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Phosphate sorption in some representative soils of Bangladesh
Abstract
An experiment was conducted to observe the phosphate sorption potential of some soils of Bangladesh. Three soil series of calcareous origin, namely Sara (Aquic Eutrochrept), Gopalpur (Aquic Eutrochrept) and Ishurdi (Aeric Haplaquept), and two soil series of non-calcareous origin, namely Tejgaon (Rhodic Paleustult) and Ghatail (Aeric Haplaquept), were selected. The soils were equilibrated with dilute solution of calcium chloride containing graded concentrations of phosphate (0, 1, 2, 5, 10, 25 and 50 μg P mL), and the amount of phosphate sorbed or desorbed was determined. Although all the soils showed potential for sorbing phosphate from applied phosphorus, their ability to sorb phosphorus differed. Increasing rates of phosphate application increased the amount of P sorption but reduced phosphate sorption percentage in all soils except Tejgaon. Phosphate was sorbed by the soils in the order: Tejgaon > Ghatail > Ishurdi > Gopalpur > Sara at 50 μg P mL application. Soils possessing higher amounts of free iron oxide and clay sorbed more phosphate from applied phosphorus.
... The highest P sorption capacity of the Amjhupi soil series might be attributed due to its high organic matter and clay content. Significant relationships between P sorption capacity and several soil properties like organic matter and clay contents have been reported by Toor et al. (1997), Daly et al. (2001) and Hossain et al. (2012). Soil containing high contents of clay adsorbs more P than those with small amounts (Borrero et al., 1988;Pena and Torrent, 1990;Solis and Torrent, 1989;Afif et al., 1993). ...
... Phosphate sorption capacity of different soils series as affected by varying rates of phosphate application At 0 µg P mL -1 , there was some desorption in all the soil series. Similar result was reported byVaananen et al. (2008),Hossain et al. (2012) andAfsar et al. (2012). In the study, phosphate sorption increased gradually with increasing phosphate application in all the soil series.Naseri et al. (2010),Hossain et al. (2012) andAfsar et al. (2012) also reported increase in P sorption with increasing phosphate in equilibrium solution. ...
... Similar result was reported byVaananen et al. (2008),Hossain et al. (2012) andAfsar et al. (2012). In the study, phosphate sorption increased gradually with increasing phosphate application in all the soil series.Naseri et al. (2010),Hossain et al. (2012) andAfsar et al. (2012) also reported increase in P sorption with increasing phosphate in equilibrium solution. At all phosphate application rates, the Amjhupi and Ishurdi soil series sorbed the highest and the Sara soil series sorbed the lowest amount of phosphate.Relationships between soil properties and phosphate adsorption: Physical and chemical properties of the studied soils are presented in ...
Three representative soils belonging to Amjhupi, Ishurdi and Sara series from the Ganges meander floodplain soils in Jessore district were collected to observe phosphate sorption characteristics and to evaluate the best fitted adsorption equation for the soils. The highest phosphate sorption was observed in Amjhupi series and the lowest was in Sara soil series. Differences in P sorption were significantly (p<0.05) influenced by clay content, CEC and pH of the soils. Free CaCO3, EC, OM and available P were found insignificant in affecting P adsorption. The Langmuir equation was best fitted to the equilibrium P sorption data and maximum R-square. Amjhupi soil series would require more P to be supplied to maintain a desired P level in soil solution than others.
... Soluble P-fertilizers applied to the soil are very rapidly changed to less soluble compounds which, with time, become less and less available to plants [7]. Even though there is a fertilizer recommendation guide in Bangladesh for applying phosphorus fertilizer, the farmers do not generally follow the fertilizer guide [8]. Consequently, fertilizers are applied arbitrarily and not based on any science, which not only poses an environmental concern but also lowers the benefit/cost ratio. ...
... Some desorption was noticed in all the soils when no P was applied. That phosphate gets desorbed when equilibrated with phosphate-free water is a common phenomenon and was observed by a number of researchers [8,[18][19][20]. With few exceptions, the amount of P sorption progressively increased with increasing P application in all the soils. ...
An experiment was carried out to study the phosphate sorption capacities of five soil series, namely Noadda, Salna, Gerua, Belabo and Chandra in the Madhupur Tract of Bangladesh. Nine composite soil samples representing the five soil series were found to exhibit varied sorption capacities. However, most of the soils showed the highest amount of phosphate sorption at 25 µg P/mL of application. The sorption data for most of the soils showed a good fit into Langmuir adsorption isotherm. The values of Langmuir-derived maximum sorption capacity (Q 0) varied widely and was in the following order: Belabo, site 9 (1000 µg/g) > Gerua, site 5 (995 µg/g) > Noadda, site 4 (500 µg/g) > Noadda, site 7 (250 µg/g) = Belabo, site 2 (250 µg/g) > Salna, site 6 (167 µg/g) = Gerua, site 8 (167 µg/g) > Salna, site 3 (143 µg/g) > Chandra, site 1 (56 µg/g). The highest sorption capacity of Belabo (site 9) soil could be attributed to its total Al, total Mn, and amorphous Fe contents. The calculated Langmuir coefficient b values were found to be higher than the threshold value of 0.07 mL/µg for the soils in question meaning the soils are not prone to loss via surface and subsurface flow. A strong relationship (r = 0.799**) was obtained between phosphate sorption at 10 µg P/mL of application and the clay content in the studied soils. The aluminium content was also found to have a significant relationship (r = 0.684*) with the phosphate sorption at 10 µg P/mL of application. However, the total free iron oxides and the amorphous Fe did not correlate well with the phosphate sorption at 10 µg P/mL of application. Therefore, the clay and total aluminium contents were primarily responsible for the phosphate sorption capacity of the acidic soils of the Madhupur tract under investigation.
... However, when no phosphate was added to the soils, i.e. at 0 µg P/ml, some desorption was noticed in all the soils. This phenomenon was reported by other scientists working with calcareous and non-calcareous soils (23,24,25) . In the calcareous soils, phosphate sorption increased gradually up to 100 µg PO4 3--P/ml and beyond that concentration, the amount of sorption decreased substantially. ...
... In Ishurdi soil series, the percentage of sorption decreased gradually with an increase in phosphate loading concentration (63.3 to 18.6). A similar kind of phenomenon was reported by other scientists in Ishurdi soil series (23) . On the other hand, the non-calcareous soils exhibited varying sorption capacities. ...
An experiment was carried out to study the effects of calcareousness on phosphate sorption indices of soils using three representative calcareous soils, namely Sara (Aquic Eutrochrept), Gopalpur (Aquic Eutrochrept), and Ishurdi (Aeric Haplaquept) series of Bangladesh. Three non-calcareous soils, namely Belabo (Typic dystrudepts), Sonatala (Aeric Endoaquepts) and Ghatail (Aeric Haplaquept) series were also selected for comparison purposes. Phosphate sorption indices of soils were calculated using Langmuir and Freundlich isotherms. Isotherms were constructed taking one gram of air-dried sieved (< 2 mm) soil into a 50 ml centrifuge tube, and subsequently adding seven initial P concentrations, namely 0, 1, 10, 25, 50, 100 and 150 µg/ml to each centrifuge tube employing a soil/solution ratio of 1 : 20 (w/v). According to the Langmuir equation, the amount of phosphate sorbed followed the order: Sonatala > Ghatail > Sara = Gopalpur > Ishurdi > Belabo. The abundance of amorphous iron rather than the calcareousness was putatively responsible for the high phosphate sorption capacity of soils. Maximum phosphorus buffering capacity (MPBC) of the calcareous soils ranged from 33.4-62.8 l/kg. Langmuir and Freundlich equations produced different values for soil P requirements (SPR) at 0.2 and 1.0 mg P/l. Calcareous soils would require 27-44 mg P/kg soil to attain 0.2 mg P/l soil solution, which is deemed sufficient for crop growth. The soils would require 32-58 mg P/kg soil to reach 1.0 mg P/l soil solution, which is regarded to be safe for soils in terms of susceptibility to P losses. The calculated Langmuir constant b values were higher than the threshold value of 0.07 l/mg for two of the calcareous soils. Therefore, even though the non-calcareous soils sorbed more phosphate, higher bonding energy of P sorption for calcareous soils makes them less vulnerable to loss via surface runoff.
... Two drops of toluene were added to prevent microbial growth. The centrifuge tubes were shaken and equilibrated at 25 • C for 16 h [28]. The samples were centrifuged at 2500 rpm for 10 min. ...
Transformations of applied phosphorus (P) fertilizer to inaccessible residual soil P is the main cause of inadequate P availability to plants in the majority of the cultivated soils. This study investigated the effect of organic wastes (rice-residue biochar, farmyard manure (FYM), poultry manure (PM), green manure (GM), and wheat straw (WS) on residual-P mobilization and its bioavailability in maize crops under different P status soils. Surface soil samples of ‘medium-P’ (12.5–22.5 kg P ha⁻¹) and ‘high-P’ (22.5–50.0 kg P ha⁻¹) status soils were collected from a long-term differential P fertilization experiment on maize-wheat rotation and were subjected to examine P adsorption/desorption, phosphatase activity and microbial biomass P (MBP) after incubation with organic amendments of varying elemental composition. The incorporation of organic manures decreases P sorption with maximum decrease in FYM-treated soils, indicating increased P concentration in soil solution. In contrast, WS due to its wider C/P ratio increased P sorption and did not produce any significant impact on the bioavailability of P. High-P status soils witnessed lower P sorption than medium-P soils. The MBP increased in the order of PM > FYM > GM > WS > biochar irrespective of soil P status. The availability and mobility of residual-P with FYM and PM was significantly higher than that of residual-P from biochar, GM and WS. Organics with wider C/P ratio immobilize bioavailable P in the short term regardless of soil P status.
... The variability of phosphate sources has led to the development of a variety of tests, which are generally based on extractable phosphorus measurements to rate the value of the phosphate fertilizers (Jalali 2006;Pal 2011;Hossain et al. 2012). Such approach, however, cannot fully account for the complex reaction between the soil medium and the applied fertilizers. ...
The geochemical reactivity of single superphosphate (SSP), triple superphosphate (TSP), phosphate rock (PR), partially acidulated phosphate rock (PAPR) and potassium dihydrogen phosphate (KH2PO4) was evaluated in an incubation trial. The soil was Anthrosols, Ap horizon (Sandy loam). Solubility equilibrium of phosphates was calculated by phosphate (PPot = logH2PO4 – pH) and calcium (CaPot = logCa + 2pH) potentials. Next, activity ratio (ARo) and Woodruff potential (ΔF) were considered for estimating phosphate dynamics in the soil.
Data showed that phosphate potentials stressed on significant solubility process and varied accordingly to the rates of the fertilizers: -5.50, -4.81, -4.47 and -4.09 for 0, 50, 100 and 150 kg P ha⁻¹. The values of the Woodruff potential (Δ⌁) varied widely from -1929 to 8573 cal mol⁻¹, i.e., from marginal supplying power in the case of the control treatment to very high supplying power for the TSP (Triple superphosphate). These findings are of practical value for the following reasons: TSP and KH2PO4 are recommended for quick and high P supply to plants; SSP and PAPR for moderate supply and finally PR for slow and low supply. Phosphorus efficiency should be treated with priority particularly for areas with intensive cropping and susceptibility to runoffs.
... A drop of chloroform was added in each centrifuge tube to inhibit the microbial growth during shaking. The centrifuge tube was then shaken and equilibrated for 16 h (Hossain, Hoque, & Osman, 2012). The equilibrated mixture was centrifuged, and the supernatant was analyzed for phosphate following ascorbic acid reduction method (Murphy & Riley, 1962). ...
Manure application changes the phosphorus (P) sorption behavior of soil, which may help release P to surface water. Excess P may result in degradation of quality of receiving water. In this study, effects of dairy, poultry, and goat manure applications on various soil phosphorus sorption indices were estimated for a silt loam Bangladeshi agricultural soil. The soil was incubated with manures for a month, and sorption experiments were conducted using incubated soil. The soil P adsorption isotherms conformed to S-curve shape for the both manure treated and untreated soils. Adsorption data conformed to the isotherms in the order of Freundlich > Temkin > Langmuir for poultry and goat manure treated soils and Langmuir > Freundlich > Temkin for dairy manure treated soil. Manure treatment decreased all the sorption parameters; the highest decrease was observed from dairy manure treated soil. Maximum P buffering capacity and standard phosphate requirement were decreased for all manure treatments, meaning that less fertilizer would be needed to maintain P concentrations in soil solution if manure amendment is used. Results of this study could be utilized for better fertilizer and manure management to reduce the waste of valuable fertilizer and to decrease water pollution.
... Some desorption was noticed at 0 mg P dm -3 treatment (i.e., control). Desorption of P at control was also reported by several other scientists (21)(22). In the present investigation, the amount of P sorption gradually increased with increasing P application in all the soil series. ...
To investigate the phosphate sorption potential of soils, an incubation experiment was performed with five representative soil series of Bangladesh namely the Borkal (Typic Dystrudepts), the Pahartali (Aeric Endoaquepts), the Raojan (Aeric Endoaquepts), the Noapara (Typic Endoaquepts) and the Manu (Aeric Dystrudepts). Calcium chloride solution of 0.01 M containing 0, 1, 10, 25, 50 and 100 mg phosphorus dm-3 was used to equilibrate the soils and then the sorbed phosphate was measured. The phosphate sorption curves showed almost similar magnitude of changes. Phosphate sorption by the soils was observed in the order of Borkal>Noapara>Manu>Raojan>Pahartali soil series and reflected with the organic matter content of soils. Between Freundlich and Temkin equation, Freundlich model showed better fit to sorption data at higher P concentrations. The coefficient of determination (R 2) values were used to compare the suitability and applicability of Freundlich and Temkin equation. Equilibrium P concentration (EPC 0) value (P concentration at zero fixation) was estimated by using Temkin adsorption equation and the values were between 0.05 mg dm-3 and 0.45 mg dm-3. The highest EPC 0 was obtained for Pahartali and the lowest for Noapara soil series. Therefore, Freundlich equation may be more suitable for evaluating phosphate sorption capacities of agricultural soils.
... In the present study, phosphate sorption increased gradually with increasing phosphate application in both Bajoa and Sara soil series in control (Fig 4.1.). Increase in P sorption with increasing phosphate in equilibrium solution was also reported by other scientists (Naseri et al., 2010;Hossain et al., 2012;Afsar et al., 2012). ...
... The CEC of the Gopalpur and Bajoa soil series were 17 Cmol (+) kg -1 and 22 Cmol (+) kg -1 of soils (Table 4.1). Hossain et al. (2012) reported that CEC varied from 9.22 to 24.4 ...
... The CEC of the Gopalpur and Bajoa soil series were 17 Cmol (+) kg -1 and 22 Cmol (+) kg -1 of soils (Table 4.1). Hossain et al. (2012) reported that CEC varied from 9.22 to 24.4 ...
The present study was conducted to show the sulfate sorption capacity within two soil series by comparing their best suitability in different adsorption isotherm and the effects of acetate anion on sulfate sorption. Between two soil series, Bajoa soil possessed the greater sorption (645.12 µg/g soil) with increasing the sulfur concentration. Beside this, the Gopalpur soil series showed sulfate sorption (550.76 µg/g soil) probably due to its higher pH (7.9); lower CEC (17 Cmol(+)kg-1), organic C (0.64%) and clay content (31%) than Bajoa (pH 6.9; CEC 22 Cmol(+)kg-1; Organic C 0.70; clay content 35%). On the other hand, at the presence of acetate anion, the amount of sulfate sorption in both soil series was decreased due to the competition between the sulfate and acetate anion on the exchange site.
The Frundlich equation showed the best fit with higher value of coefficient followed by Langmuir and Temkin. The Langmuir equation has explained the Maximum Buffering Capacity (MBC) and the binding energy (kL) of sulfate ion on the Bajoa soil series.
To study the phosphate sorption potential of soils, an experiment was conducted with eight different soil series of Bangladesh. The soils were equilibrated with 0.01 M calcium chloride solution containing 0, 1, 2, 4, 8, 16, 25, 50, 100 and 150 μg phosphorus mL-1 and the amount of phosphate sorbed was determined. Calcareous soils sorbed more phosphorus than non-calcareous soils. The sorption curves showed more or less similar pattern of changes. Langmuir model showed better fit to sorption data at higher P concentrations. Phosphate sorption was highly correlated with Fe oxide and clay content of the soils. Freundlich constant kf and n, Phosphorus Sorption Maximum (Sma,x) and EPC0 values were positively correlated with both the above soil properties. On the contrary, phosphate binding strength (b) was negatively correlated. It is suggested that Langmuir equation might be more suitable for commercial soil-testing laboratories for routine determination of phosphate sorption characteristics of soils.
Phosphate sorption equations have been widely used to characterize soils with respect to their phosphorus requirements (Preq). For the sorption study, the soils were equilibrated with 0.01 M CaCl2 solution containing graded concentrations of phosphate (0, 1, 10, 25, 50, 100 and 150 mg P L-1). The Preq values of four calcareous soils were determined from the Langmuir, Freundlich and Temkin equations. The Langmuir equation was best fitted to the P sorption data. Among the four soil series, the Ghior soil series occupying the lowest position of catena sorbed the highest amount of phosphate. The amounts of sorbed P maintaining 0.2 mg P L-1 in soil solution ranged from 14.14 to 33.56, 27.99 to 45.80 and 16.16 to 51.72 mg kg-1 soil which were derived from the respective Langmuir, Freundlich and Temkin equations. Preq values derived from the Freundlich and the Langmuir equations were negatively correlated with Olsen-P content of the soil (r >-0.975, p<0.05). Again, Preq values determined from the Freundlich equation were positively correlated with percent clay content (r >0.901, p<0.05) of the soil. Phosphate was sorbed by the soils in the following order: Ghior>Ishurdi>Gopalpur>Sara soil series. However, based on their Preq values, the soils can be arranged in the following order: Ishurdi>Ghior>Gopalpur>Sara soil series. To maintain a desired P concentration in the soil solution, the Ishurdi soil will be required to supply more P than others.
Phosphorus (p) adsorption characteristics of 5 soil samples were studied in soils of Southeastern Iran during 2009/2010 cropping season. Some soil properties as well as selected P-adoption characteristics were studied in these soils, Results show for this study Freundlich adsorption isotherm has good match with phosphorus adsorbed data and has good R-square. Freundlich sorption isotherms were used to evaluate the P requirement of 5 soils in a lab study. The soils were medium to heavy textured, acidic in reaction and were highly calcareous. Amount of P sorbed by the soils increased with increasing P in equilibrium solution. Quantities of P retained on sod solid phase were significantly correlated (p<0.05) with clay content of the soils. Maximum P was sorbed by a soil that had the maximum (64%) Clay content, there were negative relationship between P adsorption capacity and SOC and Ca content of soils.
The capacity of 36 Western Australian soils to adsorb phosphorus (P) was measured by three different methods: P retention index (PRI), P buffering capacity (PBC), and P adsorption (PA). The P adsorption values measured by all three methods varied markedly with soil type. When the P adsorption values were correlated with several soil properties, using simple and multiple linear regressions, PRI, PBC, or PA values were found to be significantly correlated with the aluminium oxide content of the soils. In addition, PBC and PRI was correlated with organic carbon content. The role of aluminium oxide (Al2O3) in the soil was apparently more important in determining the P adsorption capacity of the soils than that of iron (Fe), even though the iron oxide (Fe2O3)content of all the soils studied was consistently higher than the aluminium oxide content. The relationship between P adsorption and the selected soil properties, as determined by multiple linear regression, explained 45–59% of the variation: arabicPRI = ‐10.87 + 9.94 organic C (%) + 160.02 Al2O3 (%), r = 0.45.arabicPBC = ‐0.004 + 1.532 organic C (%) + 22.26 Al2O3 (%), r = 0.57.arabicPA = 3.52 + 248.75 Al2O3 (%), r = 0.59.
Surface samples of fifteen soils, developed
on a range of parent materials and varying
widely in crystalline iron oxide content, sorbed
between 60 and 490 μgP/g of added P (500
μgP /g added as KH2PO4) . Although P sorption
was weIl correlated with exchangeable Al
(r = 0.84), removal of exchangeable Al caused
only a relatively smaIl decrease in the amount
of P sorbed. Removal of amorphous Fe and
Al component~ by oxalate treatment reduced P
sorption by 19 to 100 per cent, compared to
that of the untreated sample. The amount of P
sorbed by untreated samples was less weIl correlated
with oxalate Fe (r = 0.47) than with
oxalate Al (r = 0.78), suggesting that amorphous
Fe components are less active per unit
weight than amorphous Al in the sorption of
added P by untreated soils. Citrate-dithionite bicarbonate
(CDB) treatment removed large
amounts of Fe and associated Al but the reduction
in P sorption after CD B (-12 to 84 per
cent compared to that of the untreated sample)
was less than after oxalate treatment.
Sorption of added P following CDB was well
correlated with the amounts of amorphous aluminosilicates
in the soils (r = 0.99), which were
probably occluded within crystalline iron oxides
and exposed by CDB treatment. Amorphous aluminosilicates
in the soils sorbed substantial
amounts of added P and also had native inorganic
P associated with them; in some cases the
amorphous aluminosilicate-associated native inorganic
P constituted a high proportion (up to
44 per cent) of total soil P. P sorption by amorphous
material-free kaolinitic clays appeared to
be related to the degree of order of the kaolinite.
Sorption of added P was always better correlated
with the Al parameters than with the Fe
parameters considered. It is difficult to identify
the soil parameters most responsible for P sorption
because they are themselves correlated to a
considerable degree.
The Transkei is the largest consolidated area in South Africa where land is held by small-holder farmers but little is known about the extent of phosphate fixation in the region. This study was conducted to determine the phosphate sorption properties and external P requirements (EPR) of selected soils from the Transkei region, South Africa and to relate derived sorption values to selected soil parameters. The P sorption maxima and EPR values varied widely ranging from 192.3 to 909.1 mg P kg −1 and from 2 to 123 mg P kg −1 soil, respectively. Citrate dithionite bicarbonate-extractable aluminum explained most of the observed variations in P sorption. About 43% of the soils were found to be moderate P fixers and may need management interventions to ensure adequate P availability to crops. The single point sorption index accurately predicted the EPR of the soils obviating the need to use multiple point sorption isotherms. The results sug-gested that the use of blanket phosphate fertilizer recommendations may not be a good strategy for the region as it may lead to under-application or over-application of P in some areas.
Phosphorus Sorption Characteristics of Red Soils from Lampung, West- and Central Java (S.A. Siradz ): Red soilis a common name used to identify any soil showing yellowish to reddish colour, these soils mainly occur in tropicaland subtropical regions. The term is frequently used to convey an image of red, infertile, acid soils in the tropics andis associated with tropical and subtropical climates which are characterized by high temperature and humidity. Majorsoil constraints to crop production may include low pH, low available P and high P fixation capacity, toxicity due toAl and sometimes Mn and Fe, deficiencies of N, Ca, Mg, K, and micronutrients e.g. Mo, Zn and Cu, low CEC and lowbase saturation, and very low content of weatherable minerals. The aim of this study was to determine the phosphorussorption characteristics of red soils from Lampung, West Java and Central Java. Soils were sampled at depth of 0-20cm from minimally disturbed sites after discarding the uppermost few cm consisting of an accumulation of litter. Thesamples were air-dried, crushed using a ceramic mortar and pestle and then passed through a 0.5 mm stainless steelsieve. Measurements of P sorption were conducted by equilibrating 200 mg of air dry soil (<0.5 mm) in 20 mL 0.2 M KClcontaining 0-30 g PmL-1. P concentrations in filtrate were determined by the molybdate blue method. Phosphorussorption data for soils were fitted to simple Langmuir and Freundlich isotherm equations and both equations describedthe data equally well. Langmuir P sorption maximum (xm) for soil ranged from 719-2747 μg Pg-1, with median values of1.825 μg Pg-1. There were systematic decreases in the values of Langmuir sorption maximum (xm) for soils fromLampung > West Java and Central Java. Values of pH(NaF), Ald, and exchangeable Ca were most predictive of Psorption in these soils.
A standard P adsorption procedure was proposed and the ability of four laboratories to produce consistent results over a wide range of soils was determined. For this procedure, 0.5 to 1.0 g of soil were shaken in 0.01 mol L-1 CaCl2 at a soil/solution ratio of 1:25 in containers allowing a 50% head space for 24 h at 24 to 26°C on an end-over-end shaker. Initial dissolved inorganic P concentrations of 0 to 323 μmol P L-1 (as KH2PO4 or NaH2PO4) were used and microbial activity inhibited by 20 g L-1 chloroform. Excellent agreement between the four laboratories was obtained for the amount of P adsorbed by the 12 soils studied, with a mean coefficient of variation (CV) over all P levels and soils of 0.91%. The laboratories also exhibited a high degree of replication of individual treatments with no laboratory showing a strong consistent bias across all soils and P levels in terms of P adsorption. Langmuir, Freundlich, and Tempkin adsorption models were highly correlated with the adsorption data. Respective mean correlations for the 12 soils were 0.98, 0.97, and 0.95. The proposed method, therefore, has the potential to produce consistent results that can be used to predict partitioning of dissolved inorganic P between solid and solution phases in the environment.
A single solution reagent is described for the determination of phosphorus in sea water. It consists of an acidified solution of ammonium molybdate containing ascorbic acid and a small amount of antimony. This reagent reacts rapidly with phosphate ion yielding a blue-purple compound which contains antimony and phosphorus in a 1:1 atomic ratio. The complex is very stable and obeys Beer's law up to a phosphate concentration of at least 2 μg/ml.The sensitivity of the procedure is comparable with that of the stannous chloride method. The salt error is less than 1 %.
P-incubation experiments were conducted on 19 soils from different agricultural areas of West Asia-North Africa. The soils contrasted widely in clay, CaCO3, and Fe oxide contents. The availability index (AI), the ratio between the increase in Olsen P and P applied, was determined between 30 and 240 d after applying rates between 20 and 500 mg P kg-1 soil. The results support the idea that P reactions in calcareous soils differ according to the P application rate, and raise caution about the incubation conditions in the laboratory that are used to estimate the loss of P availability in calcareous soils. -from Authors
The influence of seven organic residues on sorption and desorption of P by a high P‐fixing soil was determined after 30, 75, and 150 days of incubation. After incubating for 30 days, all residues decreased the amount of P sorbed by the soil, resulting in higher equilibrium solution P levels. However, after incubating for either 75 or 150 days, the P content of the organic residues had a marked influence on sorption of added P and desorption of sorbed P. The critical value of P in organic residues which resulted in no tie‐up of soil P was 0.3%. Sawdust, wheat straw, and cornstalks which contained < 0.3% P decreased labile soil P and increased sorption by soil after incubating for 75 or 150 days. Alfalfa ( Medicago sativa ), barley ( Hordeum vulgare ), beans ( Phaseolus vulgaris ), and poultry manure that contained P in excess of 0.3% decreased sorption of P. The results suggest that P fertilizer rates estimated from sorption isotherms may need to be modified following addition of organic residues.
The understanding of phosphorus (P) sorption and desorption by soil is important for better managing soil P source and relieving water eutrophication. In this study, sorption-desorption behaviour of P was investigated in purple soils, collected from 3 kinds of purple parent materials with different kinds of land cover, in the upper reaches of Yangtze River, China, using a batch equilibrium technique. Results showed that most of the farmed purple soils had P sorption capacity (PSC) values ranging from 476 to 685 mg P/kg, while higher PSC values were observed in the soils from forestland and paddy field. A single-point P sorption index (PSI) was found to be significantly correlated with PSC (R-2 = 0.94, P < 0.001), suggesting its use in estimating PSC across different types of purple soils. The PSC of purple soils was positively and strongly related to the contents of amorphous Fe and Al oxides (r = 0.73, P < 0.001), clay (r = 0.55, P < 0.01), and organic matter (r = 0.50, P < 0.05). Furthermore, the constant relating to binding strength was positively correlated with the content of amorphous Fe and Al oxides (r = 0.66, P < 0.01), but negatively correlated with labile Ca (r = - 0.43, P < 0.05) and soil pH (r = - 0.53, P < 0.01). Some acidic purple soils with high binding energy featured a power desorption curve, suggesting that P release risk can be accelerated once the P sorbed exceeds a certain threshold. Other soils with low binding energy demonstrated a linear desorption curve. The P desorption percentage was significantly correlated with soil test P (r = 0.78, P < 0.01) and the degree of P saturation (r = 0.82, P < 0.01), but negatively correlated with PSC (r = - 0.66, P < 0.01).
Iron and aluminum were determined in acid ammonium oxalate extracts and in dithionite–citrate–bicarbonate extracts of a wide range of Canadian soils, several oxide and silicate minerals, and some amorphous preparations of iron or aluminum and silica. The oxalate extraction dissolved much of the iron and aluminum from the amorphous materials but very little from crystalline oxides, whereas the dithionite extraction dissolved a large proportion of the crystalline iron oxides as well as much of the amorphous materials. Oxalate-extractable iron and aluminum gave a useful indication of Bf horizon development in many soils, even if the parent materials were high in iron oxides. In one class of Gleysolic soils, however, the Bfg horizons were high in dithionite-extractable iron and low in oxalate-extractable iron. An accumulation of goethite was found in the Bfg horizon of some of these soils. In some other Gleysolic soils iron was depleted in the A horizon but there was no horizon of iron accumulation. Extraction of soils with oxalate as well as with dithionite is useful in differentiating certain classes of soils and in identifying horizons of accumulation of secondary sesquioxides.
Phosphate sorption characteristics of soil material from selected soil profiles of West Africa were studied. These soils represent a wide range of parent materials and agroclimatic conditions. Phosphate concentration in soil solutions was almost invariably low in comparison with the requirements for most crops. In comparison with many soils of the humid tropics, the surface horizons have low to medium standard P requirements (or the amounts of P required to attain 0.2 ppm P in solution). Phosphorus sorption capacity is mainly related to soil mineralogy, which in turn is related to soil parent materials, BET-surface area, and free Fe oxide content of the soils. Of the profiles studied, Alfisols and Ultisols derived from basalts have the highest standard P requirement. Ultisols have higher standard P requirements than Alfisols.
(C) Williams & Wilkins 1977. All Rights Reserved.
Phosphate sorption by calcareous soils has been studied mainly on heavily fertilized agricultural soils and soils with calcite as the main carbonate mineral. We examined factors affecting phosphate adsorption in the soils of a semi-arid, mediterranean, dolomitic, soil and vegetation chrono-sequence in southeastern Spain. The youngest soils are highly eroded, Sandy Regosols (Typic Xerorthents) under gorse-scrubland vegetation. These have small P sorption capacities, large Mg-Ca carbonate contents but small amounts of Fe and Al oxides. Small total P (HNO3/HClO4 digestion) concentrations (30–130 μg P g−1), of which up to 90% is Ca-bound (HCl-extractable), are typical of these young soils. P sorption markedly increased when Ca2+ was added to the solution. The fractionation of previously sorbed P indicates that the fate of most of this extra-sorbed P is the labile-P fraction sorbed on to (carbonate) surfaces and the apatite-like fraction (NaHCO3-extractable and HCl-extractable fractions). At the other extreme, older more-intensively weathered, sandy-clay-loam rendzinas (Entic Haploxerolls), supporting dense mature garrigue, have a much greater P adsorption capacity and larger clay and Fe and Al oxide concentrations. They have more total P (ca 400 μg P g−1), much of it in occluded form (residual fraction). These soils show no significant differences in P sorption whether or not CaCl2 was used as a background electrolyte. Considering the overall variations within the chronosequence, dithionite extractable Fe and Al are the properties best correlated with P sorption. This support the general finding that crystalline Fe-oxides (e.g. goethite and haematite) appear to be the most important P-sorbing component for soils in the Mediterranean region, rather than amorphous Fe-oxides (e.g. ferrihydrite) as is reported for more mesic areas. Stepwise multiple regression and fractionation data, however, suggest that, provided the soil solution is rich in Ca2+, carbonate may also be a significant contributing factor to P sorption, especially in the youngest of these dolomitic soils.
Potassium pyrophosphate (0.1m) removes very little Fe from crystalline Fe oxides at pH 10, but peptizes finely divided hydrous amorphous oxides and organic matter in soils.
Fe and C contents of extracts from each horizon of twenty-six British soil profiles show distinctive patterns, independent of the residual dithionite-soluble Fe. Thus extracts of humus Fe podzols have maximum Fe and C in the B horizon, peaty gley podzol has maximum Fe in the B horizon but maximum C in the surface. These groups are differentiated from non-podzols which have maximum pyrophosphate extractable Fe and C in the surface horizon, decreasing with depth. Intermediate patterns help to quantify differences in soils of classes having properties of more than one soil group.
The availability of fertilizer P in six P‐deficient tropical soils from Brazil, Kenya, Malaysia and Indonesia was assessed by grass in a pot experiment. Grass dry matter yield ( D ) and fertilizer P( F ) were fitted to a Mitscherlich equation: D = a−b exp(−cF), and P uptake ( U ) and F to the linear equation: U=α+β F . Fitted parameter β equals the proportion of P recovered in one crop and it varied widely between soils, ranging from 12 to 51%. Quantitative assessments of fertilizer‐P availability could also be made using dry‐matter data alone if the rates of fertilizer used were well distributed along the response curve, when Mitscherlich parameter c was correlated well with β.
Chemical measurements were made on uncropped soil. Phosphate sorption isotherms were measured, using ³² P to assess exchangeable and non‐exchangeable phosphate. The availability parameters c and β were correlated best with parameter b e , the phosphate buffer capacity derived from the fitted Freundlich isotherm for exchangeable phosphate, suggesting that the mobility of exchangeable phosphate is a major influence on P availability. Al and Fe were extracted with acid oxalate, citrate‐dithionite and pyrophosphate reagents, and parameters c and β correlated best with Al extracted by acid oxalate. These relationships were inverse, showing that Al in disordered mineral forms lowers the availability of fertilizer P.
The phosphate adsorption capacity (Pmax) of samples from various horizons of five Danish podzolized soils were investigated before and after organic matter removal. Removal of organic matter had no direct influence on Pmax suggesting that organic matter did not compete with phosphate for adsorption sites. In the soils investigated aluminium and iron oxides were the main phosphate adsorbents. Thus, more than 96% of the variation in Pmax could be accounted for by poorly crystalline aluminium and iron oxides (extractable by oxalate) and by well-crystallized iron oxides (taken as the difference between dithionite-citrate-bicarbonate-extractable iron and oxalate-extractable iron).
Organic matter affected phosphate adsorption indirectly by inhibiting aluminium oxide crystallization. The resulting poorly crystalline oxides had high Pmax. In contrast, the influence of organic matter on the crystallinity of the iron oxides, and therefore on their capacity to adsorb phosphate, seemed limited.
Phosphate adsorption isotherms were determined for 20, mostly very acidic, soils from the Mekong Delta. The experimental data were well described by a binary Langmuir equation which considers two groups of sorption sites that differ in their P bonding energies. The maximum P‐sorption capacities of these sites were related to the soil properties by simple linear correlation and by stepwise multiple regression. Results suggest that high energy sites are on Al‐oxihydroxides or small Al‐substituted Fe‐oxides and, to a lesser extent, on poorly ordered Fe‐oxihydroxides. On the other hand, the P‐sorption capacity of low energy sites is mainly related to clay content, and it increases as pH decreases. These sites are also positively correlated with organic carbon and poorly crystalline Fe‐oxihydroxides. However, as these two variables are closely correlated with each other, organic matter is likely to be considered as an indirect factor of P fixation through its association with Fe‐oxihydroxides and not as an important source of P‐sorption sites.
The maximum sorption capacity, i.e. the sum of sorption capacities of the two groups of sites, is well described (r ² = 0.88) by an equation that takes into account the four variables identified above: Al‐bearing oxihydroxides, poorly ordered Fe‐oxihydroxides, clay content and pH. Grouping the soils according to the orders of Soil Taxonomy, the P‐sorption capacity increases in the following sequence: ultisols < entisols < inceptisols.
A P concentration often considered adequate for plant nutrition is 0.2 mg P 1 ⁻¹ solution, and only the high energy sites are involved in sorption at that concentration. Thus an equation including only Al‐ and Fe‐oxihydroxides could be used to fix P norms in these soils.
A single solution reagent is described for the determination of phosphorus in sea water. It consists of an acidified solution of ammonium molybdate containing ascorbic acid and a small amount of antimony. This reagent reacts rapidly with phosphate ion yielding a blue-purple compound which contains antimony and phosphorus in a 1:1 atomic ratio. The complex is very stable and obeys Beer's law up to a phosphate concentration of at least 2 μg/ml.The sensitivity of the procedure is comparable with that of the stannous chloride method. The salt error is less than 1 %.RésuméUne méthode spectrophotométrique est décrite pour le dosage du phosphate dans l'eau de mer, an moyen de molybdate d'ammonium, en présence d'acide ascorbique et d'antimoinc. Il se forme rapidement un composé violet bleu, renfermant antimoine et phosphore dans un rapport atomique de 1:1.ZusammenfassungBeschreibung einer Methode zur Bestimmung von Phosphat in Mecrwasser mit Hilfe von Ammoniummolybdat in Gegenwart von Ascorbinsäure und Antimon. Der gebildete blau-violette Komplex wird spektrophotometrisch gemessen.
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