh river water quality.

EC meq/L RSC iw pH SAR dS/m 3- - 2- 2+ 2+ + + meq/L HCO Cl SO4 Ca Mg Na K 1.48 7.95 2.51 6.49 4.33 4.25 3.3 6.51 0.13 3.35 1.23 have been reduced considerably. The 2001. The main objectives of the dam dam was completed on the Karkheh are to produce hydropower energy (1000 river in 1999 and became operational in GW/h/year), flood water control, and

8 Fig. 1.2. Karkheh river monthly discharge at Hamidiyeh gauging station, 1987-1998 a regulated flow of water for irrigation improper slope of drainage lines) and also of more than 340,000 ha of land due to problems concerning the outlets. downstream. These arable lands are Gravitational drainage to outlet is not located in different plains situated in the feasible and pumping is required. lower parts of the KRB (Mahab-e-Ghods 1992). The quality of Karkheh river water, as a surface resource, is generally good Salinity and waterlogging (Table 1.4), though it varies seasonally and also along the river towards to the The main problems limiting agricultural outlet (Fig. 1.3), which reaches up to 2.4 production in this region are waterlogging dS/m near the Hoor-Al-Azim swamp. and salinity. As indicated before, saline- sodic soils constitute a vast area of There are limited irrigation networks Dasht-e-Azadegan. Soil studies show that in the region (mainly pumping from around 99% of the area of the region river to the canal). The main canals has been faced with either high or low and drains are constructed or under salinity or sodicity for a long time (Table completion (main irrigation and drainage 1.5). Generally, natural and man-made canals in Kout and Hamoodi are under factors are involved in the soil quality of construction). But unfortunately there the region. are no secondary or tertiary canals or lateral drains. At present, despite the Based on the field studies, the soils construction and operation of main of the Dasht-e-Azadegan region are drains, the system is not functioning divided into two types of saline soils and properly in all areas. This is mainly due saline-sodic soils. The smaller portion of to technical and excavation problems (i.e. the region, referring to the Fenikhi soil

9 Saline-sodic soils have some different properties from both saline and sodic soils. If attempts are made to leach out the soluble salts of saline-sodic soils with good quality water, the exchangeable Na+ levels and also pH would increase and therefore, the soil would take on the adverse characteristics of sodic soils. Therefore, attention must first be given to reducing the levels of exchangeable Na+ ions and then to the problem of excess soluble salts.

The situation in Dasht-e-Azadegan seems to be different. Based on the results of leaching experiments and a number of other observations, it is unlikely that the problem of sodicity will be encountered in leaching of these soils without any other treatment. The result of a leaching experiment in the Hofel soil series is given in Table 1.6. Soil salinity and sodicity of the profile to a depth of 150 cm before leaching (zero depth of application) and with application of water in 0.25-m depth increments up Fig. 1.3. Water quality changes along the to 1 m is given (Mahab-e-Ghods 1993). main branches of the Karkheh river After leaching, soil salinity and SAR are both reduced. A regular practice by the farmers is that after the fallow period series, is covered by saline soils with during summer, the soil is leached electrical conductivity (EC) > 4 dS/m, generously with one or two applications exchangeable sodium percentage (ESP) < of water to reduce the accumulated salt 15% and pH of less than 8.5. In contrast, in the seed bed. If there were a danger most of the DA region has saline-sodic of sodic soil development, this regular soils with EC > 4 dS/m, ESP > 15% and practice would result in such soils, but pH of less than 8.5. The Abu-Homayzeh, they are not actually observed. Also, Ahmad Abad, Karkheh, Karami and Yazd- as shown by the data in Table 1.4, the e-Now soil series belong to the saline- SAR of irrigation water is low, which is sodic soil class. It is expected that the favorable for leaching these soils. high values of sodium to calcium plus magnesium ratio would be relatively Leaching experiments of the Karkheh soil dominant. The sodium absorption ration series show an interesting feature (Table (SAR) values varied from 6 to 66 and 1.7). Soil salinity in the lower depths more, out of which most of the samples (below 50 cm) remains the same even had an SAR of more than 13. Table 1.5 after 75 cm of water is applied, indicating shows the extent of saline lands with that water is not moving through these salinity and alkalinity rates (Mahab-e- layers and bypass flow is occurring due Ghods 1993). to deep cracks. This may have great

10 11 120 (0.1) 1290 (1.4) 6810 (7.4) S4A4 10 810 (0.9) 7610 (8.4) 1180 (1.3) S4A3 9 391 (0.4) S3A2/ S2A2 8 1457 (1.5) 4803 (5.3) 1460 (1.6) S3A3 7 783 142 (0.9) (0.2) 5988 (6.5) 3360 (3.6) 5860 (6.4) 2917 (3.2) S3A2 6 887 (1.0) 1037 (1.1) 2240 (1.0) 5816 (6.4) 4830 (5.3) (2.5) 4659 (5.1) S2A2 5 2491 (2.7) 49 (0.1) 986 S2A1 4 31 193 427 276 (0.2) (0.0) (0.5) (0.3) 2002 (2.2) S1A13 S2 2 449 429 568 100 4100 (4.5) (0.5) (0.5) 2450 (0.1) 3289 (2.7) (3.6) (0.6) S1 1 -- (0.1) Sarhangiyeh Hamidiyeh Sariyeh Hovayzeh Karkheh Golbahar Fenikhi Sousangerd 70 Yazd-e-Now Abu- Homayzeh Kout Ahmad-Abad Soil series S0 Hofel Karami Table 1.5. Extent of saline lands with salinity and alkalinity classes (Mahab-e-Ghods 1993)

11 implications in terms of water 11 loss during irrigation episodes, 230 2890 (3.2) (0.2) (12.3 where inefficient surface 11340

S4A4 irrigation is practiced in the area. Improvement of leaching 10 efficiency and irrigation application efficiency should 9600 (10.6)

S4A3 require further research in these soils. 9 391 (0.4)

S3A2/ S2A2 Major causes of soil

8 salinity

7720 (8.4) Major factors causing S3A3 soil salinization in the lower Karkheh basin can 7 be classified as follows

1620 (1.8) (Ghobadian 1969; Cheraghi et 20670 (22.6)

S3A2 al. 2008): • High groundwater table

6 • Salt-containing layers • Inadequate drainage 380 (0.4) 20835 (22.8) facilities S2A2 • High evaporation

5 • Salt intrusion by wind • Sediment transport during 515 (0.5) 3055 (3.3) flood periods. S2A1 9- EC=8-32, ESP=15-30 8- EC=16-32, ESP=30-50 11- EC>50, ESP>50 7- EC=16-32, ESP=15-30 10- EC>32, ESP=30-50 High groundwater level

4 High water tables are the 1150 (1.3) 1150 (1.3) major factor in soil salinization in Khuzestan province. The salt concentration in groundwater is extremely 2929 (3.2)

S1A13 S2 high, exceeding 100 g/L in many cases. It should be mentioned that groundwater 2 285

(0.3) could cause salinity in cases 6- EC=8-16, ESP=15-30 4- EC=8-16, ESP<10 5- EC=8-16, ESP=10-15 11670 (12.8) S1 where its level is higher than a certain depth. This specific 1

70 depth of groundwater is called (0.1) *Electrical conductivities (EC) are in dS/m, ESP is exchangeable sodium percentage, and numbers on *Electrical conductivities (EC) are in dS/m, ESP is exchangeable the parenthesis are areas in percent the critical depth, which varies between 2.5 and 3.5m. It means that soil salinization due to capillaries and its accumulation in the plow layer Total will be expected if the distance

Miscellaneous between the soil surface and Jarrahiyeh Louliyeh Kout Sum Machriyeh Soil series S0 Shat-e-Abbas Table 1.5. (continued) 1- EC<4, ESP<10 3- EC=4-8, ESP=10-15 2- EC=4-8, ESP<10

12 Table 1.6. Soil analyses before and after salt leaching from the Hofel soil series (Mahab-e-Ghods 1993)*

Applied water (cm) Soil depth (cm) ECe (dS/m) SAR 0-25 28 23.4 25-50 25.5 16.6 0 50-75 24.2 21.5 75-100 24.2 16.8 100-150 26.4 15.5 0-25 18.5 17.2 25-50 25.3 - 25 50-75 23.6 15.6 75-100 22.9 16.5 100-150 7.3 18.4 0-25 8.3 9.9 25-50 15.8 - 50 50-75 22.9 17.2 75-100 26.4 19.3 100-150 5.1 19.9 0-25 7.6 5.8 25-50 10.8 9.2 75 50-75 24.5 17.6 75-100 24.8 20.9 100-150 8.9 20.8 0-25 8.3 12 25-50 10.1 11.6 100 50-75 11.1 14.5 75-100 19.3 13.5 100-150 - 19.3

*Characteristics of the soil profile: soil texture, silty loam; soil salinity-sodicity class, S3A2; water table depth, 0.5 m; hydraulic conductivity (K), 0.98 m/d; depth of impermeable layer, > 4 m; salinity class of applied water, C3S1 (EC=1.75 dS/m, SAR= 1.8 , pH= 7.6) the water table is smaller than the above- agricultural practices are more intensified, mentioned depth. In arid and semi-arid the problem is more severe. In LKRB, regions such as the Khuzestan province, the groundwater level in non-arable where upward water flux due to high land (or specific locations which had evaporation is considerable, even fresh not been cultivated during the Iran-Iraq groundwater causes soil salinization war 1979-1989) varies between 4 and because of high groundwater levels. 7 m, while its level is about 1.2-3.0 m Investigations have shown that in most in cultivated land. This difference shows parts of Khuzestan, the groundwater level the significance of agricultural return flow is higher than the critical depth. This case effects. is especially true for the regions where extended agriculture has developed. It A high groundwater level for extended is observed that in non-arable lands, the periods, especially in the hot season, groundwater level is usually deeper than causes specific morphological the critical depth, but near villages where characteristics in the soil profile, which

13 Table 1.7. Result of soil analyses before and after salt leaching in the Karkheh soil series (Mahab-e- Ghods 1993).

Applied water (cm) Soil depth (cm) ECe (dS/m) SAR 0-25 61 66 25-50 59 53 0 50-75 54 50 75-100 56 60 100-150 52 61 0-25 9 62 25-50 22 51 25 50-75 58 58 75-100 62 53 100-150 64 54 0-25 3.4 6 25-50 19 31 50 50-75 55 50 75-100 65 44 100-150 64 36 0-25 3 8 25-50 10 23 75 50-75 54 42 75-100 61 48 100-150 58 45 0-5 3 7 0-25 3 4 25-50 5 10 100 50-75 54 41 75-100 59 37 100-150 47 36 are the results of periodic oxidation- Ramazam road and near Shatt-e-Abbas, reduction conditions due to variations with Machriyeh, Jarrahieh, and Lulieh soil in the groundwater level. These specific series, which are generally flooded during symptoms are more pronounced in early winter up to late spring, the soil the presence of organic carbon and is usually waterlogged half of the year. sesquioxides. One of the most popular Therefore, the soil moisture regime at the signs of this kind is mottling (segregation moisture control section of these profiles of subdominant color different from is aquic with diagnostic symptoms of surrounding region’s color). In the mottling and gley spots. Ahmadabad soil series (west of Dasht-e- Azadegan), which is heavy textured and Salt-containing layers has a hard massive structure, gley spots A salt containing layer is a horizon or a are observed in some profiles below 1m layer of geological material in which salt depth. In the Abohomayzeh soil series, content is not only high but also higher weak gley spots and mottling can be than the rest of the soil profile. If these observed. West of the Bostan-Pol-e- layers are located at a depth less than

14 0.5m below the soil surface, especially in dry season, which is related to the high heavy textured soils, topsoil salinization clay content of these soils. As a result, occurs, as in the case of Khuzestan. infiltration rates are low.

In the Dasht-e-Azadegan plain, despite High evaporation the high calcium carbonate and calcium One of the factors that accelerates soil sulfate content of the soil, no calcic or salinization under high groundwater gypsic diagnostic horizons were identified. conditions is high evaporative However, accumulation of hygroscopic demand, which causes upward flux salts such as CaCl , MgCl , MgSO and KCl 2 2 4 of salt-containing water to the topsoil in combination with NaCl can be observed continuously, or at least in the warm on both sides of the river banks. High season. The critical depth of the temperature differences between river, groundwater table that will cause soil lateral canals and irrigated land cause salinization is highly dependent on moisture diffusion and evaporation that evaporation rate as well as the soil type. in turn leaves huge amounts of salt For example in Khuzestan such depth on the soil surface. Salic diagnostic had been reported to be range between horizons have been identified only in 2.5 and 3.5 m, based on soil type and Abohomayzeh, Kout and Jarahyeh soil evaporation demand. Periods of 260 dry series. In Abohomayzeh and Jarahyeh days in Hamidiyeh, and 290 dry days in series, soil surface is highly dispersed. , are climatic characteristics of the region. In Hamidiyeh, annual precipitation Inadequate drainage facilities is 245 mm, while annual evaporation Most of Khuzestan’s soils are heavy is 2205 mm, or an evaporation to textured and have a slight slope and precipitation ratio exceeding nine. Surface therefore, the importance of adequate evaporation is one of the most important drainage facilities is obvious. However, in meteorological factors in the region many cases little attention has been paid significantly affecting the soil genesis to this problem. Drains, which had been processes. High evaporation leads to a dogged, are generally the main drains capillary rise of soluble salts and their and are deep. Although these drains can accumulation at the soil surface. partly absorb the drainage water of the surrounding area, their effective radius Salt intrusion by wind is small. Natural drains, which discharge The dominant directions of winds in to the main outlet of the region (Hoor- this region are west, northwest, and Al-Azim), are not functioning well due to southeast, which occur as dust storms. technical and environmental problems They carry huge quantities of sediments and due to the very low slope of land. that are mostly deposited on the surface Problems associated with inadequate of the plains. It has been estimated that drainage are more serious in low lands in each storm event 5-50 kg salts/ha and areas with low slope. are deposited on the soil surface, which accumulates to 200-1000 kg/ha annually. The west side of Dasht-e-Azadegan is It is suggested that the deposited salts usually flooded during winter and spring. originate from the coastal lands of both During summer, salts, which have been sides of the Persian Gulf and of the Gulf leached into the sub-soil, tend to rise and of Oman. They represent salt intrusion accumulate on the soil surface due to the by wind erosion. These salt deposits are high evaporation. The surface of these translocated within the region. It has soils is often cracked during the hot and been estimated for Khuzestan province

15 that 10-50 t salts/ha are translocated management to reduce the impact of from one point to another. It should be salinity are suggested to have a rather mentioned that the risk of accumulation temporary effect. To avoid the further of these salts is more serious around the salinization of agricultural soils, the villages (Ghobadian 1969). communities and agricultural agencies are called to apply sound management Sediment transport in the flood practices until adequate drainage is periods installed. The origin of most of the soil series in One of the most important pre-requisites Dasht-e-Azadegan derives from the to enable permanent crop production sediments of Karkheh river and its in this region is the development of a tributaries, except for the lowlands. network to monitor the effect of different Hence, the salt content of sediments from management practices on the salt content Karkheh river affects the salinity and of groundwater, as well as the salt and sodicity of these soils. After flood periods, water balance of the root zone. These a large part of the region is submerged. regular measurements will provide the During the dry season, water drawing data basis required to suggest the best back from land of higher elevation leads methods to prevent restoration of salinity to the formation of small swamps (hour) in the root zone and groundwater. On and permanent ponds in the lowlands. the other hand, water and salt balance Typical examples are the small swamps studies on the watershed scale will around the Hour-Al-. In 1968, increase our ability to predict the role about 3000-4000 km2 of Khuzestan of any hydrological unit in the fate and province were covered with floodwater. behavior of catchments. Cheraghi (2008) The sediment deposited about 1.5 monitored salinity and depth to a shallow million tonnes of salt on the soil surface water table with observation wells during (Ghobadian 1969). November 2003 to April 2004 in Dasht-e- Azadegan. There was a large variation in Amelioration and management salinity of groundwater ranging between 4 strategies and 100 dS/m. No trend was found in the Availability of drainage facilities is way in which salinity changed throughout fundamental to improve the quality of the study area. Salinity variation could be salt-affected soils. It reduces the adverse partly explained because of variation in effects of shallow water tables and soil textures. Salinity of groundwater in waterlogging, and hence, improves crop light-textured soils was less than that of production. There is no doubt that one heavier textured soils. Salinity was also of most important needs for the study lower in the vicinity of the river tributary area is to complete an adequate drainage rather than further away from the river. network for the entire irrigated area. The depth to water table was lowest Encouraging efforts has been initiated, in April as a result of deep percolation but the drainage system is incomplete. from winter rain, over-irrigation of fields, Lateral connections are lacking, and the river flooding, and seepage from earth drainage system covers only a limited channels. The depth to water table area under irrigation. It is noted that reached its maximum in September due agricultural management practices to high evaporation during the hot dry cannot serve as a substitute for adequate summer. This pattern seems to repeat drainage of salt-affected and waterlogged itself throughout the years, hence soils. Most efforts in improved accumulating salt in the soil.

16 Appropriate irrigation schedules based Conclusions on soil-moisture depletion or climatic data would prevent excess losses of KRB is one of the major river basins in irrigation water into the subsoil or the Khuzestan province consisting of groundwater. Land leveling could improve two main sub-basins namely Karkheh water distribution and limit waterlogging Olia (upstream) and Karkheh Sofla problems. Further attention should be (downstream). Agriculture in the paid to the irrigation system. To increase upstream basin is mainly rain fed, the efficiency of water use the irrigation while the downstream basin is mostly water must be applied uniformly. Some irrigated. Dasht-e-Azadegan plain is the of these issues were tested in the field terminal basin of the Karkheh river so as part of this project and the results are all of its tributaries end in this basin. given in Chapter III. The main problems limiting agricultural production in this region are salinity and Generally speaking, the agricultural waterlogging. Saline-sodic soils constitute cropping systems and practices in a vast area of Dasht-e-Azadegan. About the subject area are suboptimal and 99% of the area of the region has been should be improved. At present, the faced with salinity or sodicity for a long crop varieties used by farmers are not time. The salinization of land and water adapted to the prevailing soil conditions. resources has been the consequence of Significant improvements in production both anthropogenic activities (causing could be realized by introducing salt- human-induced or secondary salinity tolerant varieties. As was discussed and/or sodicity) and naturally occurring earlier, 90% of the cultivated area is phenomena (causing primary fossil allocated to wheat. The two varieties salinity and/or sodicity). Major factors grown, Chamran and Verinak, give causing soil salinization in the lower average yields of 2 t/ha. Testing high- Karkheh basin are the high groundwater yielding varieties, available in the country, table, salt-containing layers, inadequate in the area may introduce a more suitable drainage facilities, high evaporation, salt variety for the area. Some varieties that intrusion by wind and sediment transport are bred for salinity tolerance such as during flood periods. Kavir, Bam, Sistan, etc. were tested as part the CPWF projects for improving The management strategies for water productivity in the area and the sustainable utilization of salt-affected results are presented in Chapters IV and soils in Dasht-e-Azadegan should V of this report. consider: installation of a drainage network for the entire irrigated area, Another important factor limiting crop leaching of salts to reduce the adverse production is the accumulation of effects of salt on crop establishment, salt in the top soil that mainly occurs appropriate irrigation scheduling and during the fallow period when the soil water distribution systems, introduction is uncultivated. Leaching of salts before and use of salt tolerant crops, sowing can reduce the adverse effects of improvement of the agricultural cropping salt on crop establishment. Other suitable systems and practices, and development practices are trash mulching and suitable of a network for monitoring the effect of crop rotations. different management practices on the salt content of groundwater as well as salt and water balance of the root zone.

17 References 1995. Salinization of land and water resources. Wallingford, UK: CABI. Abtahi, A., C. Sys, G. Stoops, and H. Ghobadian, A. 1969. Causes leading to soil Eswaran. 1979. Soil forming processes salinity in Khuzestan and their control. under the influence of saline and alkaline Publication number 1. Ahvaz, Iran: College groundwater in the Sarvestan Basin (Iran). of Agriculture, Jundi Shapur University. Pédologie 29: 325-357. Koocheki, A, and Moghaddam, P.R. 2004. Alizadeh, A., I. Malak-Mohammadi, and G.A. History of research on salt-affected lands of Kamali. 2004. Sustainable utilization Iran: present status and future prospects. of saline water in agriculture based on In Prospects of Saline Agriculture in the indigenous knowledge. In Prospects of Arabian Peninsula: Proceedings of the Saline Agriculture in the Arabian Peninsula: International Seminar on Prospects of Proceedings of the International Seminar Saline Agriculture in the GCC Countries, on Prospects of Saline Agriculture in the 18-20 March 2001, eds. F.K. Taha, S. GCC Countries, 18-20 March 2001, eds. Ismail, and A. Jaradat, 507-520. Dubai, F.K. Taha, S. Ismail, and A. Jaradat, 483- United Arab Emirates: AEHS. 490. Dubai, United Arab Emirates: AEHS. Mahab-e-Ghods. 1993. Soil reclamation Anon. 2000. Evaluation of methods and studies of Dasht-e-Azadegan development, amount of the salinization in capable irrigation and drainage plan of Karkheh, lands of Khuzestan province. Management Mahab-e Ghods consulting engineers, and Planning Organization of Khuzestan 1993, Tehran, Iran. Province, Ahvaz, Iran. Mahab-e-Ghods. 1992. Studies of agricultural Banie, M.H. 2001. Soils Map of Iran: Land development plan of Dasht-e-Azadegan, Resources and Potentialities. Tehran, Iran: irrigation and drainage plan of Karkheh, Soil and Water Research Institute. Mahab-e Ghods consulting engineers, Cheraghi, S.A.M. 2008. Evaluation of soil 1992, Tehran. salinity in wheat irrigated fields in several Mahjoory, R.A. 1979. The nature and genesis regions in the country. Final report. Tehran, of salt-affected soils in Iran. Soil Science Iran: Agricultural Research and Education Society of America 43: 1019-1024. Organization. Matsumoto, S. and T. Cho. 1985. Field Cheraghi, S.A.M. 2004. Institutional and investigation on the agricultural scientific profiles of organizations working development of arid regions in Iran. on saline agriculture in Iran. In Prospects III. Soil profile investigations and salt of Saline Agriculture in the Arabian accumulation related to the depth of Peninsula: Proceedings of the International groundwater level. Journal of the Faculty of Seminar on Prospects of Saline Agriculture Agriculture, Tottori University 20: 86-97. in the GCC Countries, 18-20 March 2001, Moghaddam, P.R. and A. Koocheki. 2004. eds. F.K. Taha, S. Ismail, and A. Jaradat, History of research on salt-affected lands of 399-412. Dubai, United Arab Emirates: Iran: present status and future prospects AEHS. – halophytic ecosystems. In Prospects of Cheraghi, S.A.M, Y. Hasheminejhad, and N. Saline Agriculture in the Arabian Peninsula: Heydari. 2008. Causes and management Proceedings of the International Seminar of salt-prone land degradation in lower on Prospects of Saline Agriculture in the Karkheh River Basin. In A Compendium of GCC Countries, 18-20 March 2001, eds. Review Papers, eds. T. Oweis et al. , 81-91. F.K. Taha, S. Ismail, and A. Jaradat, 83-95. ICARDA, Aleppo, Syria. Dubai, United Arab Emirates: AEHS. Dewan, M.L. and J. Famouri. 1964. The soils Soil Survey Staff. 2003. Keys to Soil of Iran. Rome, Italy: FAO. Taxonomy, Ninth edition. Washington DC, Ghassemi, E., A.J. Jakeman, and H.A. Nix. USA: USDA-NRCS.

18