几株高效溶磷菌株对不同磷源溶磷活力的比较

在液体培养条件下,研究了4株溶磷菌株(Bmp5、Bmp6、Bmp7和Fmp9)对不同磷源溶解能力的差异并与荧光假单孢菌As1.867和巨大芽孢杆菌As1.223进行了比较,探讨了菌株组合培养对溶磷活力的影响。结果表明,4株菌株对磷酸钙、磷酸铝、磷酸氢钙溶解能力明显高于磷酸铁和卵磷脂。以磷酸钙为磷源时,Fmp9的溶磷量比As1.867和As1.223分别高出约92%和48%;而以磷酸铝为磷源时,As1.223的溶磷量明显高于其他菌株;在磷酸氢钙为磷源的条件下,Bmp6为优势菌株,溶磷量高达785.51mg/L。对比研究发现,Bmp5、Bmp6、Bmp7及Fmp9的优势磷源分别为卵磷脂、磷酸氢钙、磷酸铝和磷酸钙。组合培养表明,Bmp5+Fmp9和Bmp6+Fmp9较单株菌的溶磷量有所增加,为较好的组合。试验得到的溶磷微生物配方已经应用于生物复合肥料的研究,并进行了盆栽实验,得到了较好的效果。该研究可为土壤生物肥料工业的微生物学研究提供借鉴。     

On the use of phosphorus solubility parameters for the evaluation of phosphate plant availability

Abstract

Several phosphate solubility and availability parameters were obtained for calcareous soil samples fertilized with superphosphate, partially acidulated phosphate rock and a mixture of the two. Plant response to the fertilizer application was studied in a greenhouse experiment. The ionic product of calcium carbonate phosphate [Ca₃(HCO₃)₃PO₄] correlated best with the plant response parameters. The correlations of the plant response parameters with the other solubility parameters (CaPO₄, H₂PO₄ or HPO₄ potentials) were higher than that obtained with conventionally determined available soil phosphorus (P).     

Evaluation of Phosphorus Mobilization Potentials of Six Bacterial Strains from Four Insoluble Phosphorus Sources

A laboratory experiment was conducted to evaluate the P mobilization potentials of six bacterial strains isolated from three wheat-growing soils of Australia. Four different forms of insoluble phosphorus (P) were used in this experiment. Two strains (Pantoea ananatis and Pantoea sp.) mobilized more P from calcium phosphate [Ca₃(PO₄)₂] when ammonium sulfate [(NH₄)₂SO₄] was used as a source of nitrogen (N) compared to ammonium nitrate (NH₄NO₃) as the N source. The remaining four strains showed increased P-mobilizing ability with nitrate as sources of N. Cultures containing Burkholderia sp. showed a greater net increase in soluble P from rock phosphate compared to Ca₃(PO₄)₂. Mobilization of P from aluminium phosphate (AlPO₄) and iron phosphate (FePO₄) was much lower than from calcium P sources in cultures containing all the bacterial strains tested. Pantoea ananatis and Pantoea sp. were significantly better than other strains in mobilizing P from AlPO₄ whereas Pantoea sp. was identified as a minor P mobilizer from FePO₄.     

从不同浸提剂所浸出的磷酸盐形态探讨几种速效磷测定方法的意义

在前一报告中^[1],作者通过室内化学分析及生物试验证明,在所试的六种测定土壤有效磷的方法中,以Olsen的0.5M NaHCO₃法与生物反应的相关性最好,马乞金的1%(NH₄)₂CO₃法和Radet的3.5%柠檬酸钠法次之,Egner-Rim的乳酸钙法、Burriel-Hern-ando的混合浸提液法和Joret-Herbert的草酸铵法又次之。另外,从浸提出的磷量看,碳酸氢钠法、马乞金法和柠檬酸纳法相当接近,可以列为同一数量级。乳酸钙法、混合浸提液法和草酸铵法浸出的磷量也很接近,可以列为另一较高的数量级。     

Quantification of individual phosphorus species in sediment: a sequential conversion and extraction method

Common sequential phosphorus (P) extraction methods are not specific to particular chemical species and have several limitations. This work presents the first chemical method for quantification of individual mineral and sorbed P species. It was developed by combining a conversion technique with a sequential extraction procedure. Mangrove sediments with different characteristics were incubated in pH‐adjusted 0.01 M CaCl₂ with and without reference material additions of octacalcium phosphate (Ca₈H₂(PO₄)₆·5H₂O; OCP), hydroxyapatite (Ca₅(PO₄)₃OH), strengite (FePO₄·2H₂O) or variscite (AlPO₄·2H₂O). The changes in soluble phosphate concentration were measured in the supernatant solution, while pH‐induced variations in P composition were determined by subsequent sequential extraction of the sediments. Dissolved phosphate concentration was controlled by adsorption below pH 7.8. Above this pH, soluble phosphate concentration was governed by OCP, which was qualitatively determined by plotting the experimental values of pH + pH₂PO₄ and pH – 0.5 pCa on a solubility diagram including the isotherms of known crystalline phosphate compounds. In contrast to the often‐predicted slow dissolution rate of crystalline phosphates in soils or sediments, drastic changes in P composition by dissolution, precipitation and adsorption processes were detected after 7 days. These were mainly not observed indirectly by changes in dissolved phosphate through adsorption effects, but were determined quantitatively by subsequent sequential extraction, thus enabling the quantification of individual species. Evaluation of the method was performed by standard addition experiments. Besides P species quantification, the method provides the means for other applications, such as the determination of P mineral dissolution kinetics in soils and sediments, the prediction of P composition in changing environmental settings and the refinement of theoretical models of phosphate solubility in soil and sedimentary environments.     

Diagnosing phosphorus deficiency in irrigated durum wheat using basal stem phosphate tissue analysis

Abstract

The occurrence of phosphorus (P) deficiencies in small grain crops are normally predicted through the use of preplant soil analysis and verified by tissue analysis for total ? often at the beginning of reproductive growth. Few studies have addressed the potential use of tissue phosphate (PO₄‐P) tests to characterize the ? status of grain crops during early vegetative growth which could allow for correction of ? deficiency in irrigated production systems during the current season. Three field experiments were conducted in southeastern Arizona from 1986–89 to examine the effects of ? applications, and residual soil ? on tissue phosphate (PO₄‐P) concentrations and yield of irrigated durum wheat (Triticum turgidum L. var durum cv. Aldura). Fertilizer ? additions resulted in significant increases in basal stem and leaf tissue PO₄‐P concentrations at GS 2, 6 and 10. Fertilizer ? applications of up to 40 kg P/ha increased extractable ? levels in the soil by 82% at the beginning of the next growing season but had no significant effect on grain yields or tissue PO₄‐P concentrations of the succeeding wheat crop. Band applications of ? resulted in higher tissue PO₄‐P concentrations versus broadcast applications. While both basal stem and upper leaf tissue PO₄‐P concentrations were responsive to differences in ? availability, routine use of basal stems for nitrate testing and significantly higher PO₄‐P levels in basal stems at GS 2 and GS 6 favor its use in diagnosing ? deficiency. Basal stem tissue PO₄‐P analysis seemed to accurately reflect ? nutrition of durum wheat from GS 2 to 10. Preliminary critical levels of PO₄‐P in basal stem tissue of irrigated durum wheat were 2000, 1200 and 500 mg/kg at GS 2, 6 and 10, respectively.     

Response of wheat to foliar phosphorus treatments under field and high temperature regimes

Potassium phosphate (KH₂PO₄) is applied commonly in dilute foliar sprays to wheat (Triticum aestivum L.) in China. Yield responses to foliar P sources have also been reported for several crop species in other countries. Experiments were conducted to determine efficacy of four P sources and four rates of KH₂PO₄ as foliar treatments on wheat under field conditions and KH₂PO₄ under two controlled temperature regimes. Grain yields were increased most by KH₂PO₄ followed by β‐glycerophosphate and tripolyphosphate; only phytic acid was ineffective. All rates of 1 to 4 kg ha^‐1 KH₂PO₄ increased grain yields. Foliar KH₂PO₄ applications increased grain weight early under low controlled temperatures, but did not affect final grain weight under either temperature regime. Beneficial effects of foliar P treatments were associated with increased plant P content, which may have increased cell sugar content and protected membranes. Although preliminary results are favorable, additional research is needed to determine optimum methods and conditions for treating wheat with foliar P sources.     

Characterization of brushite as a re-crystallization product formed during bacterial solubilization of hydroxyapatite in batch cultures

Two strains of bacteria (Burkholderia sp., strain FeGL01, and Burkholderia caribiensis, strain FeGL03) were isolated from a Brazilian high phosphorus iron ore. The capacity of both strains to solubilize hydroxyapatite, Ca₅(PO₄)₃(OH), was assessed in plate and batch cultures. In batch cultures, the concentration of solution-P showed two kinetics: an initial one, characterized by a continuously increasing kinetics and a second one, characterized by oscillatory kinetics. To understand the nature of these oscillations, phosphatic residues in the spent broth were collected before, during and after the oscillations, and characterized using scanning electron microscopy (SEM), energy-dispersive X-ray chemical microanalyses (EDX) and X-ray diffraction (XRD). From these studies, it was found that drops in P concentration were related to the formation of an intermediate phosphate in the residues, identified as brushite, CaHPO₄·2H₂O. Later increase of available P in the solution was found to be a consequence of re-dissolution of brushite crystals previously formed. Re-crystallization of brushite was also detected in plate cultures after 12-14 days of incubation     

Changes in soil phosphorus pools of grasslands following 17 yrs of balanced application of manure and fertilizer

Limiting the use of phosphorous (P) in intensive agriculture is necessary to decrease losses to surface waters. Balanced fertilizer application (P supply equals P offtake by the crop) is a first step to limit the use of P. However, it is questioned whether this balance approach is sufficient to maintain soil fertility. A long‐term field experiment (17 yr), on grazed grassland, has been conducted on sandy soil, marine clay soil and peat soil to obtain insight into the effects of balanced P fertilizer application on soil test P values and to explain the results by changes in P pools in the soil. The balance approach led to a gradual decline in plant available P, measured as P‐AL, in the topsoil (<0.10 m deep). This decline was accompanied by a decline in oxalate extractable P, dithionite extractable P and inorganic P (0.5 m H₂SO₄). The decline in these mineral P pools in the topsoil was (partly) compensated by an increase in the amount of organic P. There was evidence for the accumulation of P in an occluded form, especially at one of sites which received P as Gafsa rock phosphate [Ca₃(PO₄)₂].     

Magnesium-fortified phosphate fertilizers improve nutrient uptake and plant growth without reducing phosphorus availability

Magnesium (Mg) deficiency can significantly limit crop yield and quality. Separate application of straight Mg fertilizer is unattractive because of additional labor costs. Meanwhile, bulk blending Mg with other macronutrient fertilizers is also a suboptimal solution because bulk blended fertilizers often yield poor nutrient distributions. One rapid and economical alternative to alleviating Mg deficiency is to co-granulate macronutrient fertilizers with Mg. However, few commercial products have implemented this approach. One of the barriers hindering the production of Mg-fortified phosphorus (P) fertilizers is the assumption that precipitation of P with Mg will reduce P solubility. In this study, four Mg compounds, anhydrous magnesium sulfate (MgSO₄), magnesium oxide (MgO), anhydrous magnesium chloride (MgCl₂), and dolomite (CaMg(CO₃)₂), were co-granulated with mono-ammonium phosphate (MAP), and their granule strength, Mg and P availabilities, and agronomic effectiveness were evaluated. Results showed that there were no significant differences in P solubility between Mg-fortified MAP and MAP treatments. X-ray diffraction (XRD) indicated that the Mg species after co-granulation were boussingaultite (Mg(NH₄)₂(SO₄)₂·6H₂O), schertelite (Mg(NH₄)₂H₂(PO₄)₂·4H₂O), magnesium hydrogen phosphate (Mg(H₂PO₄)₂), and dolomite (CaMg(CO₃)₂). A pot experiment using an acidic soil demonstrated an average 9.6-fold increase in shoot Mg uptake, 3.0-fold increase in shoot P uptake, and 3.2-fold increase in soybean shoot dry matter in Mg-fortified MAP treatments, compared to those in MAP treatment. The current study provides a simple, effective, and low-cost approach for the addition of Mg to macronutrient fertilizers, to minimize Mg deficiency.     

Immobilization of trace metals by phosphates in contaminated soil near lead/zinc mine tailings evaluated by sequential extraction and TCLP

Purpose

The combined contamination of Pb, Zn, Cu, Cd, and As in the soils near lead/zinc mine waste posed a potential threat to the surrounding environment. Mitigation methods are needed to reduce the environmental risk. The aims of this paper were to evaluate the feasibility and efficiency of different forms of phosphates in remediating combined contamination caused by multi-metals and arsenic near the lead/zinc mining tailings.

Materials and methods

The tested soil was taken from a clayey illitic thermic typic epiaquepts soil (depth of 0–20 cm) near a lead and zinc mine tailing, located in Shaoxing, Zhejiang Province, China. Four pure chemical reagents, K₂HPO₄, Ca(H₂PO₄)₂.2H₂O, Ca₃(PO₄)₂, and Ca₅(PO₄)₃OH, were added to the soil in solution form as the trace metal stabilizing additives at a P application rate equivalent to 2,283 mg P/kg-soil and P/Pb molar ratio of 1. Shifts in trace metal speciation were determined using sequential extraction procedures and relative toxicities were evaluated using the standard EPA toxicity characteristic leaching procedure (TCLP).

Results and discussion

The addition of K₂HPO₄, Ca₃(PO₄)₂, Ca₅(PO₄)₃OH, and Ca(H₂PO₄)₂.2H₂O in the contaminated soil at the phosphorus application rate 2,283 mg P/kg-soil reduced Pb concentrations in TCLP extraction solution from 90.47 to 56.05, 83.80, 67.78, and 86.32 mg/kg (38.0, 7.36, 25.1, and 4.59% reduction), respectively. Sequential extraction analysis showed that phosphate treatments caused the transformation of easily available trace metal species to more stable forms. However, TCLP As in the soil increased from its initial value of 0.23 to 2.1, 0.70, 0.67, and 0.77 mg/kg, respectively, for the four treatments. The TCLP leachable As concentration of the K₂HPO₄-treated soil was about nine times of that from the untreated soil.

Conclusions

The addition of K₂HPO₄, Ca₃(PO₄)₂, Ca₅(PO₄)₃OH, and Ca(H₂PO₄)₂.2H₂O were effective in reducing water soluble and exchangeable Pb, Zn, Cu, and Cd, and minimizing TCLP-extractable Pb, Zn, and Cu. The sequential extraction test and the TCLP indicate that Ca₅(PO₄)₃OH treatment has a higher potential in immobilizing Pb, Zn, Cu, and Cd, though a slight enhancement of As mobility, comparing with other phosphate treatments.     

Influence of cationic impurities in acidulated phosphates on the availability of phosphorus to two corn crops

Abstract

Based on the problems that arises from the presence of cationic impurities in rock phosphates for fertilizer production, a greenhouse experiment consisting of two consecutive corn crops was conducted in order to evaluate the plant availability of phosphorus (P) in the fraction soluble only in neutral ammonium citrate (NAC) and also in the NAC+H₂O fraction of acidulated phosphate fertilizers produced from Brazilian raw materials with different amounts of cationic impurities. The experiment was conducted with samples of a Red‐Yellow Latosol (Typic Hapludox) in a completely randomized design with four replications. Four acidulated phosphates obtained by sulfuric acid (H₂SO₄) solubilization of different Brazilian raw materials were studied. Monocalcium phosphate [Ca(H₂PO₄)H₂O] (MCP) was included as a standard source of P as well as samples which were previously leached to remove the water‐soluble P, and therefore, contained essentially the NAC‐soluble fraction. The fertilizers were thoroughly mixed with the whole soil in the pots (mixed application), or with only 1% of its volume (localized application), at the rates of 50 and 100 mg P kg^‐1, based on the calculated content of P soluble in NAC+H₂O. Corn (Zea mays L.) was the test crop grown in two sequences of 35 days. After each 35‐day period, dry matter yield and P accumulated in the plant tops were determined. Results were evaluated by analysis of variance considering the factors, (i) acidulated phosphates, (ii) rate of P application, (iii) leaching, and (iv) methods of application. In a second analysis, the leached phosphates were considered as additional levels of the phosphate factor as well as for MCP. The Tukey test at the 0.05 significance level was utilized for mean separation. Results from this study clearly demonstrated that increasing the amounts of cationic impurities in the raw materials decreased the concentration of water‐soluble P and NAC+H₂O‐soluble P as well as water‐soluble P and NAC+H₂O‐soluble P ratio of the fertilizer obtained. From the results in the first corn cropping, the P in the NAC fraction for the studied Brazilian phosphate was not as available to plants as was the P in the NAC+H₂O fraction or in the pure MCP. The NAC+H₂O method was not an adequate index for evaluating the P availability of the studied sources. No interaction between P sources, leaching, and method of application was found in the second corn cropping.     

Interaction of salinity,nitrogen, and phosphorus fertilization on wheat

This study determined whether the application of nitrogen (N) and phosphorus (P) could ameliorate salt‐induced reduction in wheat production. Saline irrigation water (0.5, 4.0, 8.2, and 12.5 dS/m) and N and P fertilizers (150 kg N/ha and 37.5 kg P₂O₅/ha) were applied to wheat (Triticum aestivum L. ‘Saka 92') grown on a calcareous soil in a greenhouse experiment. Plants received equal amounts of each fertilizer, but the time and frequency of application differed. All salinity levels reduced straw and grain yields, leaf soluble proteins, nitrate (NO₃) content, actual and potential nitrate reductase activity (NRA), and grain protein content. The delay in pollen meiotic cell division increased with salinity. Under saline conditions, applying N and P fertilizers at the end of the grain filling stage improved yield and metabolic performance of the plants compared to other fertilizer treatments.     

Isolation and characterization of mineral phosphate-solubilizing bacteria naturally colonizing a limonitic crust in the south-eastern Venezuelan region

With the aim to explore the possible role of mineral phosphate-solubilizing bacteria (PSB) in phosphorus (P) cycling in iron-rich, acidic soils, we conducted a survey of PSB naturally colonizing a limonitic crust in the south-east region of Venezuela (Bolívar State). A total of 130 heterotrophic bacterial isolates showing different degrees of mineral tri-calcium phosphate (Ca₃(PO₄)₂)-solubilizing activities were isolated from NBRIP plates. In contrast, no isolates showing iron phosphate (FePO₄)- or aluminum phosphate (AlPO₄)-solubilizing activities were detected by this experimental approach. The 10 best Ca₃(PO₄)₂-solubilizers were selected for further characterization. These isolates were shown to belong to the genera Burkholderia, Serratia, Ralstonia and Pantoea by partial sequencing analysis of their respective 16S rRNA genes. All the PSB isolates were able to mediate almost complete solubilization of Ca₃(PO₄)₂ in liquid cultures; in contrast, the PSB isolates were less effective when solubilizing FePO₄. Two groups of PSB isolates were clearly differentiated on the basis of their Ca₃(PO₄)₂ solubilization kinetics. Acidification of culture supernatants seemed to be the main mechanism for P solubilization. Indeed, gluconic acid was shown to be present in the supernatant of five isolates. Furthermore, detection of genes involved in the production of this organic acid was possible in three isolates by means of a PCR protocol.     

Monopotassium phosphate as a phosphorus and potassium source for greenhouse‐winter‐grown cucumber and muskmelon 1

Glasshouse experiments were conducted at the Newe Ya'ar Research Center in the winter seasons of 1992/93 and 1993/94 to examine a phosphorus/ potassium (PK) fertilizer for cucurbit crops. Monopotassium phosphate [(MKP), KH₂PO₄] was found to be very effective as a P and K source for cucumber (Cucumis sativus L.) and muskmelon (Cucumis melo L.) plants grown in soilless container conditions. The efficiency of MKP was essentially not different from that of the combination of phosphoric acid (H₃PO₄) and potassium chloride (KCl) which is widely used in the commercial production of vegetables. Appropriate fertilization of cucumbers with MKP in 1992/93 affected late‐season yield more than early‐season yield. Deficiency of P and K in Gala muskmelon inhibited vegetative growth and decreased yield. The reduced yield resulted from both less fruit‐setting and smaller fruit size. The MKP rates required by cucumber plants in 1993/94 depended primarily on growth medium composition. Generally, plants grown in inert tuff (volcanic gravel) and sandy media responded more significantly to MKP than did those grown in media rich in organic matter. There are at least three reasons for preferring the use of MKP, first it is much safer to handle than is H₃PO₄, second it is highly soluble and can be easily incorporated in fertigation systems, and third it has a high PK content.     

Influence of Biofertilizers and Phosphate Sources on the Phosphorus Uptake of Lettuce and Chemical Forms of Phosphorus in Soil

A greenhouse experiment was conducted with a factorial arrangement in a completely randomized design with three replications. Treatments consisted of two levels of plant growth promoting rhizobacteria (PGPR) (Pseudomonas fluorescens) (with and without inoculation), two levels of vermicompost (0 and 1% w/w), and four phosphate (P) sources (control, rock phosphate powder (RP), tricalcium phosphate (TCP), and triple super phosphate (SP) at 25 mg P kg^?1 level). Co-application of PGPR and RP in non-vermicompost treatments significantly increased shoot fresh weight, shoot dry matter yield, shoot P uptake, soil Ca₂-P concentration, but it significantly decreased soil Ca₈-P and Ca₁₀-P concentrations. The maximum shoot P uptake was obtained in combined application of RP with vermicompost which had no significant difference with the co-application of SP with vermicompost in bacterial and non-bacterial treatments. There was a negative correlation coefficient between shoot P concentration and chemical forms of phosphorus. It may be concluded that application of biofertilizers changed the chemical forms of inorganic phosphorus and increased P uptake by plant.     

Phosphate solubilizing microorganisms isolated from rhizosphere of maize cultivated in an oxisol of the Brazilian Cerrado Biome

Many soil microorganisms are able to transform insoluble forms of phosphorus to an accessible soluble form, contributing to plant nutrition as plant growth-promoting microorganisms (PGPM). The objective of this work was to isolate, screen and evaluate the phosphate solubilization activity of microorganisms in maize rhizosphere soil to manage soil microbial communities and to select potential microbial inoculants. Forty-five of the best isolates from 371 colonies were isolated from rhizosphere soil of maize grown in an oxisol of the Cerrado Biome with P deficiency. These microorganisms were selected based on the solubilization efficiency of inorganic and organic phosphate sources in a modified Pikovskaya's liquid medium culture containing sodium phytate (phytic acid), soybean lecithin, aluminum phosphate (AlPO₄), and tricalcium phosphate (Ca₃(PO₄)₂). The isolates were identified based on nucleotide sequence data from the 16S ribosomal DNA (rDNA) for bacteria and actinobacteria and internal transcribed spacer (ITS) rDNA for fungi. Bacteria produced the greatest solubilization in medium containing tricalcium phosphate. Strains B17 and B5, identified as Bacillus sp. and Burkholderia sp., respectively, were the most effective, mobilizing 67% and 58.5% of the total P (Ca₃(PO₄)₂) after 10 days, and were isolated from the rhizosphere of the P efficient L3 maize genotype, under P stress. The fungal population was the most effective in solubilizing P sources of aluminum, phytate, and lecithin. A greater diversity of P-solubilizing microorganisms was observed in the rhizosphere of the P efficient maize genotypes suggesting that the P efficiency in these cultivars may be related to the potential to enhance microbial interactions of P-solubilizing microorganisms.     

施磷水平对晋南旱地冬小麦产量及磷素利用的影响

在自然降水条件下, 通过大田试验研究了施磷量对晋南旱地冬小麦部分抗性指标、产量、磷素利用率以及1 m土壤磷素形态分布特征的影响。结果表明: 施磷可以提高旱地冬小麦抗逆性、穗数, 进而提高产量, 但对穗粒数和千粒重影响不明显。在0~120 kg(P₂O₅)·hm^-2施磷范围内, 小麦生育期旗叶硝酸还原酶(NR)活性、穗数和产量随施磷量增加显著增加, 丙二醛(MDA)和脯氨酸(Pro)含量随施磷量增加显著降低。当施磷量达到180 kg(P₂O₅)·hm^-2时, 旗叶中MDA、Pro含量降低幅度较小, 甚至会升高; NR活性除抽穗期外不再有显著变化, 穗数和产量变化亦不显著。磷素施入土壤后易固定, 导致磷肥利用率偏低, 当季回收率仅为9%~13%, 以施磷60~120 kg(P₂O₅)·hm^-2为最高。1 m土壤各土层Hedley形态磷分布特征表现为: HCl-Pi>Residual-P> HCl-Po>NaOH-Pi>NaHCO₃-Pi>NaOH-Po>H₂O-Pi>NaHCO₃-Po>H₂O-Po, 其中以HCl-P和Residual-P为主, 分 别占全磷的75%和20%左右, H₂O-P、NaHCO₃-P和NaOH-P含量共占全磷的5%左右。施入土壤中的磷素当 季主要被固定在0~20 cm土层, 不同Hedley形态磷增加量总体在0~39.11 mg·kg^-1之间, 且施磷越多, 被固定磷素就越多。综合考虑冬小麦抗逆性、产量及磷素利用率, 当地旱作冬小麦施磷量(P₂O₅))以120 kg·hm^-2左右为宜。     

磷胁迫条件下油菜、肥田萝卜对难溶性磷的活化与利用

通过砂培试验研究了北方食用油菜和南方绿肥作物肥田萝卜两种植物在缺磷胁迫条件下对难溶性磷酸盐Ca₃(PO₄)₂和AlPO₄的活化利用情况。试验结果表明,在仅供应一种难浴性磷酸盐时,油菜和肥田萝卜对磷酸铝和磷酸三钙都有较大程度的活化与利用。在施用AlPO₄时肥田萝卜地上部吸磷量达到供应等磷量水溶性磷酸盐时的90％;在施用Ca₂(PO₄)₂时油菜地上部吸磷量达到供应等磷量水溶性磷酸盐时的49％。植物干物重的测定结果说明,在缺磷时,难溶性的Ca₃(PO₄)₂及AlPO₄对油菜和肥田萝卜均有促进生长的作用。但是,油菜与肥田萝卜对Ca₃(PO₄)₂和AlPO₄的活化利用程度却存在着一定差异。表现为油菜对Ca₃(PO₄)₂的利用能力强,而肥田萝卜对AlPO₄的利用能力强。     

Phosphorus Stress-Induced Differential Growth,and Phosphorus Acquisition and Use Efficiency by Spring Wheat Cultivars

ABSTRACT

Phosphorus (P) is a finite, non-renewable, and natural resource and a vital major nutrient for plant metabolic and developmental processes. However, adverse soil biogeochemical characteristics of alkaline-calcareous soils (especially Aridisols) and highly weathered acid soils (i.e., Ultisols and Oxisols) render orthophosphate (Pi) as the least available major nutrient due to P complexation, sorption, and/or fixation. In such soil environments, plant bioavailable P is only a small fraction of total soil P, seriously limiting crop growth and production. Different plant species, and even cultivars of the same species, may display a suite of growth responses that enable them to solubilize and scavenge soil P either by enhancing external Pi acquisition or reprioritizing internal Pi use under P-stress soil environments. This paper reports relative growth responses, P acquisition and P-use efficiency characteristics by 14 cultivars of spring wheat (Triticum aestivum L.) grown in solution culture with high/low P supply induced by applying soluble NH₄H₂PO₄, sparingly soluble rock phosphate, and Ca₃(PO₄)₂. The wheat cultivars exhibited considerable genetic diversity in biomass accumulation, P concentrations, P contents, factor (PSF) and P efficiency characteristics [i.e., P utilization efficiency (PUE), P efficiency (PE), and PE ratio (PER)]. Plant growth and PE parameters were significantly correlated, while P uptake was linearly related with biomass increase and solution pH decrease. The wheat cultivars with high PUE, PER and P uptake, and low PSF, and plant P concentration were more efficient in utilizing P and, hence, more tolerant under P-stress environment. Biomass and P contents of “P efficient/low-P tolerant” wheat cultivars were superior to “P inefficient/low-P sensitive” cultivars at all P-stress levels. Hence, “P efficient/low-P tolerant” cultivars are the most desirable wheat genotypes for P-stress environments because they are able to scavenge more P from sparingly soluble P sources or soil-bound P forms.