Effects of Shaking Times on Phosphorus dsorption by Some Laotian Ferric and Haplic crisols Souphalak tbandit*, Pirmpoon Keerati-Kasikorn*, Krirk Pannangpetch** and Jilavat Sanitchon** bstract Phosphorus (P) adsorption could be used to estimate P requirement for a plant. Very little study on P adsorption of Laotian soils had been previously reported. Contact time between soil and added P was a basic element required in common adsorption procedure. The objective of this investigation was to determine shaking time required for P adsorption by some Laotian soils to reach equilibrium. Four Ferric crisol and three Haplic crisol samples were taken from Savannakhet and Vientiane provinces, Lao P. D. R. Ten grams of soil sample was shaken (for a 30 minutes period twice daily) with 100 ml of 0.01 M CaCl 2 containing P concentration ranging from 1 to 15 mg P L -1 for 24, 72 and. P concentration in the supernatant liquid was then determined. The amount of adsorbed P was obtained by the difference. The P adsorption increased with increases in shaking times and in amounts of added phosphate. On average, added P was adsorbed by 88, 91 and 92 % in 24, 72 and, respectively. Reasonably stable levels of P adsorption occurred after shaking time. P adsorption of the Laotian soils positively correlated to dithionite-citrate-bicarbonate extractable iron and oxalate extractable iron at all levels of added P. Positive correlation with organic matter and clay or negative correlation with ph were found only at high level of added P. Key words: phosphorus adsorption, shaking time, Ferric crisol, Haplic crisol, e-mail address: souphalakabt @yahoo.com, pirm@kk.ac.th *Department of Land Resources and Environment, Faculty of griculture, Khon Kaen University, Khon Kaen 40002. ** Department of gronomy, Faculty of griculture, Khon Kaen University, Khon Kaen 40002.
Introduction Phosphorus adsorption by a soil plays an important role in determining the availability of phosphorus fertilizer to plant. Could be estimated from the adsorption isotherm. Phosphorus fertilizer needed for a plant (Fox and Kamprath, 1970). n amount of phosphorus adsorbed from fertilizers varied with soil types. It is of interest to investigate the adsorption capacity of Laotian soil since very little work on phosphorus adsorption has been undertaken on the soils. However in a procedure of phosphorus adsorption determination, the length of shaking time required for solution to reach equilibrium must be specified. Due to the lack of information on this matter, it is necessary to establish the equilibration time prior to studying phosphorus adsorption by the soils. Therefore the objective of this study was to investigate the effects of shaking time on phosphorus adsorption by some Ferric and Haplic crisols of Lao P. D. R. Materials and Methods Soils Seven crisols* were sampled at cm (surface soil) and cm (subsoil) depth from Savannakhet and Vientiane Plain, Lao P.D.R. There were four Ferric crisols and three Haplic crisols samples (Table 1). Soil sample were air-dried, passed through a 2mm sieve, and stored for subsequent analyses. Organic matter was determined by the method of Walkley and Black (1934). ph was measured: at 1:1 ratio in water, in 1 N KCl, and 0.01 M CaCl 2 ; and at 1:5 in water. Iron was extracted by dithionite-citrate-bicarbonate (DCB) and ammonium oxalate (ph 3) (Mckeague, 1967) and pyrophosphate (Mckeague and Day, 1966). Iron in the extracts were determined by colorimetric method at 510-nanometer wavelength (Patcharapreecha, 2003). Cation exchange capacity was determined by the method of Chapman (1965). vailable phosphorus was extracted by Bray II (0.1 N HCl+0.03 N NH 4 F) and phosphorus in the supernatants was determined by the method of Murphy and Riley (1962). Particle-size distribution was determined by the pipet method (Day, 1965) Phosphorus adsorption Ten grams of soil were shaken at 25 o C with 100 ml of 0.01 M CaCl 2 containing phosphorus concentration (as KH 2 PO 4 ) ranged from 0-15 mg P L -1. Two drops of toluene were added per sample. They were shaken on an end-over-end shaker for a 30-minute period twice daily for 24, 72 and. fter filtering, phosphorus in the supernatant liquid was determined by the method of Murphy and Riley (1962). The amount of phosphorus sorbed was calculated by subtracting the amount of phosphorus in the supernatant solution from the amount of phosphorus initially added. Data was subjected to statistical analysis by MSTT program. * classified by the FO - UNESCO Soil Classification System which is equivalent to Ultisols in USD soil Taxonomy.
Table 1 Some physical and chemical properties of the studied Laotian soils Location Soil no. Great group Depth (cm) %OM Bray II extr.p CEC (mg Pkg -1 ) (cmol c kg -1 ) H 2 O (1:1) H 2 O (1:5) ph Fe (mgkg -1 ) Particle size distribution KCl (1:1) CaCl 2 (1:1) Fe dcb Fe ox Fe pyro % sand % silt % clay Texture 1 Ferric crisols 0.58 2.38 2.19 4.13 4.33 3.46 3.46 1.21 0.47 0.43 87.0 8.8 4.3 SL 0.43 2.77 1.41 4.06 4.10 3.16 3.20 0.45 0.26 0.50 87.1 8.0 5.0 SL Savannakhet 2 3 Ferric crisols Haplic crisols 0.67 1.21 2.97 3.93 4.50 3.53 3.43 0.20 0.10 0.39 72.0 19.1 9.1 CL 0.36 1.68 5.10 3.96 4.33 3.30 3.30 0.21 0.10 0.57 64.0 19.3 17.0 CL 0.62 3.81 2.29 3.86 4.30 3.00 3.06 0.59 0.37 1.54 68.3 14.2 17.5 SL 0.56 2.28 3.03 4.03 4.23 3.30 3.30 0.55 0.51 1.94 63.0 13.2 24.0 SCL 4 Haplic crisols 1.17 1.26 7.03 3.90 4.13 2.96 3.26 0.62 0.45 0.95 29.0 48.4 23.0 L 0.10 1.11 9.29 4.33 4.40 3.13 3.30 0.52 0.02 0.06 35.0 35.0 30.5 L 5 Ferric crisols 1.43 2.42 7.70 3.59 3.60 2.98 3.05 0.31 0.18 0.44 31.4 33.6 35.0 CL 1.43 0.58 14.10 4.31 4.35 3.65 3.60 0.42 0.15 0.68 17.2 36.0 47.1 C Vientiane 6 Ferric crisols 0.95 9.12 2.11 4.76 5.00 4.13 4.13 3.27 1.15 0.44 63.0 28.0 10.0 SL 0.51 5.62 3.71 4.76 4.93 3.96 3.93 0.14 0.13 0.09 60.4 33.0 7.0 SL 7 Haplic crisols 1.39 7.31 3.67 3.69 3.70 2.25 2.40 0.62 0.49 0.85 55.452 31.568 12.981 SL 0.45 5.15 3.74 3.70 3.78 2.30 2.35 0.58 0.37 0.67 56.096 27.002 16.902 SL
Results and Discussion Sample characteristics Some physical and chemical properties of the soil samples are shown in Table 1. Soil texture that ranged from sandy loam to clay loam. They were acid soils, having ph values in water (1:1 ratio) ranged from 3.6 to 4.8 for both surface soil and subsoils. Most of the soils were deficient in phosphorus. Five out of seven soils contained less than 4 mg P L -1. The other two had less than 10 mg P L -1. Suwannarit et al. (1978) studied some of the Northeast Thai soils and reported that soils with 4.2 mg P kg -1 (by Bray II s method) were deficient in phosphorus and would respond to phosphorus application whereas soils with higher than 11.3 mg P kg -1 did not give any response. However, the value of Bray II extractable phosphorus between 4.3 and 11.2 were not tested (Suwannarit et al., 1978). Ho and Sittibusaya (1984) reported that to obtain 90% of the maximum yield of soybean, sugarcane and cotton, the critical concentration of available phosphorus (Bray II extractable P) were 17, 20 and 16 mg P kg -1, respectively. Phosphorus adsorption Increasing shaking time and phosphorus concentration in soil solution increased phosphate adsorption by all soils (some results are shown in Figure 1). similar result was reported by Fox and Kamprath (1970) that the length of shaking time required for adsorption depended on concentration of initial added phosphorus. s shown in Figure 2, when the low phosphorus concentration at 1 mg PL -1 was added, phosphorus adsorption at of shaking time was not different from at. This happened with all fourteen soils. With increased P concentration in soil solution, a higher number of soils significantly adsorbed higher phosphorus at shaking time than. dsorption of four, ten and eleven soils was higher at for the added phosphorus concentration at 3, 6 and 15 mg P L -1. The soils in these groups were not confined to the same soil sample number. dsorbed P (mg P kg -1 ) 160 140 120 100 80 60 40 20 0 subsoil Ferric crisol surface soil 0 1 2 3 4 5 6 7 8 9 10 dsorbed P (mg P kg -1 ) 160 140 120 100 80 60 40 20 0 subsoil 144 72 0 1 2 3 4 5 14 72 surface soil Haplic crisol 24 24 P concentration in solution (mg P L -1 ) P concentration in solution (mg P L -1 ) Figure 1 Effect of shaking time on phosphorus adsorption by Ferric crisol (No.6), and Haplic crisol (No. 3) using 0-15 mg P L -1 added phosphorus.
Surface soils Subsoil (mg Pkg -1 ) dsorped P 11 10 9 8 7 B B 1 mg PL -1 added P B B B B B B B B B B dsorbed P ( mg Pkg -1 ) 11 10 9 8 7 B B 1 mg PL -1 added P B B B B B 6 1 2 3 4 5 6 7 6 1 2 3 4 5 6 7 dsorbed P (mg Pkg -1 ) 70 60 50 40 30 BB 6mg PL -1 added P C B B C BC B C dsorbed P (mg Pkg -1 ) 70 60 50 40 30 6 mgpl -1 added P B 20 1 2 3 4 5 6 7 20 1 2 3 4 5 6 7 dsorbed P (mg Pkg -1 ) 200 150 100 50 C B 15 mg PL -1 added P B B dsorbed P (mg Pkg -1 ) 200 150 10 0 50 15 mgpl -1 added P 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7 Figure 2 Effect of shaking time on phosphorus adsorption by surface soils and subsoils of Laotian Ferric crisols and Haplic crisols. 1, 2 (Ferric crisols), 3, 4 (Haplic crisols) of Savannakhet. 5, 6 (Ferric crisols), 7 (Haplic crisols) of Vientiane. * For each soil number, means of the three shaking times having a common letter on the bars are not significantly different at 95 % level. The percentage of added phosphorus adsorbed by the soils decreased with phosphorus concentration in solution but increased with shaking time (Table 2). By average, added phosphorus was adsorbed by 88, 91 and 92% in 24, 72 and, respectively the level of added phosphorus sorbed appeared to be stable after. This mean that the adsorption by the studied Laotian soils reach equilibrium after of contact time (shaking time). Fox and Kamprath (1970) investigated the effect of various equilibration times ranging from 16 h to 264 h on phosphate adsorption. They showed that reasonably stable levels of phosphorus adsorbed could not be expected during the first 6 days of equilibration and that sorption isotherms shift rapidly during the first several days of equilibration (16, 48, 96 and ). The shaking time or equilibration time used by Fox and Kamprath
(1970) was. Their method of using phosphorus adsorption isotherms to determine the phosphorus requirements of soils for various plants was well known and widely used. For Laotian soils, the same procedure to establish phosphorus adsorption isotherms could be followed with shaking time. Table 2 Percentage of added phosphorus sorbed by some Laotian Ferric and Haplic crislos. dded P (mg % of dded P sorbed Location no. Soil Great group Depth(cm) P L -1 ) 1 97.2 98.2 98.8 6 79.1 86.8 90.5 1 Ferric crisols 15 42.1 58.1 62.5 1 98.3 99.3 99.3 6 89.2 91.8 94.2 15 56.6 64.3 69.9 1 99.6 98.6 98.8 6 96.8 90.6 99.1 2 Ferric crisols 15 58.1 62.7 72.3 1 98.6 98.4 98.7 6 98.2 98.4 98.6 Savannakhet 15 80.0 83.2 85.0 1 99.7 99.4 99.4 6 92.9 95.6 95.6 3 Haplic crisols 15 70.4 78.8 78.8 1 99.4 99.3 99.3 6 96.6 97.1 97.1 15 76.2 87.7 87.7 1 97.8 98.6 99.3 6 99.2 99.4 99.5 4 Haplic crisols 15 91.4 96.2 96.9 1 100.0 100.0 100.0 6 100.0 100.0 100.0 15 99.3 99.6 99.8 1 96.0 96.8 97.6 6 95.8 96.7 98.4 5 Ferric crisols 15 88.2 91.2 94.4 1 99.3 99.4 100.0 6 99.4 99.6 100.0 15 98.4 99.3 99.4 1 94.2 97.1 97.6 6 56.0 63.0 70.6 Vientiane 6 Ferric crisols 15 40.1 48.3 49.6 1 98.8 99.7 99.7 6 90.6 95.4 97.3 15 65.6 78.0 82.5 1 96.1 96.4 97.5 6 92.4 96.0 97.3 7 Haplic crisols 15 78.8 86.7 90.5 1 98.1 98.6 99.4 6 94.7 96.5 97.6 15 83.5 88.7 91.3
Phosphorus adsorption and soil properties Figure 2 demonstrates that the adsorption capacity of soils was not related to Great Group but to individual soil sample. Soils in the same Great Group adsorbed different amount of phosphorus. The capacity of the soil was related more with some soil properties, such as iron oxides, organic matter and clay Table 3 shows that phosphorus adsorption at all level of added phosphorus concentration (crystalline and poorly crystalline iron oxides) was positively correlated to dithionite-citrate-bicarbonate extractable and oxalate extractable (amorphous iron oxides) iron. ll of the studied soils were acid (Table 1). Many reported that in acid soils, the oxides, hydroxides and oxyhydroxides of iron and aluminum were the components that predominantly influenced phosphorus adsorption (Parfitt, 1989; Borggaard, 1990). It was noticed that only at highest level of added phosphorus concentration, 15 mg P L -1, the adsorption was positively correlate with organic matter and clay but negatively correlate with ph irrespective of ratio and type of solution. Table 3 Correlation coefficients (r) between the amounts of P adsorbed by soils with different amounts of added P and soil properties Soil properties dded P (mg PL -1 ) 1 6 15 %OM 0.059 ns 0.111 ns 0.510* Bray II extr.p (mg Pkg -1 ) -0.085 ns -0.105 ns -0.120 ns CEC (cmol c kg -1 ) -0.199 ns 0.001 ns 0.316 ns ph-h 2 O(1:1) -0.375* -0.305 ns -0.554** ph-h 2 O(1:5) -0.127 ns -0.125 ns -0.504** ph-kcl(1:1) -0.165 ns -0.144 ns -0.436** ph-cacl 2 (1:1) -0.215 ns -0.148 ns -0.432** Fe-DCB 0.708** 0.964** 0.695** Fe-OX 0.679** 0.872** 0.620** Fe-Pyro -0.025 ns -0.168 ns -0.229 ns % sand 0.287 ns 0.068 ns -0.193 ns % silt -0.192 ns -0.174 ns 0.072 ns % clay -0.361 ns 0.113 ns 0.332* * Significance at 95 % ** Significance at 99 % ns Non significance
Conclusion Phosphorus adsorption of Ferric and Haplic crisols increased with shaking time and amount of added phosphorus. The appropriate shaking time for phosphorus adsorption to reach equilibrium was. The capacity of soil to adsorb phosphorus varies with individual samples, not with the Great Groups, showing that adsorb ability of soils related to their properties. Dithionite-citratebicarbonate extractable iron and oxalate extractable iron in the soil played the most important role, followed by the organic matter, clay and ph of the soils. cknowledgement We would like to express our thankfulness to Mr.Khamphou Phouthavong and Mr.Sanalith Sisouroth, Soil Survey and Land Classification Center, Ministry of griculture and Forestry, Lao P.D.R. for soil sampling and to the Office of International griculture, Faculty of griculture, Khon Kaen University and the Rockefeller Foundation for financial support. References Borggaard, O. K., S. S.Jorgensen, J. P. Moberg and B. Raben-Lange, 1990. Influence of organic matter on phosphate adsorption by aluminum and iron oxides in sandy soils. J. Soil Sci. 41: 443-449. Chapman, H. D. 1965. Cation exchange capacity by ammonium saturation method, pp. 894-895. In Method of Soil nalysis. Part 2. Chemical and Microbiological Properties. C.. Black et al. (eds) m. Soc. gro. No. 9. Madison, Wisconsin. Day, P. R. 1965. Particle fractionation and particle-size analysis, pp. 545-567. In Method of soil nalysis, Part 1. C. Black et al (eds.). gronomy 9. m. Soc. gron., Madison, Wisconsin. Fox, R. L. and E. J. Kamprath. 1970. Phosphate sorption isotherms for evaluating the phosphate requirements of soils. Soil Sci. Soc. mer. Proc. 34: 902-907. Ho, C. T. and C. Sittibusaya. 1984. Fertilizer requirements for field crops in Thailand, pp. H 1.1-19. In Fifth SEN soil Conference. June 1984. Bangkok, Thailand. Mckeague, J.. 1967. n Evaluation of 0.1 M pyrophosphate and pyrophosphate-dithionite in comparison with oxalate as extractants of the accumulation products in Podzols and some orther soils. Can. J. Soil Sci. 46: 13-22 Mckeague, J.. and J. H. Day. 1966. Dithionite and oxalate extractable Fe and l as aids in differentiating various classes of soils. Can. J. Soil Sci. 46: 13-22.
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