K3解磷菌的解磷机理及其对缓冲容量的响应

以对磷酸三钙具有高效溶解作用且对玉米苗生长有促生效果的假单胞菌K3为模式菌株,采用NBRIP液体培养基研究了解磷菌K3的解磷机制及缓冲容量对其解磷量的影响。结果表明,解磷菌K3液体摇瓶培养7 d后,培养液中水溶性磷从6.54 μg/mL增加至655.23 μg/mL,pH从7.00降至3.99。高效液相色谱测定发现,K3菌液中的主要代谢产物为苹果酸、乳酸和草酸,浓度分别为47.39 mmol/L、25.67 mmol/L和1.89 mmol/L。人工模拟K3菌株产生的有机酸及调节培养基不同pH值对磷酸三钙溶解度影响的试验表明,有机酸的螯合作用是解磷细菌K3菌株解磷的主要机理,而调节培养基pH对解磷的作用有限。液体摇瓶和土培试验结果显示,土壤缓冲容量对K3解磷菌的解磷效应有显著的抑制作用。     

Exchangeability of phosphate extracted by four chemical methods

Isotopically exchangeable phosphate (P) is a major source of P for plants. In practice, however, plant‐available P is assessed by chemical extractions solubilizing a mixture of P forms the availability of which is ill defined. We undertook an isotopic approach to assess the exchangeability of P extracted by (1) CO₂‐saturated water (P‐CO₂), (2) ammonium acetate EDTA (P‐AAEDTA), and (3) sodium bicarbonate (P‐NaHCO₃) compared to the exchangeability of P extracted by water. Five topsoils with similar P‐fertilization histories but different soil properties were studied. Phosphorus was extracted from soils labeled with carrier‐free ³³P after 1 week of incubation, and the specific activity (SA = ³³P / ³¹P) of the extracts was compared with the SA of P extracted by water to calculate the amount of P isotopically exchangeable that had been solubilized during the extraction. P‐CO₂ extracted between 20 and 100 times less P than P‐AAEDTA and P‐NaHCO₃. The SA of P‐CO₂ was not different from the SA of water‐extractable P, showing that P‐CO₂ solubilized similar forms of P as water and that these forms can be considered as available. The SA of P extracted by the two other methods ranged between 25% and 63% for P‐AAEDTA and 66% and 92% for P‐NaHCO₃ of the SA of water‐extractable P. The fraction of exchangeable P extracted by AAEDTA decreased linearly with increasing soil pH, suggesting that this method dissolves slowly or non‐exchangeable P from calcium phosphates.     

Soil testing of horticultural substrates (iv) Desirable phosphorus values for the 1: 1.5 water and Olsen's extracts

Abstract

The initial phosphorus desirable value (DV) to give maximum dry weight and maximum growth rate for various growing periods has been estimated for the 1: 1.5 water extraction procedure and Olsen's procedure by regressing dry weight and net growth rate against soil test values using a quadratic function. DV for dry weight and growth rate has been estimated for chrysanthemum and verbena (2 trials each) and for dry weight for tomato (1 trial) in a number of substrates.

The DV for water extractable P to give maximum dry weight and growth rate in the tomato, chrysanthemum and one verbena trial tended to be higher for peat than for other substrates. For tomatoes the DV for maximum dry weight ranged from about 2 ppm in JIP to about 40 ppm in peat but the range was smaller for other substrates (14.3 ‐ 24.7 ppm). The DV for Olsen's extract was much less affected by substrate; it varied from 27.6 ‐ 32.5 μg/ml to 53.8 ‐ 62.3 μg/ml. The DV to give maximum dry weight for chrysanthemum varied from 2.3 ‐ 2.4 ppm in peat + soil to 19.0 ‐ 23.6 ppm in peat for the water extract, and 14.8 ‐ 18 μg/ml in peat + sawdust + sand (PSS) to 7 4 ‐ 78 μg/ml in peat for Olsen's method. For the verbena trials the DV to give maximum dry weight for the water extract varied from 3.0 ‐ 3.2 ppm in PSS to 17.7 ‐ 20.1 ppm in peat, and for Olsen's method 12.0 ‐ 14.2 μg/ml in peat to 27.8 ‐ 33.1 μg/ml in bark. The DV estimated for maximum growth rate were similar to those for maximum dry weight for both extracts.     

Phosphate sorption curves as a soil testing technique: A simplified approach

Abstract

Single point phosphate sorption curves effectively estimated phosphate fertilizer requirements while requiring less work than multiple point curves. Correlation coefficients of 0.961 and 0.981 were obtained when phosphate rates, estimated using single point curves, were compared with those from multiple point curves. Reducing the ionic strength of the supporting electrolyte solution by using 0.001 M CaCl₂ or water rather than 0.01 M CaCl₂ during equilibration increased dissolved inorganic phosphate 73% and 141% on the average thus improving analytical precision. The relative effects of salt concentration were sufficiently independent of pH and phosphorus concentration to suggest that a simple conversion factor can be used to convert external P requirements from one set of equilibrium conditions (salt concentration) to another.     

Analysis of sugarbeet petioles for phosphorus

Abstract

The influence of method of drying on concentrations of total P, extractable phosphate and two N fractions in petioles from recently matured sugarbeet leaves was studied. Method of drying had no or small effects on total P, total N and nitrate‐N. However, method of drying had a marked effect on the value of extractable phosphate. Concentrations of phosphate‐P extractable with water and 2% acetic acid were least with freeze‐dried material and increased as temperature of oven drying was varied from 70 to 100°C. Extractable phosphate‐P in tissue dried by a particular method was lower when acetic acid was the extractant. Quantity of extract‐able phosphate‐P in oven‐dried material was not influenced by substitution of ascorbic acid for stannous chloride and elimination of the H₂O₂ oxidation step in the analytical procedure. Leaf position greatly affected concentrations of total P and acetic‐acid soluble phosphate‐P. Both parameters at a given sampling date decreased with increasing age of leaf.     

New method of phosphorus determination with improved pretreatment of occluded iron phosphate fraction in soils

Abstract

In the sequential fractionation of phosphorus (P), a modified approach in the oxidation process of the occluded fraction of P (in iron oxides in soils) using redox titration in nitric acid (HNO₃) medium is presented. Also a new spectrophotometric method to determine that P fraction as the phosphomolybdate complex using a mixture of isobutyl acetate and methyl isobutyl ketone to extract the formed complex into the organic phase. Radioactive tracer (³²P) and sequential extraction is used to state the yield of extraction of the phosphomolybdate complex. Accuracy, precision, detection limit, and the linearity of the present method are 1.04%, 0.0322 μg mL^‐1, 0.0038 ug mL^‐1, and 0–15 ug mL^‐1, respectively. The results correlate significantly with the results of the standard method of Petersen and Corey (1966), and the procedure saves time (50 min) and chemicals.     

Evaluation of anion exchange membranes to estimate bioavailable phosphorus in native grasslands of semi‐arid Northwestern Australia

Abstract

Anion exchange membranes (AEMs) were used to assess the P status of semi‐arid sub‐tropical soils of high P sorption capacity from the Pilbara region in northwestern Australia. We determined the most appropriate procedure for using AEMs in these soils using a factorial of extraction ratios and shaking times and compared the method with extraction by water. Significantly more inorganic P (Pi) was extracted by the membranes (AEM‐Pi) than by water, and the amount extracted increased with extraction time but was generally independent of the extraction ratio. Maximum AEM‐Pi was 3.61 μg g^‐1 after eight hour extraction. The AEM procedure was compared with traditional extraction procedures using 0.5 M sodium bicarbonate (NaHCO₃) and 0.1 M sodium hydroxide (NaOH) to assess ability to detect spatial heterogeneity. The amount of Pi extracted decreased in the order: AEM>NaOH>NaHCO_3* The AEM method detected a significant effect of depth on Pi (P=0.0001), while the NaOH method detected both site and treatment effects (P<0.05). Inorganic P extracted by NaHCO₃ did not vary by site, treatment, or depth. Coefficients of variation were generally least using the AEM method. We recommend that studies of spatial and temporal dynamics of P on highly‐weathered soils in semi‐arid regions include measurement of both AEM‐Pi and NaOH‐extractable Pi.     

Simple and Inexpensive Water Extraction Method for Assaying Potassium Concentration in Tobacco Plant Tissue

Potassium (K) in plant tissue is not bound to organic compounds and occurs in soluble forms, thus indicating the ease of its extractability. The conventional methods of plant-sample preparation for K determination are often tedious, time-consuming, and/or require chemicals, making the analysis expensive. In this investigation, we propose a water extraction method for assaying K concentration in tobacco leaf tissue and evaluate it for analytical accuracy and precision in comparison to the established methods, namely, triacid digestion, 1 N ammonium acetate (NH₄OAc) extraction, and 0.5 N hydrochloric acid (HCl) extraction. The proposed method entails extracting K from 0.5 g finely ground plant tissue (<0.5-mm sieve) with distilled water at a 1:100 ratio (sample weight to water volume, w/v) by shaking for 20 mins and filtering before K measurement by flame photometry. Results with 25 tobacco leaf samples having a wide range in K concentrations showed very close agreement between the values of K determined by the proposed water extraction method and the established methods. The mean K concentration obtained with water extraction method was within 3 to 6% of those measured by established methods. The correlations between the K values obtained by the established methods and the water extraction method were highly significant (P?=?0.01), and the relationships are best described by linear regression equations with high values of R² (>0.99). The standard errors (SEs) and coefficient of variation (CV) for K measurements by different methods followed the order water extraction < HCl extraction < triacid digestion < NH₄OAc extraction. The results suggest that the water extraction method is comparable in accuracy and superior in precision to the established methods for K determination. Being simple, rapid, and inexpensive, the water extraction method could be used as an alternative to the most commonly employed standard, triacid digestion, for routine analysis of K in tobacco plant tissue.     

Effect of water management on the vivianite content of paddy-rice roots

Abstract

Vivianite is a hydrated ferrous phosphate mineral that can form in reducing environments, and it was recently identified on aged paddy rice (Oryza sativa, L., cultivar Hitomebore) roots. However, the formation and dissolution of vivianite appear highly susceptible to the soil redox potential. We examined the effect of water management on the vivianite content of rice roots in three experimental micro (1 m²) paddy fields. The vivianite content of the roots was estimated using a method based on the alteration of vivianite after heating at 105°C for 48 h. This alteration steeply lowers the dissolution of phosphate from the roots in a mixed acid solution of 0.1 mol L^?1 of hydrochloric acid (HCl) and 1 mol L^?1 of acetic acid (CH₃COOH). Efficiency of the method was confirmed regarding heating temperature and duration of heating. Using this method, we found that water management significantly influenced the vivianite content of the rice roots. The vivianite content of the rice roots was highest, i.e., 2.3 g phosphorus (P) kg^?1 expressed by its estimated P content, when the paddy field was continuously flooded from May to until early September. After flooding stopped, the soil was gradually oxidized, leading to a decrease in vivianite content. In the micro plot exposed to midseason drainage, the vivianite content increased to the level of the continuously flooded plot after reflooding, and finally decreased after flooding was stopped in late August. The plots exposed to midseason drainage followed by intermittent irrigation presented the lowest vivianite contents among the three experimental paddy fields. These results confirm that increases and decreases in the vivianite contents of paddy-rice roots strongly depend on water management.     

Release of soil phosphate by sequential extractions as a function of soil properties and added phosphorus

Abstract

A study of sequential phosphate (P) extraction by water and iron oxide‐impregnated paper strip procedures was carried out on three Italian soils ranging widely in soil characteristics and enriched with three rates of fertilizer P. The degree of change was dependant on P addition, soil P properties, and type of extraction. For the Fe‐oxide strip procedure, a greater release of P than for water extraction was observed for soils with and without added P. At a given level of added P, more P was released from the soil with the lowest P sorption index (SI). However, at a given level of NaHCO₃‐extractable P, less P was released from the soil with lower SI than from soil with a higher SI, indicating that a greater available P content was necessary for low P sorbing soils to maintain a given rate of P release. The variation of SI accounted for 96% and 92% of the variation in amount of water‐extractable and Fe‐oxide strip P at a given P addition. Furthermore, SI accounted for 97% and 98% of the variation in water‐extractable and Fe‐oxide P at a given increase in available soil P. Inclusion in a soil testing program of an estimate of the P Sorption Index, that accounts for the overall effect of soil properties affecting sorption in soils (clay content and type, iron and aluminum oxide content, surface area, etc.), may improve fertilizer P requirements for optimum crop growth for certain soils.     

Extraction methods for aluminium and iron in relation to phosphate adsorption

Abstract

Three extraction methods for aluminium and two for iron were compared with phosphate sorptivity (Bache and Williams index) for 40 tropical and 40 British soil samples. Extractable aluminium was well correlated with phosphate sorptivity in both groups, but extractable iron was well correlated only in British soils. In general methods which extracted more sesquioxides gave higher correlation coefficients. With aluminium, N ammonium acetate (pH 4.8) or 0.1N HCl gave better correlation than N KCl, while with iron dithionitecitrate was better than 0.1N HCl.     

An automated turbidimetric method for total sulfur in plant tissue and sulfate sulfur in soils

Abstract

An automated turbidimetric method has been developed for the rapid and accurate determination of sulfate. The method is practical and useful for accurately measuring total sulfur in plant tissues, and extractable sulfate in soils. The principle of intermittent reagent addition is used which eliminates drift and sensitivity changes caused by coating of BaSO₄ on tubing and cell walls. Also, the appropriate chemistry is used to minimize interactions of the wash with the sample at a sampling rate of 30/H. The sensitivity of the method is excellent with a working range of 0 to 15 ppm sulfur for soils. For plant digests the sample solutions are diluted to 0–35 ppm S. The precision as determined by repeated analysis of a soil sample extract was 0.58% RSD with a mean of 9.26 pg/g extractable SO⁼ ₄‐S. On another soil sample using a different extractant and extraction procedure the RSD was 0.64%, mean of 9.26 μg/g. Multiple automated sulfur analyses on a plant tissue digest resulted in an RSD of 0.41% for a sample containing 0.21% S. The automated turbidimetric method for sulfate has excellent precision and sensitivity in plant tissue and soil analyses where gravimetric BaSO₄ assays are not practical.     

不同施磷水平对土壤中重金属镉的钝化效果评价

通过室内培养试验,以P/Cd摩尔配比分别为0,2∶3,3∶2,2∶1,4∶1进行了不同磷肥钝化修复Cd污染土壤试验。采用毒性淋溶提取法(TCLP)和形态分析法评价了磷酸氢二铵(DAP)、磷酸二氢钾(MPP)、过磷酸钙(SSP)和磷酸钙(TCP)对污染土壤中Cd的钝化效果。结果表明,4种磷肥的钝化效果依次为:MPPDAPSSPTCP,4种磷肥的钝化处理可显著降低土壤中TCLP提取态Cd含量,在磷肥剂量水平P/Cd为4∶1时对土壤中Cd的钝化效果最佳,最大降低幅度为49%;添加磷肥能够大幅度提高土壤中速效磷的含量,相同磷水平下,土壤中速效磷含量高低次序为:MPPDAPSSPTCP,TCLP提取态Cd含量随土壤速效磷含量升高而显著降低(R=-0.903**);DAP,MPP,SSP和TCP处理后交换态Cd的浓度降幅分别为23.75%,39.06%,16.60%和18.36%,而碳酸盐结合态(WSA)、铁锰氧化物结合态(Fe-Mn-OX)、有机结合态(OM)和残渣态(RES)Cd的含量均有所升高,表明磷素是通过改变Cd的存在形态而降低其有效态含量的。     

Manure Phosphorus Fractions: Development of Analytical Methods and Variation with Manure Types

Abstract

Manure phosphorus (P) extraction and storage procedures were evaluated, and manure types were characterized for extractable P. The objectives of this research were to evaluate manure P extraction and sample storage procedures and to characterize manure types for water‐extractable P (WEP) and NaHCO₃ P (BiEP). Manure P was extracted at dry matter–to–water extraction ratios of 0.5 g/200 mL, 2 g/200 mL, 2 g/20 mL, and 20 g/200 mL. Shaking times of 0.5 h, 1 h, or 2 h were evaluated along with filter paper types (Whatman No. 42, Whatman No. 40, and 0.45‐µm). Single or sequential extractions and repeated extractions with water or NaHCO₃ were also compared on various manure sources. Manure types were treated as replications in the analysis of variance to reduce the probability of making a Type I error in applying the results to diverse manure types. Dry matter–to–water extraction ratios more concentrated than 1 g/100 mL removed less P than extraction at 1 g/200 mL, which removed a similar percentage of total P (TP) as 0.5 g/200 mL ratio. A single extraction with a 1 g/200 mL or more dilute ratio with 1 h of shaking time was found to give a good estimate of extractible P. Extracted manure P was similar for three sequential extractions of 1 g/100 mL dilution ratio compared to one extraction with 1 g/300 mL. Filter paper type did not affect the amount of P extracted. Phosphorus extraction was more consistent with samples stored dry as compared to refrigerated or frozen conditions. Extractible P in swine manure, as a percentage of TP, was more than for other manure types.     

Root exudation,organic acids,and element distribution in roots of Norway spruce seedlings treated with aluminum in hydroponics

Seedlings of Norway spruce (Picea abies [L.] Karst.), which had been grown under sterile conditions for three months, were treated for one week in a hydroculture system with either 500 μM AlCl₃ or 750 μM CaCl₂ solutions at pH 4. Organic acids were determined in hot‐water extracts of ground root tissue. Oxalate (3.3—6.6 μmol (g root dry weight)^—1) was most abundant. Malate, citrate, formate, acetate, and lactate concentrations ranged between 1—2 μmol (g root dry weight)^—1. Organic substances and phosphate found in the treatment solutions at the end of the experimental period were considered to be root exudates. Total root exudation within a 2‐day period ranged from 20—40 μmol C (g root weight)^—1. In root exudates, organic acids, and total carbohydrates, total amino acids, and total phenolic substances were quantified. Citrate and malate, although present in hot‐water extracts of root tissue, were not detected in root exudates. Phosphate was released from Ca‐treated plants. In Al treatments, there was indication of Al phosphate precipitation at the root surface. Oxalate and phenolics present in the exudates of Norway spruce seedlings are ligands that can form stable complexes with Al. However, concentrations of these substances in the treatment solutions were at micromolar levels. Their importance for the protection of the sensitive root apex under natural conditions is discussed.     

Spectrophotometric determination of phosphate in waters of Egypt

The proposed method is used for determination of trace amounts of phosphate in water samples especially of Dakahlia Governorate. The recommended procedure is based on the formation of molydophosphoric acid which upon, selective reduction with the reducing agent oxalyldihydrazide produces a blue color due to the molybdenum blue. The intensity of the blue color is proportional to the amount of phosphate initially incorporated in the heteropoly acid. The resulting blue complex could be determined in the range of 2.25 to 22.46 μg P with molar absorptivity of 33418 L^?1 mol^?1 cm^?1 at 880 nm. The reduction of phosphomolybdate complex by oxalyldihydrazide is chosen in the work and the result is compared with those obtained with the reducing agent potassium antimonyl tartrate, the reduction methods are frequently recommended for manual analysis of waters and wastes for P.     

K_3解磷菌的解磷机理及其对缓冲容量的响应

以对磷酸三钙具有高效溶解作用且对玉米苗生长有促生效果的假单胞菌K3为模式菌株,采用NBRIP液体培养基研究了解磷菌K3的解磷机制及缓冲容量对其解磷量的影响。结果表明,解磷菌K3液体摇瓶培养7 d后,培养液中水溶性磷从6.54μg/mL增加至655.23μg/mL,pH从7.00降至3.99。高效液相色谱测定发现,K3菌液中的主要代谢产物为苹果酸、乳酸和草酸,浓度分别为47.39 mmol/L、25.67 mmol/L和1.89 mmol/L。人工模拟K3菌株产生的有机酸及调节培养基不同pH值对磷酸三钙溶解度影响的试验表明,有机酸的螯合作用是解磷细菌K3菌株解磷的主要机理,而调节培养基pH对解磷的作用有限。液体摇瓶和土培试验结果显示,土壤缓冲容量对K3解磷菌的解磷效应有显著的抑制作用。     

棉田土壤上几种磷肥用量估算法的比较研究

本文通过田间试验和室内模拟试验研究了不同磷肥估算法在棉田土壤上的应用。结果表明: 肥效函数法、土壤吸附等温线法、土壤磷酸盐吸收系数法和磷指标法均能应用于棉田土壤,砂壤质棉田由此估算的施磷量分别为P2O5 148、173、168和150 kg/hm2,壤质棉田施磷量分别为P2O5 138、160、153和172 kg/hm2,其中以土壤磷酸盐吸收系数法操作最简便且精度与肥效函数法相当。     

Automated determination of micro amounts of phosphate in dilute calcium chloride extracts of soils

Abstract

An Auto Analyzer II method for the colorimetric determination of micro amounts of phosphorus (<100 μg/L) in 0.01 M CaCl₂ soil extracts is described. The automated procedure gave results not significantly different from manual determinations.

Using data derived from four soils extracted in triplicate on three separate occasions, the relative confidence intervals for a single sample determination were found to be ± 10.6%.     

Soil and peach seedling responses to soluble phosphorus applied in single or multiple doses

Abstract

Two methods of measuring phosphate (P) adsorption were assessed as a means of predicting soil and plant responses to P fertigation for four British Columbia (B.C.) orchard soils. In Method 1, soils at 0.1 bar moisture tension were incubated for 1, 7, 14, 28, 56, or 84 days with solutions of H₃PO₄ supplied as a single or eight weekly doses. In Method 2, soils were equilibrated with P solutions at 1:10 soil:solution ratio for one day. Langmuir adsorption maxima calculated from the latter data ranged from 99 to 372 mg/kg. Solution P concentrations after one day for single dose incubations and 1:10 soil:solution equilibrations were highly correlated. Solution P concentrations remained elevated for 12 weeks after both single and weekly doses in incubated soils. Four availability indices were derived from the adsorption studies:solution P after one day equilibration for both methods and the fraction of the P adsorbing surface covered by added P at either one or fifty‐six days.

Peach seedlings (Prunus persica L. Batsch) were grown for 12 weeks in the greenhouse in a randomised complete block experiment with five levels of P (0, 15.5, 31, 62, and 124 mg P/kg) supplied as H₃PO₄ on the same schedule as for the incubated soils. Top dry matter increased in response to the first level of added P for three soils but was not correlated with any of four P availability indices measured. Initial soil solution P concentration was a better indicator of response to P fertilizer than Kelowna‐extractable (0.25 M HCl + 0.015 M NH₄F) P. Estimated critical values of soil solution P for the two adsorption methods were 0.85 μg/mL (Method 1) and 0.42 μg/mL (Method 2).