Phosphorus Adsorption In Soil Research Articles

Study on vertical variation characteristics of soil phosphorus adsorption and desorption in black soil region of Northeast China.

The adsorption and desorption of phosphorus (P) in soil constitute a crucial internal cycle that is closely associated with soil fertility, exerting direct influence on the quantity, form, and availability of P within the soil. The vertical spatial variation characteristics of soil adsorption and desorption were investigated for the 0-100 cm soil layer in the northeast black soil region in this study. The maximum adsorption capacity (Qmax) and maximum adsorption buffer capacity (MBC) of black soil in the study area ranged from 313.8 to 411.9 mg kg-1 and from 3.1 to 28.8 L kg-1, respectively, within the soil layer of 0-100 cm depth, exhibiting an increasing trend with greater soil depth. The degree of P adsorption saturation (DPS) exhibited a contrasting trend with the variations in Qmax and MBC, ranging from 3.8% to 21.6%. The maximum desorption capacity (Dmax) and desorption rate (Dr) of soil P ranged from 112.8 to 215.7 mg kg-1 and 32.1% to 52.5%, respectively, while the readily desorbable P (RDP) in soil was within the range of 1.02 to 3.35 mg kg-1. Both Dmax, Dr, and RDP exhibited a decreasing trend with increasing soil depth before showing an upward trend. These research findings not only provide essential background data for the systematic investigation of soil P in the black soil region but also serve as a valuable reference for assessing soil quality in this area.

Effect of filling materials on reconstructed soil phosphorus adsorption and desorption in mining area

Utilization of alternative soil substrates for minesoil reconstruction can affect the nutrient status of reclaimed minesoil (RMS), particularly the availability of phosphorus. This study investigated the adsorption and desorption capacities of phosphorus in three typical reclamation lands using coal gangue (CGR), lake mud (LMR), and Yellow River sand (YSR) as filling materials. The results showed that (i) the phosphorus adsorption capacity of all RMS samples was lower than that of the normal cultivated soil (NCS), the YSR was lower than the CGR and LMR in phosphorus adsorption capacities, while the YSR had better phosphorus desorption capacity than the CGR and LMR. (ii) The specific surface area, pore size, soil texture, mineral composition, functional group composition, and iron/aluminum element content of RMS were varied after the filling of alternative soil substrates, and (iii) the surface characteristics played a vital role in driving the phosphorus adsorption-desorption, while soil texture, and organic matter drove the phosphorus desorption behavior via non-linear ways. This study reveals the difference of phosphorus adsorption-desorption in RMS, and provides a theoretical basis for the rational utilization of alternative soil substrates and the improvement of reclamation land in coal mining subsidence areas.

Mineralogy and Fixation Isotherms to Evaluate Phosphorus Needs of Wet and Dry Land Rice Soils in the Bambalang-Ndop Plain in the North West Region of Cameroon

The sorption processes of Phosphorus (P) in soils contribute to important problems in agriculture. The Mineral structure of the clay fraction plays an important role in soil P adsorption, but its influence on P sorption remains unclear and needs to be elucidated to improve the ability to effectively manage soil P. The aim of this research was to investigate the influence of mineralogy on P fixation. The study was carried out on three wet land and one dry land soil. Soil samples were characterised for their physicochemical and mineralogical properties using standard methods. Soil phosphorus adsorption isotherms were determined with the batch sorption technique by equilibrating 5.00 g of soil samples with 25 ml of KH2PO4 containing 0, 10, 50, 100, 250, and 500 mg P/L. 0.01M CaCl2 background solution. Our results indicated that the wetland soils were dominated by geothites, while the dryland was rich in monthmorillonite, as revealed by the mineralogical analysis. In addition to Ca, exchangeable acidity, organic matter, clay, and pH influenced P fixation; other soil properties such as CEC and exchangeable Na also contributed significantly. The results were interpreted with the Langmuir and Freundlich isotherms, with the Freundlich modes giving the best fit for the adsorption data. The amount of P available in all soils was far below the adequate limit (25 mg P kg-1). Fixation of P was site-specific and revealed that soils can adsorb up to 333.33 mgPkg-1. Therefore, it can be concluded that the Freundlich isotherm should be used to monitor P, thereby minimizing P losses and maximizing crop yield and water quality.

Effects of straw mulching and phosphorus application on forms and availability of soil phosphorus in hilly dryland of Sichuan, China

We conducted a two-factor split-plot experiment to examine the alteration of soil inorganic phosphorus forms and phosphorus availability under straw mulching and phosphorus fertilizer rates. The main factor was straw mulching and non-mulching, while the sub-factor was phosphorus supply rates, including 0, 75, and 120 kg·hm-2. We analyzed the characteristics of phosphorus adsorption-desorption, the content of inorganic phosphorus components and their relationship with available phosphorus in hilly upland purple soil in Sichuan. Results showed that compared with the non-mulching, the maximum phosphorus adsorption capacity of straw mulching was notably decreased by 7.7% and 7.4% in the two experimental years from 2018 to 2020. The degree of phosphorus saturation and readily desorbable phosphorus of straw mulching were remarkably increased by 35.4% and 21.6% in 2019 and 18.6% and 35.2% in 2020, respectively. The maximum buffer capacity of phosphorus was not different between straw mulching and non-mulching. The maximum phosphorus adsorption capacity and maximum buffer capacity of phosphorus were significantly lower, and the degree of phosphorus saturation was notably higher in the phosphorus application treatment than that under no phosphorus treatment. The readily desorbable phosphorus increased with the increases of phosphorus rates. The contents of dicalcium phosphate (Ca2-P), octa-calcium phosphate (Ca8-P) and iron phosphorus (Fe-P) in straw mulching treatment were notably higher than those in non-mulching treatment, whereas the content of aluminum phosphorus (Al-P) significantly lower under the straw mulching. Meanwhile, the contents of occluded phosphate (O-P) and apatite (Ca10-P) tended to decrease in the straw mulching compared with that under the non-mulching. Phosphorus application increased the content of different inorganic phosphorus components. Compared with the non-mulching, soil available phosphorus content and the phosphorus activation coefficient of straw mulching remarkably increased by 23.2% and 21.3% in 2019, and 9.6% and 8.9% in 2020, respectively. Soil available phosphorus content and phosphorus activation coefficient increased with the increases of phosphorus rate. Results of regression analysis showed that the contribution of inorganic phosphorus components to the availability of available phosphorus in purple soil was Ca2-P > Fe-P > Al-P > Ca8-P > Ca10-P > O-P. Therefore, straw mulching combined with a reasonable phosphorus fertilizer rate could promote the decomposition and transformation of insoluble soil phosphorus to moderately active or easily absorbed phosphorus forms, reduce soil phosphorus adsorption, stimulate soil phosphorus desorption, and improve soil phosphorus availability. Based on the economic benefits, phosphate fertilizer application at the rate of 75 kg·hm-2 combined with straw mulching was recommended in Sichuan hilly dryland, which would be more beneficial in improving soil phosphorus availability.

Phosphorus adsorption prediction through Decision Tree Algorithm under different topographic conditions in sugarcane fields

Phosphorus availability in the soil is essential for plant growth. In Brazil, phosphorous is poorly available in the soil due to its high adsorption in the form of phosphates. This phenomenon requires much studying to assist in the nutritional management of crops. To that end, predicting the fraction of adsorbed phosphorus can be approximated by using attributes that influence soil formation and structure. This study aimed to predict soil phosphorus adsorption based on soil attributes in sugarcane crops with different relief types using data mining techniques. The experiment was carried out in sugarcane agricultural areas, experimental plots with differentiated relief (concave or convex), and identical agricultural practices. The soil was classified as an Alfisol with udic moisture (Udalf) regime and medium to clayey texture. The dataset constituted a matrix of 4580 observations. The analyzed variables corresponded to the chemical, physical, geophysical, and mineralogical attributes in the 0–0.2 m topsoil. Data analysis was carried out based on a decision tree induction model, with an 85% accuracy rate and a high level of agreement between variables. The decision tree recognized magnetic susceptibility as the attribute with the most significant influence on the prediction of soil phosphorus adsorption, validating the relation among adsorption processes and the magnetic properties of oxide minerals characteristic of Brazilian agricultural regions.

Lime Amendments to Enhance Soil Phosphorus Adsorption Capacity and to Reduce Phosphate Desorption

Reduction in the dissolved phosphorus (P) desorption from agricultural soils could be an effective measure to prevent eutrophication. Lime is a high calcium–containing mineral that can have promising but varying responses on P desorption depending on soil type. The main objective of this research was to evaluate and compare the potential of hydrated lime and lime kiln dust, its cheaper alternative, as soil amendments to increase soil P adsorption capacity and to reduce dissolved P desorption from four soil types (sandy, sandy loam, loam, and clay loam). A batch adsorption study with varying P concentrations of 0, 0.2, 0.4, 0.6. 0.8, and 1.0 mM P and an adsorbent dose of 1% lime by air-dried soil mass at a fixed pH of 6.5 was carried out. The adsorption data fit best the Freundlich adsorption isotherm model. Both hydrated lime and lime kiln dust significantly increased the Freundlich adsorption coefficient by 3.2, 2.4, 2.0, and 1.6 times in loam, sandy, sandy loam, and clay loam soils, respectively. Although the hydrated lime showed a higher potential to increase the Langmuir maximum adsorption capacity in comparison to lime kiln dust, they both exhibited similar performance at lower P concentration ranges that are representative of the soil solution. The cumulative phosphorus desorption in the ten consecutive days agreed with the adsorption results. Therefore, lime kiln dust as a by-product could be a promising soil amendment to increase soil phosphorus adsorption capacity leading to less phosphorus desorption to water bodies. Further studies on its interaction with crop growth at field scale are required.

Soil properties governing phosphorus adsorption in soils of Southern Brazil

Southern Brazil is carachterized by soil classes with contrasting mineralogical composition and chemical behavior that directly affect the P adsortion capacity. This study is a first detailed regional assessment of the main factors (including mineralogical composition, total organic C, and specific surface area) that determine P adsorption in 60 representative soils of southern Brazil under natural vegetation. Most soils showed medium to clay texture. Organic C increased with increasing altitude and rainfall but decreasing temperature. Kaolinite, goethite and hematite were the dominant minerals in the highly weathered soils (Ferralsols and Nitisols), associated with smaller amounts of 2:1 clay minerals, quartz and gibbsite. In soils with a textural gradient (Acrisols, Alisols and one Plinthosol), minerals in the clay fraction consisted of kaolinite and quartz together with lower proportions of Fe oxides, 2:1 clay minerals and mica. The less weathered soils (Cambisols, Chernozems, Vertisols and Luvisols) abounded with kaolinite and 2:1 clay minerals in addition to goethite, ferrihydrite and quartz. P adsorption was positively correlated with clay and organic C content and specific soil surface area. The mineral most strongly influencing P adsorption was gothite, and hematite and gibbsite to a lesser extent.

Soil factors affecting phosphorus adsorption in soils of the Cerrado, Brazil

This study aimed to determine the maximum phosphorus adsorption capacity (MPAC) in seven distinct soil classes from the Brazilian Cerrado and to evaluate possible interactions with soil chemical and physical properties by principal component analysis (PCA). The sampled were collected from the depth ranges of 0.0 to 0.20 and 0.20 to 0.40 m and then analysed. First, remaining phosphorus (Prem) content was determined. Then, P doses to be added to solutions were estimated. Finally, MPAC was evaluated using the Langmuir equation. The MPAC varied considerably among seven distinct soil classes (from 72 to 928 mg kg−1 de P at two depth ranges 0.0–0.20 and 0.20–0.40 m). The variation was significantly correlated with the clay, silt, organic matter, iron available and binding energy. The use of only clay content for phosphorus interpretation and recommendation in soils may lead to errors in the soil fertility management, especially in Cerrado soils, as a function of the complexity of the interactions involved in the process. Principal component analysis can be a useful tool for understanding the dynamics of the soil MPAC, as it is sensitive in discriminating the studied soils.

Effects of selective cutting disturbance on soil phosphorus adsorption and desorption in a Korean pine and broad-leaved mixed forest in the Xiaoxing'an Mountains, China.

This study examined the characteristics of phosphorus (P) adsorption and desorption in surface soil (0-10 cm) of a secondary forest after selective cutting disturbance at three levels of intensity (low, medium, high) in order to reveal the effects of different disturbance intensities on soil P adsorption and desorption. Maximum adsorption amount (Qm), adsorption intensity factor, maximum buffer capacity, maximum desorption amount, average desorption rate and readily desorptable phosphorus were measured. Qm in the focal forests was 1383.93-1833.34 mg·kg-1, and Qmin forests with middle and high disturbance intensities was significantly higher than that in forests with low disturbance intensity and in primary forests. P adsorption intensity was 0.024-0.059 L·mg-1, and forests with high and low disturbance intensities increased the P adsorption intensity significantly. The maximum buffer capacity varied from 35.68 to 97.97 L·kg-1, with the highest value found in the forest with the highest disturbance intensity. Selective cutting significantly reduced the potential for phosphorus supply in the forest soils. The maximum desorption amount, average desorption rate and readily desorptable phosphorus content in the focal forests were 526.32-797.54 mg·kg-1, 14.7%-25.5% and 1.79-5.41 mg·kg-1, respectively, indicating that the ability of soil to release phosphorus significantly decreased with increasing disturbance intensity. Selective cutting changed the phosphorus adsorption and desorption characteristics by reducing the supply and release of soil phosphorus.

Impacts of soil properties on phosphorus adsorption and fractions in purple soils

Information on phosphorus (P) adsorption and its impacts on the redistribution of the P fraction in soil profiles are important for environmental management under intensive agricultural practices. To clarify the dominant factors influencing soil phosphorus adsorption in an Entisol (locally known as purple soil), P adsorption experiments were conducted in Sichuan Basin of southwestern China for cropland and woodland soils with acidic, neutral and calcareous origins throughout their profile. After various doses of P were added during incubation experiments, soil P fractions were also analyzed. The results showed that there were no significant differences in Fe-oxides and P adsorption along the vertical gradients. Agricultural practices and lower pH conditions reduced the P adsorption capacity of purple soils throughout the soil profiles. For acidic and neutral purple soil profiles, the P adsorption capability was mainly influenced by Fe-oxides and soil texture. Ca-bound P and Fe-Al-bound P represented the majority of the total inorganic P of calcareous soils. There was a saturation of adsorption capacity by sesquioxide and a high risk of dissoluble reactive P (NH4Cl-P) being released out of the soil profile in acidic and neutral purple soils after the greatest P addition, indicated by the higher proportions of NH4Cl-P (over 40%) and decreasing Fe-Al-P fraction. P fractions migrated with greater difficulty in calcareous purple soil profiles as Ca-P fraction peaked over 65% when adding a P dose at or greater than 80 g P kg-1, indicating the high potential of P adsorption. The X-Ray Diffraction analysis also verified the formation of brushite. Adaptive management practices should be designed to alleviate P losses for acidic and neutral purple soils.

Phosphorus adsorption in soils under forest and savanna from Northern Amazon, Brazil

Studies on maximum phosphorus adsorption capacity (MPAC) in soils from Roraima State and attributes that interfere with the magnitude of this characteristic are relevant and motivated this study. In this context, topsoil samples (0–0.20 m) from four soil classes (Oxisol–LA and Oxisol–LV [ITÃ, Caracaraí]; Oxisol–LA [Serra da Prata, Mucajaí]; Oxisol–LA and Ultisol–PA [CCA, Boa Vista]; Oxisol–FT [Bonfim] and Alfisol –SN [Surumu, Pacaraima]) representative of Roraima State were used in this study in order to determine the influence of soil physical, chemical, and mineralogical attributes on MPAC. Air-dried soil samples of 2.5 g and 0.01 mol L?1 CaCl2 (25 mL) solution were stirred for 24 h, being added P in the form of KH2PO4 at concentrations of 0–60, 0–80, and 0–110 mg L?1. P was analyzed in the supernatant for determining its adsorbed amount (P-rem). Adsorption values were fitted to the Langmuir isotherm in order to assess MPAC. Correlation tests were performed between MPAC and binding energy, pH, organic matter, clay, and CEC. MPAC values ranged from 14.50 to 527.93 mg kg?1 in the soil. The soils FT–Bonfim and LV–ITÃ presented a higher MPAC. Considering the representative soil classes in the State, MPAC does not correlate with any of the assessed attributes. In the soil classes Oxisol and Ultisol, MPAC has a negative and significant correlation with binding energy.

Effect of Cow Dung, Biogas Slurry and Vermicompost on Phosphorus Adsorption Behavior of Soil

One of the approaches for phosphorus fertilizer management is controlling the soil phosphorus adsorption behavior. To examine the effect on phosphorus adsorption behavior, three amended soil samples were prepared by mixing 10% (w/w in dry basis) cow dung, biogas slurry and vermicompost with soil. Phosphorus adsorption behavior was examined by using Langmuir, and Temkin adsorption isotherms. Initially, biogas slurry and vermicompost increased the maximum phosphorus adsorption capacity (MPAC) of soil from 461 µg g-1 (control) to 558.0357 and 586.17 µg g-1 respectively, and then decreased steadily and reached 429.92 and 398.41 µg g-1 respectively in five weeks. Whereas in case of cow dung, MPAC was initially decreased, then reached maximum in 17 days and ultimately decreased. Thus application of cow dung along with phosphate fertilizer seems to increase the loss of the fertilizer through runoff and leaching. Conversely, biogas slurry and vermicompost prevent phosphorus loss by regulating phosphorus release through initial enhancement followed by gradual decrease in phosphorus adsorption capacity of soil. Both biogas slurry and vermicompost can be considered as good soil amendments as they have the ability to control the release of phosphorus fertilizer as per the need of the plants.

Phosphorus Adsorption Isotherm: A Key Aspect for Soil Phosphorus Fertility Management

Characterization of soils in terms of phosphorus adsorption capacity is fundamental for effective soil phosphorus fertility management and for efficient utilization of phosphorus fertilizers. Thus, this study was conducted to investigate the phosphorus adsorption characteristics of soils of two farms and to elucidate the implication of soil phosphorus adsorption isotherm studies for soil phosphorus fertility management. The two farms, representing the major farming systems of the respective districts, were selected from Adele village in Haramaya district and Bala Langey village in Kersa district in eastern Ethiopia. Soil samples were collected from the crop fields at Adele and Bala Langey farms. Two different P-bearing sources, potassium dihydrogen phosphate (KH2PO4) and diammonium phosphate (DAP-(NH4)2HPO4), were used for the adsorption isotherm studies. The adsorption data were fitted to the linear and Freundlich adsorption isotherm models. Both models revealed that soils of both farms had different P adsorption capacity from the two P sources. Amount of P adsorbed from DAP solution was higher than the amount of P adsorbed Original Research Article Wogi et al.; AJEA, 6(2): 74-82, 2015; Article no.AJEA.2015.066 75 from KH2PO4 solution in soils of both farms. Phosphorus adsorption capacity of Adele farm soils was higher than that of Bala Langey farm soils. Therefore, soils of the two farms should be managed differently for P fertility. Percentages of P adsorbed (% Pa) and P remained in the equilibrium solution (% EC) were also calculated. By plotting the two percentages i.e. % Pa and % EC against the initial concentration of P (IC), two regions were observed. The two regions were described as P intensity and quantity factor windows. Based on the intensity and quantity factor windows, at currently existing soil condition, between 200 and 500 kgha -1 P should be applied as fertilizer to soils of Adele at 0-30 cm depth for immediate benefits and soil P fertility maintenance.

<b>Mineralogy and phosphorus adsorption in soils of south and central-west Brazil under conventional and no-tillage systems

The low phosphorus availability in tropical and subtropical soils, normally related to adsorption of phosphate to the minerals surfaces, can be attenuated when organic matter (OM) accumulates in the soils. Herein, we report the results of long-term experiments (18–32 years) aimed at quantifying the maximum phosphorus adsorption capacity (MPAC) and its determinant mineralogical variables in Brazilian soils and at assessing the effect of no-tillage (NT) in mitigating the phosphorus adsorption of soils. The MPAC of soils ranged from 297 to 4,561 mg kg-1 in the 0.00–0.10 m layer and from 285 to 4,961 mg kg-1 in the 0.10–0.20 m layer. The MPAC was correlated with the concentrations of iron oxides, goethite and ferrihydrite, gibbsite/(gibbsite+kaolinite) ratio and the specific surface area. The OM increased in the 0.00–0.10 m layer of NT soils, which was not reflected on the decrease of MPAC for the no-tillage soils.

Effect of Freeze-Thaw Action on Phosphorus Adsorption and Desorption in Forest Wetland Soils at High Latitudes

To clear the effect of freezing and thawing on the soil phosphorus adsorption and desorption of northeast China high latitude forest wetland, the change of soil phosphorus elements after five complete freeze-thaw cycles was analyzed with Wuyiling National Wetland as experimental subjects. Result shows that the soil phosphates desorption increased after influenced by five complete freezing and thawing. Soil sample which initial phosphates concentration is 40、80、240 mg/L reached minimum value after three freeze-thaw cycle and then increased. Compared to the without freeze-thaw soil, phosphorus adsorption capacity of different initial concentrations of phosphate solution samples was increased after five freeze-thaw cycles indicating that freeze-thaw cycle has obvious effect on soil phosphorus adsorption and desorption.

Carbono, matéria orgânica leve e fósforo remanescente em diferentes sistemas de manejo do solo

O objetivo deste trabalho foi avaliar os teores de carbono orgânico total (COT), matéria orgânica leve (MOL) e fósforo remanescente (Prem), em áreas de cerrado sob sistema de plantio direto com diferentes cultivos de coberturas do solo, e compará-los aos de áreas sob preparo convencional e pousio. O experimento foi conduzido em campo, em um Latossolo Vermelho, de agosto de 2000 a março de 2007. O delineamento utilizado foi o de blocos ao acaso com parcelas subdivididas, sendo as parcelas constituídas pelos cinco sistemas de manejo do solo avaliados - pousio, preparo convencional e plantio direto com uso dos cultivos de cobertura crotalária (Crotalaria juncea), milheto (Pennisetum americanum) e braquiária (Urochloa brizantha) -, e as subparcelas pelos cultivos de soja e milho. Em março de 2007, coletaram-se amostras de solo das profundidades 0,0-0,025, 0,025-0,05, 0,05-0,10 e 0,10-0,20 m, das quais foram quantificados COT, MOL, estoques de COT e Prem. Em áreas sob plantio direto, o aumento nos teores de MOL pode reduzir a adsorção de fósforo ao solo. Sistemas de manejo que não envolvem revolvimento do solo favorecem o aumento do estoque de carbono orgânico nas camadas superficiais, enquanto o preparo convencional e o plantio direto com uso do milheto como planta de cobertura propiciam a incorporação mais profunda do carbono.

Phosphorus Adsorption and Bioavailability in a Paddy Soil Amended with Pig Manure Compost and Decaying Rice Straw

Phosphorus (P) availability in soil is closely related not only to soil P content but also to soil physicochemical and biological properties, which are closely associated with P sorption and biochemical transformation. The aims of this study were to determine the effects of pig manure compost (PMC) or decaying rice straw (DRS) added to a paddy soil on soil pH, soil organic carbon (SOC), dissolved organic carbon (DOC), acid phosphatase, microbial biomass P, soil test P (Olsen P), and P uptake by rice (Oryza sativa L. cv. ‘Liaoyan’). Phosphorus adsorption characterization affected by PMC‐ or DRS‐derived DOC was also studied. Compared with the control, both PMC and DRS treatments increased soil pH, SOM, DOC, microbial biomass P, and Olsen P, and the activity of acid phosphatase during the 110‐day incubation period. Phosphorus adsorption in soil decreased with DOC extracted from PMC and DRS and was well fit by the Langmuir equation. The Olsen P in the PMC‐ and DRS‐treated soil was correlated with both DOC content and acid phosphatase activity. Both PMC and DRS treatments significantly increased dry‐matter yield and P uptake in rice shoot. In conclusion, the increased P availability in the paddy soil was not only a result of direct P supplied following organic manure incorporation, but also an indirect result of reduction in P sorption on the solid phase of the paddy soil by DOCs which were derived from DRS or PMC.

Effects of Anaerobically Digested Poultry Manure on Soil Phosphorus Adsorption and Extractability

AbstractResearch in the past has indicated that large additions of animal manures to soil can reduce soil P adsorption and increase P extractability. However, application rates used in many studies are unrealistic with respect to crop fertilization and land disposal due to the excessive quantities of N applied with the manures. The objective of this study was to evaluate effluent from a poultry manure anaerobic digester applied to a Hayesville loam soil (clayey, oxic, mesic, Typic Hapludult) on soil P adsorption and extractability after three incubation periods (0, 30, and 90 d). Effluent solids were applied at rates corresponding to 753 through 7530 mg N kg−1 soil.Langmuir equation parameters (from least square fitted data; R2 > 0.98) were used as a basis to compare the influence of treatments on P adsorption properties of the soil. The P adsorption maxima parameter was not influenced by any of the effluent treatments. The parameter related to P bonding energy of the soil was reduced 33 and 41%, respectively, by mid and high rate effluent applications. A similar reduction was not observed for the low rate treatment, which corresponded to fertilizer application of 100 mg N kg−1 soil.Extractable soil P increased in a predictable manner with increased effluent solids application for all three incubation periods. These increases in extractable P could be described by linear regression equations. The slopes of these lines indicate that a 1‐g addition of effluent solids to 1‐kg soil accounts for increases in extractable P of 3 to 6 mg kg−1.