This study was performed to determine the forms of P and to examine the influence of oven-drying on P forms in different organic amendments. Samples of biosolids, beef and dairy cattle manures, and hog manures from sow and nursery barns were used in this study. Both fresh and oven-dried amendments were analyzed for inorganic (Pi), organic (Po), and total phosphorus using a modified Hedley fractionation technique. Water extracted about 10% of total biosolids P and 30 to 40% of total hog and cattle manure P. The amount of P extracted by NaHCO3 ranged from 21 to 32% of total P in all organic amendments except in the dairy cattle manure with 45% of total P. The labile P fraction (sum of H2O- and NaHCO3-extractable P) was 24% of biosolids P, 60% of hog manure P, and 70% of dairy cattle manure P. The residual P was about 10% in biosolids and cattle manures and 5 to 8% in hog manures. Oven-drying caused a transformation in forms of P in the organic amendments. In hog manures, H2O-extractable Po was transformed to Pi, while in the dairy manure NaHCO3-extractable P was converted to H2O-extractable Pi with oven-drying. Therefore, caution should be exercised in using oven-drying for studies that evaluate forms of P in organic amendments. Overall, these results indicate that biosolids P may be less susceptible to loss by water when added to agricultural land.

No abstract

The chemical forms of phosphorus in organic amendments are essential variables for proper management of these amendments for agro-environmental purposes. This study was performed to elucidate the forms of phosphorus in various organic amendments using state-of-the-art spectroscopic techniques. Anaerobically digested biosolids (BIO), hog (HOG), dairy (DAIRY), beef (BEEF), and poultry (POULTRY) manures were subjected to sequential extraction. The extracts and residues after extraction were analyzed by solution (31)P nuclear magnetic resonance (NMR) and synchrotron-based P 1s X-ray absorption near-edge structure (XANES) spectroscopies, respectively. Most of the total P analyzed by inductively coupled plasma- optical emission spectroscopy in the sequential extracts of organic amendments was orthophosphate, except POULTRY, which was dominated by organic P. The labile P fraction in all the organic amendments, excluding POULTRY, was mainly orthophosphate from readily soluble calcium and some aluminum phosphates. In the poultry litter, Ca phytate was the main P species controlling P solubility. The recalcitrant fraction of BIO was mainly associated with Al and Fe. Those of HOG, DAIRY, and POULTRY were calcium phytate, which were identified only as organic species in the XANES spectra. The combination of the three techniques-sequential chemical extraction, solution (31)P NMR spectroscopy, and P 1s XANES-provided molecular characterization of P in organic amendments that would not have been possible with just one or a combination of any two of these techniques. Therefore, P speciation of organic amendments should use solid-phase and aqueous speciation techniques as deemed feasible.

The degree of phosphorus saturation (DPS) has been used in evaluating the risk of P loss from soil to runoff. While techniques are available for calculating DPS for acid soils, no widely used technique exists for neutral to calcareous soils that are typical of the Northern Great Plains, including Manitoba (Canada) soils. This study aimed to develop techniques of calculating the DPS of neutral to alkaline soils. Four measures of soil labile P and ten indices of P sorption capacity were used to calculate the DPS of 115 Manitoba soils. The various DPS calculated were evaluated using water-extractable ((H2O)) P as an index of P susceptibility to runoff loss. The DPS obtained using Olsen-extractable ((Ols)) P and the Langmuir adsorption maximum (ES(max)) ranged from 0.5 to 31.9% while those obtained from P(Ols) and the single-point adsorption index (P(150)) ranged from 0.9 to 73.9%. Of all the DPS evaluated, those that included P(Ols) and Mehlich 3-extractable ((M3)) P as the numerator with either P(150) or ES(max) as the denominator were fairly well correlated with P(H2O) (r values ranged between 0.45 and 0.63). Along with ES(max) and P(150), a new method of calculating DPS was formulated as the ratio of P(Ols) or P(M3) to Ca(M3) or (Ca + Mg)(M3). We found that the ratio of ammonium oxalate-extractable ((ox)) P to (Al + Fe)(ox), which has been widely used to calculate DPS in acid soils, was not suitable for neutral to alkaline soils of Manitoba. In these neutral to alkaline soils, Ca(M3) or (Ca + Mg)(M3) were better indices of P sorption capacity while P(Ols) and P(M3) provided better estimates of labile soil P. The DPS calculated using Ca(M3) or (Ca + Mg)(M3) were well correlated with P(H2O); however, they were numerically smaller than those obtained from the Langmuir adsorption maximum. As such, a saturation coefficient (alpha) with a value of 0.2 was generated to improve the numerical values of the newly estimated DPS. This new approach can be used to estimate the DPS in neutral and calcareous soils without the need to generate a P adsorption maximum.

Ige, D. V., Akinremi, O. O., Flaten, D. M., Ajiboye, B. and Kashem, M. A. 2005. Phosphorus sorption capacity of alkaline Manitoba soils and its relationship to soil properties. Can. J. Soil Sci. 85: [417][418][419][420][421][422][423][424][425][426]. The establishment of the P retention capacity of soil in Manitoba is essential for effective management of P in the region. However, the methods for determining the P retention capacity for neutral to calcareous soils in the Eastern Prairies are not well developed. The objectives of this study were to determine the P retention capacity of Manitoba soils and to generate equations that relate these capacities to other soil properties. One hundred and fifteen archived surface soils were selected and their physico-chemical properties were measured. These soils were used to generate a single-point P adsorption index by equilibrating 2 g of soil in 20 mL of 0.01 M KCl solution containing either 150 (P 150 ) or 400 (P 400 ) mg P L -1 . A subset of 26 of these soils was used for multipoint isotherms with P concentrations in the range of 0-1000 mg P L -1 . The data obtained were fitted to the Langmuir isotherm and the adsorption indices were correlated with the various soil properties that were then used to developed predictive equations of the P retention capacity of the soil. The values of the adsorption index, P 150, obtained from the single point adsorption study using 150 mg P L -1 , ranged between 88 and 891 mg P kg -1 , while that of P 400 ranged between 100 and 1250 mg P kg -1 . A better correlation was obtained between P 150 and soil properties compared with P 400 . For the 26 soil subset, the adsorption indices, S max 1 to S max 6, obtained from the Langmuir isotherm, ranged from 300 to 1330 mg kg -1 . A good correlation was obtained between the single point index and the multipoint isotherm (r = 0.93). Hence, S max for the 115 soils was estimated from the relationship between P 150 and S max 3 of the 26 soils. The best relationships between the adsorption parameters, P 150 and S max , and the soil properties were obtained with the sum of Mehlich-3 extractable Ca and Mg (R 2 = 0.66) and the sum of exchangeable Ca and Mg (R 2 = 0.64). Mehlich-3-Ca and -Mg each explained 56% of the variation, while clay content explained 40% of the variation in the P retention capacity of these soils. Unlike the widely reported influence of Al and Fe in acid soils, our study showed that the retention of P in Manitoba soils was influenced more by Ca and Mg and soil texture. Pour bien gérer l'utilisation du P au Manitoba, il est essentiel de connaître la capacité de rétention des sols. Malheureusement, les méthodes permettant de déterminer cette dernière dans les sols neutres ou calcaires de l'est des Prairies ne sont pas très développées. L'étude devait établir la capacité de rétention du P de ces sols au Manitoba et produire des équations reliant cette capacité à d'autres propriétés du sol. Les auteurs ont sélectionné 115 sols de surface en archive et mesuré leurs propriétés physicoc...

. 1996. Simulating soil moisture and other components of the hydrological cycle using a water budget approach. Can. J. Soil Sci. 75: tlt_t[2. Accurate simulation of soil moisture content at any time of th. y.r, ir*i.po.tunt to a!.icutture in dry regions due to the vital role soil moisture plays in crop production' In certain applicationi, such as drought moiitoring, other components of the hydrologic cycle such as runoff, snowmelt runoff, deep drainage and evaporative loss must also be accurately estimated. The goal bf *rls stuOy was to develop a model wltich accurately accounts for the major components of the hydrologiial cycle in ordeito simulate soil moisture content for drought monitoring and crop yield prediction. Thi versatile soil moistuie budget (vsMB) was evaluated and modified to improve the prediction of soil moisture content, runoff from rainfall and snowmelt, drainage of moisture out of the root zone and soil surface temperature' The modified components of the model were independently testJd and validated using field and published data. The soil moisture output from our modified model correlated well with observed changes in soil moiJture during the growing season under wheat. fallow and over the winter. The moisture content of the surface layei was simulated with greater accuracy than that of deeper layers' The soil moish,,e simulated by the modified model compares bltter with measured values than that simulated using the original version o-f the VSMB. The simulation of snow dynamics at Lethbridge, a chinook-dominated region, gave credibility to the snowmelt runoff predicted by the model. Model Testing and ValidationThe crop coefficients that produced the best agreement between-simulated and observed soil moisture during the testing stage ( [1967][1968][1969][1970][1971][1972][1973][1974][1975][1976][1977][1978] using the original and modified VSMB. Measured moisture content (m3m'3) uous wheat at Lethbridge (Fig. a) (Fig. a).

Knowledge of the dominant P species present in the soil following the application of organic amendments and fertilizer is important in understanding the fate of P in the environment. This study was performed to identify P species in two calcareous soils, an Osborne series (Typic Humicryert) and a Lakeland series (Typic Calciudoll), treated with organic amendments (biosolids and hog and dairy cattle manure) and fertilizer (monoammonium phosphate, MAP). Phosphorus 1s x‐ray absorption near‐edge structure (XANES) spectroscopy was used to speciate P compounds in these amended soils. The result showed that “adsorbed P” was the dominant P species in both soils. For the Osborne soil, the unamended soil (control) and those amended with biosolids and MAP contained an appreciable amount of hydroxyapatite (HAP), the most thermodynamically favored Ca phosphate. In addition, soils amended with biosolids or hog or dairy manures contain β‐tricalcium phosphate (TRICAL), a more soluble form of Ca phosphate than HAP. The amended Lakeland soils contained a variety of species in addition to the dominant “adsorbed P.” While TRICAL was found in all the amended soils except in that amended with hog manure, HAP was present in appreciable amount only in the unamended soil. Overall, the adsorbed P, most likely through inner‐sphere complexation, in these amended soils may not be readily available as a source of P into the environment. In addition, the HAP and TRICAL will have limited solubility, and thus, are probably only a very minor source of P in the environment.

The quantitative approach used in x‐ray absorption spectroscopy (XAS) experiments is oftentimes based on statistical goodness‐of‐fit criteria, which do not explain the accuracy of the components obtained from the fittings. This study was performed to validate the linear combination (LC) approach used in quantitative XAS analysis by estimating the accuracy of this procedure. Near‐edge Kα1 fluorescence XAS spectra were acquired for known binary mixtures of Ca, Al, and Fe phosphates in varying proportions and for the individual compounds. All combinations of the spectra of model compounds were fitted to the spectra of the known mixtures to obtain their relative abundance. The binary combinations produced the best fit with χ2 values ranging from 0.02 to 0.25. The relative error associated with the fitting ranged from as low as 0.8 to 17% for thoroughly mixed samples. The relative error was small when the proportion of Ca phosphate in the mixture was high but the error was large at low abundance of this component in the mixture. Because the interpretation of the XANES result largely depends on the relative proportion of species in the sample obtained by LC, we therefore recommend acquiring a spectrum for a mixture of certified reference compounds that mimics the composition of the sample being investigated at the beamline to estimate the accuracy of the proportions obtained from quantitative x‐ray absorption near‐edge structure (XANES) analysis.