Asian Journal of Chemistry; Vol. 26, No. 15 (2014), 4794-4800 ASIAN JOURNAL OF CHEMISTRY

http://dx.doi.org/10.14233/ajchem.2014.16229

Interactions Between Acidic (Al3+, Fe2+) and Basic (Ca2+, Mg2+) Cations in Oxisol and Ultisol under Acidification Induced by Simulated Acid Rain

1,2,* 3 4 2 RAB NAWAZ , MUHAMMAD ARSHAD , MUHAMMAD SHAHZAD SARFRAZ , MUHAMMAD WASEEM ASHRAF , 2 2 5 MUHAMMAD UMAR HAYYAT , RASHID MAHMOOD and PREEDA PARKPIAN

1Department of Geosciences and Geography, University of Gujrat, Gujrat 50700, Pakistan 2Government College University Lahore, Lahore 54000, Pakistan 3Department of Agriculture and Food Technology, Karakoram International University, Gilgit-Baltistan 15100, Pakistan 4Department of Computer Science, National University of Computer and Emerging Sciences, Chiniot-Faisalabad Campus, Pakistan 5Environmental Engineering and Management, Asian Institute of Technology, Pathumthani 12120, Thailand

*Corresponding author: Tel: +92 53 3643117; E-mail: [email protected]

Received: 24 August 2013; Accepted: 15 November 2013; Published online: 16 July 2014; AJC-15574

This study focuses on the interactions of aluminum and iron with exchangeable bivalent base cations (Ca2+ and Mg2+) at different acidity levels in soils treated with acidic solutions. Acidic (pH 5.0, 4.0, 3.5, 3.0, 2.5, 2.0) and non-acidic (7, control) solutions were applied to the soil columns for 45 days representing average annual rainfall. Soil samples from different depths were analyzed for soil pH (acidity) and target elements (Ca2+, Mg2+, Al3+ and Fe2+). The extractable aluminum and iron increased with a decrease in the concentration of exchangeable calcium and magnesium as the soil pH drops to 5 or low particularly in the upper layers of the investigated soils. The concentrations of soluble base cations increased as soil pH became moderately acidic and decreased as soil pH became highly acidic. However, concentration of exchangeable base cations decreased at higher levels of acidity due to accelerated transformations of exchangeable forms into soluble ones.

Keywords: Soil acidity, Base cations, Trace elements, Acidic deposition, Southeast Asia, Thailand.

INTRODUCTION soils are very highly weathered soils, often rich in Al and Fe oxide minerals, having low cation exchange capacity and The depletion of acid neutralizing capacity (ANC) of soil occupying 7.5 and 8.1 % of the land area, respectively. These + due to inputs of H is called soil acidification, while an increase soils are strongly leached soils with low fertility and are found + in acid neutralizing capacity due to consumption of H is in inter-tropical regions (oxisols) and humid temperate and known as soil alkalinization. There is a variety of processes tropical areas (ultisols) of the world5. Leaching of base cations + that add H ions to the soil system and therefore contribute to and quantification of soil acidification under simulated acid acidification. Although most of these processes occur naturally, rain have already been studied on these highly weathered soils human activities have a major impact on some of them. The of Northeast region of Thailand6,7. The main objective of this + sources of H ions in the soils include acid deposition, biolo- paper was to find out the interactions between soil base cations gical metabolism and accumulation of organic matter, oxida- and extractable aluminum and iron at different acidic condi- 1 tion of sulfur and nitrogen and plant uptake of soil base cations . tions in oxisol and ultisol treated with acidic solutions. Soil acidity affects several chemical and biological properties and reactions that control availability of plant nutrients and EXPERIMENTAL toxicity of certain elements2,3. The availability of plant nutrients (N, P, K, S and Mo) increases, while availability of Fe, Zn, Soil samples of oxisol (Pak Chong) and ultisol (Korat) Mn, Co and Cu increases as the soil becomes more acidified. soils were collected from agricultural fields in the Northeast Soil acidity also affects the microbial activity in soils1. region of Thailand. Samples were prepared for the laboratory Agricultural soils in the Northeast region of Thailand experiments by air drying, mixing thoroughly and sieving belong to oxisols and ultisols soil orders. Kaolonite is the most (2 mm). Samples were analyzed in the laboratory for soil pH, important clay mineral in the soils of the study area4. Such particle size distribution by hydrometer method8, soil organic Vol. 26, No. 15 (2014) Interactions Between Acidic and Basic Cations in Oxisol and Ultisol 4795 matter by wet-oxidation method9, cation exchange capacity Sample preparation and chemical analysis: Soil was (CEC) by 1N ammonium acetate10 and extractable aluminum removed from the columns after experiments. Samples were by 1N KCl11. PVC plastic cylinders (height = 30 cm × diameter prepared for cations and aluminum and iron extraction. Soluble = 15 cm) were used to prepare soil columns for the leaching and exchangeable forms of cations were extracted from soil experiments. samples by water12 and 1N ammonium acetate13, respectively. Nitric acid and sulfuric acid were used to simulate acidic Aluminum and iron were extracted by 1N KCl11 and 0.01 N 14 solutions with pH 5.0 (T2), 4.0 (T3), 3.5 (T4), 3.0 (T5), 2.5 CaCl2 , respectively. The target cations in the extract samples (T6) and 2.0 (T7). To represent unpolluted rain, de-ionized were determined by ICP-OES. water with pH 7.0 (T1) was used as control treatment. The RESULTS AND DISCUSSION radius of soil column (r) and average annual precipitation (h) were used to calculate the volume of the applied solutions Table-1 shows the selected physical and chemical pro- (V), by an equation i.e. V = π r2 h. The experiments were carried perties of the investigated soils. Oxisol (Pak Chong soil) with out on 42 soil columns i.e. 2 soil × 7 pH levels of applied clayey texture has higher CEC due to more clay and organic solutions × 3 replications for each treatment. matter contents as compared to ultisol (Korat soil) having sandy Application of treatment solutions to soil columns: The texture. Pak Chong soil also has higher amounts of total exchan- simulated solutions were applied to the soil columns for a geable bases (TEB) contributing to its higher base saturation period of 45 days representing average annual rainfall (1379.1 (BS) and consequently, lowering sensitivity to acid deposition. mm). Effluent samples were collected at regular intervals and Both soils are slightly acidic in nature. were analyzed for base cations (Na+, K+, Ca2+ and Mg2+) and Interactions of extractable aluminum with exchangeable aluminum (Al3+) using Inductively Coupled Plasma-Optical bivalent base cations: Figs. 1 and 2 show the relationships of Emission Spectrometry (ICP-OES). extractable soil aluminum with exchangeable calcium and

400 180 4000 1200 (a) Ultisol: surface soil (a) Ultisol: surface soil 350 160 3500 1000 300 140 3000 120 800 250 2500 2+ 100 2+ 200 3+ 2000 600 3+ 80 150 1500 60 400 100 40 1000 200 50 500 20 Al Extractable soil) (mg/kg Al Extractable soil) (mg/kg Exchangeable CaExchangeable soil) (mg/kg 0 0 CaExchangeable soil) (mg/kg 0 0 5.91 5.68 5.13 3.75 3.41 3.10 2.83 6.28 6.23 5.98 5.07 4.71 3.71 3.13

400 140 4000 900 (b) Ultisol: middle soil layer (b) Oxisol: middle soil layer 350 120 3500 800 300 3000 700 100 250 2500 600 2+ 2+ 80 3+

500 3+ 200 2000 60 400 150 1500 40 300 100 1000 200

20 Al Extractable soil) (mg/kg 50 500 100 Al Extractable soil) (mg/kg Exchangeable Ca Exchangeable soil) (mg/kg Exchangeable CaExchangeable soil) (mg/kg 0 0 0 0 6.01 5.83 5.41 4.61 4.04 3.34 2.88 6.29 6.31 6.02 5.84 5.41 4.63 3.31 400 120 4000 800 (c) Ultisol: subsoil layer (c) Oxisol: subsoil layer 350 3500 700 100 300 3000 600 80 250 2500 500 2+ 2+ 200 60 3+ 2000 400 3+ 150 300 40 1500 100 1000 200 20 50 100 Extractable Al Extractable soil) (mg/kg 500 Al Extractable soil) (mg/kg Exchangeable CaExchangeable soil) (mg/kg 0 0 Ca Exchangeable soil) (mg/kg 0 0 6.01 5.81 5.45 4.98 4.07 3.38 2.94 6.2 6.3 6.09 5.88 5.44 5.04 3.92 Soil acidity (pH levels) Soil acidity (pH levels)

2+ 3+ 2+ 3+ Exchangeable Ca Extractable Al Exchangeable Ca Extractable Al

Fig. 1. Interactions between extractable aluminum and exchangeable calcium at different acidic conditions in surface, middle and sub-surface layers of oxisols and ultisols 4796 Nawaz et al. Asian J. Chem. magnesium at different levels of soil acidity in different soil Chong soil, similar trend has been observed starting at lower layers of the investigated soils. The concentration of aluminum acidity level (pH 5) particularly in the surface soil layer. increased with a decrease in the concentration of exchangeable However acid rain with pH 2.5 and 2 caused mobilization of calcium and magnesium particularly when the soil pH drops aluminum even in middle and subsoil layers. The concentration to 4.5 or low in almost all the soil layers of Korat soil. The of Al3+ in the surface layer reached 57.0, 130.8, 341.8 and concentration of Al3+ in the upper layer reached 83.2, 108.6 957.4 mg/kg soil at 2707.4, 1792.7, 1205.7 and 602.7 mg Ca2+/ and 163.7 mg/kg soil at 21.1, 85.3, 73.2 and 55.0 mg Ca2+/kg kg soil and 226.3, 152.1, 103.2 and 52.1 mg Mg2+/kg soil as soil and 20.3, 13.3, 14.8 and 9.3 mg Mg2+/kg soil as soil pH soil pH dropped to 5.1, 4.7, 3.7 and 3.1, respectively. These dropped to 3.8, 3.4, 3.1 and 2.8, respectively. In case of Pak large amounts of aluminum in oxisol and ultisol are due to

TABLE-1 BASIC PROPERTIES OF THE INVESTIGATED SOILS Soil Depth Bulk density Particle size distribution (%) pH SOM TEB CEC BS Soil texture type (cm) (Mg m -3) Sand Silt Clay (1:1) (%) (cmol kg -1) (%) (%) Kr 0-30 1.53 80.30 12.43 7.27 Loamy sand 5.82 0.19 2.23 2.75 80.94 Pc 0-30 1.18 34.30 18.43 47.27 Clay 6.31 2.94 17.23 17.72 97.27

40 180 350 1200 )

l (a) Ultisol: surface soil (a) Oxisol: surface soil i

o 35 160 s 300 1000 g

k 140 / 30 g 250 m

( 120 800

+ 25 2 2+

g 100 200 3+ 3+ M

20 600 e l 80 150 b

a 15 e 60 400 g

n 100

a 10

h 40

c 200 x 5 Al Extractable soil) (mg/kg 50 Al Extractable soil) (mg/kg E 20 Mg Exchangeable soil) (mg/kg 0 0 0 0 5.91 5.68 5.13 3.75 3.41 3.1 2.83 6.28 6.23 5.98 5.07 4.71 3.71 3.13

140 45 350 900 (b) Ultisol: middle soil layer (b) Oxisol: middle soil layer 40 800 120 300 35 700 100 250 30 600 2+ 2+ 80 25 200 3+ 500 3+ 60 20 150 400 15 300 40 100 10 200 Extractable Al Extractable soil) (mg/kg Extractable Al Extractable soil) (mg/kg

20 5 Mg Exchangeable soil) (mg/kg 50

Exchangeable Mg Exchangeable soil) (mg/kg 100 0 0 0 0 6.01 5.83 5.41 4.61 4.04 3.34 2.88 6.29 6.31 6.02 5.84 5.41 4.63 3.31

45 120 350 800 (c) Ultisol: subsoil layer (c) Oxisol: subsoil layer 40 300 700 100 35 600 250 80 30 500 2+

2+ 25 200 3+ 400 60 3+ 20 150 300 15 40 100 200 10 20 Extractable Al Extractable soil) (mg/kg 50 100 5 MgExchangeable soil) (mg/kg Al Extractable soil) (mg/kg Exchangeable MgExchangeable soil) (mg/kg 0 0 0 0 6.01 5.81 5.45 4.98 4.07 3.38 2.94 6.2 6.3 6.09 5.88 5.44 5.04 3.92 Soil acidity (pH) levels Soil acidity (pH) levels

2+ 3+ 2+ 3+ Exchangeable Mg Extractable Al Exchangeable Mg Extractable Al

Fig. 2. Interactions between extractable aluminum and exchangeable magnesium at different acidic conditions in surface, middle and sub- surface layers of oxisols and ultisols Vol. 26, No. 15 (2014) Interactions Between Acidic and Basic Cations in Oxisol and Ultisol 4797 development of soil acidity because of significant and profound soils having higher acidic conditions. Such conditions were leaching of calcium from the soil receiving acid rain with pH induced by higher acidic treatments (pH 2.5 and 2.0) 6. In Pak 3.5. Calcium plays a primary role in the amelioration of pH Chong soil, the concentration of Fe2+ reached 8.6 (pH 3.7) and and aluminium-toxicity through Al-Ca interactions improving 15.5 (pH 3.1) in upper, 5.8 (pH 4.6) and 6.4 (pH 3.3) in middle physiological and biochemical processes in plants. As a result and 2.8 (5.0) and 4.5 (pH 3.9) in lower layers. In case of Korat of the negative effects of toxic aluminium, root metabolic soil, the concentration of Fe2+ reached 10.6 (pH 3.1) and 21.2 processes, such as water and nutrient absorption, are disturbed (pH 2.8) in upper, 13.2 (pH 3.3) and 51.4 (pH 2.9) in middle and with an associated decrease in calcium uptake15. Aluminum in 42.8 (3.4) and 54.7 (pH 2.9) in lower layers. At highly acidic the soils increased due to the mobilization as the pH of simu- conditions, exchangeable bivalent cations in three soil layers lated acid rain and soil decreased16. dropped to 55.0, 74.5 and 84.8 mg Ca2+/kg and 9.3, 11.1 and Interactions of extractable iron with exchangeable 12.4 mg Mg2+/kg soil in Korat soil and 602.7, 924.8 and 1029.9 bivalent base cations: Figs. 3 and 4 show the relationships of mg Ca2+/kg soil and 52.1, 63.2 and 102.2 mg Mg2+/kg soil Pak extractable soil iron with exchangeable calcium and magne-sium Chong soil. Strong interactions of extractable Fe2+ with exchan- at different levels of soil acidity in different soil layers of the geable Ca2+ and Mg2+ was found at higher acidity levels caused by investigated soils. Significantly increased concentration of acid rain with pH 2.5 and 2.0. Iron in the soils increased due to its extractable iron has been observed in all the layers of both the mobilization as the pH of simulated acid rain and soil decreased16.

400 25 4000 18 (a) Ultisol: surface soil (a) Oxisol: surface soil 350 3500 16 20 300 3000 14 12 250 15 2500 2+ 2+ 10 200 2+ 2000 8 2+ 150 10 1500 6 100 1000 5 4

50 FeExtractable soil) (mg/kg 500 2 Exchangeable CaExchangeable soil) (mg/kg CaExchangeable soil) (mg/kg Extractable Fe Extractable soil) (mg/kg 0 0 0 0 5.91 5.68 5.13 3.75 3.41 3.10 2.83 6.28 6.23 5.98 5.07 4.71 3.71 3.13

400 60 4000 8 (b) Ultisol: middle soil layer (b) Oxisol: middle soil layer 350 3500 7 50 300 3000 6 40 250 2500 5 2+ 2+ 2+ 200 30 2+ 2000 4

150 1500 3 20 100 1000 2 10 Extractable FeExtractable soil) (mg/kg 50 Fe Extractable soil) (mg/kg 500

Exchangeable Ca Exchangeable soil) (mg/kg 1 Exchangeable Ca Exchangeable soil) (mg/kg

0 0 0 0 6.01 5.41 4.04 2.876666667 6.19 6.31 6.02 5.84 5.41 4.63 3.31

400 70 4000 5.0 (c) Ultisol: subsoil layer (c) Oxisol: subsoil layer 4.5 350 60 3500 4.0 300 3000 50 3.5 250 2500 3.0 2+ 40 2+ 2+ 200 2+ 2000 2.5 30 150 1500 2.0 20 1.5 100 1000 1.0 Extractable FeExtractable soil) (mg/kg 50 10 FeExtractable soil) (mg/kg 500

Exchangeable CaExchangeable soil) (mg/kg CaExchangeable soil) (mg/kg 0.5 0 0 0 0 6.01 5.81 5.45 4.98 4.07 3.38 2.94 6.20 6.30 6.09 5.88 5.44 5.04 3.92 Soil acidity (pH) levels Soil acidity (pH) levels

2+ 2+ 2+ 2+ Exchangeable Ca Extractable Fe Exchangeable Ca Extractable Fe

Fig. 3. Interactions between extractable iron and exchangeable calcium at different acidic conditions in surface, middle and sub-surface layers of oxisols and ultisols 4798 Nawaz et al. Asian J. Chem.

40 25 350 18 (a) Ultisol: surface soil (a) Oxisol: surface soil 35 300 16 20 14 30 250 12 25 15 2+ 2+ 200 10 2+ 20 2+ 8 10 150 15 6 100 10 5 4

Extractable Fe Extractable soil) (mg/kg 50 5 2 Fe Extractable soil) (mg/kg Exchangeable Mg Exchangeable soil) (mg/kg Exchangeable MgExchangeable soil) (mg/kg 0 0 0 0 5.91 5.68 5.13 3.75 3.41 3.10 2.83 6.28 6.23 5.98 5.07 4.71 3.71 3.13

45 60 350 8 (b) Ultisol: middle soil layer (b) Oxisol: middle soil layer 40 7 50 300 35 250 6 30 40 5 2+ 2+ 25 200 2+ 30 4 2+ 20 150 3 15 20 100 10 2 10 50 Extractable FeExtractable soil) (mg/kg 5 1 Fe Extractable soil) (mg/kg Exchangeable MgExchangeable soil) (mg/kg Exchangeable MgExchangeable soil) (mg/kg 0 0 0 0 6.01 5.83 5.41 4.61 4.04 3.34 2.88 6.29 6.31 6.02 5.84 5.41 4.63 3.31

45 70 350 5.0 (c) Ultisol: subsoil layer (c) Oxisol: subsoil layer 40 4.5 60 300 35 4.0 50 250 3.5 30 3.0 2+ 25 40 2+ 200 2+ 2+ 2.5 20 30 150 2.0 15 20 100 1.5 10 1.0 10 50 Extractable Fe Extractable soil) (mg/kg 5 FeExtractable soil) (mg/kg 0.5 Exchangeable MgExchangeable soil) (mg/kg Exchangeable MgExchangeable soil) (mg/kg 0 0 0 0 6.01 5.81 5.45 4.98 4.07 3.38 2.94 6.2 6.3 6.09 5.88 5.44 5.04 3.92 Soil acidity (pH) levels Soil acidity (pH) levels

2+ 2+ 2+ 2+ Exchangeable Mg Extractable Fe Exchangeable Mg Extractable Fe

Fig. 4. Interactions between extractable iron and exchangeable magnesium at different acidic conditions in surface, middle and sub-surface layers of oxisols and ultisols

Interaction between total exchangeable base cations Interaction between total soluble and exchangeable and total trace elements: Fig. 5 shows the relationships between base cations: Fig. 6 shows the relationships between total total extractable trace elements (Al3+, Fe2+ and Mn2+) and total amounts of different forms (soluble and exchangeable) of soil exchangeable base cations (Na+, K+, Ca2+ and Mg2+) at different base cations (Na+, K+, Ca2+ and Mg2+) at different levels of soil levels of soil acidity at different soil depths of the investigated acidity in different soil depths of the investigated soils. No soils. Very strong interaction of trace elements has been found significant change has been observed in the concentration of with total exchangeable base cations in almost all the soil layers total exchangeable base cations under slightly acidic conditions of both soils investigated, particularly under higher acidity in both soils. This is because of smaller leaching of base cations levels caused by higher acidic treatments due to significant under lower acidic treatments7. However, a sharp and conti- leaching of base cations out of the soil column and increased nuous decrease in the exchangeable base cations occurred as mobilization of trace elements in the soils. The concentration the soils became moderately and highly acidic due to very of trace elements increased with a decrease in concentration high leaching and depletion of base cations under higher acidic of exchangeable base cations as the soil pH dropped to 3.8 treatments. (upper), 4.6 (middle) and 5.0 (lower layer) in Korat and 5.1 Soluble base cations also did not show significant change (upper), 5.8 (middle) and 5.0 (lower layer) in Pak Chong soil. in their concentrations at slightly acidic conditions of both the Decreased concentration of base cations was due to their soils. However, contrary to exchangeable form, concentrations leaching under higher acidic treatments7. of soluble base cations increased as soil pH became moderately Vol. 26, No. 15 (2014) Interactions Between Acidic and Basic Cations in Oxisol and Ultisol 4799 ) 500 200 4000 1200 (a) Ultisol: surface soil (a) Oxisol: surface soil layer 450 180 3500 1000 400 160 3000 350 140 800 2500 300 120 250 100 2000 600

200 80 1500 400 150 60 1000 100 40 200 500 50 20 0 0 Total extractable trace elements (mg/kg (mg/kg soil) trace elements extractable Total Total extractable trace elements (mg/kg soil) (mg/kg traceelements extractable Total

0 (mg/kg soil cations base exchangeable Total

Total exchangeable base cations (mg/kg soil) (mg/kg cations base exchangeable Total 0 5.91 5.68 5.13 3.75 3.41 3.10 2.83 6.28 6.23 5.98 5.07 4.71 3.71 3.13

500 200 4500 1000 (b) Ultisol: middle soil layer (b) Oxisol: middle soil layer 450 180 4000 900 400 800 160 3500 350 140 700 3000 300 120 600 2500 250 100 500 2000 200 80 400 1500 150 60 300 100 40 1000 200 50 20 500 100

0 0 soil) elements (mg/kg trace extractable Total Total extractable trace elements (mg/kg soil) traceelements (mg/kg extractable Total Total exchangeable base cations (mg/kg soil) cations (mg/kg base exchangeable Total 0 0 Total exchangeable base cations (mg/kg soil) (mg/kg base cations exchangeable Total 6.01 5.83 5.41 4.61 4.04 3.34 2.88 6.29 6.31 6.02 5.84 5.41 4.63 3.31

500 180 4000 800 (c) Ultisol: subsoil layer (c) Oxisol: subsoil layer 450 160 3500 700 400 140 3000 600 350 120 2500 300 500 100 250 2000 400 80 200 1500 300 60 150 1000 200 100 40 500 100 50 20 0 0

0 soil) (mg/kg trace elements extractable Total 0 soil) (mg/kg trace elements extractable Total Total exchangeable base cations (mg/kg soil) (mg/kg cations exchangeable base Total Total exchangeable base cations (mg/kg soil) (mg/kg cations base exchangeable Total

6.01 5.81 5.45 4.98 4.07 3.38 2.94 6.20 6.30 6.09 5.88 5.44 5.04 3.92 Soil acidity (pH) levels Soil acidity (pH) levels

Total exchangeable base cation Total extractable trace elements Total exchangeable base cation Total extractable trace elements

Fig. 5. Interactions between total exchangeable base cations and total extractable trace elements at different acidic conditions in surface, middle and sub-surface layers of oxisols and ultisols acidic and decreased as soil pH became highly acidic. This is cations (calcium and magnesium) as the soil pH drops to 5 or because of transformations of exchangeable base cations into low particularly in the upper layers of the investigated soils. It soluble ones at moderate acidic treatments and accelerated can be concluded that acidic and basic cations in soils have leaching and depletion of exchangeable forms of base cations antagonistic interactions under higher acidic conditions. from the soils under higher acidic treatments. Soluble base cations increased under moderate acidic soil pH In Korat soil, soluble base cations increased from 74.8 and decreased under highly acidic soil pH. Exchangeable base (original, pH 5.8) reaching 113.7 (pH 3.4), 123.3 (pH 4.0) cations decreased at higher acidic conditions due to accelerated and130.5 mg/kg soil (pH 4.1) in upper, middle and lower layer, transformations of exchangeable base cations into soluble respectively. In Pak Chong soil, soluble base cations increased forms. from 162.5 (original, pH 6.3) to 284.8 (pH 4.7), 281.3 (pH 5.4) and 302.4 mg/kg soil (pH 5.4) in upper, middle and lower ACKNOWLEDGEMENTS layer, respectively. Conclusion Thanks are extended to Higher Education Commission The extractable acid cations (aluminum and iron) increased of Pakistan (HEC) and Environmental Research and Training with a decrease in the concentration of exchangeable base Centre (ERTC), Thailand for financing the research work. 4800 Nawaz et al. Asian J. Chem.

500 140 4000 350 (a) Ultisol: surface soil (a) Oxisol: surface soil 450 120 3500 300 400 3000 350 100 250 2500 300 80 200 250 2000 150 200 60 (mg/kg soil) (mg/kg (mg/kg soil) (mg/kg 1500 150 40 100 1000 100 20 50 50 500 Total exchangeable cationsbase exchangeable Total Total exchangeable cationsbase exchangeable Total Soluble base cations (mg/kg soil) cations (mg/kg base Soluble

0 0 soil) (mg/kg base cations soluble Total 0 0 5.91 5.68 5.13 3.75 3.41 3.10 2.83 6.28 6.23 5.98 5.07 4.71 3.71 3.13

500 160 4500 350 (b) Ultisol: middle soil layer (b) Oxisol: middle soil layer 450 4000 140 300 400 3500 120 250 350 3000 300 100 2500 200 250 80 2000 150 (mg/kg soil) (mg/kg (mg/kg soil) (mg/kg 200 60 1500 150 100 40 1000 100 50 Total exchangeable base cationsbase exchangeable Total Total exchangeable base cationsbase exchangeable Total 50 20 500

0 0 (mg/kg soil) cations soluble base Total 0 0 6.01 5.83 5.41 4.61 4.04 3.34 2.88 6.29 6.31 6.02 5.84 5.41 4.63 3.31 soil) (mg/kg base extractable cations Total

500 160 4000 350 (c) Ultisol: subsoil layer (c) Oxisol: subsoil layer s

n 450

o 140 3500 i 300 t

a 400 c 120 3000 e 250

s 350 a

b 100 2500 300 e

l 200 b

a 250 80 2000 e

g 150

n 200

(mg/kg (mg/kg soil) 60 1500 (mg/kg soil) (mg/kg a h

c 150 100 x 40 1000 e

l 100 a t 20 500 50 o 50 T Total exchangeable cationsbase exchangeable Total Total soluble base cations (mg/kg soil) (mg/kg base cations soluble Total 0 0 0 0 soil) cations (mg/kg base soluble Total 6.01 5.81 5.45 4.98 4.07 3.38 2.94 6.20 6.30 6.09 5.88 5.44 5.04 3.92 Soil acidity (pH) levels Soil acidity (pH) levels

Total exchangeable base cation Total soluble base cations Total exchangeable base cation Total soluble base cations Fig. 6. Interactions between total exchangeable base cations and total soluble base cations at different acidic conditions in surface, middle and sub-surface layers of oxisols and ultisols

REFERENCES biological Properties, Chap. Total Carbon, Organic Carbon, and Organic Matter, Madison, Wisconsin: SSSAJ, pp. 539-579 (1982). 1. N.C. Brady and R.R. Well, The Nature and Properties of Soils, Pearson 10. W.H. Hendershot, H. Lalande and M. Duquette, in ed.: M.R. Carter, Education, New York, USA, edn 13 (2002). Soil Sampling and Methods of Analysis, Chap. Ion Exchange and 2. M.E. Sumner, M.V. Fey and A.D. Noble, in eds.: B. Ulrich and M.E. Exchangeable Cations, Boca Raton, FL: Canadian Society of Soil Science, Sumner, Nutrient Status and Toxicity Problems in Acid Soils, Chap. Lewis Publishers, pp. 197-206 (2006). Soil Acidity, Springer-Verlag, Berlin, pp. 149-182 (1991). 11. R. Barnhisel and P.M. Bertsch, in eds.: eds. A.L. Page, R.H. Miller and 3. P. Lavelle, A. Chauvel and C. Fragoso, Plant Soil Interactions at Low D.R. Keeney, Methods of Soil Analysis, Part 2: Chemical and Micro- pH: Principles and Management, ed. R.A. Date et al., Chap. Faunal biological Properties, Chap. Aluminum, Madison, Wisconsin: SSSA, Activity in Acid Soils, Kluwer Acad. Publ., Dordrecht, The Netherlands, pp. 275-300 (1982). pp. 201-211 (1995). 12. J.D. Rhoades, in eds.: A.L. Page, R.H. Miller and D.R. Keeney, Methods 4. K. Yoothong, L. Moncharoen, P. Vijarnson and H. Eswaran, Appl. Clay of Soil Analysis, Part 2: Chemical and Microbiological Properties, Sci., 11, 357 (1997). Soluble Salts, Madison, Wisc.: SSS, pp. 167-179 (1982). 5. US Department of Agriculture, USDA, The Twelve Soil Orders: Soil 13. G.W. Thomas, in eds.: A.L. Page, R.H. Miller, and D.R. Keeney, Methods Taxonomy (2011); http://soils.cals.uidaho.edu/soilorders/index.htm. of Soil Analysis, Part 2: Chemical and Microbiological Properties, 6. R. Nawaz, S. Ahmad, M. Arshad and P. Parkpian, Int. J. Food Agric. Chap. Exchangeable cations, Madison, Wisc.: SSSA, edn 2, pp. 159- Environ., 10, 956 (2012). 165 (1982). 7. R. Nawaz, P. Parkpian, H. Garivait, P. Anurakpongsatorn, R.D. DeLaune 14. R.V. Olson and R. Ellis Jr., in eds.: A.L. Page, R.H. Miller and D.R. Keeney, and A. Jugsujinda, Commun. Soil Sci. Plant Anal., 43, 1382 (2012b). Methods of Soil Analysis, Part 2: Chemical and Microbiological Prop- 8. B.H. Sheldrick and C. Wang, in ed.: M.R. Carter, Soil Sampling and erties, Chap. Iron, Madison, Wisconsin, edn 2, pp. 301-312 (1982). Methods of Analysis, Boca Raton, FL: Lewis Publishers, Chap. Particle 15. C. Meriño-Gergichevich, M. Alberdi, A.G. Ivanov and M. Reyes-Díaz, Size Distribution, Canadian Society of Soil Science, pp. 499-511 J. Soil Sci. Plant Nutr., 10, 217 (2010). (1993). 16. R. Nawaz, P. Parkpian, M. Arshad, F. Ahmed, H. Garivait and A.S. Ali, 9. D.W. Nelson and L.E. Sommers, in eds: ed. A.L. Page, R.H. Miller and Asian J. Chem., 25, 9891 (2013). D.R. Keeney, Methods of Soil Analysis, Part 2: Chemical and Micro-