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1.
Abstract

Phosphate sorption isotherms were determined for 16 representative major soils developed from different parent materials on Okinawa. Phosphate sorption characteristics were satisfactorily described by the Langmuir equation, which was used to determine phosphorus (P) sorption maxima of the soils. Phosphate sorption maxima ranged from 630 to 2208 mg P kg‐1 soil (mean 1,362 mg P kg‐1). The standard P requirement (i.e., the amount of P required to attain 0.2 mg P L‐1 equilibrium solution) followed the same trend as sorption maximum (r =0.94***), with values ranging from 132 to 1,020 mg P kg‐1 soil (mean 615 mg P kg‐1). This mean value corresponds to fertilizer addition of 923 kg P ha‐1 indicating that the soils have high P fertilizer requirements. Results of simple linear regression analysis indicated that sorption maximum was significantly correlated with clay content, organic matter, oxalate iron (Fe), pyrophosphate Fe, DCB aluminum (Al), oxalate Al, and pyrophosphate Al, but not with DCB Fe, pH, or available P content. The best regression model for predicting sorption maximum was the combination of clay, organic matter, pyrophosphate Fe, and DCB Al which altogether explained 79% of the variance in sorption maximum. The equation obtained could offer a rapid estimation of P sorption in Okinawan soils.  相似文献   

2.
Abstract

The immobilization of P is a significant fertility limitation of Andisols in Central America. It is believed that soil Al and Fe fractions have an important influence on P availability. This study was conducted to obtain information on the various forms of Al and Fe in ten pedons derived from volcanic ash in Panama and Costa Rica. Correlations between these Al and Fe fractions and P immobilization were measured by different methods.

The Al and Fe fractions, extracted by acid ammonium oxalate, 4M KOH, sodium pyrophosphate and dithionite‐citrate, were determined, and the correlations between these fractions, P immobilization, and other soil properties made.

It was observed that oxalate extractable Al correlated significantly with P immobilization, which had values of over 85% by the New Zealand method and 96% by the isotherm method. The Al concentration corresponding to this immobilization was over 2%. The difference between oxalate extractable Al and pyrophosphate extractable Al (inorganic Al fraction) correlated with P immobilization also. The pyrophosphate extractable Al fraction had the lowest concentrations and did not correlate with P immobilization. The NaF‐pH and dithionite‐citrate extractable Al correlated significantly with P immobilization.

Oxalate extractable Fe correlated with the P retained by the isotherm method, but dithionite‐citrate extractable Fe was negatively correlation with P immobilized. No correlations were found between the pyrophosphate extractable Fe and other soil properties.  相似文献   

3.
Abstract

Surface horizons from Podzolic and Gleysolic soils were collected in various parts of the province of Quebec, Canada, and equilibrated with various amounts of KH2PO4 in 0.01 M CaCl2 for 48 hours. P sorption data conformed to the linear form of the Langmuir and Freundlich equations. P solubility isotherms showed evidence of hydroxyapatite formation in most samples studied, whereas equilibration solutions of only few samples were saturated with respect to either dicalcium phoshate dihydrate or octocalcium phosphate. These reaction products were associated to soil pH and levels of added phosphate. The average values of the Langmuir sorption maximum for these studied Gleysolic and Podzolic samples were 763 and 1096 μg/g respectively. These values were higher than those obtained by the segmented and modified Freundlich models.

Relationships between the soil characteristics and P sorption parameters were evaluated by regression analysis. Among all variables, oxalate‐extractable Fe plus Al content of the Podzolic samples and the ratio of oxalate—extractable Al to clay of the Gleysolic samples gave the best significant correlation coefficients. Furthermore, soil pH and various ratios such as pyrophosphate‐extractable Fe and Al, oxalate‐extractable Fe and organic matter to clay were found to be significantly correlated only with the P sorption parameters of the Gleysolic samples.  相似文献   

4.
Abstract

Studies were conducted to investigate phosphorus (P)‐sorption characteristics of some intensely weathered soils in south‐central Kentucky. Phosphorus adsorption characteristics reflected the chemical and mineralogical properties of the soils studied. All adsorption data were adequately described by first order kinetic reactions which implied that the soils have uniform surfaces for P sorption. In spite of the limitations of the Langmuir equation, its usefulness in summarizing data into one adsorption maximum value was demonstrated by nearly identical adsorption maxima estimated by three linear transformations of the equation and small deviations from the observed maxima. Variations in adsorption maxima between surface and subsoils and among soils were best correlated with extractable aluminum (Al) (r = 0.93, p<0.01) and crystalline iron (Fe) oxy‐hydroxides (r = 0.97, p<0.01). Clay content was also highly correlated with P sorption (r = 0.97, p <0.01) as well as with extractable Al (r = 0.83, p<0.05) and crystalline Fe oxides (r = 0.92, p<0.01) suggesting that its contribution may have been through its association with these soil components. In contrast, organic matter had a negative association with P sorption (r = ‐0.83, p<0.05). The results indicate higher P sorption in subsoil than in surface horizons, controlled mainly by extractable Al and crystalline Fe oxyhydroxides.  相似文献   

5.
Abstract

The efficiency of Mehlich‐3 reagent as an extractant for aluminum (Al) and iron (Fe) was studied in Galician coal mine soils, in the process of reclamation. Mehlich‐3 Al and Fe values were compared to those from other Al and Fe tests and with phosphorus (P) sorption. The soils are very heterogeneous, consisting mainly of carbonaceous and non‐carbonaceous clays and shales, which are often rich in pyrite. Some of them have been amended with topsoil or fly ash. One hundred forty samples, from 0 to 15 or 15 to 30 cm, were analyzed. The pH values ranged from 2.7 to 8.4; oxalate and pyrophosphate Al from 0 to 1.17%, and 0.02 to 0.58%, respectively; and oxalate and pyrophosphate Fe from 0.02 to 2.25% and 0 to 1.28%, respectively; PSI (P sorption index) values varied between 0 and 55.1. The Mehlich‐3 Al values ranged from 24 to 2600 mg kg‐1. A close relationship was observed between Mehlich‐3 and oxalate Al values (r=0.77), although the regression line tended to be curvilinear. Mehlich‐3 Al was better correlated than oxalate Al to pyrophosphate Al (r=0.66 vs. r=0.59) and also to pH‐NaF (r=0.89 vs. r=0.74). The Mehlich‐3 Al is almost as good as oxalate Al in estimating non‐crystalline Al, the correlation coefficients between log PSI and log (Mehlich‐3 Al) or log (oxalate Al) being 0.51 and 0.57, respectively. The Mehlich‐3 Fe correlated to available (r=0.63), exchangeable (r=0.65) and soluble Fe (r=0.66), but not to non‐crystalline Fe.  相似文献   

6.
Abstract

In nineteen surface horizons of red Mediterranean soils from various locations of Greece, phosphorus (P) sorption experiments were conducted and the sorption characteristics were studied in relation to soil properties. Phosphate sorption data were fitted both to the Langmuir and Freundlich equations. From these equations, the following P sorption parameters were determined from the Freundlich equation, X = ACn, the parameters A (the phosphate sorbed at C = 1 mg P/L), n (the P sorption intensity), the P sorption index (PS = X/log C) and maximum P sorption (Xmfr). From the Langmuir equation, C/X = 1/KXm + C/Xm, the parameters K (showing the bonding energy), maximum P sorption (Xmla), the quantity of P adsorbed at a standard concentration of 0.2 mg P/L (P0.2), and P maximum buffering capacity (PMBC). The Freundlich parameter A was strongly correlated to the clay and sesquioxides ("free”; iron and aluminum oxides and amorphous iron oxides) content. Seventy‐four percent of the variance of this parameter was explained by clay and “free”; iron (Fe) content. The Freundlich parameter n was significantly correlated with pH and amorphous iron oxides content, while 52% of its variance was explained by amorphous Fe and dithionite extrac‐table aluminum (Al). The P sorption maxima calculated from the Freundlich equation were in general lower than those calculated by the Langmuir equation. Both these parameters were strongly correlated with clay and more slightly with sesquioxides content. About 50% of their variance was explained by clay content of the soils. The P sorption index was strongly correlated with the clay content and less strongly with dithionite‐extractable Fe and Al. The P‐buffering capacity calculated from the data of Langmuir equation was also strongly correlated with these two parameters. In addition, clay content and dithionite‐extractable Fe and Al were well correlated to the amounts of P required to obtain an equilibrium concentration of 0.2 mg P/L while 61% of the variation of this parameter was explained by the clay and the dithionite‐extractable Fe content. From these findings, it seems that for the red Mediterranean soils from Greece, P sorption is affected by clay content and iron and aluminum oxide contents.  相似文献   

7.
Abstract

Phosphorus sorption studies were conducted on volcanic ash influenced surface horizons of 29 northern Idaho soils. Results show that the amount of P sorbed was significantly correlated with citrate‐dithionite extractable aluminum (r = .64**), but not with Fe. Other significantly correlated soil properties were: percent base saturation (r = ‐.73**), percent clay (r = .42**), and exchangeable acidity (r = .39*).  相似文献   

8.
Abstract

Soil test recommendations currently used in Alaska are based on a limited amount of in‐state data along with consideration of data from other states. Recently, Mehlich 3 extractable P has been found to be highly correlated to yield on representative agricultural soils in Alaska. To fully use its multi‐element capability, a study was conducted to correlate Mehlich 3 extractable P and cations (K, Ca, and Mg) with the P and cations extracted by the Bray 1 and ammonium acetate methods respectively.

When Mehlich 3 extractable K and Mg were regressed with ammonium acetate extractable K and Mg respectively, the relationship was essentially one‐to‐one and the relationship held across all soils tested. Significant variation was observed among soils in the extraction of Mehlich 3‐P and Ca relative to Bray 1‐P and ammonium acetate‐Ca. Individual soil character appeared to affect the regressions for extractable P and Ca, even though the R2 values were generally high. The regression slopes for Mehlich 3‐P versus Bray 1‐P ranged from 1.01 to 1.88 with Mehlich 3 extracting an average of 66% more P than Bray 1 in the volcanic ash soils, and 12% more in the loess soils. The regression slopes for Mehlich 3‐Ca versus ammonium acetate‐Ca ranged from 0.95 to 1.33, and the former extracted an average of 17% more Ca than the latter. It is suggested that the regression data of P and Ca can be extrapolated to other soils based on soil classification; to extend the soil test data over a geographic base.  相似文献   

9.
Abstract

A laboratory study was conducted to evaluate P sorption in the Ap horizon of four soil series in the Ultisol order (Benndale Is, Hartsells fsl, Lucedale fsl, and Dewey sicl) receiving the same fertility treatments since 1929. Soil was collected in the spring of 1985 from 4 treatments: i) no‐lime, plus P (total fertilizer P = 1584 kg/ha from 1929 to 1985); ii) no‐K, plus P (total fertilizer P = 1584 kg/ha); iii) low‐P (total fertilizer P = 442 kg/ha); 4) standard treatment (total fertilizer P = 2376 kg/ha). The soils and treatments within a soil varied in pH, total P, Mehlich 1 extractable P, K, Ca and Mg, and KC1 extractable Al. The four soils had large differences in P sorption capacity which increased with increasing clay content. The Dewey (27 % clay) soil had the highest P sorption capacity and the Benndale (4 % clay) soil had the smallest P sorption capacity. Sorption of P within a soil was affected by the rate of added P and past fertility treatment. Treatment differences in P sorption were due primarily to the level of extractable P and soil pH. Within a given soil, P sorption (at a given rate of added P) generally decreased as the level of extractable P increased. Regression analysis of P sorption data for equilibrium P concentrations of 1 to 32 μmol/L showed that the parti‐ tioning between sorbed and solution P (buffer power) had not been changed by 56 years of annual applications of P. The maximum P sorption capacity of the four soils was decreased slightly by P fertilization.  相似文献   

10.
Abstract

Iron (Fe)‐enriched concretions, a complex natural matrix with high chemical heterogeneity and phosphate‐sorption capacity, is widespread in soils with restrictive drainage in Greece. However, the phosphorus (P) status and related characteristics of Fe‐enriched concretions in agricultural soils in areas where P fertilization is mainly inorganic are relatively unknown. Active noncrystalline Fe and aluminum (Al) oxides (Feox, Alox), oxalate extractable P (Pox), P sorption capacity (PSC), and the degree of P saturation (DPS) of Fe‐enriched concretions from agricultural imperfectly drained soils in central Greece were determined using the acid ammonium oxalate method. The concretions contain 13 times as much Feox, twice as much Alox, and almost 15 times as much Pox than the surrounding soil matrix. Pox accounted for 50–80% of total P of the soil concretions, indicating strong accumulation of noncrystalline P components (Al‐ and Fe‐P). The PSC, expressed as a 0.5 (Alox+Feox), ranged from 184.7 to 314 mmol kg?1, demonstrating the strong affinity of the Fe‐enriched concretions for P. The DPS, which represents the fraction of concretion sorbent surface coverage by P, was computed as 100 (Pox/PSC) with values ranging from 6 to 13% (mean=8%). The results of this study indicate that the Fe‐enriched concretions, due to their high noncrystalline Fe and Al oxides content, act as major sink of phosphate, controlling the location, mobility, and dynamics of P in agricultural soils with restrictive drainage.  相似文献   

11.
Abstract

Acid oxalate reagent was used at various concentrations, pH values, shaking times, and soil to solution ratios to find the optimum conditions for the extraction of Al, Fe, and Si from short‐range‐order materials in soils and stream‐bed deposits. The optimum conditions vary with the nature of the soil sample and its components. For most soils maximum amounts of Al, Fe, and Si were extracted with 0.15M acid oxalate reagent at pH 3.0 with a soil to solution ratio of 1:100 and shaking for 4 h in the dark at 20°C. Soils with more than 5% oxalate‐extractable Al or Fe require a 0.20M oxalate solution at pH 3.0 with a soil to solution ratio of 1:200.

Allophane is extracted by acid oxalate reagent after shaking for 2 h and it may be estimated from the 4 h oxalate‐extractable Si values. Ferrihydrite is extracted after shaking for 4 h, and it may be estimated from the oxalate‐extractable Fe values. Either sodium oxalate or ammonium oxalate may be used  相似文献   

12.
Abstract

P status of soils derived from volcanic ash in Guatemala was investigated. Growth chamber and greenhouse studies were conducted with H‐3 hybrid corn (Zea mays). All plants exhibited P deficiency symptoms and yielded less dry matter when they were grown on soils that received only lime at a rate equivalent to 2,240 and 4,480 kg/ha. The P content of plants was low and correlated with P deficiency symptoms. Application of P (336 and 672 kg/ha) under constant liming corrected the P deficiencies and increased dry matter. In comparative studies, plants grown on a highly fertile, non‐volcanic soil showed vigorous growth and yielded high dry matter. Apparently, P was limiting productivity in volcanic ash soils of Guatemala, and due to low exchangeable Al, addition of only lime did not produce beneficial results. The soils responded to P fertilization and they should be supplied large quantities of this macronutrient.  相似文献   

13.
Abstract

Twelve soils with low‐medium phosphorus (P) retention capacities were equilibrated for 3 months with soluble phosphate at a rate of 100 mg P kg‐1 soil. The P sorption properties of these soils both with and without added P were studied, including equilibrium P concentration (EPCo), standard P requirement (SPR), soil P sorption capacity (b), maximum buffer capacity (MBC), and P sorption index (P‐SI). In general, the soils with no added P showed low values of all the above parameters. Oxalate extractable aluminum appeared to be the major responsible element for the control of P sorption in these soils. The addition of P to these soils had a considerable effect on their P sorption properties. The changes in EPCo were well correlated with P sorption index (r=0.80; p≤0.01 ). The EPCo values of the soils with and without added P were closely correlated to bicarbonate extractable P (P0lsen) and calcium chloride extractable P (PCaC12), with r=0.80, and r=0.99 (p≤0.001), respectively. Ninety percent of the variability in EPCo was explained by the corresponding variability in POlsen when a curvilinear relationship was adopted. The P sorption properties examined appear to be useful parameters to assess the environmental impact of soil P on the quality of surface waters.  相似文献   

14.
Abstract

Few studies have utilized a statistical approach for the evaluation and comparison of breakthrough profiles obtained from soil column investigations. Our objective was to investigate the use of nonlinear estimation techniques to identify the phosphorus (P) breakthrough point and other parameters endemic to breakthrough data. Four soils exhibiting a range in physical and chemical properties were leached under saturated‐flow conditions with a 10 mg P/L solution for 34 d. Leachate P concentrations were analyzed by flow injection colorimetric analysis. A four‐parameter segmented exponential model provided a good fit for the breakthrough data in each soil tested. In addition to identifying the breakthrough point, the model parameters provided estimates of other identifiable aspects of a breakthrough profile including background P concentration, equilibrium P concentration, and the rate of concentration change once breakthrough is attained. Estimation of these parameters also facilitated statistical comparison of breakthrough profiles from different soils. Single and joint hypothesis tests showed that significant differences existed among the breakthrough profiles, the breakthrough points, and the rates of concentration change. Additionally, simulation was used to examine the correlation structure between the estimated breakthrough point and 17 soil properties. The simulation showed that 6 soil properties— ammonium oxalate extractable aluminum (Al) and iron (Fe), citrate dithionite extractable Al, CaCl2 and acetate extractable P, and P sorption capacity— were strongly correlated with P breakthrough.  相似文献   

15.
Abstract

Several rainwater samples and 14 profiles of Hawaii's volcanic ash‐derived soils were analyzed for sulfur (S). Atmospheric deposition was an important S source at the coast (24 kg S/ha), but its contribution decreased with increasing distance from the sea (1 kg S/ha at 24‐km inland). The S concentration of rainwaters also decreased linearly with increasing rainfall.

Several thousand mg SO4‐S/kg can be extracted from many volcanic ash‐derived soils of Hawaii, and it was often required at least four extractions [0.04 M Ca(H2PO4)2, 1:10 soil to solution ratio] to completely desorb this SO4. There was a close association of high SO4 retention with high rainfall. This might have resulted from (1) the development of a solid phase with high SO4 retention under intense weathering conditions, (2) more total SO4 received by the soils from atmospheric deposition, and (3) past fertilization of sugarcane grown in high rainfall areas.

Low concentrations of soil solution SO4‐S in relation to large amounts of P‐extractable SO4 suggest that a S bearing mineral, such as basaluminite, may be controlling soil‐solution SO4. Furthermore, SO4 adsorption isotherms of these volcanic soils generally show a bi‐phasic property, and suggest that 40 to 80 mg SO4‐S/kg is required to maintain 3 ‐ 6 mg SO4‐S/L in the soil solution, a concentration range considered adequate for the growth of most crops.  相似文献   

16.
Abstract

The importance of various soil components on copper (Cu) retention by Spodosois was investigated. Copper sorption and extraction were conducted on samples from the B horizon from six Danish Spodosois. The investigation was conducted on untreated samples, on hydrogen peroxide‐treated samples (to remove organic matter), on oxalate‐treated samples [to remove amorphous to poorly crystalline aluminum (Al) and iron (Fe) oxides], on hydroxylamine‐treated samples [to remove manganese (Mn) oxides]. Subfractions treated with hydrogen peroxide (H2O2) were further treated with oxalate and citrate‐bicarbonate‐dithionite (CBD). Sorption of Cu from an initial 10‐6 M solution after 48 hours was determined in the pH range 3 to 7 using 0.1M sodium nitrate (NaNO3) as the background electrolyte. The pH‐dependent sorption curve (sorption edge) was shifted to a higher pH with decreasing Al oxide content in the soils, and for the treated sample after removal of organic matter and Al and Fe oxides. A negligible effect was seen after removal of the Mn oxides because of their low abundance. Extraction of sorbed Cu at pH 4 to 6 with 0.1M nitric acid (HNO3) for 24 hours confirmed the sorption results, in inasmuch as removal of the Al (and Fe) oxides increased Cu extractability. Therefore, it was concluded that in the soils investigated, Cu retention is mainly determined by the oxalate‐extractable Al fraction with a minor contribution due to crystalline Fe oxides.  相似文献   

17.
Trace metal behaviour in volcanic ash soils displays distinctive features related to the soils’ large contents of metal‐binding phases and to the rapid release of trace metals from glasses and weatherable minerals. In this work, the BCR (Community Bureau of Reference) sequential extraction scheme (exchangeable + weak acid soluble, reducible, oxidizable, and non‐extractable metal fractions) was applied to selected COST‐622 European reference volcanic soils to determine partitioning of zinc and copper between various solid‐phase constituents, along with the major elements Al, Fe and Mn. The total extracted Al (ΣAl) was strongly correlated with acid ammonium oxalate extractable Al (Alo) (ΣAl = 0.985Alo+ 0.11, R2= 0.98), while the total extracted Fe clearly underestimated the amorphous fraction. Large values for the non‐extractable Al fraction were associated with the presence of gibbsite and phyllosilicates. Although the Zn and Cu contents of the soils were generally large, total amounts extracted (the potentially mobilizable fraction) were small, especially for Zn and for soils with crystalline secondary minerals. The fraction of the total Cu which was potentially mobilizable generally exceeded that of Zn. In the potentially mobilizable Cu the oxidizable fraction was generally dominant. Biocycling appears to play an important role in the surface enrichment of potentially mobilizable Zn and Mn. Although further methodological research seems necessary, the BCR sequential extraction appears to be a valuable tool for studies on metal dynamics in soils with andic properties.  相似文献   

18.
Abstract

Different forms of soil aluminum (Al) are involved in the retention of anions and cations, phytotoxicity of Al in acid soils, CEC reduction and soil physical properties such as aggregate stability and water infiltration. Therefore it is desirable to quantify the different forms of Al in soil especially acidic soils. A rationale was developed from a literature survey to identify the following fractions of Al: (a) exchangeable quantified by 1M KC1 extraction; (b) organic bound quantified by 0.1M CuCl2 + 0.5M KCl extraction; (c) sorhed Al extractable with 1M NE4OAc at pH 4.0; (d) amorphous Al oxide and hydroxide and amorphous aluminosilicates (if present) extractable with 0.2M ammonium oxalate at pH 3.0; and (e) interlayered Al extractable with 0. 33M sodium citrate at pH 7.3. Pools (a), (b), and (c) are extracted sequentially. Amorphous Al oxide and hydroxide (pool d) is calculated from ammonium oxalate extractable Al minus (a + b + c). Interlayered Al is calculated from sodium citrate extractable Al minus ammonium oxalate extractable Al. The latter two extractions are done on separate subsamples of soils. From preliminary studies and data for 13 soil samples it is suggested that this fractionation of soil Al is more meaningful than that obtained by the KCl ‐> K4P2O7 ‐> ammonium oxalate > citrate‐bicarbonate‐dithionite extraction sequence.  相似文献   

19.
Abstract

Phosphate (P) sorption characteristics of six natural Ghanaian Oxisols, selected because of their hydrological and topographical suitability for agriculture, were evaluated. Availability of P appears to be adequate for half of the soils as suggested by the Bray P1 test and determination of the standard P requirement (SPR), i.e., the amount of P sorbed at a concentration of 0.2 ppm P (6.46 μM). The SPR was found to be very closely related to Pmax (Langmuir P sorption capacity), which in turn, was significantly correlated with oxalate‐extractable aluminum (Al) (Alo) and iron (Fe) (Feo) and related (not significantly) to the difference between dithionite‐citrate‐bicarbonate‐extractable Fe (Fed) and oxalate‐extractable Fe. Accordingly, Pmax is fairly well predicted by the model of Borggaard: Pca]e=0.211#lbÀlo+0.115#lbFeo+ 0.05#lb(Fed‐Feo)+0.3, except for one soil strongly enriched in Fe oxides, mainly goethite. This goethite was found by X‐ray diffraction analysis to consist of crystals larger than normally found for pedogenic Fe oxides. The difference between Pmax and Pcalc for this soil could, therefore, be attributed to the occurrence of these large Fe oxide crystals, because P sorption will decrease with increasing crystal size (decreasing specific surface area).  相似文献   

20.
Abstract

Spatial variation of bicarbonate soil test phosphorus (P) and bicarbonate soil test potassium (K) was studied by measuring soil test values for 40 individual soil samples collected from random locations within eight uniform 100 m by 100 m field sites in south‐western Australia. In addition, for five of the sites, spatial variation of the three P sorption indices (ammonium oxalate extractable iron, ammonium oxalate extractable aluminum, and the P retention index) and of organic carbon (C) was measured for 20 individual soils samples. Spatial variation was found to be large, with coefficient of variation (CV) exceeding 20% in most cases, and 50% in some cases. It is therefore essential to collect an adequate number of soil samples from uniform areas in paddocks in order to provide a representative composite sample to measure the soil properties.  相似文献   

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