J. R. Freney

University of Melbourne, Melbourne, Victoria, Australia

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Publications (98)217.91 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: As farmers in southern Australia typically apply nitrogen (N) to cereal crops by top-dressing with ammonia (NH3) based fertilizer in late winter or early spring there is the potential for large losses of NH3. This paper describes the results of micrometeorological measurements to determine NH3 loss and emission factors following applications of urea, urea ammonium nitrate (UAN), and ammonium sulfate (AS) at different rates to cereal crops at two locations in southern Australia. The amounts of NH3 lost are required for farm economics and management, whilst emission factors are needed for inventory purposes. Ammonia loss varied with fertilizer type (urea > UAN > AS) and location, and ranged from 1.8 to 23 % of N applied. This compares with the emission factor of 10 % of applied N advocated by IPCC ( 2007). The variation with location seemed to be due to a combination of factors including soil texture, soil moisture content when fertilizer was applied and rainfall after fertilizer application. Two experiments at one location, 1 week apart, demonstrated how small, temporal differences in weather conditions and initial soil water content affected the magnitude of NH3 loss. The results of these experiments underline the difficulties farmers face in timing fertilization as the potential for loss, depending on rainfall, can be large.
    Nutrient Cycling in Agroecosystems 01/2012; 93(2). · 1.42 Impact Factor
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    ABSTRACT: Much of the fertiliser nitrogen (N) used in agriculture is lost to the atmosphere as nitric oxide and nitrogen dioxide (collectively referred to as NOx), ammonia (NH3), and nitrous oxide (N2O). The lost N is not only an economic problem for the farmer; it also contaminates the environment and affects human health. Because the values obtained for NOx and NH3 loss to the atmosphere from agriculture in Monsoon Asia have been questioned, we quantitatively determined, using new techniques, the emission of these gases from a maize crop fertilised with urea in northern China. The fertiliser was deep-placed by traditional farmers’ practice and emissions of NOx and NH3were determined with a chemiluminescence analyser and a backward Lagrangian stochastic dispersion technique. The emission measurements indicate that 1.2% of the applied N was lost as NOx. This loss is far greater than measured or derived by other researchers, and we suggest that this is because our measurements were made continuously rather than as spot measurements with static chambers. The results for NH3 show that, although the fertiliser was placed below the soil surface, a small amount (7% of the applied N) was still lost to the atmosphere. Soil analyses indicate that the rate of nitrification in this soil was low, and the maximum nitrate (NO3–) concentration found in the soil (31.4 µg N/g) was only 3.9% of the fertiliser N added. Thus, there is little potential for NO3– to be leached down the profile. A study using soil cores and acetylene inhibition to measure denitrifying activity suggested that the rate of denitrification in this soil was also very low. The results suggest that in this soil with slow nitrification and denitrification rates and little potential for leaching, deep placement of the urea to limit NH3 volatilisation is an effective method for increasing fertiliser use efficiency.
    Soil Research. 08/2011; 49(5):462-469.
  • Agriculture Ecosystems & Environment - AGR ECOSYST ENVIRON. 01/2011; 142(3):437-438.
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    ABSTRACT: This study conducted in the Wimmera, a major cropping area in western Victoria Australia, evaluated a backward Lagrangian stochastic (bLs) dispersion model for measuring ammonia (NH3) loss and compared NH3 losses from a wheat crop after top-dressing with urea or “Green Urea”. Green Urea contained 45.8% nitrogen (N) as urea and “Agrotain” (N-(n-butyl) thiophosphorictriamide) @ 5.0 L/t. The two products (80 kg N ha−1) were applied to circular plots of 25 m radius and losses were determined for a period of 23 days using mass balance micrometeorological methods. When the NH3 concentration in the air at the stability independent height, 0.8 m above the crop, was used there was a strong relationship between the vertical flux density of NH3 as determined by the full profile method and that determined by the bLs method (r = 0.86). Rates of ammonia loss from the urea treatment ranged from 0.2 to 2.1 μg N m−2 s−1, while those from the Green Urea treatment never exceeded 0.35 μg N m−2 s−1. Cumulative NH3 losses for the urea and Green Urea treatments were 7.6 kg N ha−1 (9.5% of applied N) and 0.8 kg N ha−1 (1.0% of applied N), respectively. The results indicate that use of Green Urea instead of regular urea in Victorian wheat growing could substantially reduce NH3 emission.
    Agriculture Ecosystems & Environment 01/2010; 137:261-266. · 3.20 Impact Factor
  • O.T. Denmead, J.R. Freney, F.X. Dunin
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    ABSTRACT: We first present the elements of an inverse Lagrangian model of gas transport in plant canopies. The model allows the inference of sites of gas exchange in the canopy and their source and sink strengths from measured profiles of mean gas concentration and statistics of the canopy turbulence. The practical application of the model is demonstrated through a case study of the fate of ammonia volatilized from fertilizer applied to the floor of a sugarcane crop. Some of the lost ammonia was absorbed by the foliage of the crop; the rest was lost to the atmosphere above. While there was excellent agreement between model predictions of the net flux from the canopy and independent micrometeorological measurements of ammonia flux in the air-layer above it, verification of flux predictions within the canopy was much more difficult. Appeal was made to a process-based model of canopy gas exchange that describes gas transport to and from foliage surfaces in terms of diffusion across aerodynamic, boundary-layer and stomatal resistances in response to a difference in ammonia concentration between the air and leaf sub-stomatal cavities. There was acceptable agreement between the two models in their predictions of foliage ammonia uptake. Next, we apply the process model to a study of the recapture of volatilized ammonia by sugarcane crops with different leaf area indices (LAI). The study indicated recoveries increasing almost linearly with LAI and suggested probable recoveries in excess of 20% for canopies with LAIs of 2 or more. These and other published studies of ammonia exchange between canopy and atmosphere that employed both the inverse Lagrangian and process models suggest that their coupling provides a powerful tool for studying canopy gas exchange.
    Atmospheric Environment 05/2008; · 3.11 Impact Factor
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    ABSTRACT: 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.
    Australian Journal of Soil Research 01/2008; · 3.44 Impact Factor
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    ABSTRACT: The effectiveness of two polyolefin coated products, ‘Meister 70’ and ‘Meister 270’, as slow-release sources of nitrogen (N) for irrigated cotton, and uncoated calcium carbide as a source of acetylene to inhibit nitrification of urea-N and reduce losses by denitrification were studied. The crop was grown on a grey clay in the Namoi Valley of north western New South Wales. The fertilisers were applied at 50 and 150kgN/ha, combined factorialy with two application times, either pre- or post-sowing. Meister 270 did not release N fast enough to supply the plant’s requirements, and is not recommended as a source of N for cotton. Meister 70 was worthy of further study as a pre-sowing source of N because it maintained a higher concentration of ammonium in the soil for longer than urea, resulted in lower soil nitrate concentrations at all times, and increased the apparent recovery efficiency of fertilizer N. The uncoated calcium carbide was not as effective as the wax-coated material tested in previous studies.
    Nutrient Cycling in Agroecosystems 01/2008; 81(3):245-254. · 1.42 Impact Factor
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    ABSTRACT: Organic sulphur in soil appeared to be stable in mildly alkaline solutions at 20°, and thus reagents such as bicarbonate or the sodium form of a chelating resin may be used for the partial extraction of organic sulphur in a chemically unmodified form. More complete extraction of organic sulphur from soil could be achieved by the use of sodium hydroxide solutions at pH 12.6, but degradation of humic acid sulphur to fulvic acid sulphur and conversion of organic sulphur to inorganic sulphur occurred in both hot and cold hydroxide solutions at this pH. A comparison of N : S ratios and percentages of reducible sulphur in soils and extracts suggested that none of the reagents studied extracted a sample of organic matter that was fully representative of the organic matter in soil. The results confirm that most of the sulphur in these surface soils is organic and that there is very little inorganic sulphate present.Sulphur that could be reduced by hydriodic acid occurred in compounds of both high and low molecular weight but data obtained from extraction with bicarbonate and the chelating resin suggested that much of the reducible sulphur occurred in the high molecular weight fraction of soil organic matter.
    Journal of the Science of Food and Agriculture 05/2006; 20(7):440 - 445. · 1.88 Impact Factor
  • J R Freney
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    ABSTRACT: After addition to farms by fertilizer, crop residues, biological fixation and animal excreta, nitrogen can be lost through gaseous emission, runoff and leaching to contaminate the atmosphere and water bodies, and cause adverse health effects. The efficiency of fertilizer nitrogen can be increased and losses reduced, by matching supply with crop demand, optimizing split application schemes, changing the form to suit the conditions, and use of slow-release fertilizers and inhibitors. In addition, agronomic practices such as higher plant densities, weed and pest control and balanced fertilization with other nutrients can also increase efficiency of nitrogen use. Efficiency of use by animals can be increased by diet manipulation. Feeding dairy cattle low degradable protein and high starch diets, and grazing sheep and cattle on grasses high in water soluble carbohydrate result in less nitrogen excretion in urine and reduced ammonia volatilization.
    Science in China Series C Life Sciences 09/2005; 48 Suppl 2:861-70. · 1.61 Impact Factor
  • Arvin R Mosier, J Keith Syers, John R Freney
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    ABSTRACT: Nitrogen (N) availability is a key role in food and fiber production. Providing plant-available N through synthetic fertilizer in the 20th and early 21st century has been a major contributor to the increased production required to feed and clothe the growing human population. To continue to meet the global demands and to minimize environmental problems, significant improvements are needed in the efficiency with which fertilizer N is utilized within production systems. There are still major uncertainties regarding the fate of fertilizer N added to agricultural soils and the potential for reducing losses to the environment. Enhancing the technical and economic efficiency of fertilizer N is seen to promote a favorable situation for both agricultural production and the environment, and this has provided much of the impetus for a new N fertilizer project. To address this important issue, a rapid assessment project on N fertilizer (NFRAP) was conducted by SCOPE (the Scientific Committee on Problems of the Environment) during late 2003 and early 2004. This was the first formal project of the International Nitrogen Initiative (INI). As part of this assessment, a successful international workshop was held in Kampala, Uganda on 12 -16 January, 2004. This workshop brought together scientists from around the world to assess the fate of synthetic fertilizer N in the context of overall N inputs to agricultural systems, with a view to enhancing the efficiency of N use and reducing negative impacts on the environment. Regionalization of the assessment highlighted the problems of too little N for crop production to meet the nutrient requirements of sub-Saharan Africa and the oversupply of N in the major rice-growing areas of China. The results of the assessment are presented in a book (SCOPE 65) which is now available to provide a basis for further discussions on N fertilizer.
    Science in China Series C Life Sciences 09/2005; 48 Suppl 2:759-66. · 1.61 Impact Factor
  • C. J. SMITH, K. M. GOH, W. J. BOND, J. R. FRENEY
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    ABSTRACT: The reactions of two organic (citrate and fulvate) and two inorganic (chloride and phosphogypsum) calcium compounds were studied during leaching of columns of unsaturated acidic soil. The potential of these compounds to decrease the aluminium concentration in the soil solution and remove exchangeable aluminium, and their effects on soil acidity are described.The calcium citrate solution increased the soil solution pH from 5 to a maximum value of 7 in the upper portion of the column. In contrast, the fulvate, calcium chloride and phosphogypsum solutions had little effect on soil-solution pH. Treatment with calcium citrate, or fulvate solution that contained 51 mm Na, removed most of the exchangeable aluminium from the column. The cation exchange sites in the upper portion of the column were saturated with calcium, and the cation exchange capacity of the soil was increased from 35 to c. 80 mmolc kg−1 in the calcium citrate treatment. Leachate from this treatment contained low (< 2 mm) calcium concentrations and high aluminium concentrations. In contrast, the above changes were not shown by the calcium chloride and phosphogypsum treatments. In these treatments the calcium concentration in the leachate was equal to that in the inflowing solution, which indicated that calcium was transported through the entire column. These results suggest that calcium alone was ineffective in displacing aluminium from the cation exchange sites and a strong complexing agent such as citrate or fulvate is needed to mobilize the exchangeable aluminium.
    European Journal of Soil Science 08/2005; 46(1):53 - 63. · 2.65 Impact Factor
  • P.J. Randall, J.R. Freney, K. Spencer
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    ABSTRACT: The effect of varying the sulfur (S) and nitrogen (N) supply on theyield and composition of brown rice (Oryza sativa L.)grainwas studied to determine whether grain analysis could be used for the diagnosisof S deficiency in this crop. Plants were grown to maturity in an S deficientyellow podzolic soil, under flooded and upland conditions in a glasshouse. Inthe first experiment there were six application rates of S combined with threeapplication rates of N. The amount of grain per plant varied from 0.69 to 7.62g, depending on the level of S and N supplied. Rice grown underflooded conditions produced approximately twice the grain yield of upland ricegrown at field capacity. Grain from the flooded series generally had a lower Sconcentration, and apart from the grain from the low N treatment, had lower Nconcentrations than the grain from the upland series. The grain S concentrationvaried from 0.069% to 0.154% and the N concentration ranged from 1.06% to 2.14%with changing S and N supply. Strong positive relationships were obtainedbetween grain yield and grain S concentration, and negative relationshipsbetween grain yield and the N:S ratios in the grain. The critical Sconcentration determined for 90% maximum yield in plants well supplied with Nwas not sufficient to distinguish between S responsive and unresponsive plantswhen N was limiting; both grain S concentration and N:S ratio are necessary todetermine the S status of the rice crop. Deficiency was indicated when the Scontent of the grain was less than 0.1% and the N:S ratio was wider than 14:1,and the same criteria applied to rice grain from flooded and upland treatments.Note that these values were derived in a glasshouse experiment using one ricecultivar on one soil and are therefore preliminary and require confirmationbefore practical application in the field. The second experiment examined theeffect of supplemental S applied after anthesis on grain composition. Latesupplemental S had no effect on grain yield, or on the composition of grainfromplants adequately supplied with S. In marked contrast, S concentration in grainof previously S deficient plants increased from 0.08% to 0.2%, well above thehighest level achieved by applying S at sowing. It is concluded that grainanalysis can be used to diagnose retrospectively S status for yield, provided Ssupply does not increase between the stage when grain yields are beingdetermined and the subsequent grain filling stage. An increase in S supplybetween these two stages will change the relationship between grain Scomposition and yield and complicate interpretation of grain analysis fordiagnosis. The advantages of using grain analysis for retrospective diagnosisofS deficiency are discussed, and the preliminary results suggest that theconcepts warrant further testing in the field.
    Nutrient Cycling in Agroecosystems 02/2003; 65(3):211-219. · 1.42 Impact Factor
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    ABSTRACT: This paper reports on the fate of nitrogen (N) in a first ratoon sugarcane (Saccharum officinarum L.) crop in the wet tropics of Queensland when urea was either surface applied or drilled into the soil 3–4 days after harvesting the plant cane. Ammonia volatilization was measured with a micrometeorological method, and fertilizer N recovery in plants and soil, to a depth of 140 cm, was determined by mass balance in macroplots with 15N labelled urea 166 and 334 days after fertilizer application. The bulk of the fertilizer and soil N uptake by the sugarcane occurred between fertilizing and the first sampling on day 166. Nitrogen use efficiency measured as the recovery of labelled N in the plant was very low. At the time of the final sampling (day 334), the efficiencies for the surface and subsurface treatments were 18.9% and 28.8%, respectively. The tops, leaves, stalks and roots in the subsurface treatment contained significantly more fertilizer N than the corresponding parts in the surface treatment. The total recoveries of fertilizer N for the plant-trash-soil system on day 334 indicate significant losses of N in both treatments (59.1% and 45.6% of the applied N in the surface and subsurface treatments, respectively). Drilling the urea into the soil instead of applying it to the trash surface reduced ammonia loss from 37.3% to 5.5% of the applied N. Subtracting the data for ammonia loss from total loss suggests that losses by leaching and denitrification combined increased from 21.8% and 40.1% of the applied N as a result of the change in method of application. While the treatment resulted in increased denitrification and/or leaching loss, total N loss was reduced from 59.1% to 45.6%, (a saving of 13.5% of the applied N), which resulted in an extra 9.9%of the applied N being assimilated by the crop.
    Nutrient Cycling in Agroecosystems 01/2002; 62(3):229-239. · 1.42 Impact Factor
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    ABSTRACT: The inhibition of nitrification in soils has been pursued as a strategy to improve recovery of fertilizer nitrogen (N) by crops through lowering losses by leaching of nitrate or denitrification, in order to benefit yields and the environment. Acetylene is known to inhibit nitrification in soils and recently, we have described a novel matrix consisting of calcium carbide and polyethylene which delivers acetylene in soil over an extended period, resulting in delayed nitrification. In work with irrigated maize, the matrix delayed the disappearance of ammonium derived from urea fertilizer, but gave no benefit for crop yield in a soil that was highly responsive to N. One possibility is that the loss processes (nitrate leaching and/or denitrification) were not significant at the site. Also, it was shown in a pot experiment that seedling growth of maize was impaired by the matrix, and this may provide another explanation for the lack of yield response noted in the field. Further tests are required before the matrix can be recommended for practical use.
    12/2001: pages 774-775;
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    ABSTRACT: This paper reports a study in the wet tropics of Queensland on the fate of urea applied to a dairy pasture in the absence of grazing animals. A nitrogen balance was conducted in cylindrical plots with N-15-labelled urea, and ammonia volatilisation was determined using a mass balance micrometeorological method. The pasture plants took up 42% of the applied nitrogen in the 98 days between fertiliser application and harvest. At harvest 18% of the applied nitrogen was found in the soil, and 40% was lost from the plant-soil system. The micrometeorological study showed that 20% of the unrecovered nitrogen was lost by ammonia volatilisation. As there was no evidence for leaching or runoff losses it was concluded that the remaining 20% of the applied nitrogen was lost by denitrification. It is evident from these results that fertiliser nitrogen is not being used efficiently on dairy pastures, and that practices need to be changed to conserve fertiliser nitrogen and reduce contamination of the environment.
    09/2001;
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    ABSTRACT: The human induced input of reactive N into the globalbiosphere has increased to approximately 150 Tg N eachyear and is expected to continue to increase for theforeseeable future. The need to feed (125 Tg N) andto provide energy (25 Tg N) for the growing worldpopulation drives this trend. This increase inreactive N comes at, in some instances, significantcosts to society through increased emissions of NOx,NH3, N2O and NO3 – and deposition of NOy and NHx.In the atmosphere, increases in tropospheric ozone andacid deposition (NOy and NHx) have led toacidification of aquatic and soil systems and toreductions in forest and crop system production. Changes in aquatic systems as a result of nitrateleaching have led to decreased drinking water quality,eutrophication, hypoxia and decreases in aquatic plantdiversity, for example. On the other hand, increaseddeposition of biologically available N may haveincreased forest biomass production and may havecontributed to increased storage of atmospheric CO2 inplant and soils. Most importantly, syntheticproduction of fertilizer N has contributed greatly tothe remarkable increase in food production that hastaken place during the past 50 years.The development of policy to control unwanted reactiveN release is difficult because much of the reactive Nrelease is related to food and energy production andreactive N species can be transported great distancesin the atmosphere and in aquatic systems. There aremany possibilities for limiting reactive N emissionsfrom fuel combustion, and in fact, great strides havebeen made during the past decades. Reducing theintroduction of new reactive N and in curtailing themovement of this N in food production is even moredifficult. The particular problem comes from the factthat most of the N that is introduced into the globalfood production system is not converted into usableproduct, but rather reenters the biosphere as asurplus. Global policy on N in agriculture isdifficult because many countries need to increase foodproduction to raise nutritional levels or to keep upwith population growth, which may require increaseduse of N fertilizers. Although N cycling occurs atregional and global scales, policies are implementedand enforced at the national or provincial/statelevels. Multinational efforts to control N loss tothe environment are surely needed, but these effortswill require commitments from individual countries andthe policy-makers within those countries.
    Biogeochemistry 01/2001; 52(3):281-320. · 3.53 Impact Factor
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    ABSTRACT: This paper reports a study in the wet tropics of Queensland on the fate of urea applied to a dry or wet soil surface under banana plants. The transformations of urea were followed in cylindrical microplots (10.3 cm diameter 23 cm long), a nitrogen (N) balance was conducted in macroplots (3.85 m 2.0 m) with 15N labelled urea, and ammonia volatilization was determined with a mass balance micrometeorological method. Most of the urea was hydrolysed within 4 days irrespective of whether the urea was applied onto dry or wet soil. The nitrification rate was slow at the beginning when the soil was dry, but increased greatly after small amounts of rain; in the 9 days after rain 20% of the N applied was converted to nitrate. In the 40 days between urea application and harvesting, the macroplots the banana plants absorbed only 15% of the applied N; at harvest the largest amounts were found in the leaves (3.4%), pseudostem (3.3%) and fruit (2.8%). Only 1% of the applied N was present in the roots. Sixty percent of the applied N was recovered in the soil and 25% was lost from the plant-soil system by either ammonia volatilization, leaching or denitrification. Direct measurements of ammonia volatilization showed that when urea was applied to dry soil, and only small amounts of rain were received, little ammonia was lost (3.2% of applied N). In contrast, when urea was applied onto wet soil, urea hydrolysis occurred immediately, ammonia was volatilized on day zero, and 17.2% of the applied N was lost by the ninth day after that application. In the latter study, although rain fell every day, the extensive canopy of banana plants reduced the rainfall reaching the fertilized area under the bananas to less than half. Thus even though 90 mm of rain fell during the volatilization study, the fertilized area did not receive sufficient water to wash the urea into the soil and prevent ammonia loss. Losses by leaching and denitrification combined amounted to 5% of the applied N.
    Nutrient Cycling in Agroecosystems 12/2000; 59(1):65-73. · 1.42 Impact Factor
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    ABSTRACT: The paper examines the strengths and weaknesses of a rangeof meteorological flux measurement techniques that mightbe used to verify predictions of greenhouse gas inventories.Recent research into emissions of methane (CH4)produced by enteric fermentation in grazing cattle and sheepis used to illustrate various methodologies. Quantifying thisimportant source presents special difficulties because the animalsconstitute moving, heterogeneously distributed, intermittent, pointsources. There are two general approaches: one, from the bottom up,involves direct measurements of emissions from a known number ofanimals, and the other, from the top down, infers areal emissions ofCH4 from its atmospheric signature. A mass-balance methodproved successful for bottom-up verification. It permits undisturbedgrazing, has a simple theoretical basis and is appropriate for fluxmeasurements on small plots and where there are scattered pointsources. The top-down methodologies include conventional flux-gradientapproaches and convective and nocturnal boundary-layer (CBL and NBL)budgeting schemes. Particular attention is given to CBL budget methods inboth differential and integral form. All top-down methodologies require ideal weather conditions for their application, and they suffer from the scattered nature of the source, varying wind directions and low instrument resolution. As for mass-balance, flux-gradient micrometeorological measurements were in good agreement with inventory predictions of CH4 production by livestock, but the standard errors associated with both methods were too large to permit detection of changes of a few per cent in emission rate, which might be important for inventory, regulatory or research purposes. Fluxes calculated by CBL and NBL methods were of the same order of magnitude as inventory predictions, but more improvement is needed before their use can be endorsed. Opportunities for improving the precision of both bottom-up and top-down methodologies are discussed.
    Boundary-Layer Meteorology 07/2000; 96(1):187-209. · 2.29 Impact Factor
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    ABSTRACT: Acetylene at partial pressures of 0.1 to 10 Pa blocks nitrification, but because it is a gas, it is difficult to apply and maintain at the required concentration in soil to inhibit the oxidation of ammonium. This problem may be overcome by coating calcium carbide with wax, or by forming a matrix with an insoluble material, to slow its reaction with water, and produce acetylene in situ in soil. This paper reports research which was conducted to develop and evaluate the effectiveness of polyethylene and polypropylene matrices, containing small particles of calcium carbide (1–200 m dia.) and various additives, to act as slow release sources of acetylene to inhibit nitrification in soil. The additives were used to provide microbridging in the matrix and hence controlled water penetration and acetylene generation and release. The matrices and wax coated calcium carbide (2 mm dia.), which has been used successfully for this purpose, were evaluated by following the oxidation of ammonium to nitrate in a fine textured grey clay. All matrices were at least as good as wax coated calcium carbide, at the same rates of active ingredient, as inhibitors of nitrification and some were considerably better. A matrix containing 21% calcium carbide proved to be a better inhibitor than the other materials. This matrix inhibited nitrification until day 90, and considerably slowed the oxidation to day 178. As wax coated calcium carbide has been shown to inhibit nitrification in fields of irrigated wheat, maize, cotton, and flooded rice, the results suggest that this matrix would be effective in preventing nitrification of fertilizer and soil nitrogen.
    Nutrient Cycling in Agroecosystems 01/2000; 56(3):241-251. · 1.42 Impact Factor
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    ABSTRACT: Methane (CH4) emissions from animals represent a significant contribution to anthropogenically produced radiatively active trace gases. Global and national CH4 budgets currently use predictive models based on emission data from laboratory experiments to estimate the magnitude of the animal source. This paper presents a method for measuring CH4 from animals under undisturbed field conditions and examines the performance of common models used to simulate field conditions. A micrometeorological mass difference technique was developed to measure CH4 production by cattle in pasture and feedlot conditions. Measurements were made continuously under field conditions, semiautomatically for several days, and the technique was virtually nonintrusive. The method permits a relatively large number of cattle to be sampled. Limitations include light winds (less than approximately 2 m/s), rapid wind direction changes, and high-precision CH4 gas concentration measurement. Methane production showed a marked periodicity, with greater emissions during periods of rumination as opposed to grazing. When the cattle were grazed on pasture, they produced .23 kg CH4 x animal(-1) x d(-1), which corresponded to the conversion of 7.7 to 8.4% of gross energy into CH4. When the same cattle were fed a highly digestible, high-grain diet, they produced .07 kg CH4 x animal(-1) x d(-1), corresponding to a conversion of only 1.9 to 2.2% of the feed energy to CH4. These measurements clearly document higher CH4 production (about four times) for cattle receiving low-quality, high-fiber diets than for cattle fed high-grain diets. The mass difference method provides a useful tool for "undisturbed" measurements on the influence of feedstuffs and nutritional management practices on CH4 production from animals and for developing improved management practice for enhanced environmental quality.
    Journal of Animal Science 07/1999; 77(6):1392-401. · 2.09 Impact Factor

Publication Stats

2k Citations
217.91 Total Impact Points

Institutions

  • 2008–2011
    • University of Melbourne
      • Department of Resource Management and Geography
      Melbourne, Victoria, Australia
  • 1992–2006
    • The Commonwealth Scientific and Industrial Research Organisation
      • Division of Plant Industry
      Canberra, Australian Capital Territory, Australia
  • 2005
    • University of Florida
      • Department of Agricultural and Biological Engineering
      Gainesville, FL, United States
  • 2000
    • University of Wollongong
      • School of Chemistry
      Wollongong, New South Wales, Australia
  • 1995
    • International Fertilizer Development Center (IFDC)
      Washington, Washington, D.C., United States
  • 1988
    • International Rice Research Institute
      Лос-Баньос, Calabarzon, Philippines