Phosphorus Sorption-Desorption Characteristics of Selected Acid Upland Soils in Indonesia

Soil Sci. Plant Nutr., 51 (6), 787-799, 2005 787

Phosphorus Sorption-Desorption Characteristics of Selected Acid Upland Soils in Indonesia

Arief Hartono', Shinya Funakawa, and Takashi Kosaki"

Laboratory of Soil Science, Graduate School of Agriculture, Kyoto University, Sakyo-ku, Kyoto, 606-8502 Japan; and *Laboratory of Terrestrial Ecosystems Management, Graduate School of Global Environmental Studies,

Kyoto University, Kyoto, 606-8501 Japan

Received July 22,2004; accepted in revised form June 13,2005

Phosphorus (P) sorption-desorption isotherms were studied in several acid upland soils developed from different parent materials in Indonesia. The soils varied in their chemical and physical properties. P sorption characteristics were satisfactorily described by the Langmuir equation, which was used to determine P sorption maxima and bonding energies. The soils varied widely in their capacity to sorb P. P sorption maxima ranged from 0.294 to 1 . 4 3 ~ 1 0 ~ mg P kg-' (mean 0.620XlOS mg P kg-') and bonding energies ranged from 0.64 to 9.00 L mg-' (mean 3.42 L mg-'). The standard P requirements (P sorbed at 0.2 mg P L-') ranged from 36 to 909 mg P kg-' (mean 231 mg P kg-'). Parent materials affected the P sorption maxima and bonding energies. Soils developed from andesite and volcanic ash exhibited signifkantly higher P sorption maxima and bonding energies with a larger vari- ability than the soils developed from sedimentary rock and volcanic sediments. Principal component analysis demonstrated that three principal components in Indonesian acid upland soils influenced P sorption, namely oxide-related factor (aluminum (Al) plus l/2 iron (Fe) (by ammonium oxalate), crystalline Al and Fe oxides, cation exchange capacity, and clay content), acidity plus 1.4 nm mineral-related factor (exchangeable Al and 1.4 nm minerals) and organic carbon (C)-related factor (organic C and organically bound Fe). Stepwise regression demonstrated that the oxide-related factor was the main component actively contributing to P sorption maxima and bonding energies in these acid soils. It was demonstrated that the acidity plus 1.4 nm mineral-related factor led to the decrease of P sorption maxima. The organic C-related factor did not influence the P sorption maxima but decreased the P bonding energies. The results suggested that not only Al and Fe oxides but also soil acidity which is associated with exchangeable Al and 1.4nm minerals of which smectite and vermiculite are common, should be included in models to estimate P sorption maxima in Indonesian acid upland soils. Furthermore, organic C content and organically bound Fe should be included in the models to estimate P bonding energies. Extraction with 0.01 mol L-' CaCI, led to a low soil desorbability of sorbed P (45%) and the desorbability was highly significantly correlated with the bonding energies during sorption.

Key Words: acid upland soils, Indonesia, P sorption-desorption, soil properties.

Upland soils in Indonesia account for about 75% of the total land area. Approximately 57% of these upland soils are acidic, and are distributed mostly in western Java, Sumatra and Kalimantan (Subagyo et al. 2000).

The majority of these soils exhibit a low nutrient status and are extremely deficient in phosphorus (P). Gen- erally, since the total and available P contents are low, P fertilizer application is recommended. Because P fertilization must be based on a sound knowledge of the

' E-mail: [email protected]

behaviour of P added to soil, it is important to study the P sorption-desorption characteristics of some major acid upland soils.

P sorption characteristics of different types of soils have been determined by a number of investigators. P sorption is generally attributed to hydrous oxides of Fe and Al, particularly in tropical soils with a low pH (San- yal and De Datta 1991). Other soil characteristics such as pH, clay content, organic matter content, exchangeable cation contents, ionic strength, redox potential, temperature and surface area have been found to influ-

788 A. HARTONO. S. FUNAKAWA. and T. KOSAKI

ence P sorption by soils (Mokwunye 1975; Juo and Fox 1977; Agbenin and Tiessen 1994). Moreover, P sorption isotherms have been used to obtain information about the capacity and intensity aspects of P availability (Fox and Kamprath 1970), and the amount of P sorbed at a standard supernatant concentration has been used as an estimate of the amount of fertilizer P required for optimum plant growth (Fox and Kamprath 1970; Juo and Fox 1977).

Recent studies have provided more detailed information about the active components in P sorption. They have shown for example that the soil components actively engaged in P sorption differed according to the regions. It appears that the P sorption behaviour is location-specific, depending particularly on the degree of soil weathering and the microclimatic conditions (van der Zee and Riemsdijk 1988; Beauchemin and Simard 2000; Dodor and Oya 2000; Dubus and Becquer 2001; Maguire et al. 2001; Henry and Smith 2002; Agbenin 2003; Bertrand et al. 2003).

Although P sorption has been studied in other countries and different soil types, published information about the P sorption-desorption characteristics and appropriate models to estimate the P sorption capacity of Indonesian acid upland soils are not available.

The objectives of the present study were to provide data on P sorption and desorption isotherms of these acid soils and to examine the soil components active in

influencing P sorption-desorption in these soils.

MATERIALS AND METHODS

Soil samples. Thirty samples were collected from the surface and subsurface horizons of 15 acid upland soils in Sumatra, Java and Kalimantan. The location of the sites where the soil samples were collected is presented in Fig. 1.

Methods of soil analyses. Soil samples were air- dried and crushed to pass through a 2-mm mesh sieve. Selected chemical properties that can affect P dynamics were analyzed. pH was measured in a 1 : 1.5 (w/v) water solution using a pH meter. Clay content was determined by the pipet method. Clay minerals were identified by X-ray diffraction analysis (Rigaku RAD-2RS Diffracto- meter). Clay mineralogical composition was semiquan- titatively assessed by measuring the 0.7 nm, 1.0 nm and 1.4 nm peak areas on the X-ray diffraction diagram for the oriented specimens of magnesium-saturated and air- dried clay, and calculating the area of each peak as the percentage of the total area of the three peaks (Kawa- guchi and Kyuma 1977). The 0.7 nm minerals are considered to include 1:l type clay minerals of the kaolin group, and 1 .O nm minerals as illite or clay micas. The 1.4 nm minerals consisted mainly of smectite, vermiculite, and Al-interlayered vermiculite-chlorite intergrades.

0 South China Sea

c,

Kalimantan tr Sumatra

Kota Bumi Java sea

Kartng Pandan

t Darmaga

Tegal Garu Sampling site Indian Ocean

Pringsurat 200 km

I 4 1

100' 1050 1100 1150 12OoE

Fig. 1. Location of soil sampling sites.

P Sorption-Desorption of Acid Soils in Indonesia 789

The content of organic carbon (C) in soil was measured with a NC analyzer (Sumigraph NC analyzer NC-800- 13 N, Sumika Chem. Anal. Service). Available P content was obtained by the Bray 1 method (Bray and Kurtz 1945), while the absorbance at 693 nm was determined using a UV-VIS spectrophotometer (UV- 1200, Shima- dzu Corporation, Japan). Cation exchange capacity (CEC) was obtained by extraction with 1 mol L-' NH,OAc pH 7.0 and the contents of exchangeable bases (calcium and magnesium) were determined by atomic absorption spectrophotometry (AA-640- 12, Shimadzu Corporation) while those of exchangeable potassium and sodium were determined by flame emission spectrophotometry (AA-640- 12, Shimadzu Corporation). Base saturation was defined as the ratio of total exchangeable bases to CEC, expressed as a percentage. Exchangeable A1 was extracted with 1 mol L-' KCl.

The contents of dithionite-citrate-bicarbonate-extractable iron (Fe) and aluminum (A1 ) (Fed and Al,) were determined according to the method of Mehra and Jack- son (1960). The contents of oxalate-extractable Fe and A1 (Fe, and Al,) were obtained by extraction with 0.3 mol L-' ammonium oxalate, at pH 3 for 4 h in a dark room (McKeague and Day 1966). Organically bound Fe and A1 (Fep and Alp) contents were obtained by extraction with 0.1 mol L-' sodium pyrophosphate at pH 10 (McKeague 1967). Extracted Fe and A1 of Fed and Al, and of Al, and Fe, were filtered through a syringe filter with a 0.45 bm pore size (Minisart RC 15, Sartorius, Hannover, Germany), while those of Fe, and Alp were filtered through a Millipore filter with a 0.025 brn pore size (Millipore Corporation, Bedford, USA). Contents of extracted Fe and A1 were then determined by induc- tively coupled plasma-atomic emission spectroscopy (SPS 1500, SEIKO).

P sorption data were obtained using the procedure described by Fox and Kamprath (1970). Duplicate 3 g samples (<2 mm) from each of the 30 samples were equilibrated in 30 mL of 0.01 rnol L-' CaCl, containing P at various concentrations (0-100 mg L-') as KH,PO, for 6 d at 25°C. Two drops of toluene were added to sup- press the microbial activity, and the suspension was shaken for 30 min twice daily. At the end of the equilibration period, the soil suspensions were centrifuged at 1,400Xg for 15 min and filtered (filter paper No. 6, Advantec Toyo, Tokyo, Japan). The amount of P in the supernatant solution was determined by the procedure of Murphy and Riley (1962). The absorbance at 693 nm was determined using a UV-VIS spectrophotometer (UV-1200, Shimadzu Corporation). The amount of P sorbed by the soils was calculated as the difference between the amount of P added and the amount remaining in solution. Since P sorption usually varies with the pH, experiments were conducted at soil pH values natu-

rally occurring. The P sorption data were fitted to the linear form of

the Langmuir equation, as described below, to determine the maximum sorption capacity and bonding energy.

clq = c/b + 1 IKb

Where, c=the equilibrium concentration of P in the soil solution, q=the quantity of P sorbed per unit mass of sorbent, b=P sorption maximum, K=a constant related to the bonding energy of sorption.

For studying P desorption, the soil from an adsorption run (after the supernatant solution was decanted off) was resuspended with vigorous shaking in an aliquot of 28 mL of 0.01 mol L-' CaCl, (Fox and Kamprath 1970). Samples were further shaken for a 30-min period twice daily for 6 d for equilibration. At the end of the period, the soil suspensions were centrifuged at 1,400Xg for 15 min and filtered (filter paper No. 6, Advantec Toyo). P content in the supernatant solution was determined by the procedure of Murphy and Riley (1962). The absorbance at 693 nm was determined using a UV-VIS spectrophotometer (UV- 1200, Shimadzu Corporation). The amount of P sorbed after desorption was calculated as the difference between the amount of intial P sorbed and the amount remaining in solution. Desorption experiments were conducted at 25°C. Data obtained were fitted to the Langmuir equation.

Standard P requirement, which is expressed as the amount of P sorbed when the equilibrium concentration was 0.2 mg P L-' was also determined.

Statistical analyses. Correlation analysis and ANOVA followed by a Tukey's test were applied. Prin- cipal component analyses (PCA) and stepwise multiple regression were also applied. SYSTAT 8.0 was used for the analyses (SPSS, Inc. 1998).

RESULTS AND DISCUSSION

Soil characteristics and their relationships Parent materials and distribution of silicate clay min-

erals are presented in Table 1. Samples from Java were taken from soils mostly developed from quaternary andesite and volcanic ash, except for the Gajrug soils which were developed from a volcanic ash-sedimentary rock mixture. The soils from Sumatra were developed from quaternary andesite, granite, volcanic sediments, and a volcanic ash-sedimentary rock mixture. All the samples taken from Kalimantan were derived from soils with tertiary sedimentary rock. Judging from the parent materials, the soil samples from Java and Sumatra were younger than those of Kalimantan. The dominant silicate clay minerals in the samples from Java and Sumatra were 0.7 nm minerals with a small amount of 1.4 nm

790 A. HARTONO, S. FUNAKAWA, and T. KOSAKI

Table 1. Parent materials and distribution of silicate clay minerals in the soils used.

Location Depth (cm)

Parent material

~~ ~ ~~ ~

Type of silicate clay mineral

0.7 nm 1.0 nm 1.4 nm

Java Darmaga

Gajrug

Tegal Garu

Karang Pandan

Pringsurat

Sumatra PD I

PD2

Kota Bumi

Rimbo Bujang

Sitiung

Kalimantan Sebuluh

Kota Bangun

SM-BP

SM 1

Teluk Dalam

0-13 54-94 0-14

38-60 0-15

42-60 0-10

15-42 0-9

19-52

0-14 14-35 0-27

27 -40 0-20

20-47 0-4

40-70 0-14

45-70

0-9 20-37 0-4 4-42 0-1 1

11-30 0-10

10-30 0-9

20-30

Andesite

Volcanic ash-sedimentary rock mixture

Volcanic ash

Volcanic ash

Volcanic ash

Andesi te

Granite

Volcanic sediments

Volcanic sediments

Volcanic ash-sedimentary rock mixture

Sedimentary rock

Sedimentary rock

Sedimentary rock

Sedimentary rock

Sedimentary rock

94 81

5 2

92 96 94 98 94 43

71 55 98 98

100 100 97 98 94 94

52 24 92 87 88 88 68 43 76 93

%

0 0 0 0 4 2 3 1 3

43

0 0 1 1 0 0 0 0 2 1

0 0 0 0 0 0 0 0 0 0

6 19 95 98 4 2 3 1 3

14

29 45

1 1 0 0 3 2 4 5

48 76 8

13 12 12 32 57 23

7 0.7 nm: kaolin group; 1.0 nm: illite or clay micas; 1.4 nm: smectite, vermiculite and Al-interlayered vermiculite-chlorite intergrades.

minerals of which smectite was the most common. However, some soils from these regions displayed a different silicate clay mineral distribution. Soil from Pring- surat, Java, in the subsurface also contained the same amount of 1.0 nm minerals as that of 0.7 nm minerals. Soil from PD 1, Sumatra, in the subsurface horizons showed a comparable amount of 1.4 nm minerals (Al- interlayered vermiculite-chlorite intergrade). Soils from Gajrug, Java, were dominated by 1.4nm minerals (smectite). The dominant silicate clay minerals in the Kalimantan samples were 0.7 nm minerals and 1.4 nm minerals (vermiculite).

Selected chemical and physical properties of the soils are listed in Table 2. The pH values ranged from 4.04 to 5.61 in the surface and 4.03 to 5.37 in the subsurface horizons. The clay content of the soil samples developed from andesite and volcanic ash (e.g. soil samples from Java, and some soil samples from Sumatra) exceeded 60% for both surface and subsurface horizons. Sandy soils from Kalimantan and soils from Sumatra which

were developed from granite (e.g. PD2), and volcanic sediments (e.g. Kota Bumi and Rimbo Bujang) mostly showed low clay contents (<40%). Organic C contents ranged from 11.0 to 53.9 g kg-' in the surface and 3.90 to 15.4 g kg-' in the subsurface horizons. Exchangeable A1 contents ranged from non-detectable (nd) levels to 23.1 cmol, kg-' in the surface and nd levels to 24.4 cmol, kg-' in the subsurface horizons. The highest value of exchangeable A1 was observed in the soil sample from Gajrug. This high level of exchangeable Al was assumed to be due to the presence of 1.4 nm minerals (smectite). Some soils from Java (e.g. Karang Pandan and Pringsurat) and from Sumatra (e.g. PD1, PD2 and Kota Bumi) did not contain exchangeable Al. All the soil samples from Kalimantan contained exchangeable Al. The contents of available P (as measured by Bray 1) ranged from 0.90 to 48.0 mg P kg-' in the surface and from nd levels to 3.22 mg P kg-' in the subsurface horizons. The values of Bray 1-P were relatively low except for those from Teluk Dalam (Kalimantan), presumably

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792 A. HARTONO, S. FUNAKAWA. and T. KOSAKI

Table 3. Simple correlation coefficient (Pearson r ) among soil properties.

Clay Organic Base Exchange- Bray 0.7 nm 1.4 nm minerals minerals C Alp Fep A I o + I n CEC saturation able A1

PH H,O 0.31 0.45 -0.20 0.02 0.51 0.62* 0.43 0.07 0.63* -0.42 -0.13 0.16 -0.25 Clay 0.02 0.28 -0.00 0.53 0.62* 0.88** 0.64* 0.08 0.19 -0.39 -0.00 -0.10 Organic C 0.27 0.54 0.49 0.42 0.05 0.16 0.46 -0.04 0.04 0.06 -0.01

0.24 0.14 -0.03 0.46 -0.03 0.53 0.10 -0.43 0.48 A1,+1/2 Fe, 0.84** 0.38 0.44 0.16 0.06 -0.27 -0.06 0.06 AI,-AI, 0.66** 0.45 0.16 -0.05 -0.30 0.00 -0.02 Fed-Fe, 0.49 0.17 0.03 -0.31 -0.06 -0.05 CEC -0.18 0.78** -0.23 -0.52 0.50 Base saturation -0.48 0.22 0.18 -0.22 Exchangeable At -0.08 -0.65* 0.70** Bray I-P 0.06 -0.03 0.7 nm minerals -0.97**

0.74** 0.26 0.15 0.13 0.83** -0.27 0.92** -0.09 -0.60 0.65* '41, Fe,

*p<0.05; **p<O.OI with Bonfemni Probabilities. The subscripts p, 0, d denote selective extractions with pyrophosphate, oxalate, and dithionite- citrate-bicarbonate, respectively.

due to the low P fertilization levels, since most of the land is used for subsistence upland agriculture and agro- forestry. CEC values ranged from 5.74 to 40.3 cmol, kg-' in the surface and from 3.92 to 42.2 cmol, kg-' in the subsurface horizons. The highest values of CEC were recorded in the soil samples from Gajrug. The CEC values seemed to increase with increasing amounts of clay and were also determined by the types of clay minerals in the soils. The high CEC values in the Gajrug soils were due to the predominance of 1.4 nm minerals (smectite). Soils from Kalimantan showed very low CEC values (mostly were below 15 cmol, kg-I). In general, the CEC values in the subsurface horizons were higher than those in the surface horizons. Base saturation ranged from 7.27 to 62.5% in the surface and 0.41 to 38.2% in the subsurface horizons. Base saturation was directly related to the soil pH. In some soils (e.g. Karang Pandan, Pringsurat, PDl, and Kota Bumi) with higher pH values the base saturation levels exceeded 35% . The values of Fed and Al, were higher than those of Feu and Al, except for the Kota Bangun soils, suggesting that most oxides were well-crystallized. Alp contents ranged from 0.25 to 4.97 g kg-' in the surface and from 0.17 to 4.00 g kg-' in the subsurface horizons. Fe, contents ranged from nd levels to 4.15 g kg-' in the surface and from nd to 0.91 g kg-' in the subsurface horizons.

Simple correlation coefficients (Pearson r ) among the soil properties are presented in Table 3. Oxalate-extractable-A1 and Fe oxide were expressed as Alu+ 112 Fe,, as one of the andic soil properties (Soil Survey Staff 1998) and crystalline Al and Fe were denoted as A1,-AI, and Fed-Feu respectively (Table 3).

The clay content was highly significantly @<0.01) correlated with the Fed-Fe, content and significantly QK0.05) correlated with the AId-AI, content and CEC. It was also correlated with the Al,+ 1/2 Fe, content but

this correlation was statistically not significant. Sandy soils which developed from sandstone (sedimentary rock) in Kalimantan, and granite in Sumatra, contained lower amounts of Fed-Fe,, and AI,-Alu. The clay content of these soils was mostly below 40%.

The Alp content was highly significantly (p<O.Ol) correlated with the Fe, content, CEC and exchangeable Al content but not significantly correlated with the organic C content. A large part of Alp in these soils may occur as exchangeable Al, which contradicts the close positive relationship between the Alp and organic C contents reported by Dubus and Becquer (2001). Moreover the exchangeable Al content was highly significantly (p<O.Ol) correlated with the content of 1.4 nm minerals, indicating that the presence of exchangeable A1 was associated with 1.4 nm minerals of which smectite and vermiculite were the most common.

P sorption parameters Langmuir P sorption maxima, bonding energies and

standard P requirements (P sorbed at 0.2 mg P L-' ) as well as R2 values for the Langmuir equation are presented in Table 4. The P sorption data were satisfactorily described by the Langmuir equation with regression coefficients ranging from 0.90 to 0.98 (Table 4) even in the high equilibrium P concentration range. These results agreed with the findings of Dodor and Oya (2000) but contrasted with the reports of Quang et al. (1996) and Henry and Smith (2002), who suggested that the equation could be used for simulation only in a lim- ited range of equilibrium P concentrations. Selected soils representing low P and high P equilibrium concentrations are presented in Fig. 2. The P sorption maxima varied among the soils, ranging from 0.294 to 1.43X 10' mg P kg-' with a mean value of 0.621 X lo3 mg P kg-' and a standard deviation of 0.33 1 X 10" mg P kg-'. Bonding energies also varied, ranging from 0.64 to


'hble 4. at 25°C.

Equilibrium Langmuir sorption maxima (h), bonding energies (K), standard P requirements of the soils and R-' value

Sorption maximum P sorbed at 0.2 mg R? value of P L-1 Langmuir equation Bonding energy ( K )

(b) Location Soil order" Depth

Java Darmaga Inceptisols

Ultisols

Ultisols

Alfisols

Alfisols

0- 13 54-94 0- 14 38-60 0- 15 42-60 0- 10 15-42 0-9 19-52

0.526 0.500 0.625 0.556 0.556 0.556 1.11 1.11 1.11 1.25

6.33 5.00 8.00 9.00 3.60 3.60 3.00 4.50 4.50 8.89

294 250 385 357 233 233 417 526 526 800

0.98 0.96 0.96 0.98 0.96 0.98 0.98 0.98 0.98 0.98

Gajrug

Tegal Garu

Karang Pandan

Pringsurat

Sumatra PD 1 Ultisols

Ultisols

Alfisols

Ultisols

Ultisols

0- 14 14-35 0-27 27-40 0-20 20-47 0-4 40-70 0- 14 45-70

1.43 1.43 0.435 0.476 0.526 0.4 17 0.417 0.435 0.588 0.588

3.50 8.75 1.64 2.33 1.19 1.85 0.86 1.92 5.67 8.50

588 909 108 152 101 112

120 313 370

61.0

0.98 0.98 0.98 0.98 0.94 0.94 0.98 0.98 0.98 0.98

PD2

Kota Bumi

Rimbo Bujang

Sitiung

Kalimantan Sebuluh Ultisols

Ultisols

Ultisols

Ultisols

Ultisols

0-9 20-37 0-4 4-42 0-11 11-30 0-10 10-30 0-9 20-30

0.400 0.385 0.303 0.294 0.500 0.400 0.455 0.435 0.417 0.400 0.62 I 0.33 1

0.64 I .53 0.65 1.55 0.95 1.19 0.92 1.05 0.80 0.83 3.42 2.84

45.5 90.1 34.7 69.4 80.0 76.9 70.4 75.2 57.5 57.1 250 23 1

0.94 0.98 0.98 0.98 0.90 0.98 0.98 0.98 0.98

. 0.98

Kota Bangun

SM-BP

SM 1

Teluk Dalam

Mean SD

"Soil Survey Staff (1998).

a b

0.006 0 Kota Bangun 0-7 cm

A PD 2 0-27 cm

0.07 Rz = 0.98 /" 0 Sebuluh0-9cm :::: [ y m = o . o 0 3 3 x +0.0051

0 Darmaga 0- I3 cm

AGajrug0-14cm yD = 0 . 0 0 2 ~ + 0.0004

R2 = 0.98 0.005

3 0.004

5 m 0.003

0.002

0.00 I

0

- - M

\ 0

0 Sitiung0-14 cm

yS=O.O017x +0.0003 R2 = 0.98

yG=O.O016x +0.0002 R2 = 0.96

0 1 2 3

0.06

2 0.05

0.04 2-

0.03

0.02

0.0 I

0

- ,0039 ysB = 0 . 0 0 2 5 ~ + 0

R2 = 0.94

R2 = 0.98

0 5 10 I5 20 25 c (mg P L') c (mg P L-I)

Fig. 2. Langmuir adsorption isotherm for P sorption by soils at 25°C with low equilibrium P concentration (a) and with high equilibrium P concentration (b). q denotes the amount of P sorbed by unit weight of soil and c denotes the equilibrium P concentration.

794

800 '=: 700

B 6 o o - .C 8 500 S m - : 300

C

A. HARTONO, S. FUNAKAWA, and T. KOSAKI

r = 0.92 - -

-

#* ** ** -

Table 5. Effect of parent materials on sorption maxima (b) and bonding energies (0.

Parent material Sorption maximum

(b) SD Bonding energy (K) SD

(mg P kg-9 (L mg-9 Andesi te 971a 45 8 5.90ab 1.93 Granite 456ab 20.7 1 . 9 9 ~ 0.35 Volcanic ash 949a 283 4.68b 1.96 Volcanic sediments 449b 45.5 1.4% 0.45 Volcanic ash-sedimentary rock mixture 589ab 24.6 7.79a 1.28 Sedimentary rock 399b 59.4 1.01c 0.3 I

Means followed by the same letter within a column are not significantly different (Tukey's test, p<O.Ol).

h

-2 a900 loOo r:

Fig. 3. P requirements.

Correlation between P sorption maxima and standard

9.00L mg-' with a mean value of 3.42L mg-' and a standard deviation of 2.84 L mg-' (Table 4).

Some soils from Java and Sumatra (e.g. Karang Pan- dan, Pringsurat, Darmaga, Gajrug, Tegal Garu, Sitiung and PD1) exhibited higher sorption capacities (0.500 to 1.50X lo3 mg P kg-') and higher bonding energies (3 to 9 L mg-') in contrast to the soils from Kalimantan in which the P sorption maxima ranged from 0.294 to 0.500X lo' mg P kg-' and bonding energies from 0.64 to 1.55 L mg-'. Low P sorption maxima and bonding energies were also found in the soils derived from granite or volcanic sediments (e.g. from PD2, Kotabumi and Rimbo Bujang). These soils contained a large amount of quartz and the clay content was similar to that of the soils from Kalimantan.

Further analyses showed that the parent materials affected the P sorption maxima and bonding energies (Table 5) . It was shown that the soils developed from andesite or volcanic ash exhibited significantly higher P sorption maxima and bonding energies than the soils developed from sedimentary rock and volcanic sediments. However, the variation in their P sorption maxima and bonding energies was high (Table 5). P sorption maxima of andesite or volcanic ash soils were not significantly different from those of the soils derived from

granite and a volcanic ash-sedimentary rock mixture. Soils derived from a volcanic ash-sedimentary rock mixture exhibited the highest value of bonding energy (e.g. from Gajrug). The relatively low standard deviation of P sorption maxima and bonding energies exhibited by the soils from granite, volcanic sediments and sedimentary rock indicated that their P sorption maxima and bonding energies were relatively homogenous. In general, high sorption values are probably due to the high clay content of the soils which offers a large specific surface area for P sorption (Uehara and Gillman 1981).

Compared with the values from other countries-for example from south-westem Australia (Singh and Gilkes 1991); Okinawa, Japan (Dodor and Oya 2000) and oxide-rich Ferralsols of New Caledonia (Dubus and Becquer 2001)-the P sorption maxima in the soils studied were generally low, especially in the soils from Kalimantan. Dodor and Oya (2000) reported that the P sorption maxima in Okinawa, Japan, ranged from 630 to 2,208 mg P kg-' with a mean value of 1,362 mg P kg-', while Dubus and Becquer (2001) reported that the P sorption maxima in the oxide-rich Ferralsols of New Caledonia ranged from 6,400 to 9,250 mg P kg-'.

The quantity of P sorbed at the equilibrium P concentration of 0.2 mg P L-' was reported to be the amount that will satisfy the P requirement of many crops and is widely accepted as the standard P requirement of soils (Fox and Kamprath 1970; Juo and Fox 1977). The amount of P sorbed at 0.2 mg P L-' ranged from 35 to 909 mg P kg-' with a mean value of 250 mg P kg-' and a standard deviation of 231 mg P kg-' (Table 4). Stan- dard P requirements followed a similar trend to that of the P sorption maxima. Soils with higher P sorption maxima exhibited higher standard P requirements (Fig. 3). In general, the P standard requirements were higher for the subsurface than for the surface soils (Table 4).

Since the soils used in the present study represented the major acid upland soils in Indonesia, information about P sorption maxima, standard P requirements and P bonding energies gathered in this study could be used to group these acidic upland soils for fertilizer recommen- dation purposes.


Table 6. Principal components (PC) and component loadings extracted from 13 original soil chemical and physical variables; original variables with underlined component loading were used to interprete the PC.

Principal components

1 2 3 Variables

PH CEC Base saturation Exchangeable Al

Clay content Organic C content Bray I-P

Fed-Fe, Al,+ 1/2 Fe, 0.7 nm minerals I .4 nm minerals

Fe,

AI,-AI,

0.477 0.812 0.1 1 1 0.400 0.436 0.760 0.425

-0.376 0.819 0.712 0.775

-0.370 0.325

-0.669 0.427

-0.590 0.841 0.438

-0.220 -0.26 0.048

-0.390 -0.289 -0.275 -0.759

0.812

0.277 -0.121

0.505 -0.055

0.585 -0.486

0.727 0.488 0.023

-0.403 0. I28

-0. I53 0.219

Multivariate analysis for determining the factors controlling P sorption

By applying the principal component analysis (PCA), three principal components (PCs) were extracted from the chemical and physical properties of 13 original soils (Table 6). The content of Alp was excluded in the PCA analyses because it was highly significantly correlated with the content of exchangeable A1 and it was difficult to distinguish between Alp and exchangeable Al.

The first PC explained 32%, the second 27% and the third 15% of the total variance. High loadings for the first PC were given to variables related to the CEC, clay content, as well as A1,-Al,, Fed-Fe, and Al,+1/2 Fe, contents. Therefore, the first PC (PC,) was interpreted as an oxide-related factor. The contents of exchangeable A1 and 1.4 nm minerals showed positively high loadings for the second PC (PC,). Therefore, PC, was interpreted as an acidity plus 1.4 nm mineral-related factor. Since the third PC (PC,) was characterized by the organic C and Fe, contents, it was interpreted as an organic C-related factor.

By applying a stepwise regression, the results indicated that the optimum regression model for predicting P sorption maxima was a combination of oxide-related and acidity plus 1.4 nm mineral-related factors, as in the equation below:

Y =621+237 PC, -168 PC, (R2=0.77**)

The equation shows that the active component of P sorption in these soils was an oxide-related factor.

According to this equation, the acidity plus 1.4 nm mineral-related factor decreased the P sorption maxima,

suggesting that exchangeable A1 and 1.4 nm minerals of which smectite and vermiculite were common in these acid soils decreased the P sorption maxima. These results contradict a report indicating that exchangeable A1 is an active component of the P sorption mechanism in acid soils (Iyamuremye et al. 1996).

There are conflicting reports on the reactivity of phosphate with exchangeable Al. Nanzyo (1995) reported that H,P04- is more reactive with Al-humus and fenyhydrite than with exchangeable Al. In addition, Nanzyo et al. ( 1995) observed that when 10 mg P L-' of KH,P04 was added to soils, no significant correlation was obtained between the content of exchangeable A1 and the decrease in phosphate sorption due to the removal of exchangeable Al.

The graph (Fig. 4) of PC, and PC, (explaining 57% of the total variance) more clearly demonstrated that the high P sorption maximum was characterized by the positive values of oxide-related factor scores and negative values of acidity plus 1.4 nm mineral-related factor scores (e.g. soils from Karang Pandan, Pringsurat and PDl). The low P sorption maximum was characterized by the negative values of oxide-related factor scores and positive values of acidity plus 1.4 nm mineral-related factor scores (e.g. some soils from Kalimantan).

This study also revealed that the organic C-related factor did not influence significantly the P sorption maxima, suggesting that the contents of organic C and Fe, did not influence the P sorption maxima. These results contradict a report indicating that the Fe, content was positively correlated with P sorption maxima (Dodor and Oya 2000). Contradictory results concerning the organic C content have been reported by other investigators. Dodor and Oya (2000) reported that the organic C content was the active component of P sorption in Oki- nawa soils, while Dubus and Becquer (2001) stated that there was a strong negative correlation between P sorption and the organic C content in the oxide-rich Ferral- sols of New Caledonia.

Compared with other investigators, Dodor and Oya (2000) observed that the optimum regression model for predicting P sorption maxima was the combination of the clay, organic matter, Fe, and Al, contents. It was also found that the P sorption maxima were not correlated with the Fed content, which in contrast, was strongly correlated with P sorption in the present study. In less weathered soils, prediction variables for P sorption models included mostly Al, and Fe, (van der Zee and Riems- dijk 1988; Borggaard et al. 1990; Yuan and Lavkulich 1994; Beauchemin and Simard 2000). The dominant influence of Al, and Fe, on P sorption in less weathered soils suggested that the ratio of oxalate-extractable P (Pox) to Al, + Fe, represented the P saturation index of soils in less weathered (van der Zee and Riemsdijk

796

3.00

2.50 0 - 2 2.00

.: 1.00

r 4 1.50 D

0.50

.a 0.00

0 -0.50 2

p. - - EL

.- g -1.00

-1.50

A. HARTONO, S. FUNAKAWA, and T. KOSAKI

- - - - - - -

-

Gajrug

Low P sorption J A

0 Sumtra

0 Java

A K a h n t a n

maxima (< 500 mg kg")

Kalimantan

High P sorption maxima

P D I / Pringsurat I

Karang Pandan'"-----. -____________. ey,,' - -;.-.- -2.00 ' I

-2.00 -1.00 0.00 1 .oo 2.00 3.00

pc , "Oxide-related

1988; Beauchemin and Simard 2000; Pautler and Sims 2000) and acidic soils in Ireland (Maguire et al. 2001), indicating that the content of Al, and Fe, are good esti- mates of P sorption sites in such soils. In another recent study, it was observed that the Al, and Fed contents were well correlated with P sorption maxima in savanna soils, but not with the Al, and Fe, contents (Agbenin 2003).

As for the A1 and Fe oxides, in the present study, it was observed that in the Indonesian acid upland soils, Al,+ 1/2 Fe,, Fed-Fe, and AId-AI, were active components in P sorption. Furthermore, the clay content, the contents of exchangeable A1 and 1.4 nm minerals should be included in the model to estimate P sorption maxima.

The model proposed for less weathered soils by van der Zee and Riemsdijk (1988) and Maguire et al. (2001) for acidic soils in Ireland which used Al, and Fe, and the Dodor and Oya (2000) model for soils in Okinawa, Japan are not appropriate for predicting P sorption maxima in the acidic upland soils of Indonesia.

Models to predict the P bonding energy have not been well developed. P bonding energy affects the amount of P in the soil solution for the same amount of P sorbed. By applying a stepwise regression, the results indicated that the optimum regression model for predicting the P bonding energy was a combination of the oxide-related factor and the organic C-related factor, as in the equation below:

Y=3.42+2.32 PC,- 0.79 PC, (R2=0.74**)

The equation showed that the active component for the P bonding energy in these acid soils was represented by the oxide-related factor. The equation showed that the organic C-related factor decreased the P bonding energy, implying that the P bonding energy may decrease with an increase in the organic C and Fe, con-

(=- 1000

Fig. 4. Plot of the factor scores of PC, and PC, in relation to sam- pled region.

tents. Regarding the organic C content, this finding agrees with the report of Sui and Thompson (2000) who indicated that the addition of biosolids to a Mollisol did not influence the P sorption maxima but decreased significantly the P bonding energy.

P desorption P bonding energies during sorption and desorption are

presented in Table 7. Bonding energies during desorption were much higher than during sorption, indicating there was a transformation to a stronger P bond. P sorption isotherms obtained during the sorption and desorption of selected soils (Darmaga, Gajrug, PD2 and Sebuluh) are presented in Fig. 5. The shift from the sorption to desorption lines was due to the hysteresis phenomenon caused by an irreversible reaction.

Percentages of P desorbed at the time of the initial addition of 50 mg P L-' are listed in Table 7. Table 7 indicates that the soils from Kalimantan and PD2 from Sumatra, which showed low amounts of A1 and Fe oxides and a low clay content, desorbed P more actively than the soils with relatively high amounts of A1 and Fe oxides and a high clay content (e.g. Darmaga, Gajrug, and Sitiung). Correlations between the P bonding energy during P sorption and P desorption are presented in Fig. 6, indicating that all the factors that influence the bonding energy are likely to influence P desorption. The organic C content which was considered to decrease the bonding energy could increase P desorption, as evi- denced by the surface soils from PD2, Sitiung and Sebu- luh.

In general, the amount of P desorbed by selected soils was low (<5%). This low P desorption may be due to several mechanisms. It may correspond to irreversible reactions of adsorbed P with soil compounds that lead to


'hble 7. centage of P desorbed at the time of the initial addition of 50 mg P L-'.

Equilibrium Langmuir bonding energies (K) of selected soil samples during sorption and desorption at 25'C and per-

Percentage of P P sorbed at the time of

50 mg P L-' Location Soil order" Depth Bonding energy (K) the initial addition of P desorbed desorbed

Sorption Desorption

(cm) L mg-' mg P kg-' (%)

Java Darmaga Inceptisols 0- 13 6.33 18.0

54-94 5.00 21.1 Gajrug Ultisols 0- 14 8.00 10.0

38-60 9.00 20.0 Tegal Garu Ultisols 0- I5 3.60 8.00

42-60 3.60 9.00

PD2 Ultisols 0-27 1.64 4.60 27-40 2.33 7.67

20-47 1.85 4.00 Sitiung Ultisols 0- 14 5.67 25.7

45-70 8.50 56.7

Sumatra

Kota Bumi Ultisols 0-20 1.19 2.00

Kalimantan Sebuluh Ultisols 0-9 0.64 4.33

20-37 1.53 6.25 a Soil Survey Staff (1998).

Darmaga (0-13 em) 600

0

E 0

u -g 200

loo 0 i.... 0 0.5 1 1.5 2

P in solution (mg L-I)

PD2 (0-27 em) 500

200

100

0

c 51

Gajrug (0-14 em)

.El 200

0 0 0.5 I 1.5

P in solution (mg L-I)

506 499 545 555 520 499

41 1 41 1 520 499 534 542

388 399

3.46 4.75 2.37 3.46 5.07 5.92

14.4 11.4 15.0 15.5 3.38 1.31

17.5 17.0

0.68 0.95 0.44 0.62 0.98 1.19

3.5 1 2.78 2.89 3.1 1 0.63 0.24

4.5 1 4.27

Sebuluh (0-9 em) 400 ; Y , o o , ,

- 200 s1 100

50

V + 150

e

0 Fig. 6. P sorption by soil samples obtained 0 5 10 I5 Is 2o during sorption-(O) and desorption (W) runs in

P in solution (mg L-I) P in solution (me L -') 0.01 mol L-I CaCI, at 25'C.

a stronger bond through rearrangement of the phosphate ions on the surface (Kuo and Lotse 1973) or it may be due to the fact that the desorption equilibrium was not reached. Desorption is a slower process than adsorption (Barrow 1983). The duration of the shaking period used

in the present study was probably not long enough for an equilibrium to be reached. Low P desorption in these soils may result in the unavailability of P to plants grown in such soils.

798 A. HARTONO, S. FUNAKAWA, and T. KOSAKI

r = 0.88

0 2 4 6 8 10

Bonding energy during sorption (Lmg-l)

Fig. 6. Correlation between P bonding energies during sorption and percentage of P desorbed at the time of the initial addition of 50 mg P L-I.

CONCLUSIONS

Acid upland soils in Indonesia differed considerably in their physical and chemical properties.

The soils varied widely in their capacity to sorb P. The Langmuir equation provided a good fit to P sorption data, with regression coefficients ranging from 0.90 to 0.98 in the soils studied. Soils developed from andesite and volcanic ash exhibited significantly higher P sorption maxima and bonding energies than the soils developed from sedimentary rock and volcanic sediments. The variations in the P sorption maxima and bonding energy values were larger than those in the soils developed from granite, volcanic sediments, a volcanic ash- sedimentary rock mixture and sedimentary rock.

The Al,+ 1/2 Fe,, AId-Al, and Fed-AI, contents and the clay content were the main active components in P sorption maxima and bonding energies. The contents of exchangeable A1 and 1.4 nm minerals decreased the P sorption maxima. Organic C and Fe, contents did not influence the P sorption maxima but decreased the P bonding energies.

The results suggested that not only A1 and Fe oxides but also soil acidity which is associated with exchangeable Al and 1.4 nm minerals of which smectite and vermiculite are common, should be included in models to estimate P sorption maxima of Indonesian acid upland soils. Furthermore, the organic C and Fe, contents should be included in models to estimate P bonding energies. Extraction of the samples with 0.01 mol L-' CaCl,, made it difficult to desorb P, as indicated by the higher bonding energy values recorded during desorption. P desorption was significantly correlated with the bonding energy during sorption.

Acknowledgments. We thank the farmers in Java, Sumatra and East Kalimantan for their assistance in the collection of the

soil samples. We also thank Tetsuhiro Watanabe for his assistance in the field, Hitoshi Shinjo for his assistance in the statistical analysis and M. Turner for his assistance in the preparation of this manuscript.

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Phosphorus Sorption-Desorption Characteristics of Selected Acid Upland Soils in Indonesia

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