Uptake of Organic Phosphorus by Arbuscular Mycorrhizal Red Clover

The capacities of two arbuscular mycorrhizal (AM) fungi, Glomus mosseae and Glomus versderme, tomineralize added organic P were studied in a sterilized calcareous soil. Mycorrhizal (inoculated with eitherof the AM fungi) and non-mycorrhizal red clover (Trghlium pmtense L.) plants were grown for eight weeksin pots with upper root, central hyphal and lower soil compartments. The hyphal and soil compartmentsreceived either organic P (as Na-phytate) or inorganic P (as KH2PO4) at tbe rate of 50 mg P kg-1. No P wasadded to the root compartments. Control pots received no added P. Yields were higher in mycorrhizal than innon-mycorrhizal clover. Mycorrhizal inoculation doubled shoot P concentration and more than doubled totalP uptake of plaflts in P-amended soil, irrespective of the form of applied P. The mycorrhizal contributionto inorganic P uptake was 80% or 76% in plants inoculated with G. mosseae or G. verefforme, respectively.Corresponding va1ues were 74% and 82% when Na-phytate was

Alleviation of Soil Acidity and Aluminium Phytotoxicityin Acid Soils by Using Alkaline-Stabilised Biosolids

A pot experiment was catried out to study alleviation of soil acidity and Al toxicity by applying analkaline-stabilised sewage sludge product (biosolids) to an acid clay sandy loam (pH 5.7) and a strongly acidsandy loam (pH 4.5). Barley (Hondeum vulgare L. cv. Forrester) was used as a test crop and was grownin the sewage sludge-amended (33.5 t sludge DM ha-1) and unamended soils. The results showed that thealka1ine biosloids increased soil pH from 5.7 to 6.9 for the clay sandy loam and from 4.5 to 6.0 for the sandyloam. The sludge product decreased KCl-extractable Al from 0.1 to 0.0 cmol kg-1 for the former soil andfrom 4.0 to 0.1 cmol kg-1 for the latter soil. As a result, barley plants grew much better and grain yieldincreased greatly in the amended treatments compared with the unamended controls. These observationsindicate that alkaline-stabilised biosolids can be used as a liming material for remedying Al phytotoxicity instrongly acid soils by increasing soil pH and lowering

Effect of Alkaline-Stabilised Sewage Sludge on Extractable Organic Carbon and Copper in Soils

An incubation experiment was conducted to evaluate the potential for water contamination with sludge-derived organic substances and copper following land application of alkaline-stabilised sewage sludge. Twocontrasting sludge-amended soils were studied. Both soils were previously treated with urban and ruralalkaline biosolids separately at sludge application rates of 0, 30 and 120 t ha-1 fresh product. The air-driedsoil/sludge mixtures were wetted with distilled water, maintained at 40 % of water-holding capacity andequilibrated for three weeks at 4 ℃ before extraction. Subsamples were extracted with either distilled wateror 0.5 mol L-1 K2SO4 solution. The concentrations of organic C in the aqueous and chemical extractswere determined directly with a total organic carbon (TOC) analyser. The concentrations of Cu in the twoextracts were also determined by atomic absorption spectrophotometry The relationship between the twoextractable organic C fractions was examined, together with

Extractability of Cu in Alkaline Biosolids-Amended Soilsas Influenced by γ-Irradiation

An incubation experiment was conducted to investigate the microbial biomass associated Cu in fourcontrasting soils to which an alkaline stabilised sewage sludge cake was applied. The organisms of sludge-amended and control soils were killed using ry-irradiation technique, and the aqueous and acid-extractable Cuconcentrations were determined. Addition of the sludge product increased significantly the concentration ofboth the aqueous and dilute HOAc-extractable Cu in all the irradiated soils compared to the non-sterilisedsludge/soil mixtures, but the increase was more pronounced in the dilute acid-extractable Cu, indicating thatthe Cu rendered extractable in water and dilute acetic acid by 7-irradiation existed in the both soil liquidand solid phases. The additional increase in extractable Cu following the biocidal treatment is likely to bedue to release of Cu from the same fraction of soil microbial biomass.

Physiological and Antioxidant Responses of Germinating Mung Bean Seedlings to Phthalate Esters in Soil

Single phytotoxicity of two representative phthalate esters(PAEs),di-n-butyl phthalate(DnBP)and bis(2-ethylhexyl)phthalate(DEHP),was tested in mung bean(Vigna radiata)seedlings germinated for 72 h in soils spiked with varying concentrations(0-500 mg kg^(-1)soil)of DnBP or DEHP.PAEs added at up to 500 mg kg^(-1)soil exerted no significant effect on germination but both pollutants significantly inhibited root elongation(P<0.01),DEHP inhibited shoot elongation(P<0.01)and DnBP depressed biomass on a fresh weight basis(P<0.05).Seedling shoot and root malondialdehyde(MDA)contents tended to be stimulated by DnBP but inhibited by DEHP.However,increases in superoxide dismutase,peroxidase,ascorbate peroxidase and polyphenol oxidase activities,as well as glutathione(GSH)content,were induced at higher concentrations(e.g.,20 mg kg^(-1))of both compounds.Accumulation of proline in both roots and shoots and the storage compounds,such as free amino acids and total soluble sugars,in whole plant was induced under the stress exerted by both PAEs.The general responses of mung bean seedlings indicated higher toxicity of DnBP than DEHP on primary growth,during which root elongation was a more responsive index.MDA and GSH were more sensitive parameters in the roots than in the shoots and they might be recommended as physiologically sensitive parameters to assess the toxicity of PAE compounds in soils in future long-term studies.

Role of Carbon Substrates Added in the Transformation of Surplus Nitrate to Organic Nitrogen in a Calcareous Soil

Excessive amounts of nitrate have accumulated in many soils on the North China Plain due to the large amounts of chemical N fertilizers or manures used in combination with low carbon inputs. We investigated the potential of different carbon substrates added to transform soil nitrate into soil organic N (SON). A 56-d laboratory incubation experiment using the 15 N tracer (K15 NO3 ) technique was carried out to elucidate the proportion of SON derived from accumulated soil nitrate following amendment with glucose or maize straw at controlled soil temperature and moisture. The dynamics and isotopic abundance of mineral N (NO3 and NH+4 ) and SON and greenhouse gas (N2O and CO2 ) emissions during the incubation were investigated. Although carbon amendments markedly stimulated transformation of nitrate to newly formed SON, this was only a substitution effect of the newly formed SON with native SON because SON at the end of the incubation period was not significantly different (P > 0.05) from that in control soil without added C. At the end of the incubation period, amendment with glucose, a readily available C source, increased nitrate immobilization by 2.65 times and total N2O-N emission by 33.7 times, as compared with maize straw amendment. Moreover, the differences in SON and total N2O-N emission between the treatments with glucose and maize straw were significant (P < 0.05). However, the total N2O-N emission in the straw treatment was not significantly (P > 0.05) greater than that in the control. Straw amendment may be a potential option in agricultural practice for transformation of nitrate N to SON and minimization of N2O emitted as well as restriction of NO3-N leaching.

Natural ^(15)N Abundance in Winter Wheat Amended with Urea and Compost: A Long-Term Experiment

We investigated15N abundance(δ15N)of winter wheat(Triticum aestivum cv.Jinmai 1)plants and soil at diferent growth stages in a field with a 13-year fertilization history of urea and compost,to determine whether or not theδ15N of plant parts can be used as an indicator of organic amendment with compost.Plant parts(roots,leaves,stems and grains)and soil were sampled at re-greening,jointing,grain filling and mature growth stages of winter wheat.There were significant diferences between the urea and compost treatments inδ15N of whole plants,plant parts and soil over the whole growing season.Determination of theδ15N of plant parts was more convenient than that of whole plant to distinguish between the application of organic amendment and synthetic N fertilizer.

Isolation and Characterization of Chlorothalonil-Degrading Bacterial Strain H4 and Its Potential for Remediation of Contaminated Soil

A chlorothalonil(CTN)-degrading bacterial strain H4 was isolated in this study from a contaminated soil by continuous enrichment culture to identify its characteristics and to investigate its potential for remediation of CTN in contaminated soil. Based on the morphological, physiological and biochemical tests and 16 S r DNA sequence analysis, the strain was identified as Stenotrophomonas sp. After liquid culture for 7 d, 82.2% of CTN was removed by strain H4. The isolate could degrade CTN over a broad range of temperatures and p H values, and the optimum conditions for H4 degradation were p H 7.0 and 30℃. Reintroduction of the bacteria into artificially contaminated soil resulted in substantial removal of CTN(> 50%) after incubation for 14 d. Soil samples treated by H4 showed significant increases(P < 0.05) in soil dehydrogenase activity, soil polyphenol oxidase activity, average well-color development obtained by the Biolog Eco plate TM assay and Shannon-Weaver index, compared with the control. Strain H4 might be a promising candidate for application in the bioremediation of CTN-contaminated soils.