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Reclamation of Highly Calcareous Saline Sodic Soil Using Atriplex Halimus and by-Product Gypsum Article in International Journal of Phytoremediation · October 2011 DOI: 10.1080/15226514.2011.573821 · Source: PubMed
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International Journal of Phytoremediation, 13:873–883, 2011 C Taylor & Francis Group, LLC Copyright ! ISSN: 1522-6514 print / 1549-7879 online DOI: 10.1080/15226514.2011.573821
RECLAMATION OF HIGHLY CALCAREOUS SALINE SODIC SOIL USING ATRIPLEX HALIMUS AND BY-PRODUCT GYPSUM
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M. A. Gharaibeh, N. I. Eltaif, and A. A. Albalasmeh Department of Natural Resources and the Environment, Faculty of Agriculture, Jordan University of Science and Technology, Irbid, Jordan The removal of sodium salts from saline soils by salt tolerant crops, as alternative for costly chemical amendments, has emerged as an efficient low cost technology. Lysimeter experiments were carried out on a highly saline sodic soil (ECe = 65.3 dS m−1, ESP = 27.4, CEC = 47.9 cmole(+) kg−1, and pH = 7.7) and irrigated with canal water (EC = 2.2 dSm−1, SAR = 4.8) to investigate reclamation efficiency under four different treatments: control (no crop and no gypsum application) (C), gypsum application equivalent to 100% gypsum requirement (G100 ), planting sea orach (Atriplex halimus) as phytoremediation crop (Cr), planting sea orach with gypsum application equivalent to 50% gypsum requirement (CrG50 ). Soil salinity (ECe) and exchangeable sodium percentage (ESP) were significantly reduced compared to the control. Average ESP and ECe (dS m−1) in the top layer were 9.1, 5.8 (control), 4.8, 3.7 (Cr), 3.3, 3.9 (CrG50 ), and 3.8, 3.1 (G100 ), respectively. Atriplex halimus can be recommended as phytoremediation crop to reclaim highly saline sodic clay loam soils. KEY WORDS phytoremediation, SAR, ESP, sea orach
INTRODUCTION Salt affected soils are widely spread in many arid and semiarid regions of the world and increasingly threatening agricultural expansion and productivity. An important category of salt affected soils is saline-sodic soils with worldwide occurrence of 560 Mha (Tanji 1990). Reclaiming these soils requires efficient, inexpensive amelioration strategies, and good management practices. Generally, sodic and saline–sodic soils exhibit structural problems such as slaking, swelling, dispersion of clay, and surface crusting. Such problems may impede water and air movement, decrease plant-available water, reduce nutrient availability, root penetration and seedling emergence, and increase runoff and erosion potential (Suarez 2001, Qadir and Schubert 2002). These soils can be ameliorated either by chemical amendments or by crops that tolerate high salinity and sodicity conditions (bioamelioration). Amelioration of with chemical
Address correspondence to M. A. Gharaibeh, Department of Natural Resources and the Environment, Faculty of Agriculture, Jordan University of Science and Technology, P.O. Box 3030, Irbid 22110, Jordan. E-mail:
[email protected] 873
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amendments is an established technology. Some amendments (e.g., gypsum) provide a source of calcium (Ca2+) to replace excessive Na+ from the cation exchange sites (Oster 1982; Shainberg et al. 1989), while others (i.e., sulphuric and phosphoric acid) increase the dissolution of calcite in calcareous saline sodic soils (Mace et al. 1999; Gharaibeh et al. 2010). The replaced Na+ is either leached from the root zone by excess irrigation, and/or taken up by crops (Qadir and Oster 2002). Recently, the cost of chemical amendments has increased due to intensive use by industry and reductions in government subsidy to farmers. Alternatively, salt tolerant crops can be used for amelioration if irrigation water and drainage are adequate and soils are calcareous. These crops increase calcite dissolution through their root activity resulting in adequate Ca2+ levels in soil solution that in turn replace exchangeable Na+. The removal of salts by crop parts can significantly contribute to the phytoremediation process when harvested plant parts are not added back to the same soil (Robbins 1986a; Qadir and Oster 2002; Qadir et al. 2005). The process of phytoremediation has been found to be driven by different mechanisms such as: increasing the partial pressure of carbon dioxide (PCO2 ) in the root zone, proton release in the rhizosphere of certain legume crops, Na+, and salt uptake by harvest shoots (Qadir et al. 2005). In addition, phytoremediation is a low cost technology that enhances plant-nutrient availability, extends the depth of ameliorated zone, and may promote stability of soil aggregates and soil hydraulic properties (Ilyas et al. 1993; Robbins 1986a; Qadir and Schubert 2002). In the Jordan Valley, more than one-third of the land suitable for agriculture (∼0.5 Mha) is salt affected soil, 12% of which has an electrical conductivity (ECe) of 4–8 dS m−1, 13% with an ECe of 8–16 dS m−1 and the rest has an ECe greater than 16 dS m−1 (Mashali 1989). As a result of overuse of poor quality irrigation water, the problems of these soils are likely to escalate in the future (Gharaibeh et al. 2009). Atriplex halimus, perennial Chamaephyte, is a highly drought resistant and salt tolerant crop that can be used to ameliorate these soils provided that material is periodically removed to prevent salt returning to the soil (Le Hou´erou 1992). A. halimus is characterized by the presence of vesiculated hairs (trichomes) on the leaf surface. These hairs absorb water from the atmosphere and secrete salts, and upon bursting they deposit salts on the surface of the leaves (Mozafar and Goodin 1970). Moreover, A. halimus is considered an excellent livestock fodder in arid regions because of its high protein content, high water use efficiency, and its ability to produce significant amounts of dry matter under very dry conditions (Le Hou´erou 1992). High adaptation to salinity and high water-use efficiency are mainly linked to the C4 metabolism (McKell 1994). A. halimus and A. nummularia are found in the eastern and the southern parts of Jordan, both species are included in many projects developed by national and international institutions (Tadros 2000). The main objective of this study is to compare the relative efficiency of gypsum and Atriplex halimus L. (Sea orach) on reclaiming calcareous saline sodic soil. MATERIALS AND METHODS Methods of Soil Analysis Surface soil samples from plough layer (20 cm) were collected from a partially cropped field in the southern parts of the Jordan Valley, 20 km north of the Dead Sea. The soil is a clay loam, classified as fine loamy, mixed, hyperthermic, Typic Xerochrept (MINAG 1993). Soil samples were air-dried, gently broken to pass through a 2-mm sieve, thoroughly mixed and analyzed for selected physical and chemical properties. Particle size
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Table 1 Selected chemical and physical properties of original soil
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Property pH ECe (dS m−1) Bulk Density (Mg m−3) Texture Sand (%) Silt (%) Clay (%) Organic Carbon (%) CaCO3 (%) Exchangeable Cations (cmole(+) kg−1) Na+ Ca2+ Mg2+ K+ CEC cmole(+) kg−1 ESP (%)
Value 7.67 65.3 1.3 clay loam 29.21 40.55 30.24 1.33 50.23 13.11 20.4 9.06 1.92 47.9 27.4
analysis was determined by the pipette method (Gee and Bauder 1986), bulk density by the core method (Blake and Hartge 1986), pH was measured in saturated paste extract (McLean 1982), cation exchange capacity (CEC) by the method of Palemio and Rhoades (1977), exchangeable sodium by the ammonium acetate method (Thomas, 1982), soil carbonates by titration method (Richards 1954), soil organic carbon (SOC) by wet oxidation (Nelson and Sommers 1982), and soil EC measured in saturated paste extract (Rhoades 1982). Selected soil properties are shown in Table 1. Column Experiments. The transport of salts and water is important in investigations involving soil chemical and physical properties. Therefore, soil column experiments provide useful information about salt removal and can be used to determine the quantity of water required and the suitable remediation practice for a specific soil. Plexiglass columns (40 cm height, 19.3 cm i.d.) were filled on the bottom with 5 cm of sand (1–2 mm) to facilitate drainage, about 9.8 kg of air-dried soil (
