Sorbed phosphate at standard supernatant concentration as an estimate of the phosphate needs of soils

1965 ◽  
Vol 5 (16) ◽  
pp. 52 ◽  
Author(s):  
RS Beckwith
Keyword(s):  
Sorption Capacity ◽  
Surface Soil ◽  
Equilibrium Concentration ◽  
Solution Concentration ◽  
Small Field ◽  
Surface Soils ◽  
Phosphate Sorption ◽  
Surface Horizon ◽  
Supernatant Solution

Phosphate sorption capacity of soils has meaning only if the equilibrium supernatant solution concentration is specified. Measurements have been made, on a variety of Queensland soils, at an equilibrium concentration of 0.2 p.p.m. P ; reasons for this choice of cencentration are discussed. Phosphate sorption values measured in this way appear to parallel the phosphate needs of legumes growing on a number of the soils examined in the laboratory. The approach is put forward for testing by others on present and future phosphate rate trials. Present phosphate sorption measurements are interpreted as indicating (1) that even where native phosphate is inadequate, or has been depleted by cropping, heavy-textured grey and brown soils of the brigalow lands will only require small field applications of superphosphate. (This statement may not apply to soils containing free carbonate in the surface). (2) that phosphate requirements of krasnozems vary considerably but may exceed 1 ton of superphosphate an acre in some areas. Loss of the surface horizon by erosion, or mixing the subsoil With surface soil, could increase the phosphate requirement of some of these soils. (3) that the phosphate status of soils formed from phyllite in the Gympie district is intermediate between these extremes. Here also the subsoils must be expected to have larger phosphate requirements than the surface soils.

Sorption of Metribuzin and Metolachlor in Alaskan Subarctic Agricultural Soils

Weed Science ◽  
1992 ◽  
Vol 40 (1) ◽  
pp. 155-160 ◽  
Author(s):  
Jeff S. Graham ◽  
Jeffery S. Conn
Keyword(s):  
Organic Carbon ◽  
Carbon Content ◽  
Soil Type ◽  
Surface Soil ◽  
Agricultural Soils ◽  
Freundlich Isotherm ◽  
Organic Carbon Content ◽  
Surface Soils ◽  
Adsorption And Desorption ◽  
Equilibration Temperature

Adsorption and desorption of metribuzin and metolachlor were studied for 0- to 15- and 30- to 45-cm soil depths and at 5 and 28 C temperatures for two subarctic Alaskan agricultural soils. Surface soils had five to eight times the organic carbon content of deeper soils and had lower Freundlich isotherm slopes (1/n) for both herbicides. Surface soil Freundlich coefficients (Kf) were affected by both soil type and equilibration temperature, with soil type accounting for greater than 80% of the variation in Kf. Surface soil mean Kfvalues ranged from 1.5 to 2.4 for metribuzin and 4.4 to 9.2 for metolachlor. For soils from the 30- to 45-cm depth, neither soil type nor temperature affected Kf. Isotherm slopes for desorption were less than adsorption, indicating hysteresis. Regressions between desorption Kfand maximum herbicide adsorbed prior to desorption were highly significant with coefficients of determination (r2) between 0.50 and 0.99.

scholarly journals Study of Adsorption from Dilute Aqueous Solutions on to Activated Carbon. Part 2. Some Exotic Adsorption Isotherms

1996 ◽  
Vol 13 (5) ◽  
pp. 341-354
Author(s):  
R. Mészáros ◽  
M. Nagy ◽  
G. Veress
Keyword(s):  
Activated Carbon ◽  
Adsorption Isotherms ◽  
Equilibrium Concentration ◽  
Model Description ◽  
Adsorption Data ◽  
Dilute Aqueous Solution ◽  
Dilute Aqueous Solutions ◽  
Error Terms ◽  
Concentration Curves ◽  
Supernatant Solution

Adsorption isotherms for the adsorption of 1-propanol and 2-propanol from dilute aqueous solution on to two types of activated carbon were presented at fixed different initial concentrations. The confidence limits for the specific excess relative to these fixed initial concentrations were also given. The high precision calculation of these error terms was based on the model description of the equilibrium concentration versus sorbent concentration curves discussed previously. The Dubinin–Radushkevich representation of the adsorption data was presented and tested for the same adsorption data. It appears that in some cases the adsorbed amount as expressed by the specific excess depends not only on the equilibrium concentration of the supernatant solution but also on the initial concentration and sorbent concentration. The so-called characteristic isotherms were also calculated in order to compare the various adsorption systems.

Geostatistical assessment of the regional distribution of phosphate sorption capacity parameters (FeOX and AlOX) in northern Belgium

Geoderma ◽  
1995 ◽  
Vol 66 (3-4) ◽  
pp. 285-296 ◽  
Author(s):  
Richard Lookman ◽  
Nadia Vandeweert ◽  
Roel Merckx ◽  
Karel Vlassak
Keyword(s):  
Sorption Capacity ◽  
Regional Distribution ◽  
Phosphate Sorption

scholarly journals 256 Evaluation of Phosphate Desorption Characteristics of Clay Minerals for Soilless Root Media

HortScience ◽  
1999 ◽  
Vol 34 (3) ◽  
pp. 486C-486
Author(s):  
Young-Mi Oh ◽  
Paul V. Nelson ◽  
Dean L. Hesterberg
Keyword(s):  
Clay Minerals ◽  
Soil Solution ◽  
Equilibrium Concentration ◽  
Solution Concentration ◽  
Reaction Chamber ◽  
Maximum Adsorption Capacity ◽  
Commercial Alumina ◽  
Root Media ◽  
Phosphate Leaching ◽  
Phosphate Desorption

Soilless root media retain very little phosphate. This characteristic necessitates continual application of phosphate, which leads to excessive application and leaching. The phosphate desorption characteristics of synthetic hematite (a-Fe2O3), goethite (a-FeOOH), allophane (Si3Al4O12*nH2O), and a commercial alumina (Al2O3), previously determined for their maximum adsorption capacities, were evaluated to determine their potential for providing a low, constant soil solution phosphate supply with low phosphate leaching from soilless root media. The desorption isotherms of the clay minerals were obtained by introducing 10 mM KCl solution at 0.2 ml/min flow rate into a stirred flow reaction chamber loaded with clay adsorbed with phosphate at maximum adsorption capacity. The suspension in the reaction chamber was held at pH 6.4 during desorption. Effluent solutions were collected for phosphorus analysis until the equilibrium concentration of phosphorus in solution reached 0.05 mg•L-1. Adsorbed phosphorus at 0.05 mg•L-1 equilibrium concentration in solution was in the order allophane (19 mg•g-1) > alumina™ goethite (8 mg•g-1) > hematite (1.3 mg•g-1). The equilibrium concentration of phosphorus in solution over time showed that allophane releases phosphate for a longer time than the other clay minerals at a desirable soil solution concentration for plants, less than 5 mg•L-1. Among the clay minerals tested, allophane showed the most favorable potential to supply phosphate to plants in soilless root media.

Phosphate sorption by soils as a measure of the phosphate requirement for pasture growth

1967 ◽  
Vol 18 (4) ◽  
pp. 601 ◽  
Author(s):  
PG Ozanne ◽  
TC Shaw
Keyword(s):  
Equilibrium Concentration ◽  
Correlation Coefficients ◽  
Laboratory Method ◽  
Phosphate Sorption ◽  
Soil Mixing ◽  
Equilibrium Concentrations ◽  
The Relationship ◽  
Pasture Plants ◽  
Different Soils

Development of a laboratory method for predicting the phosphate requirements of pasture plants, in pounds phosphorus per acre, is described. Measurement of the phosphate sorption by soil at a standard equilibrium concentration was used. Predictions made by using this method in the following year on different soils accounted for over 85% of the variability in phosphate requirement. A good correlation between phosphate sorbed and phosphate required was found. The relationship was linear over the range 0–500 p.p.m. of sorbed P. While different sampling depths, equilibrium concentrations, and degree of soil mixing affected the relationship, it remained linear and the correlation coefficients close to 0.9.

Evaluation of soil phosphate buffering indices

Soil Research ◽  
1979 ◽  
Vol 17 (3) ◽  
pp. 495 ◽  
Author(s):  
ICR Holford
Keyword(s):  
Phosphorus Uptake ◽  
Equilibrium Concentration ◽  
Solution Concentration ◽  
Parent Material ◽  
Heterogeneous Group ◽  
Homogeneous Group ◽  
Soil Phosphate ◽  
Simple Index ◽  
Natural Solution ◽  
Additional Variance

Seven phosphate buffering indices were evaluated by determining the additional variance accounted for when each index was added to a regression of plant phosphorus uptake on labile soil phosphate. The study was done on two groups of soils: one relatively homogeneous group of 24 soils all formed on the same parent material, and a heterogeneous group of 30 soils formed on a variety of parent materials. A separate pot experiment was done on each group, ryegrass being grown on the homogeneous soils and white clover on the heterogeneous soils. Only two indices did not account for a large and significant increase in variance in phosphate uptake. The extra variance accounted for was much greater in the heterogeneous group than in the homogeneous group, although the total variance accounted for by both variables was greater in the homogeneous group. The much smaller volume of soil used in the ryegrass experiment may explain the smaller buffering effect in the homogeneous soils. The three most effective and consistent indices were a simple index of the maximum buffer capacity, determined from the Langmuir isotherm over a standard range of equilibrium solution concentrations, the slope of the isotherm at the natural solution concentration, and the amount of adsorption at a standard equilibrium concentration of 0.3 pg phosphorus/ml.

Phosphate sorption capacity of European volcanic soils

2010 ◽  
Vol 59 (1) ◽  
pp. 77-84
Author(s):  
Gy. Füleky
Keyword(s):  
Sorption Capacity ◽  
Soil Property ◽  
High Ratio ◽  
Surface Reactivity ◽  
Soil Horizon ◽  
Phosphate Adsorption ◽  
Volcanic Soils ◽  
Phosphate Binding ◽  
Phosphate Sorption ◽  
Sorption Ability

The aim of the presented study was to prepare the phosphate sorption isotherms of 20 European volcanic soil profiles and some other Hungarian and German volcanic soils (n = 114) used in the experiment and to establish the soil characteristics determining the phosphate sorption capacity of these soils. The Langmuir isotherm well describes the phosphate sorption of European volcanic soils at bright concentration interval 0–600 mg·dm -3 P. The calculated phosphate adsorption maximum (P max ) is an excellent soil property for characterizing the surface activity of soils developed on volcanic parent material. The calculated phosphate sorption maxima of soils included in the experiment ranged from 0 to 10.000 mg P·kg -1 . Some of the volcanic soils sorbed a high ratio of the added phosphate at low concentrations, while others sorbed somewhat less. The difference in the phosphate binding affinity of soils caused the differences in the shape of the Langmuir adsorption isotherms. P retention % is a WRB diagnostic requirement of andic soil horizon. It was supposed that the phosphate sorption maximum (P max ) gives a better characterization of the surface reactivity of volcanic soils. As it was predicted, oxalate soluble Al is the most important soil property, which dominantly (in 73%) explained the phosphate sorption ability of European volcanic soils.

Surface-modified apricot pits as biochar feedstock and phosphate sorbent

2020 ◽  
Author(s):  
Gerhard Soja ◽  
Stefan Wyhlidal ◽  
Wolfgang Friesl-Hanl ◽  
Kathrin Zwölfer ◽  
Julia Edlinger ◽  
...  
Keyword(s):  
Surface Modification ◽  
Sorption Capacity ◽  
Vegetable Oils ◽  
Liquid Media ◽  
Phosphate Sorption ◽  
Sorption Dynamics ◽  
Negative Effect ◽  
Screw Reactor ◽  
Surface Modified

<p>Pits from fruit like apricots, peaches and cherries are an under-utilized resource. If there is any use at all, they may be extracted for special vegetable oils. Mostly the pits are combusted or left to rot. However, they are also an appropriate feedstock for pyrolytic carbonization. This study investigated the biochar produced from apricot pits for its potential to sorb phosphate from liquid media and from artificial wastewater.</p><p>Shredded apricot pits were pyrolyzed at 450 °C in a lab-scale screw reactor (Pyreka 3.0). Additionally, the impregnation of the feedstock with Mg(OH)<sub>2</sub> before pyrolysis was studied to test the hypothesis that phosphate sorption to biochar takes advantage of metal bridges on the biochar surface.</p><p>The results of isotherm sorption experiments showed that the pre-pyrolysis Mg-surface modification of the pits improved the sorption capacity of the biochar up to 42 mg PO<sub>4</sub>-P/g whereas the unmodified biochar adsorbed only about one tenth. When KH<sub>2</sub>PO<sub>4</sub> was used as the only sorbate, EDX-mapping showed the formation of K-struvite-crystals in the pores of the biochar. Desorption experiments showed a major release of the adsorbed phosphate within a few hours. Sorption competition experiments with phosphate and nitrate showed no negative effect of nitrate on phosphate sorption. Feedstock impregnation with Ca(OH)<sub>2</sub> resulted in more variable sorption dynamics.</p><p>The results could be confirmed by deploying the surface-modified apricot pit biochar for the reduction of the phosphate load in artificial wastewater.</p>

The comparative significance and utility of the Freundlich and Langmuir parameters for characterizing sorption and plant availability of phosphate in soils

Soil Research ◽  
1982 ◽  
Vol 20 (3) ◽  
pp. 233 ◽  
Author(s):  
ICR Holford
Keyword(s):  
Sorption Capacity ◽  
Plant Uptake ◽  
Langmuir Equation ◽  
Plant Availability ◽  
Phosphate Sorption ◽  
Surface Equation ◽  
Highly Correlated ◽  
Two Parameters

In studies using 62 Australian and English soils, the two parameters of the Freundlich sorption equation were compared with phosphate sorption capacity, calculated from the Langmuir 'two-surface' equation, and sorptivity and affinity indices calculated from the simple Langmuir equation applied to an isotherm concentration range of 0-5�g phosphorus/ml. The Freundlich extensive parameter was most highly correlated with sorptivity, and to a decreasing extent with sorption capacity and affinity. It appears to be fundamentally a sorptivity index which reflects the sorption capacity more than the affinity component of sorption, although greatly underestimating sorption capacity. The reciprocal of the Freundlich exponent proved to be an affinity parameter and was most useful in this role on soils of similar sorption capacity. However, conflicting results on different groups of soils showed that this parameter was less distinctive in its role than the others. Studies on two different groups of soils showed that the sorptivity and affinity parameters from the Langmuir equation accounted for more of the variance in plant uptake of labile phosphate than the Freundlich parameters.

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