B6nassy, C., 1955. R6marques sur deux Aphelinid6s: Aphelinus mytilaspidis Le Baron et Aphytis proclia Walker. Annls l~piphyt. 6: 11-17. Lord, F. T. & MacPhee, A. W., 1953. The influence of spray programs on the fauna of apple orchards in Nova Scotia II. Oyster shell scale. Can. Ent. 79: 196-209. Pickett, A. D., 1946. A progress report on long term spray programs. Rep. Nova Scotia Fruit Grow. Ass. 83 : 27-31. Pickett, A. D., 1967. The influence of spray programs on the fauna of apple orchards in Nova Scotia XIV. Can. Ent. 97: 816-821. Tothill, J. D., 1918. The predacious mite Hemisarcoptes malus Shimer and its relation to the natural control of the oyster shell scale Lepidosaphes ulmi L. Agric. Gaz. Can. 5 : 234-239.

http://link.springer.com/content/pdf/10.1007/BF01976688.pdf

Soil enzymes: Kuprevich, V. F. & Shcherbakova, T. A.: Translated from the Russian edition (1966), published by the Indian National Scientific Documentation Centre, New Delhi 1971. 392 pp., offset printing from type script, paper cover. Obtainable from U.S. Department of Commerce, National Technical Information Service, Springfield, Va. 22151

The process of microbial mineral plugging in porous media is common in nature. We examined physical and biochemical properties of CaCO3 precipitation induced by Bacillus pasteurii, an alkalophilic soil microorganism. X-ray diffraction analysis quantified the composition of the mineral deposited in sand and identified the CaCO3 crystal as calcite. Examination by scanning electron microscopy identified bacteria in the middle of calcite crystals, which acted as nucleation sites. The rate of microbiological CaCO3 precipitation correlated with cell growth and was significantly faster than that of chemical precipitation. Biochemical properties of urease (urea amidohydrolase, E.C. 3.5.1.5) from B. pasteurii that was indirectly involved in CaCO3 precipitation were examined to understand the kinetics of the microbiological process. Urease from B. pasteurii exhibited a relatively low affinity for urea at pH 7.0 with a Km of 41.6 mM and Vmax of 3.55 mM min−1 mg−1 protein and increased affinity at pH 7.7 with a Km of 26.2 mM and Vmax of 1.72 mM min−1 mg−1 protein. Results of kinetic studies indicate that urease activity and its affinity to urea are significantly high at the pH where calcite precipitation is favorable. Our findings further suggest a potential use of the microbial calcite precipitation process in remediation of the surface and subsurface of porous media.

Microbiological precipitation of CaCO3

The number of studies on priming effects (PE) in soil has strongly increased during the last years. The information regarding real versus apparent PE as well as their mechanisms remains controversial. Based on a meta-analysis of studies published since 1980, we evaluated the intensity, direction, and the reality of PE in dependence on the amount and quality of added primers, the microbial biomass and community structure, enzyme activities, soil pH, and aggregate size. The meta-analysis allowed revealing quantitative relationships between the amounts of added substrates as related to microbial biomass C and induced PE. Additions of easily available organic C up to 15% of microbial biomass C induce a linear increase of extra CO2. When the added amount of easily available organic C is higher than 50% of the microbial biomass C, an exponential decrease of the PE or even a switch to negative values is often observed. A new approach based on the assessment of changes in the production of extracellular enzymes is suggested to distinguish real and apparent PE. To distinguish real and apparent PE, we discuss approaches based on the C budget. The importance of fungi for long-term changes of SOM decomposition is underlined. Priming effects can be linked with microbial community structure only considering changes in functional diversity. We conclude that the PE involves not only one mechanism but a succession of processes partly connected with succession of microbial community and functions. An overview of the dynamics and intensity of these processes as related to microbial biomass changes and C and N availability is presented.

http://wwwuser.gwdg.de/%7Ekuzyakov/Jane-Blag_BFS_2008_Appa-Real-Priming-PE_Review.pdf

Mechanisms of real and apparent priming effects and their dependence on soil microbial biomass and community structure: critical review

The physiological effects of humic substances (HS) on some aspects of plant growth and metabolism are examined. Evidence has been presented on that the effect of HS on plant growth depends on the source, concentration and molecular weight humic fraction. While a low molecular size (LMS 3500 Da) is not absorbed and can interact only with the cell wall. Therefore, a LMS fraction is the major candidate for determining the positive effects of HS on plant growth. The latter effects are in part exerted at the level of the plasma membrane by positively influencing the uptake of some nutrients, and in particular that of nitrate. The effects on the intermediary metabolism are less understood, albeit it seems that HS may influence both respiration and photosynthesis. Humic matter appears also to display an hormone-like activity. It is not clear if this activity is strictly linked to the chemical structure of HS or whether it depends on hormones of microbial origin entrapped into them. In any case, HS exhibit stimulatory effects on plant cell growth and development.

Physiological effects of humic substances on higher plants

Ion binding to natural organic matter : competition, heterogeneity, stoichiometry and thermodynamic consistency

P-removal from soil solution is mainly due to adsorption and precipitation reactions. For calcareous soils two pathways have been proposed as being relevant: partitioning on soil surfaces and precipitation induced by Ca2+ ions in solution. To define P-speciation in soil and reduce P-immobilisation following fertilisation, the relative importance of these two reactions needs to be quantitatively established. This investigation, conducted on two calcareous soils, suggests that Ca-ion activity in the liquid phase is mainly responsible for the formation of insoluble Ca-P phases. Our study was carried out by determining: a) batch sorption isotherms at different slurry concentrations, times of contact, pH and indifferent electrolyte concentrations; b) supernatant isotherms on soil suspensions; c) insolubilisation kinetics of P added to soil columns. The shape of the sorption isotherms indicated that adsorption predominated at low concentrations (below approximately 0.5 mM); above this level precipitation became predominant. Precipitation from solution was demonstrated by adding increasing amounts of phosphate to soil suspension supernatants and precipitation levels comparable to those observed in sorption isotherms were obtained. Thus, carbonate mineral surfaces were not necessary for the induction of P precipitation. The formation of Ca-P mineral phases was increased with reaction time and was governed by the concentration of Ca-ions, pH and indifferent electrolyte concentration. P added at the top of soil columns was rapidly insolubilised: after 5 weeks the P-Olsen value was reduced to about 60% and P was not transported to the deepest layers but remained in the surface ones. These results suggest that, for soils with a high reservoir of exchangeable cations able to form insoluble P phases, precipitation is the predominant mechanism which reduces P availability for plants.

Phosphate adsorption and precipitation in calcareous soils: the role of calcium ions in solution and carbonate minerals

The aim of this study was to evaluate how the N losses through volatilization and leaching from soils fertilized with urea can be affected by the application of a urease inhibitor or a urease plus a nitrification inhibitor. The experiment was carried out using lysimeters with 15N-labelled urea and N-(n-butyl) thiophosphoric triamide (NBPT) as urease inhibitor and dicyandiamide (DCD) as nitrification inhibitor, comparing three different treatments: urea alone (U), urea + NBPT (UN) and urea + NBPT + DCD (UND). Both volatilization and leaching were significantly different in the soils used, according to their physico-chemical characteristics. However, the pattern of the loss was similar: the volatilization was significantly reduced by NBPT (UN), but the presence of DCD (UND) significantly increased the loss, with respect to UN. Considering leaching, the highest amount of NO3
– was lost with UND, the lowest with U. The greatest amount of N lost by leaching was soil-derived N produced by the N mineralization-immobilization turnover. We suggest that, by maintaining the NH4
+ in the soils, the inhibitors, in particular DCD, caused a priming effect with a subsequent increase in the rate of soil organic matter mineralization and an extra release of soil organic N. The priming effect was real in the sandy loam (SL) soil where a net N release was observed, whereas in the clay loam (CL) soil the effect of the inhibitors was less pronounced and an apparent priming effect was observed; however, a real priming effect also cannot be excluded in this soil.

Influence of urease and nitrification inhibitors on N losses from soils fertilized with urea

Removal of sulfonamide antibiotics from water: Evidence of adsorption into an organophilic zeolite Y by its structural modifications

Evolution of organic matter from sewage sludge and garden trimming during composting.

Urease purified from the soil bacterium Bacillus pasteurii was adsorbed and immobilized on a preformed network of Ca-polygalacturonate, a substrate which has a similar composition and morphology to the mucigel present at the root-soil interface. The adsorption proceeded with an essentially quantitative yield, and the immobilized enzyme showed no decrease of specific activity with respect to the free enzyme. The dependence of urease adsorption on NaCl concentration suggested that the enzyme is bound to the carrier gel through electrostatic interactions. The immobilized enzyme showed increased stability, with respect to the free enzyme, with increasing time or temperature, and in the presence of proteolytic enzymes. The pH activity profile revealed that the adsorbed enzyme showed no change in the optimum pH (8.0), but it was more active than the free form in the pH range 5–8. The Michaelis-Menten kinetic pararneters V max and K m were measured for the free ( V max = 1960 ± 250 units ml −1 ; K m = 235 ± 20 mM) and immobilized ( V max = 1740 ± 185 units ml −1 ; K m = 315 ± 25 mM) urease. The substantial similarity of V max in the two cases suggests that there were no conformational changes involving the active site upon enzyme immobilization, while substrate partitioning effects between the bulk solution and the micro-environment surrounding the immobilized enzyme must be operating so as to partly increase its K m . These results suggest that bacterial urease present in plant root mucigel plays a large role in the mobilization of urea N. Its activity is in fact significantly mantained and protected by immobilization on hydrophilic gels such as those produced by root exudates.

Carlo Emanuele Gessa

Papers

Phosphate adsorption and precipitation in calcareous soils: the role of calcium ions in solution and carbonate minerals

Influence of urease and nitrification inhibitors on N losses from soils fertilized with urea

Removal of sulfonamide antibiotics from water: Evidence of adsorption into an organophilic zeolite Y by its structural modifications

Evolution of organic matter from sewage sludge and garden trimming during composting.

Urease from the soil bacterium Bacillus pasteurii: immobilization on Ca-polygalacturonate.