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Fertiliser nitrogen use in Australia has increased from 35 Gg N in 1961 to 972 Gg N in 2002, and most of the nitrogen is used for growing cereals. However, the nitrogen is not used efficiently, and wheat plants, for example, assimilated only 41% of the nitrogen applied. This review confirms that the efficiency of fertiliser nitrogen can be improved through management practices which increase the crop's ability to compete with loss processes. However, the results of the review suggest that management practices alone will not prevent all losses (e.g. by denitrification), and it may be necessary to use enhanced efficiency fertilisers, such as controlled release products, and urease and nitrification inhibitors, to obtain a marked improvement in efficiency. Some of these products (e.g. nitrification inhibitors) when used in Australian agriculture have increased yield or reduced nitrogen loss in irrigated wheat, maize and cotton, and flooded rice, but most of the information concerning the use of enhanced efficiency fertilisers to reduce nitrogen loss to the environment has come from other countries. The potential role of enhanced efficiency fertilisers to increase yield in the various agricultural industries and prevent contamination of the environment in Australia is discussed.

AbstractDenitrification of nitrate in the soil can be a mechanism of significant loss of fertilizer and soil nitrogen, but it can also serve to remove excess NO3that is leached below the root zone. Inappropriate management of irrigation water and fertilizer N in irrigated corn has resulted in leaching of excess N from the rooting zone and contamination of groundwater and also has contributed to the increasing concentration of N2O in the atmosphere. Denitrification can be both microbial and chemical, but the microbial process dominates in most soils through a stepwise reduction of NO3to N2. Soil atmosphere O2concentration, which is regulated by soil water content interactively with soil texture and microbial respiration, is the main controller of the process. The oxygen consumption rate depends on the amount of easily degradable organic C compounds and the interplay of water and carbon in developing in the soil reduced oxic conditions, which regulate not only the amount of total denitrification but also the ratio of N2O to N2produced. Appropriate management of nutrient input, relative to crop demand and soil water status, can limit nitrogen loss from denitrification. This paper describes the role of denitrification in the nitrogen economy of crop production and the environment, describes the process involved, and presents suggestions for limiting N loss caused by denitrification.

Diagnostic methods developed under laboratory or greenhouse conditions require field confirmation. This paper reports the relative field performance of four indexes for the diagnosis of S deficiency in wheat (Triticum aestivumL.) which were previously assessed in the greenhouse. Sulfate S (as percent total S), sulfate S concentration (as ppm dry matter), total S concentration (as ppm dry matter), and total N: total S ratio in the aboveground parts of a soft white wheat cultivar, ‘Olympic’, were compared as diagnostic indexes in a factorial experiment with five rates of gypsum (0 to 50 kg S/ha) and three rates of ammonium nitrate (0 to 100 kg N/ha). A strong relationship was found between final grain yield and each index at the following stages of growth; fourth leaf (61 days from sowing), fully‐tillered (92 days), and jointing (134 days). However, as the critical value for sulfate S (as percent total S) was least affected by the age of the plant or N supply, it is considered to be the most convenient index. The overall relationship between yield and sulfate S (as percent total S) was strong (r = 0.88) and the critical value at 90% of maximum yield was 13%. This compares with r values of 0.87, 0.96, and 0.91 and critical values of 14, 12, and 11% for the plant tissue at the individual growth stages examined. Where the adequacy of the S supply to a wheat crop is in question, the proportion of total S as sulfate S in the plants is indicated as a useful guide to the need for S fertilizer in securing optimal grain yield.

The effects of a urease inhibitor, phenylphosphorodiamidate (PPD), and a nitrification inhibitor, dicyandiamide (DCD), on the losses, tranformations, and recovery of nitrogen (N) were studied when urea was applied to a flooded rice field near Griffith, New South Wales (NSW). When PPD was applied with urea to the floodwater, urea hydrolysis was not prevented but merely delayed by ∼4 d. Consequently, the accumulation of ammoniacal N in the floodwater was also delayed. The maximum ammoniacal N concentration was reached after 3 d in the urea control, and after 9 d in the urea + PPD treatment. The relative losses of ammonia (NH3) from the treatments thus depended on the temperatures and pH of the floodwater and the windspeeds prevailing during the respective periods when the concentration of ammoniacal N was high. Low windspeeds at 8 to 10‐d after application caused NH3loss on the PPD‐treated plots to be less than on urea‐only plots, but this was fortuitous and an opposite effect might have occurred. The 15N balance on microplots which received labelled urea showed that PPD addition increased recovery of urea N in the plant‐soil system from 60 to 82%. Plant uptake of labelled N was increased by 56%. After subtracting NH3volatilization and any other potential losses, the resultant N balance suggested that PPD addition had allowed more urea N to be retained in the soil surface layer (0–10 mm) in such a way that nitrification‐denitrification loss was substantially reduced. The nitrification inhibitor (DCD) had no significant effect on nitrate concentrations in the floodwater, NH3loss, or recovery of fertilizer N in plants and soil.

Two simplified methods for assessing the emission of ammonia, from fertilized, flooded rice (Oryza sativaL. cv. Inga) fields without affecting the plant's environment, are described and compared with an established micrometeorological method. Method A requires a circular plot of a 25‐m radius over which wind speed and atmospheric ammonia concentrations are observed at 0.8 m above the floodwater. Method B requires measurements of ammoniacal nitrogen concentration, pH and temperature in the floodwater, and wind speed at a fixed height. Method A is the more accurate technique and requires fewer measurements. It appears that one calibration curve relating vertical flux of ammonia to these measurements can be applied in widely different environments. Method B is not only less accurate than Method A but appears to require different calibration curves to determine vertical flux for different environments. However, this method may be more useful for comparing ammonia losses from several different fertilizer treatments since only small plot areas are required for each treatment. Method B can be calibrated easily for each site by one set of simultaneous measurements on one treatment plot, using Method A.

In irrigated agriculture, supplemental nitrogen (N) is commonly applied by dissolving ammonia (NH3) gas in the irrigation water. The operation is convenient and labor‐saving, but because NH3is volatile, the potential for loss is high. A micrometeorological method was used to measure losses of NH3gas during applications of water‐run NH3to short (0.9 m) and tall (2.1 m) maize crops. The equilibrium NH3vapor pressure of the irrigation water and wind speed both affected the loss, but the influence of the latter was very marked, volatilization increasing with the approximate square of the wind speed. Average volatilization losses were 7% of the N present in the irrigation water per hour from the short crop, and 1% from the tall crop, the difference arising from the greater attenuation of wind in the tall crop. Results for both crops were reconciled by considering transfer through an air layer close to the ground. Volatilization rate could then be expressed as the product of a wind‐dependent exchange coefficient and the NH3vapor pressure difference between the water surface and 0.3 m. Volatilization losses resulted in very uneven applications of N. The nitrogen content of the irrigation water decreased by 84% over a distance of 400 m along the furrow in the short crop, and by 59% in the tall crop. Some practical remedies are suggested, including irrigating at night. In these experiments, night‐time volatilization rates were only one‐half those observed by day for similar aqueous NH3concentrations.

Studies of the efficiency of applications of anhydrous ammonia fertilizer require a measurement of ammonia retention or loss at the time of application. Because of sampling problems, conventional measurements based on soil analysis are difficult to make in the field. A new method is described, based on calculating the aerial transport of ammonia across the downwind edge of the treated field from measurements of wind speed, wind direction, and atmospheric ammonia concentration. Ammonia losses as small as 1 kg N/ha can be easily detected. Maximum errors are reckoned at no more than 20%. In a field experiment in which anhydrous ammonia was applied at 107 kg N/ha, aerial sampling gave a loss of 1 kg N/ha. Soil sampling detected no loss because of a large sampling error (SE 15 kg N/ha).

There is a need to develop techniques for the prediction of the aerial spread of hazardous chemicals released in agricultural operations. The dispersion of ammonia (NH3) gas during soil injection of anhydrous NH3is one such example. In previous work we established that after injection NH3escaped from the soil to the atmosphere at a rate that decreased exponentially with time; in our study the whole process took about 2 h. In this paper we combine the dynamics of the emission process with existing micrometeorological theory for atmospheric dispersion from line sources, to predict NH3concentrations in the air at the downwind edge of the field. The predictions are compared with concentrations measured during an injection operation. Although the total NH3emission during the operation was only 1.2 kg/ha, NH3concentrations up to 213 µg/m3were recorded at the downwind edge in the early stages of injection. Wind speed and atmospheric stability had large influences on NH3dispersion. In light winds and stable conditions NH3concentrations > 100 µg/m3were recorded when the applicator was > 200 m upwind, and some NH3enrichment still occurred when it was 600 m upwind. The model underestimates NH3concentrations when the treated width is <30 m, but predicts them very well at greater distances in both stable and unstable conditions. The model is used to predict NH3concentrations downwind of the applicator for a range of wind speeds and emission strengths. The approach should prove useful not only for estimating NH3pollution hazards but also for predicting dispersion in related agricultural operations where a time‐dependent decay and/or a line‐source analogy are appropriate.

One hundred and sixty-nine strains of new species of the family Enterobacteriaceae, isolated mainly from the environment, were tested to determine their susceptibilities to 13 antibiotics and 4 antiseptics or disinfectants. All the species were susceptible to aminoglycosides, doxycycline, and trimethoprim but were resistant to chloramphenicol. Susceptibility to beta-lactams varied more among the strains. However, all the strains were cefotaxime susceptible, apart from some Buttiauxella agrestis strains for which MICs were greater than 256 micrograms/ml. The antiseptic MBCs were similar to those published elsewhere for species of the Enterobacteriaceae of clinical origin. No resistance to chlorhexidine was observed. On the other hand, the environmental strains presented a greater resistance to active chlorine than did the reference strains.

Objective: Staphylococcus aureusis one of the prominent causative agents of ventilator-associated pneumonia (VAP). Gram staining of bronchoalveolar lavage (BAL) fluid is not always reliable. A nonisotopid probe (Accuprobe) has been developed by Gen-Probe for the specific identification ofS. aureusisolated from cultures. This study was undertaken to assess the reliability of this probe for the early diagnosis ofS. aureusVAP. Design: A prospective study in 120 consecutive patients. Setting: Department of intensive care medicine at a university hospital. Patients: 120 ventilated patients (70 males and 50 females; mean age 52±12 years; mean simplified acute physiologic score=13±4) were studied. Interventions: 164 bronchoalveolar lavages were performed (none of the patients received prior antibiotic therapy). Measurements and results: S. aureuswas identified 29 times at significant concentrations (≥104cfu/ml) and 7 times at&lt;104cfu/ml. The sensitivity and specificity of the Accuprobe system were 100 and 96%, respectively. We found agreement between quantitative cultures and probes in 96.3% of cases. Conclusions: We conclude that this probe provides a rapid (≤7 h) and accurate diagnosis ofS. aureuspulmonary infection.

Vertical flux densities of ammonia, water vapour and sensible heat were measured over a flooded rice field in China following the application of ammonium bicarbonate fertilizer. Aqueous and gaseous phase transfer resistances for ammonia were deduced from these measurements. The aqueous phase resistance was maximal in the morning and least in the afternoon. Stable stratification of the floodwater immediately adjacent to the air-water interface was observed during the morning when evaporation rates were low, and may be responsible for inhibiting the transfer of ammonia to the atmosphere.

Emissions of nitric oxide and other odd nitrogen oxides (NOx) from a flooded rice field were studied after urea had been broadcast into the floodwater.

Urea has become the most widely used form of N fertilizer in the world, particularly in the tropics. Its efficiency, however, is decreased by losses of N through ammonia volatilization when the urea is not incorporated into the soil. High temperatures and high biological activity at the soil surface promote rapid hydrolysis of urea to ammonia and carbonate species by the soil enzyme urease, leading to large ammonia losses. These conditions have generated interest in materials that can inhibit the urease enzyme, slowing urea hydrolysis and allowing the urea to move away from the soil surface to where it is not as susceptible to ammonia loss. The phosphoryl di- and triamides, which are structural analogs of urea, meet the requirements for effective soil urease inhibition to varying degrees depending on the conditions of their use. Until the discovery of these compounds, there was little hope that urease inhibition could be achieved either economically or in an environmentally acceptable way. Included in this group is N-(n-butyl) thiophosphoric triamide (NBTPT), which is that most widely tested proinhibitor or precursor of the actual inhibitor N-(n-butyl) phosphoric triamide. Recent research in tropical rice systems indicates that urease inhibitors such as N-(n-butyl) phosphoric triamide and cyclohexylphosphoric triamide can play an important role in increasing urea efficiency. In some experiments where urease inhibition was only partially successful, better results were obtained when the phosphoroamides were used in conjunction with an algicide, to restrict ammonia loss, and nitrification inhibitors, to reduce loss of N by denitrification. Further research on tropical soils in different environments is required to determine the most suitable combination of inhibitors to reduce N loss and increase the efficiency of fertilizer N use.

Ammonia (NH3) volatilization is an important mechanism for nitrogen (N) loss from flooded rice fields following the application of urea into the floodwater. One method of reducing losses is to use a urease inhibitor that retards the hydrolysis of urea by soil urease and allows the urea to diffuse deeper into the soil. The two chemicals that have shown most promise in laboratory and greenhouse studies are phenylphosphorodiamidate [PPD] and N-(n-butyl)thiophosphorictriamide [NBPT], but they seldom work effectively in the field. PPD decomposes rapidly when the pH departs from neutrality, and NBPT must be converted to the oxygen analogue [N-(n-butyl)phosphorictriamide, NBPTO] for it to be effective. Our field studies in Thailand showed that NH3loss is markedly reduced when PPD is added with the algicide terbutryn. The studies also showed that a mixture of PPD and NBPT was even more effective than either PPD or NBPT alone. It appears that initially PPD inhibited urease activity, and during this time at least part of the NBPT was converted to NBPTO; then as the activity of PPD declined, NBPTO inhibited the hydrolysis of urea. The combined urease inhibitor treatment reduced NH3loss from 15 to 3% of the applied N, and increased grain yield from 3.6 to 4.1 t ha-1.

This paper reports a study, in a flooded rice field in Thailand, on the effects of two urease inhibitors, cyclohexylphosphorictriamide (CHPT) and N-(n-butyl)phosphorictriamide (NBPTO), the nitrification inhibitor phenylacetylene and an algicide treatment, consisting of alternate additions of copper sulfate and terbutryn at ~3 day intervals, on nitrogen (N) transformations and transfers, and grain yield. The addition of algicide reduced the growth of algae and maintained the pH of the floodwater below that of the control for 11 days. Judging from the ammoniacal N concentrations of the floodwater, phenylacetylene inhibited nitrification. The two urease inhibitors markedly reduced urea hydrolysis and CHPT was more effective than NBPTO. Addition of CHPT maintained the ammoniacal N concentration of the floodwater below 2 g m-3for 11 days and reduced ammonia loss by ~90%. All urease inhibitor treatments in combination with algicide and / or nitrification inhibitor significantly (p< 0.05) increased the recovery of applied N by the plant. Addition of NBPTO or CHPT in combination with phenylacetylene and algicide resulted in a 2 or 3 fold increase of applied N in the grain, and significantly (p< 0.05) increased grain yield.

An indirect method for evaluating the emission of ammonia from urea-fertilized upland crops or urine-affected pastures, without affecting the plant's environment, was evaluated at Yanco, N.S.W., Australia and near Lincoln University, New Zealand. The parameters measured were the ammoniacal nitrogen concentration, pH and temperature in the aqueous phase at the soil's surface, and windspeed at a reference height. The combined effect of these influences on volatilization rate were incorporated into a linear relationship of the form F =k uz?0, where F is the vertical flux of ammonia, determined by a micrometeorological method,uzis the wind speed at some reference height above the soil,?0 is the ammonia concentration in equilibrium with the liquid phase (calculated from the ammoniacal nitrogen concentration, pH and temperature) andkis a proportionality constant. Strong linear relationships of this kind were found for the data sets from both experiments. The respective correlation coefficients for the relationships at the two sites were 0.870 and 0.879, and the respective k values were 6.3 × 10-5and 7.5 × 10-5. The field measurements require little in the way of specialized equipment (e.g. flat - surface pH electrode, ammonia electrode, anemometer) and are comparatively easy to carry out. The results suggest that with some further refinement, this technique could achieve application in the calculation of ammonia losses from small plots in the field.

Losses of nitrogen were investigated after applications of ammonium bicarbonate and urea to flooded rice at transplanting. Ammonia (NH3) volatilization was determined by direct micrometeorological methods, and total loss of fertilizer nitrogen (N) was measured by15N balance. All the loss appeared to be in gaseous forms, since there was no evidence of leaching and runoff was prevented. The difference between N loss and NH3loss was thus assumed to be denitrification loss. Both NH3volatilization and denitrification losses were large, being 39% and 33%, respectively, of the ammonium bicarbonate N, and 30% and 33%, respectively, of the urea N applied by farmers' methods. Ammonia fluxes from the field fertilized with ammonium bicarbonate were very high for two days, and then declined rapidly as the NH3source in the floodwater diminished. Moderate fluxes from the field fertilized with urea continued over 6 days, but calculations showed that NH3transfer from floodwater to atmosphere was retarded during the middle period of the experiment, particularly on day 2 when a thick algal scum appeared on the water surface. The results indicate that this algal mass obstructed the transport of NH3across the water-air interface until the scum was dispersed by wind action. Nevertheless, the prolonged NH3losses on the urea treatment were due primarily to high floodwater pH values promoted by the strong algal growth during the daylight hours. Nitrogen-15 balance studies showed that incorporation of fertilizer into drained soil substantially increased recoveries of fertilizer N in rice plants and soil compared with incorporation of fertilizer in the presence of standing floodwater. Ammonia loss measurements on these treatments when urea was applied suggested that the improvement in fertilizer N efficiency was due mainly to reductions in NH3loss.

This paper reports field experiments designed to determine whether the two main processes responsible for nitrogen (N) loss from flooded rice (ammonia volatilization and denitrification) are independent or interdependent, and glasshouse studies which investigated the effect of soil characteristics on gaseous nitrogen loss. In the first field experiment ammonia (NH3) loss from the floodwater was controlled using algicides, biocides, frequent pH adjustment, shade or cetyl alcohol, and the effect of these treatments on total N loss and denitrification was determined. Most treatments reduced NH3loss through their effects on algal growth and floodwater pH. Total gaseous N loss (54% to 35%) and NH3loss (20% to 1.2%) were affected similarly by individual treatments, indicating that the amount lost by denitrification was not substantially changed by any of the treatments. In a subsequent field experiment NH3and total N loss were again affected similarly by the treatments, but denitrification losses were very low. In control treatments with different rates of urea application, NH3and total N loss were each a constant proportion of the urea applied (NH3loss was 17% and total N loss was 24%). These results indicate that techniques which reduce NH3loss can be expected to reduce total gaseous N loss. The glasshouse experiment showed that gaseous N losses could be reduced by draining off the floodwater, and incorporating the urea into the 0–0.05 m soil layer before reflooding. Even with this method, losses varied widely (6–27%); losses were least from a cracking clay and greatest from a coarse sand which allowed the greatest mobility of the applied N. Incorporation of applied urea can therefore be expected to prevent losses more successfully from clay soils with high ammonium retention capacity.

The distribution and recovery of urea N (25 kg ha-1) applied in solution by low-flow furrow irrigation to wheat, direct-drilled in rows in 1.5m wide permanent beds of a red-brown earth, was determined using15N labelled fertilizer. This method of fertilizer application resulted in an uneven distribution of applied N across the soil bed. Fertilizer N was recovered mainly in the upper 0.15m horizon of the soil. Forty seven percent of the applied N was recovered in the soil and plants within 0.20m of the point of application. Recovery rapidly decreased with increasing distance from the furrow and less than 4% of the urea N was recovered by the plants in the fourth row, 0.67m from the middle of the furrow. The recovery of fertilizer N in the crop was 23, 28, 47 and 40% at 13, 32, 59 and 86 days, respectively; the corresponding total recovery in the crop plus soil was 77, 91, 87 and 75%; the mean being 83 ± 8%. The results suggest that with this method of fertilizer application and these soil properties the furrows should be less than 0.75m apart in order to get uniform distribution of the fertilizer.

This paper reports a study on the effects of water depth in modifying rates of ammonia emission and total nitrogen loss from flooded rice fields after fertilization with urea. Ammonia loss was determined by the mass balance micrometeorological method and total nitrogen loss by15N balance. Initially ammonia was lost at a faster rate from the shallow (0.05 m) than from the deep (0.14 m) floodwater; this was due to higher ammoniacal nitrogen concentrations and higher temperatures in the shallow water. Emission rates were more nearly comparable later in the experiment, but overall, 26% of the applied nitrogen was lost as ammonia from the shallow pond and only 18% from the deep pond. Even though changes in water depth markedly affected ammonia emission rates and the amounts of ammonia lost, they did not significantly affect total nitrogen loss. The results suggest that management practices based only on changes in water depth may not result in increased efficiency of fertilizer nitrogen for flooded rice.

Ammonia loss from urea applied to dry-seeded rice, determined using a micrometeorological technique, varied considerably depending on the time of application. Ammonia volatilization was negligible, before and after flooding, when urea was applied to the dry soil surface two days before permanent flood. Before flooding, the urea prills remained undissolved and urea hydrolysis could not proceed. Thus there was no source of fertilizerderived ammonia for volatilization to occur. Upon flooding, the urea prills were washed into cracks in the soil which subsequently closed. Therefore the movement of soluble nitrogen into the floodwater was prevented, and again there was no ammonia source for the volatilization process. When urea was broadcast into the floodwater a few days after permanent flood, ammonia losses were high and varied from 11–21% of the nitrogen applied. These losses were associated with high floodwater pHs and high wind speeds near the water surface. However, when urea was applied into the floodwater at panicle initiation, ammonia losses were low (3–8% of the applied nitrogen). At this stage of growth the plant canopy shaded the floodwater, inhibiting algal photosynthesis and consequent pH elevation, thus resulting in low ammonia gas concentrations at the floodwater surface. In addition, the plant canopy restricted air movement at the water surface, thereby reducing ammonia transport away from the air-water interface. These findings provide basic information required for improving current fertilizer management practices.

We studied the interacting effects on NH3 loss and grain yield of adding (1) urease inhibitors to retard the hydrolysis of urea (2) the algicide terbutryn to limit floodwater pH increases, and (3) C2H2 (provided by waxcoated calcium carbide) to prevent NH3 oxidation. The algicide treatment maintained the floodwater pH values below 8 for the first 3 days after the urea application and depressed the maximum values below 8.5 on subsequent days. As a consequence, NH3 loss was significantly (P<0.05) reduced in all treatments containing algicide. The addition of wax-coated calcium carbide effectively inhibited nitrification, as judged by the increased ammoniacal (NH3+NH4) N concentrations in the floodwater, However, these increased ammonical-N concentrations resulted in large losses of NH3. The results also showed that the effectiveness of a urease inhibitor cannot be judged solely from the ammonical-N concentrations in the floodwater of a single treatment with the inhibitor. Additional treatments with an algicide and a nitrification inhibitor are required to determine whether the low ammoniacal-N concentrations are caused by NH3 losses and nitrification. Thus N-(n-butyl)thiophosphorictriamide (NBPT) appeared to retard urea hydrolysis when judged by the low ammoniacal-N concentrations in the floodwater; however, treatments with NBPT, algicide, and C2H2 showed that the low concentrations were mainly a result of NH3 volatilization and nitrification. Even though NBPT did not completely inhibit urea hydrolysis, some treatments with this compound reduced NH3 losses and increased grain yields by up to 31%.

The effect of acetylene (provided by wax-coated calcium carbide, CaC2) on N transformations in a red-brown earth was measured in a field experiment with irrigated wheat by determining the change in the concentration and 15N enrichment of the organic N and mineral N pools with time. The study was conducted in the Goulburn-Murray Irrigation region of south-eastern Australia using 0.3 m by 0.3 m microplots fertilized with 15N-labelled urea (10 g N m-2; 5 atom% 15N). Acetylene was effective in slowing the nitrification of both unlabelled and labelled N. Nitrate derived from the added fertilizer reached a maximum 19 days after sowing in the treatment without CaC2, whereas little nitrate accumulated in the 8 g CaC2 m-2 treatment. There was significant immobilization of the urea N by 19 days after sowing in all treatments, but the extent of immobilization was not affected by the acetylene. The addition of acetylene slowed net mineralization of labelled and unlabelled N from the organic N pool, and resulted in increased accumulation of both unlabelled and labelled N in wheat tops.

The effectiveness of wax-coated calcium carbide (as a slow-release source of acetylene) and nitrapyrin in inhibiting nitrification and emission of the greenhouse gases N2O and CH4 was evaluated in a microplot study with dry-seeded flooded rice grown on a grey clay near Griffith, NSW, Australia. The treatments consisted of factorial combinations of N levels with nitrification inhibitors (control, wax-coated calcium carbide, and nitrapyrin). The rate of nitrification was slowed considerably by the addition of wax-coated calcium carbide, but it was inhibited only slightly by the addition of nitrapyrin. As a result, the emission of N2O was markedly reduced by the application of wax-coated calcium carbide, whereas there was no significant difference in rates of N2O emission between the control and nitrapyrin treatments. Both nitrification inhibitors significantly reduced CH4 emission, but the lowest emission rates were observed in the wax-coated calcium carbide treatment. At the end of the experiment 84% of the applied N was recovered from the wax-coated calcium carbide treatment compared with ~ 43% for the nitrapyrin and control treatments.

Achromobacter xylosoxidans, a bacterial species named in 1971, is often isolated from aqueous environments, but little has been reported about its pathogenicity in humans, its epidemiological pattern, and its susceptibility to antibiotics and antiseptics. We were faced with an epidemic caused by this microorganism for 18 months in an intensive care unit. Two patients had fatal infections and 37 others were colonized. The source was the deionized water of the hemodialysis system. The 46 isolates were identified by comparison with the reference strain A. xylosoxidans ATCC 27061. The characteristic cellular fatty acids of this species were demonstrated by gas-liquid chromatography. The minimal inhibitory concentrations of 27 antibiotics were determined. The isolates were susceptible to only two: moxalactam at 4 micrograms/ml and ceftazidime at 8 micrograms/ml. The minimal bactericidal concentrations of one disinfectant and three antiseptics were: sodium hypochloride, 109 micrograms/ml; chlorhexidine digluconate in ethanol solution, 15 to 125 micrograms/ml; polyvinylpyrrolidone iodine, 750 micrograms/ml; and iodine ethanol, 312 to 625 micrograms/ml.

We compared the epidemiological markers of 13 Staphylococcus epidermidis strains isolated from an adult inpatient during a febrile episode and 23 S. epidermidis strains isolated during a presumptive outbreak of nosocomial infection in a neonatal ward. The total DNA restriction endonuclease analysis (REA) was processed along with the following conventional markers: biotyping, serotyping, phage typing, antibiotic susceptibility profiles, and plasmid profiles. The REA method was reproducible, giving stable results both in vitro and in vivo. For the hospitalized adult patient, the conventional markers of the 13 strains were concordant and the restriction profiles were identical. Five restriction groups were demonstrated during the course of the outbreak. Within two of the groups, the identities of all of the markers were used to verify whether all of the isolates belonged to the same cell clone. In a third group, combined analysis of the conventional markers and REA had to be used to demonstrate isolate similarity. On the other hand, in another group, none of the markers were similar; interpretation was not easy. An epidemiological study of S. epidermidis infections in hospitals must take into account all of the epidemiological markers: biotypes, serotypes, phage types, antibiograms, plasmid profiles, and REA.

A semi-automated commercial system (ID 32 E, bioMérieux) for 24-hour identification ofEnterobacteriaceae and other gram-negative fermentative and nonfermentative bacteria encountered in diagnostic microbiology was evaluated. Overall, the system correctly identified 506 (91.5 %) of the 553 strains tested, 94 (17.0 %) strains requiring additional tests for complete identification. Six (1.1 %) strains were misidentified and 33 (6.0 %) strains were not identified. Eight (1.4 %) strains were not present in the database and were misidentified or not identified. The system is a suitable alternative to existing systems for the identification ofEnterobacteriaceae and other gram-negative bacteria frequently encountered in clinical samples.

Technologies to reduce net emissions of carbon dioxide, methane and nitrous oxide within the agriculture sector were reviewed to estimate the global potential for mitigation of these radiatively active greenhouse gases. Our estimates of the potential reduction of radiative forcing by the agricultural sector range from 1.15-3.3 Gt C equivalents per year. Of the total potential reduction, approximately 32% could result from reduction in CO2emissions, 42% of carbon offsets by biofuel production on 15% of existing croplands, 16% from reduced CH4emissions and 10% from reduced emissions of N2O. Agriculture encompasses large regional differences in management practices and rates of potential adoption of mitigation practices. Acceptability of mitigation options will depend on the extent to which sustainable production will be achieved or maintained and benefits will accrue to farmers. Technologies such as no-till farming and strategic fertilizer placement and timing are now being adopted for reasons other than concern for climate change issues.

Phosphate interfered markedly with a Devarda's alloy distillation method for the determination of nitrate. Only 9% of added nitrate was recovered by this method when 200 mg P was present. This interference can be overcome by the addition of calcium ions, to precipitate the phosphate, and an extended distillation time.