Open Journal of Soil Science, 2012, 2, 44-49 http://dx.doi.org/10.4236/ojss.2012.21007 Published Online March 2012 (http://www.SciRP.org/journal/ojss) Analysis of Macro and Micronutrients in Soils from Palestine Using Ion Exchange Membrane Technology Zaher Barghouthi1, Sameer Amereih2, Basel Natsheh2, Mazen Salman2* 1Dpartment of Natural Resources Research, National Agricultural Research Center (NARC), Jenin, Palestine; 2Palestine Technical University-Kadoorie, Tulkarm, Palestine. Email: *salman_mazen@daad-alumni.de Received December 15th, 2011; revised January 16th, 2012; accepted January 30th, 2012 ABSTRACT Ion Exchange membrane technology (IEM) is a method that allowed a single extraction process and a single subsequent measurement of different elements that are available in soil. The values of the available forms of the different macro- and micronutrients obtained by IEM extraction were compared with the values of the soluble form obtained by conven- tional extraction methods. In surface soil sample, the concentrations of available potassium, nitrate, phosphate, iron and boron were 37.7 mg·kg–1, 17.5 mg·kg–1, 3.6 mg·kg–1, 171.0 µg·kg–1, and 4.2 µg·kg–1 respectively were greater than that of soluble forms of the same elements which were 7.0 mg·kg–1, 9.2 mg·kg–1, 0.4 mg·kg–1, 109.0 µg·kg–1, and 1.9 µg·kg–1 respectively. Keywords: Ion Exchange Membrane; Available Ions; Soil; Nutrients; Palestine 1. Introduction Soil is a diverse complex that can be defined as a mixture of minerals and organic materials, which are capable of supporting plant life [1,2]. Soil contains 13 out of 16 dif- ferent elements essential for plant growth [3]. However, only small amounts of nutrients are available for plants [4]. Nutrients become available through mineral weath- ering and through decomposition of organic matter into inorganic mineral which are absorbed by plants in the form of ions [2,4,5]. Traditionally, an assessment of the nutrient status in the soil requires a separate extraction and measurement process for most elements; this is cost- ly process in terms of both time and labor [6]. In the last decades Ion exchange resin has been used to assess the availability of plant nutrients where anion and cation ex- change resins are used in numerous ways in soil and plant analysis [7,8]. The method simulates removing ions from soil by plant roots to prevent equilibrium of ions between the solid and the solution phases [9,10]. A major problem in using bead resins is the difficulty in their separation from the soil following the extraction [9,11]. Ion exchange membrane technique (IEM) was devel- oped as an alternative to chemical extraction methods to measure nutrients bioavailability [10,11]. In addition to its simplicity, rapidness and accuracy compared to other existing methods, the technique was found to be highly suitable for soil testing because multi-element in soil can be tested [9,11]. Other advantages of IEM include greater sensitivity to environmental conditions, the potential abi- lity to mimic nutrient uptake by roots, no diffusion prob- lem due to its flat structure and minimal disturbance to soil structure [12]. IEM involves disaggregation of soil by shaking in water during 15 minutes with a glass marble, the elements transfer from the soil to the AEM and CEM during a 16 hours shaking period, removing of the mem- brane from the soil, and finally extracting the elements from the membrane (elution). IEM extraction method al- low single extraction process and a single subsequent mea- surement of the soil available nitrate, phosphate, sulfate by IC, calcium, magnesium, total phosphorous, and heavy metals by inductive coupled plasma (ICP), sodium and potassium by flame photometer, and ammonium by UV/ VIS. Commercial anion exchange resin are generally found in the chloride (Cl–) ion form while cation resin are usu- ally commercialized in the hydrogen (H+) ion form [11]. The aim of this work is to use IEM technology for si- multaneous determination of soluble and available forms of plant micro and macronutrients in surface and subsur- face Palestinian soils. 2. Materials and Methods 2.1. Materials Anion exchange membrane (AEM) and cation exchange *Corresponding author. Copyright © 2012 SciRes. OJSS
Analysis of Macro and Micronutrients in Soils from Palestine Using Ion Exchange Membrane Technology 45 membrane (CEM) were provided by BDH (55164-2S and 55165-2U, respectively). Except where stated, all chemi- cals were of analytical reagent grade. Distilled water (18.2 MΩ·cm) was used for ion chromatography (IC) mea- surements. 2.2. Soil Samples Soil samples were collected from two depths (0 - 30 cm and 30 - 60 cm) from the agricultural station, National Agriculture Research Center (NARC), Jericho, in the Jor- dan Valley in the eastern side of the West Bank. The do- minant soil texture in Jericho is sandy loam [13]. The pH of the surface soil samples was measured after suspend- ing the soil in water (1:1 w/v). The samples were air-dried and sieved using 0.3 mm sieve. 2.3. Extraction of Nutrients Soil samples (10 g each) were transferred to 250-ml Er- lenmeyer flask containing 100 ml of double distilled wa- ter. Each sample was shaken for 30 minutes at 100 rpm on a rotary shaker. The solution was filtered using Whatman #1 filter paper and the filtrate was then passed through 0.2 µm filters. 2.4. Extraction of Available Form of Nutrients CEM and AEM sheets were cut into strips (2 × 6.25 cm). Two strips of CEM and another two strips of AEM were dipped in 250-ml Erlenmeyer flask containing 10 g of soil dissolved in 100 ml of distilled water (18.2 MΩ·cm). The flask was placed on shaker at 100 rpm for 16 h. Ions were then eluted by shaking the strips in 20 ml of 0.1 M HCl for 3 h at 100 rpm. The eluent was taken for ions in- strumental measurements and the strips were regenerated in 100 ml sodium bicarbonate (0.5 M) on electronic shaker (2 hours, 100 rpm) and stored in deionized water prior to be reused. 2.5. Total Amount of Nutrients The total amount of sodium, potassium, calcium, magne- sium was determined by digesting soil sample using Mi- crowave Accelerated Reaction System Model MARS 5. The soil (0.5 g) was suspended in 10 ml distilled water containing concentrated HNO3 (5 ml), HF (4 ml), and HCl (1 ml) in digestion vessel. Digestion was done for 20 mi- nutes at 210˚C. After that 30 ml of 30% boric acid were added to each vessel and the digestion was continued for 5 minutes at 210˚C. 2.6. Extractable Sodium and Potassium Sodium and potassium were extracted according to the method of Richards 1954 [14]. Five grams of soil were suspended in 33 ml of ammonium acetate in 100 ml ele- mentary flask and shacked for five minutes at 100 rpm. Extract was filtered through Whatman #1 filter paper and transferred to 100 ml volumetric flask. The volume of the extract was adjusted to 100 ml with ammonium acetate solution, and filtered by 0.2 µm filter [14]. 2.7. Instrumental Analysis Soluble, available, extractable, and total potassium and sodium forms were measured using Jenway flame photo- meter (Clinical PFP7). The amount of potassium and so- dium in mg·kg–1 was determined according to a calibra- tion curve of potassium and sodium respectively. The VARIAN VISTA-Charged Coupled Device Axial simul- taneous Inductively Coupled Plasma-Atomic Emission Spectrometer (VISTA CCD-AES) with concentric nebu- liser was used for the analysis of soluble, available and total calcium, magnesium, phosphorous, and heavy met- als. Anions including nitrate, sulfate, and phosphate were measured using ion exchange chromatography (IC) sys- tem (Dionex 500) consisting of GP50 gradient pump, ED 40 electrochemical detector, and anion self regenerating suppressor. The stationary phase was IonPac AS11-HC analytical column, 2 mm (P/N 52961) while the mobile phase was 30 mM hydroxide solution (BAKER ANA- LYZED Reagent) with constant flow at 0.38 ml·min–1. Soluble and available ammonium was determined ac- cording to Berthelot analytical procedure [15,16] using PERKIN ELMER UV/VIS Spectrophotometer. Untritro- nic-OR (Selecta P) thermostat was used as an electronic shaker. Soil pH was measured by 3310 JENWAY pH meter. 3. Results and Discussion In past few decades, soil testing has been plagued by many problems that defy accuracy. These problems can be overcome using IEM methodology where the amount of recently nutrients that are available to the plants can be determined. 3.1. Macronutrients 3.1.1. Potassium Potassium is an essential macronutrient for plant growth and development as well as for many plant functions [17, 18]. Testing potassium availability in soil plays the major role in estimating fertilization requirements. Potassium has four soil forms: solution, exchangeable, non-exchan- geable, and mineral. The water soluble and exchangeable forms represent the available fraction of potassium. Whe- reas non exchangeable and mineral potassium forms are known to be slowly available unavailable [19]. Potassium availability is a complex situation; depletion of one form shifts the equilibrium between forms to replenish it (i.e. Copyright © 2012 SciRes. OJSS
Analysis of Macro and Micronutrients in Soils from Palestine Using Ion Exchange Membrane Technology 46 Non-Exchangeable K ↔ Exchangeable K ↔ Soil Solu- tion). Potassium uptake by plants is governed by the rate of transport from the bulk soil to the root via diffusion [20]. It is expedient to measure a parameter that is closely related to diffusion. This might be achieved by measuring the concentration of soil potassium in the solution and exchangeable forms. Figure 1 shows the amount of potassium in soluble, exchangeable, extractable, and available forms measured in soil samples at 0 - 30 and 30 - 60 cm sub surfaces. Ex- tractable potassium represents the available form which was measured by using ammonium acetate extraction me- thod [14]. In some soils (e.g. calcareous) can be estima- ted as the sum of the soluble and exchangeable forms of potassium [21]. In this study the exchangeable potassium (29.3 mg·kg–1) was calculated from the difference be- tween the extractable (36.3 mg·kg–1) and the soluble (7 mg· k g –1) forms. Available potassium was measured using IEM extraction. The available potassium form reflects soluble and exchangeable forms. Our results showed that the available potassium which was measured using the IEM in surface and subsurface soil samples was 37.7 and 27.3 mg·kg–1, respectively. The total potassium in both samples measured using flame photometer was 167 ± 2.7 and 172.4 ± 3.1 mg·kg–1 respectively. 3.1.2. Nitrogen In terms of its requirement and management in the field, nitrogen is the most important nutrient for all crop plants [22]. The availability of nitrogen is closely associated with plant productivity [23,24]. Nitrogen is used by plants in two forms, ammonium (4-N) and nitrate (3-N) [25]. Nitrate is the dominate form of mineral nitrogen available for plant use [26,27]. The sum of the two forms constitutes the pool of plant-available nitrogen [21]. Several laboratory methods have been developed to assess nitrate availability. Most of these methods are in- sensitive to environmental factors that influence the soil nitrogen such as temperature and moisture [12]. IEM is a suitable alternative to overcome environmental sensitiv- ity conditions. In the present work, both soluble and avai- lable forms of nitrate were extracted by IEM and meas- ured by ion exchange chromatography (IC) using Dionex 500 system. Soluble and available forms of ammonium were measured colorimetrically using spectrophotometer. The amount of soluble and available nitrate and ammo- nium are given in Table 1. Our results revealed that the available amount of nitrate and ammonium in both sur- face and subsurface soil were greater than that of the soluble amount. NH NO 3.1.3. Phosphorou s The concentration of available form of phosphorous in soil is very low [21]. Determination of index of available Figure 1. Soluble, exchangeable, extractable, and available forms of potassium in surface (0 - 30 cm) and subsurface (30 - 60 cm) soil samples measured by flame photometer in mg·kg–1. The value of each form in the figure is the average of nine replicates. Table 1. Soluble and available forms of macronutrients in surface (0 - 30 cm) and subsurface (30 - 60 cm) soil in mg·kg–1. Each value in the table is the average for nine replicates. Soluble Available Total 0 - 30 (cm)30 - 60 (cm) 0 - 30 (cm) 30 - 60 (cm) Nitrate 9.2 ± 0.25.6 ± 0.1 17.5 ± 0.3 10.2 ± 0.142.5 Ammonium3.6 ± 0.33.1 ± 0.2 5.0 ± 0.4 3.5 ± 0.315.2 Phosphate0.4 ± 0.10.22 ± 0.04 3.6 ± 0.2 2.9 ± 0.27.12 Sulfate 21.5 ± 0.39.7 ± 0.2 76.2 ± 1.2 44.7 ± 1.4152.1 Calcium 20.4 ± 0.516.5 ± 0.2 69.5 ± 2.1 69.8 ± 1.3176.2 Magnesium5.6 ± 0.34.8 ± 0.1 11.9 ± 0.3 12.1 ± 0.234.4 phosphorous is still a matter of interest [25]. The pool of bioavailable phosphorous is indexed by extraction of a portion of labile pool of inorganic phosphorous using che- mical extractants such as Bray 1, Mehlich 1 or 3, and Olsen’s solution [10,28]. In the present work, the avail- able form of phosphate was tested (Table 1). The amount of phosphate available, in surface and subsurface soils, which was measured using IC system was 3.6 mg·kg–1 and 2.9 mg·kg–1 respectively. The low values of phos- phate indicate phosphorous deficiency. It is well known that phosphorous is considered deficient when the con- centration of available form of phosphorous is less than 6.0 mg·kg–1. 3.1.4. Sulfur Sulfate is one of the most commonly monitored anions in Copyright © 2012 SciRes. OJSS
Analysis of Macro and Micronutrients in Soils from Palestine Using Ion Exchange Membrane Technology 47 soils and natural waters. In soil extracts, sulfate is a mea- sure of the available sulfur status [29]. Sulfate is sub- jected to leaching due to its high solubility. Therefore, it is usually found at variable depths. Our data reveal that the available amount of sulfate is greater than that of the so- luble amount (Table 1). 3.1.5. C alcium an d M agnesium Calcium and magnesium are available as exchangeable cations (Ca2+ and Mg2+). The amount available of both elements is importantly related to mineral weathering and degree of leaching [30]. In the present work the different fractions of calcium and magnesium were measured using ICP instrumental system. The available fractions of both calcium and mag- nesium, in the surface and subsurface soils, were greater than that of the soluble forms. Compared to calcium, ma- gnesium is less strongly absorbed to cation exchange sites. Thus much less available magnesium exists in soils and magnesium deficiencies have been observed frequently. The total amounts in the surface and subsurface soils of calcium were 2142.0 ± 4.9 mg·kg–1 and 2120.0 ± 14.8 mg·kg–1, respectively and the amounts of magnesium were 165.6 ± 1.6 mg·kg–1 and 160.9 ± 4.8 mg·kg–1, respec- tively. 3.2. Micronutrients The pH is a key factor that affects the availability of the micronutrient. Except for molybdenum, availability of mi- cronutrients decreases at higher pH and increased soil cal- careousness due to adsorption precipitation reactions [21, 31]. It was found that the pH of soil under investigation was around 8. In high acidic soils, there is a relative abund- ance of iron, manganese, zinc, and copper ions, which are considered to be toxic to plants. In the present work, IEM was used successfully to determine the amount (in µg·kg–1) of micronutrients cations including soluble and available forms of iron, manganese, cupper, and zinc in both surface and subsurface soils (Figure 2). Cobalt ca- tion was not detected in the soil under investigation. Our results indicated that the concentration of micronutrients in surface soils was lower than that in the subsurface soil samples (Figure 2). Unlike cations, micronutrient anions are quite different chemically, thus little similarity would be expected in their reaction with soil. Boron was measured efficiently by IEM. The soluble and available boron in surface soil samples was 1.9 ± 0.3 µg·kg–1 and 4.2 ± 0.3 µg·kg–1, re- spectively, while soluble and available boron in subsur- face soils was 1.7 ± 0.2 µg·kg–1 and 3.2 ± 0.1 µg·kg–1, respectively. Results of the current work demonstrated that the concentration of boron is within acceptable range for plant growth. In fact, when soil boron levels are less than 0.5 µg·kg–1, deficiency is likely to occur for most crops. However, toxicity may occur when boron levels are greater than 5.0 µg·kg–1 [21]. The total amounts of iron in surface and subsurface soils were 270.5 ± 1.8 and 265.1 ± 4.4 µg·kg–1, and the concentrations of manganese were 4.8 ± 0.1 and 4.6 ± 0.1 µg·kg–1 respectively. There- fore, small fraction from the total amount of micronutri- ents is available to plants. 3.3. Sodium and Some Heavy Metals The measured values of soluble, exchangeable, extract- able, and available forms of sodium in surface and sub- surface soil samples are given in Figure 3. Extractable so- dium (139.4 mg·kg–1) represents the available form which can be measured using ammonium acetate extraction me- thod [14], while exchangeable sodium (83 mg·kg–1) was calculated as the difference between the extractable and the soluble forms. Total soil sodium was determined us- ing the conventional ammonium acetate extraction method Available subsurface Figure 2. Soluble and available iron, manganese, copper, and zinc in surface and subsurface soils measured by ICP- AES in µg·kg–1. Figure 3. Soluble, exchangeable, extractable and available forms of sodium in sur face and subsurface soi l samples mea- sured by flame photometer in mg·kg–1. Each value is the av- erage for nine replicates. Copyright © 2012 SciRes. OJSS
Analysis of Macro and Micronutrients in Soils from Palestine Using Ion Exchange Membrane Technology 48 Figure 4. Soluble and available forms of chromium in differ- ent soil depths measured by ICP in µg·kg–1. (Figure 3). However, this fraction can be determined more accurately by IEM extraction method. Interestingly, the availability of heavy metals was pre- dicted by applying the IEM (Figure 4). Chromium was detected in surface and subsurface soils. 4. Conclusion IEM method allowed a single extraction and a single sub- sequent measurement of the concentrations of the avail- able forms of the different macro- and micro-nutrients. The assessment of plant available nutritional ions using IEM may be superior to the standard chemical extractions. The exchangeable quantity of nutrients, which can rela- tively easily mobilized or mineralized during the growing season, is included in IEM extraction. This leads to better evaluation of the exactly amount of the fertilizer needed for the growing crops. There are no significant differen- ces between available potassium and sodium measured by IEM or that measured by the conventional ammonium acetate extraction. The available amounts of different ions in standard soil sample were measured using IEM extrac- tion method, and the results are in good agreement with that measured by the conventional methods. 5. Acknowledgements The authors thank Prof. Mustafa Khamis and Prof. Magdy el-Dakiky for their suggestions and helpful discussions. Authors also thank the staff of the Center for the Chemi- cal and Biological Research in Al-Quds University for their technical assistance. Special thanks are due to Mr. Azmi Saleh, Palestine Technical University (PTUK) for his constructive and objective comments on the manu- script. REFERENCES [1] A. S. Ayoub, B. A. McGaw, C. A. Shand and A. J. Mid- wood, “Phytoavailability of Cd and Zn in Soil Estimated by Stableisotope Exchange and Chemical Extraction,” Plant and Soil, Vol. 252, No. 2, 2003, pp. 291-300. doi:10.1023/A:1024785201942 [2] N. C. Brady, “The Nature and Properties of Soils,” Mac- millan Publishing Company, New York, 1990. [3] P. H. Raven, R. B. Linda and B. J. George, “Environment,” Saunders College Publishing, Orlando, 1995. [4] E. O. McLean and M. E. Watson, “Soil Measurements of Plant-Available Potassium,” In: R. D. Munson, Ed., Po- tassium in Agriculture, Soil Science Society of America, Madison, 1985, pp. 227-308. [5] R. Durand, N. Bellon and B. Jaillard, “Determining the Net Flux of Charge Released by Maize Roots by Directly Measuring Variations of the Alkalinity in the Nutrient So- lution,” Plant and Soil, Vol. 229, No. 2, 2001, pp. 305-318. doi:10.1023/A:1004860326936 [6] M. J. McLaughlin, P. A. Lancaster, P. W. G. Sale, N. C. Uren and K. I. Peverill, “Use of Cation/Anion Exchange Membranes for Multi-Element Testing of Acidic Soils,” Plant and Soil, Vol. 155-156, No. 1, 1993, pp. 223-226. doi:10.1007/BF00025024 [7] K. J Greer and J. J. Schoenau, “A Rapid Method for As- sessing Sodicity Hazard Using a Cation Exchange Mem- brane,” Soil Technology, Vol. 8, No. 4, 1996, pp. 287-292. doi:10.1016/0933-3630(95)00025-9 [8] R. R. Schnabel, “Nitrate and Phosphate Recovery from Anion Exchange Resins,” Communications in Soil Science and Plant Analysis, Vol. 26, No. 3-4, 1995, pp. 531-540. doi:10.1080/00103629509369316 [9] P. Qian, J. J. Schoenau and W. Z. Huang, “Use of Ion Exchange Membranes in Routine Soil Testing,” Commu- nications in Soil Science and Plant Analysis, Vol. 23, No. 15-16, 1992, pp. 1791-1804. doi:10.1080/00103629209368704 [10] S. Sato and N. B. Comerford, “Assessing Methods for Developing Phosphorous Desorption Isotherms from Soils Using Anion Exchange Membranes,” Plant and Soil, Vol. 279, No. 1-2, 2006, pp. 107-117. doi:10.1007/s11104-005-0437-2 [11] M. B. Turrion, J. F. Gallardo and M. I. Gonzalez, “Ex- traction of Soil-Available Phosphate, Nitrate, and Sul- phate Ions Using Ion Exchange Menbranes and Determi- nation by Ion Exchange Chromatography,” Communica- tions in Soil Science and Plant Analysis, Vol. 30, No. 7-8, 1999, pp.1137-1152. [12] T. Pare, E. G. Gregorich and B. H. Ellert, “Comparison of Soil Nitrate Extracted by Potassium Chloride and Adsorbed on an Anion Exchange Membrane in Situ,” Communica- tions in Soil Science and Plant Analysis, Vol. 26, No. 5-6, 1995, pp. 883-898. doi:10.1080/00103629509369341 [13] Applied Research Institute-Jerusalem, “Environmental Pro- file for the West Bank Volume 2: Jericho District,” Ap- plied Research Institute-Jerusalem, Bethlehem, 1995. [14] L. A. Richards, “Diagnosis and Improvement of Saline and Alkali Soils,” U.S. Government Printing Office, Wash- ington DC, 1954. [15] J. F. van Staden and R. E. Taljaard, “Determination of Ammonia in Water and Industrial Effluent Streams with Copyright © 2012 SciRes. OJSS
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