Determination of sulfate in soils by reduction with tin and phosphoric acid

Abstract

A rapid and precise method for determination of SO₄ ^2‐‐S in soils is described. It involves the extraction of SO₄ ^2‐ from soils and its reduction to H₂S by a reagent containing Sn and H₃PO₄ and subsequent determination as methylene blue. The results agreed closely with those obtained by reduction with the a reagent containing HI, H₃PO₂, and HCOOH and by ion chromatrography. Tests indicated that, in addition to SO₄ ^2‐, the Sn‐H₃PO₄ reagent reduces certain organic S and reduced inorganic S compounds, but these S compounds are not present in extracts of agricultural soils. By using a bank of 10 distillation units, a single operator can perform 60 analyses in a normal working day.     

Determination of free DNA in soils

The concentration of free DNA in soils has to be determined in order to understand the fate and the transport of extracellular DNA. A protocol for the extraction and determination of free DNA was developed. The procedure uses separation steps, i.e. centrifugation and ultra‐filtration. The free dsDNA was stained with PicoGreen® and determined fluorimetrically. Samples from different soils, different soil horizons, soil waters and under different land use systems were analyzed. It was found that in nearly all samples free DNA was detectable. Free DNA concentrations of up to 1950 ng (g dried sample)^—1 could be detected depending on depth, soil type and system of land use.     

磷酸对石灰性土壤pH及微量元素有效性的影响

通过室内培养试验 ,以硫酸为对照研究了磷酸对石灰性土壤的酸化效果及微量元素有效性的影响。培养 1周结果表明 ,随酸浓度增加 ,土壤 pH降低 ,低浓度时磷酸对石灰性土壤的酸化效果强于对照硫酸 ,高浓度时硫酸酸化效果强于磷酸 ,有效Fe、Mn的含量随着酸浓度的增加先增加后降低 ,有效Zn的含量随着酸浓度的增加而增加 ,有效Cu的含量随着磷酸浓度的增加而增加 ,但随着对照硫酸浓度的增加有效Cu含量先增加后降低     

Plant availability of p in commercial superphosphate fertilizers

Abstract

The quality of phosphate rock (PR) is declining and the use of lower quality PR results In lower water‐soluble and higher citrate‐soluble P in the fertilizer product. A greenhouse study was conducted to evaluate the plant availability of P in commercial superphosphate fertilizers having various levels of water‐soluble P. Seven commercial fertilizers, Including 6 granular concentrated superphosphates and one normal superphosphate, were evaluated. Reagent grade monocalcium phosphate served as a control. The fertilizers were manufactured from PR deposits located in the United States (Florida, Idaho and North Carolina) and Morocco. Water‐soluble P ranged from 77 to 92 X of the total fertilizer P. Citrate‐soluble, water‐insoluble P ranged from 7 to 20 % of the total fertilizer P. Four of the 5 American fertilizers had a lower percentage of water‐soluble P as compared to the concentrated superphosphate from Morocco. Fertilizers manufactured from U.S. phosphate deposits contained an average of 6 times more Fe and 4 times more Al than the Moroccan concentrated superphosphate.

Each source was added to a Mountvlew slit loam soil (pH = 6.5) at rates to supply 0, 10, 20, 30, 40 and 50 mg P kg^‐1soil (0, 22.9, 45.8, 68.7, 91.6, and 114.5 ppm P₂O₅, respectively). Sorghum‐sudangrass (Sorghum bicolor) was harvested at 28 and 56 days after planting in the treated soil. Herbage yields and the P concentration in harvested forage were not affected by the source of added P. The effect of the rate of added P on forage yield and P concentration was described by polynomial regression. The granular concentrated superphosphate fertilizers used in this study contained ≥ 80 % of their plant available P in a water‐soluble form and were as effective as reagent grade monocalcium phosphate. Thus the level of water‐soluble P that will be required to reduce the performance of a fertilizer is lower than the levels currently found in American commercial concentrated superphosphates     

Reclamation of a calcareous saline-sodic soil using phosphoric acid and by-product gypsum

Phosphoric acid is increasingly used as a source of water-soluble P, but it has not been widely tested for its effectiveness in reclaiming calcareous sodic and saline-sodic soils relative to chemically equivalent rates of gypsum. In lysimeters experiments, we showed that a calcareous saline-sodic soil can be ‘reclaimed’ using phosphoric acid and leaching with moderately saline irrigation water (sodium adsorption ratio = 4.1 and electrical conductivity = 2.2 dS/m). Phosphoric acid (50% pure) was dissolved directly in the leaching water at application rates of 450, 600 and 900 kg/ha, and phosphogypsum (80% pure) was mixed with soil prior to leaching at application rates of 15, 20, 30 and 40 t/ha. Phosphoric acid was more efficient than the chemical equivalent of phosphogypsum in improving soil hydraulic conductivity, and in reducing the exchangeable sodium percentage (ESP). The ESPs after leaching were: 10 (water only), 5.5–5.3 (phosphoric acid) and 8.2–5.9 (phosphogypsum).     

Cadmium accumulation in soils from long-continued applications of superphosphate

A simple, sensitive method developed for the analysis of geostandards was used to measure the accumulation of Cd in soils from superphosphate applied annually to grass-land and arable soils for many years. Rates of application were equivalent to 33 kg P and 5 g Cd ha^?1 yr^?1 for 95 yr in three experiments in England and to 37 kg P and 20 g Cd ha^?1 yr ^?1 for 30 yr in one experiment in New Zealand. Very little Cd accumulated in the surface horizons (0–22.5cm) of either of the arable soils from England; about one-quarter of the applied Cd was detected in the sub-soil (22.5–45.0 cm) of one experiment (Broadbalk) but none in the second (Barnfield). About one-half of the applied Cd was retained in the 0–22.5 cm horizon of grassland soils from both England and New Zealand. The light (<2.2 gcm^?3) organic-rich fraction of Park Grass soil from Éngland contained about three times as much Cd as the heavier, mineral-rich fraction. This suggests that when Cd is incorporated into organic matter its mobility is decreased and soil pH then has smaller effects on its mobility. Uptake of Cd by grass-clover pasture in New Zealand averaged only 0.4 g Cd ha^?1 yr^?1 or 2% of the amount applied.     

Determination of free and conjugated indole-3-acetic acid, tryptophan, and tryptophan metabolites in grape must and wine.

Tryptophan (Trp) and its metabolites, especially indole-3-acetic acid (IAA), are considered to be potential precursors of 2-aminoacetophenone (AAP), an aroma compound that causes an "untypical aging off-flavor" (UTA) in Vitis vinifera wines. In this study, RP-HPLC with fluorescence detection was used for the qualitative and quantitative analysis of Trp and Trp metabolites in grape musts and wines to which different viticultural measures had been applied (time of harvest, soil treatment, leaf plucking, vine prune). An alkaline hydrolysis was developed to release bound IAA and Trp. A sensitive and selective determination of different Trp metabolites was achieved after solid phase extraction using a strong anion exchange material. In the examined grape musts, more than 95% of the total IAA was bound either as ester conjugate or as amide conjugate. Free IAA and other Trp metabolites were below the detection limit (<3 microg/L) or could be determined only in traces. Their amounts increased significantly during fermentation, whereas the amount of Trp decreased. It could be shown that the different viticultural measures applied (except the vine prune) as well as the climatic conditions of the vintage exhibited significant influences on the amounts of Trp and Trp metabolites in grape musts or wines.     

Reducing ammonia loss from urea and improving soil-exchangeable ammonium retention through mixing triple superphosphate, humic acid and zeolite

Ammonia losses from soil following fertilization with urea may be large. This laboratory study compared the effect of four different, urea–triple superphosphate (TSP)–humic acid–zeolite, mixtures on NH₃ loss, and soil ammonium and nitrate contents, with loss from surface‐applied urea without additives. The soil was a sandy clay loam Typic Kandiudult (Bungor Series). The mixtures significantly reduced NH₃ loss by between 32 and 61% compared with straight urea (46% N) with larger reductions with higher rates of humic acid (0.75 and 1 g kg^?1 of soil) and zeolite (0.75 and 1 g kg^?1 of soil). All the mixtures of acidic P fertilizer, humic acid and zeolite with urea significantly increased soil NH₄ and NO₃ contents, increased soil‐exchangeable Ca, K and Mg, and benefited the formation of NH₄ over NH₃ compared with urea without additives. The increase in soil‐exchangeable cations, and temporary reduction of soil pH may have retarded urea hydrolysis in the microsite immediately around the fertilizer. It may be possible to improve the efficiency of urea surface‐applied to high value crops by the addition of TSP, humic acid and zeolite.     

Determination of amino acid enantiomers in soils

Determination of amino acid enantiomers in environmental samples is difficult, because metals and organic impurities interfere with the analyses. We developed a new gas chromatographic method to assess amino acid enantiomer concentrations in complex soil matrices following hot HCl hydrolysis (6 M, 12 h, 105°C). The crucial focus was the establishment of a simple, reliable sample clean-up procedure. The presented method involved the adsorption of the enantiomers on a Dowex 50 W X8 cation exchange resin and the removal of interfering compounds with 0.1 M oxalic acid prior to amino acid elution with 2.5 M NH₄OH. After conversion to N-pentafluoropropionyl-amino acid iso-propyl esters, the diastereomers were separated by a Chirasil l-Val capillary column and quantified by a flame ionization or mass selective detector. The lower limit of quantification tested here was ≤1 pg injection amount. The recovery of amino acid enantiomers averaged 99±11% for pure standards and 97±11% for spiked soil hydrolysates. The general applicability of the method was demonstrated by determination of amino acid enantiomers in taxonomically different soils from different geographic regions. The coefficients of variation presented by d/l ratios were 12% for alanine and <10% for the other amino acids.     

Manufacture of fermentable sugar solutions from sugar cane bagasse hydrolyzed with phosphoric acid at atmospheric pressure

Sugar cane bagasse, a renewable and cheap bioresource, was hydrolyzed at 100 degrees C using phosphoric acid at different concentrations (2, 4, or 6%) and reaction times (0-300 min) to obtain fermentable sugar solutions, which have a high concentration of sugars (carbon source for microorganism growth) and a low concentration of growth inhibitors (acetic acid and furfural). Xylose, glucose, arabinose, acetic acid, and furfural were determined following the hydrolysis. Kinetic parameters of mathematical models for predicting these compounds in the hydrolysates were obtained. Derived parameters such as efficiency of hydrolysis or purity of hydrolysates were considered to select as optimal conditions 6% phosphoric acid at 100 degrees C for 300 min. Using these conditions, 21.4 g of sugars L(-)(1) and <4 g of inhibitors L(-)(1) were obtained from the hydrolysis with a water/solid ratio of 8 g of water g(-)(1) of sugar cane bagasse on a dry basis.     

Discriminating significance of the free amino acid profile in almond seeds

Known statistical techniques have been applied to the free amino acid composition of 107 samples from 10 different almond cultivars (Marcona, Desmayo-Largueta, Guara, Tuono, Ferragnes, Masbovera, Non Pareil, Titan, Texas, and Primorskyi) cultivated in seven different locations and growing conditions. It is concluded that free amino acid composition can constitute a basis for classifying and typifying these cultivars into five groups: (1) Marcona and Texas, (2) Ferragnes and Masbovera (and probably Primorskyi), (3) Tuono and Guara, (4) Non Pareil (and probably Titan), and (5) an isolated cultivar (Desmayo Largueta). As a result, an easy decision tree is proposed to discriminate the cultivar of an almond flour, as used in confectionery, if it consists of a single cultivar.     

Relation between available boron and boron extracted from soils by hot water or phosphoric acid

Abstract

A measure of biologically available B (BAB) was obtained by assaying the amount of B removed from a small volume of soil by sunflowers grown until they displayed B deficiency symptoms. Four different mineral soils and one organic soil which had been treated in the field with variable lime and B applications 2 years prior to sampling were compared. The amount of B extracted with hot water from soils before cropping was well correlated with BAB. The B extracted by the more intensive hot water extraction methods was closely related to the absolute level of BAB. Digestion of soils with concentrated H₃PO₄ resulted in the dissolution of larger amounts of B than that extracted with hot water. The proportion of H₃PO₄ soluble B that was measured as BAB was quite variable. Thus H₃PO₄ was a less suitable extractant than hot water for assaying the amount of soil B available to plants during a short growing period. In no case was the difference between the B extracted from soils before and after cropping as large as the BAB values.     

Determination of free inositols and other low molecular weight carbohydrates in vegetables

Different low molecular weight carbohydrates including saccharides, polyalcohols, sugar acids, and glycosides have been identified and quantified in different edible vegetables from Asteraceae, Amarantaceae, Amarylidaceae, Brassicaceae, Dioscoreaceae, and Solanaceae families by gas chromatography-mass spectrometry. Apart from glucose, fructose, and sucrose, other saccharides such as sedoheptulose in chicory, spinach, cabbage, purple yam, eggplant, radish, and oak leaf lettuce, rutinose in eggplant skin, and a glycosyl-inositol in spinach have been identified. chiro-Inositol was found in all vegetables of the Asteraceae family (3.1-32.6 mg 100 g(-1)), whereas scyllo-inositol was detected in those of purple yam, eggplant, artichoke, chicory, escarole, and endive (traces-23.2 mg 100 g(-1)). α-Galactosides, kestose, glucaric acid, and glycosyl-glycerols were also identified and quantified in some of the analyzed vegetables. Considering the bioactivity of most of these compounds, mainly chicory leaves, artichokes, lettuces, and purple yam could constitute beneficial sources for human health.     

过磷酸钙对石灰性土壤有效磷及无机磷组分的影响

为研究水溶性磷肥在石灰性土壤中的转化,采用室内土壤培养的方法,在土壤中分别添加过磷酸钙0、6.25、12.5、25、50和100 mg/kg干土(即P0、P6.25、P12.5、P25、P50和P100处理),保持土壤湿度为田间持水量的70%～80%,在25℃恒温培养箱中培养120 d。培养期间在第1、3、7、15、30、60和120 d连续采样,测定土壤Olsen-P、CaCl2-P和各无机磷组分的含量。结果表明,在石灰性土壤中施用过磷酸钙能显著增加土壤Olsen-P和CaCl2-P含量,在一定的培养时间内,过磷酸钙转化为土壤Olsen-P和CaCl2-P的比例不随施肥量的变化而变化。随着培养时间的延长,土壤有效磷含量逐渐下降,尤其是培养前期(前7 d)土壤有效磷含量显著下降,之后下降速率减缓。施入土壤中的过磷酸钙主要转化为Ca2-P和Ca8-P(两者之和约占90%),其次是Al-P和Fe-P(两者之和约占10%),在短期内O-P和Ca10-P相对较为稳定。随着培养时间延长,Ca2-P逐渐向Ca8-P转化,在培养的前30 d转化速率较快,之后速率减缓。随着磷肥施用量的增加,Ca2-P转化为Ca8-P所需的时间逐渐延长。Olsen-P和CaCl2-P含量均与土壤无机磷组分中的Ca2-P、Ca8-P和Al-P含量呈显著正相关,通过逐步回归分析表明,其中Ca2-P是土壤Olsen-P和CaCl2-P的主要来源。     

Conjugated linoleic acid isomers differ in their free radical scavenging properties

Conjugated linoleic acid (CLA) isomers were investigated for free radical scavenging properties against the stable 2,2-diphenyl-1-picryhydrazyl radical (DPPH(*)) by electron spin resonance (ESR) spectrometry and spectrophotometric methods. ESR measurements confirmed that both c9,t11-CLA and t10,c12-CLA directly reacted with and quenched DPPH radicals, whereas spectrophotometric analysis demonstrated that c9,t11-CLA and t10,c12-CLA differed in their kinetic and thermodynamic properties in reacting with DPPH radicals. t10,c12-CLA was shown to exhibit a greater initial velocity in CLA-DPPH radical reactions at levels of 2.5-80 mg/mL, and c9,t11-CLA scavenged more DPPH radicals at steady state. Similar dose and time relationships were observed for both isomers. In addition, a mixture of c9,t11- and t10,c12-CLA isomers demonstrated a greater initial velocity in quenching DPPH radicals than either isomer alone on the same concentration basis, suggesting that a synergistic effect between CLA isomers existed in their reactions with DPPH radicals. These results support the conclusion that individual CLA isomers differ in their biological actions and indicate that interaction(s) between isomers may contribute to their beneficial effects.     

Enhanced plant growth by uniform placement of superphosphate with rock phosphate in acidic soils

Abstract

Partially acidulated rock phosphate or compacted soluble phosphate‐rock phosphate mixture has been suggested as an alternative phosphorus (P) source for plants in acidic soils. Interaction between the soluble and the insoluble fractions would be conducive to plant utilization of both P sources in the fertilizer material. Direct evidence supports the beneficial reactions between the two P sources, however, was still insufficient. A pot experiment was hence conducted to evaluate the possible interaction of ³²P‐labeled single superphosphate (SSP) and a less reactive rock phosphate (RP) from Jinxiang mine, China. In the experiment, SSP and RP were applied to two acidic red soils (typic Hapludults) in a manner that would favor or diminish their interaction either by distributing both P sources homogeneously within the whole volume of the pot soil (uniform placement) or by separating them vertically with each being applied to half of the soil volume (fraction placement). The reference treatments of SSP and RP were arranged in similar manners. Two successive harvests of ryegrass were made during a 2‐month period. Results indicated that uniform placement of SSP and RP significantly enhanced plant growth and P uptake, and that P recovery of SSP‐P in the higher P‐fixing soil was almost twice that of the fraction placement. The data of plant PdfL% (percentage of P derived from labeled‐P), which indicated that >80% of plant P was derived from SSP, however, failed to support the idea that soluble P had increased plant utilization of RP. Alternatively, it is considered that the low grade RP had increased plant utilization of both SSP‐P and soil‐P. Uniform placement of RP and SSP also strikingly improved plant calcium (Ca) and magnesium (Mg) nutrition. The phenomenon suggested that SSP‐RP mixture might be a good P source on similar acidic soils in subtropical China.     

Determination of free phenolic acids in wort and beer by coulometric array detection

The simultaneous determination of 19 phenolic compounds was performed directly in wort and beer by a combination of reverse-phase high-performance liquid chromatography coupled with coulometric array detection. Chromatographic separation was achieved with an appropriate gradient of flow and a binary solvent based on phosphate buffer, methanol, and acetonitrile in a 45-min run. Eight serial coulometric detectors were used for on-line generation of voltammetric data to resolve coeluting compounds. The method was reliable and sensitive, the regression coefficient of standard calibration curves is 0.972 < or = r < or = 1.000, and the standard deviation value ranges from 0.010 to 0.129 mg/L for wort and from 0.002 to 0.332 mg/L for beer. The mean concentrations of phenolic acids were 22.1 and 33.8 mg/L, respectively, in worts and beers produced in Italy. These amounts represent 5 and 10% of the non-tannic, non-flavonoid phenols in wort and beer, respectively.