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Saggar S.,Landcare Research | Singh J.,Landcare Research | Singh J.,University of Melbourne | Giltrap D.L.,Landcare Research | And 6 more authors.
Science of the Total Environment | Year: 2013

Urea is the key nitrogen (N) fertiliser for grazed pastures, and is also present in excreted animal urine. In soil, urea hydrolyses rapidly to ammonium (NH4 +) and may be lost as ammonia (NH3) gas. Unlike nitrous oxide (N2O), however, NH3 is not a greenhouse gas although it can act as a secondary source of N2O, and hence contribute indirectly to global warming and stratospheric ozone depletion. Various urease inhibitors (UIs) have been used over the last 30years to reduce NH3 losses. Among these, N-(n-butyl) thiophosphoric triamide (nBTPT), sold under the trade name Agrotain®, is currently the most promising and effective when applied with urea or urine. Here we conduct a critical analysis of the published and non-published data on the effectiveness of nBTPT in reducing NH3 emission, from which adjusted values for FracGASF (fraction of total N fertiliser emitted as NH3) and FracGASM (fraction of total N from, animal manure and urine emitted as NH3) for the national agriculture greenhouse gas (GHG) inventory are recommended in order to provide accurate data for the inventory. We use New Zealand as a case study to assess and quantify the overall reduction in NH3 emission from urea and animal urine with the application of UI nBTPT.The available literature indicates that an application rate of 0.025% w/w (nBTPT per unit of N) is optimum for reducing NH3 emissions from temperate grasslands. UI-treated urine studies gave highly variable reductions (11-93%) with an average of 53% and a 95% confidence interval of 33-73%. New Zealand studies, using UI-treated urea, suggest that nBTPT (0.025% w/w) reduces NH3 emissions by 44.7%, on average, with a confidence interval of 39-50%. On this basis, a New Zealand specific value of 0.055 for FracGASF FNUI (fraction of urease inhibitor treated total fertiliser N emitted as NH3) is recommended for adoption where urea containing UI are applied as nBTPT at a rate of 0.025% w/w. Only a limited number of published data sets are available on the effectiveness of UI for reducing NH3 losses from animal urine-N deposited during grazing in a grazed pasture system. The same can be said about mixing UI with urine, rather than spraying UI before or after urine application. Since it was not possible to accurately measure the efficacy of UI in reducing NH3 emissions from animal urine-N deposited during grazing, we currently cannot recommend the adoption of a FracGASM value adjusted for the inclusion of UI. © 2012 Elsevier B.V.


Zaman M.,Ballance Agri Nutrients Ltd New Zealand | Ghani A.,Agresearch Ltd. | Kurepin L.V.,University of Western Ontario | Pharis R.P.,University of Calgary | And 2 more authors.
Journal of the Science of Food and Agriculture | Year: 2014

BACKGROUND: The effects of spraying gibberellic acid (GA3) at 20 or 30 g ha-1, with or without application of urea, on pasture dry matter (DM) yield, herbage nitrogen (N) concentration and feed quality were investigated in 2011 and 2012 for managed pastoral systems in New Zealand across a range of sites, in both autumn and spring. RESULTS: On the Waikato site (autumn and spring, 2012), and at all five sites in 2011, liquid urea applied with GA3 at 20 or 30 g ha-1 consistently produced significantly higher pasture shoot DM yield, relative to liquid urea alone. Application of GA3 alone reduced feed quality by lowering metabolizable energy, crude protein and organic matter digestibility values. However, a reduced feed quality was not observed when GA3 was applied together with liquid urea. Liquid urea applied with GA3 also reduced total N and nitrate-N concentration in herbage, relative to liquid urea applied alone. CONCLUSION: Application of GA3 together with liquid urea provides an opportunity for the strategic use of urea to meet both production and environmental goals. © 2014 Society of Chemical Industry.


Saggar S.,Landcare Research | Jha N.,Massey University | Deslippe J.,Landcare Research | Bolan N.S.,University of South Australia | And 6 more authors.
Science of the Total Environment | Year: 2013

In this review we explore the biotic transformations of nitrogenous compounds that occur during denitrification, and the factors that influence denitrifier populations and enzyme activities, and hence, affect the production of nitrous oxide (N2O) and dinitrogen (N2) in soils. Characteristics of the genes related to denitrification are also presented. Denitrification is discussed with particular emphasis on nitrogen (N) inputs and dynamics within grasslands, and their impacts on the key soil variables and processes regulating denitrification and related gaseous N2O and N2 emissions. Factors affecting denitrification include soil N, carbon (C), pH, temperature, oxygen supply and water content. We understand that the N2O:N2 production ratio responds to the changes in these factors. Increased soil N supply, decreased soil pH, C availability and water content generally increase N2O:N2 ratio. The review also covers approaches to identify and quantify denitrification, including acetylene inhibition, 15N tracer and direct N2 quantification techniques. We also outline the importance of emerging molecular techniques to assess gene diversity and reveal enzymes that consume N2O during denitrification and the factors affecting their activities and consider a process-based approach that can be used to quantify the N2O:N2 product ratio and N2O emissions with known levels of uncertainty in soils. Finally, we explore strategies to reduce the N2O:N2 product ratio during denitrification to mitigate N2O emissions. Future research needs to focus on evaluating the N2O-reducing ability of the denitrifiers to accelerate the conversion of N2O to N2 and the reduction of N2O:N2 ratio during denitrification. © 2012 Elsevier B.V.


Zaman M.,Ballance Agri Nutrients Ltd New Zealand | Nguyen M.L.,International Atomic Energy Agency
Agriculture, Ecosystems and Environment | Year: 2012

In intensively dairy-grazed pastoral systems, urine patches are the major source of nitrogen (N) losses via gaseous emissions of ammonia (NH 3) and nitrous oxide (N 2O) and nitrate (NO 3 -) leaching. Minimizing these N losses can therefore enable substantial economic and environmental gains. However, the current practice like the blanket application of nitrification inhibitor (NI) such as dicyandiamide (DCD) in suspension form after grazing is not effective at reducing these N losses. The objective of this study was to identify the best time to apply a combination of urease (UI) and NI inhibitors to reduce these N losses from urine patches. A field experiment on Typic Haplustepts silt loam soil, near Lincoln, Canterbury, New Zealand was conducted. The treatments included: a control (no urine or inhibitor), urine alone at 600kgNha -1, and urine with either double inhibitor (DI) in solid form which consists of a mixture (1:7 ratio w/w) of UI (N-(n-butyl) thiophosphoric triamide (nBTPT-trade name Agrotain ®) and DCD or DCD alone at 10kgha -1 in suspension form. The DI or DCD was applied to undisturbed lysimeters/field plots 10 and 5 days prior to, the same day, and 5 days after urine application in autumn (May 2008) and again to new lysimeters and field plots in spring (September 2008). Overall there were 10 treatments: control, urine alone and urine with DI or DCD applied at the time of urine application, 5 days before or after urine application and 10 days before urine application. After these treatment applications in 2 seasons, soil ammonium (NH 4 +) and NO 3 - concentrations, soil pH, gaseous emissions of NH 3 and N 2O, and NO 3 - leaching were monitored for different period of time and pasture growth and N uptake were measured over a year. The DI applied 5 days prior to urine application was more effective in reducing the 3N losses of NH 3 volatilization, N 2O emissions and NO 3 - leaching than its corresponding or DCD treatment applied 5 days after urine application. The DI applied 5 days prior to urine application significantly reduced soil NH 4 + and NO 3 - production from applied urine and thus exhibited a minimal increase in soil pH compared with urine alone or with DCD treatments for 4-6 weeks during the two seasons. DCD consistently increased NH 3 volatilization when applied 5 or 10 days prior to or concurrently with urine, however it decreased N 2O emissions compared to urine alone in both seasons. Applying DI 5 days prior to urine application not only decreased N 2O emissions as much as DCD did, it also significantly decreased NH 3 volatilization by 38% in autumn and 28% in spring compared to urine alone. Applying DCD or DI in autumn was more effective than spring applications probably because of the lower soil temperature (<10°C) in autumn. Compared to urine alone, DI and DCD applied 5 days prior to urine application in autumn significantly reduced NO 3 - leaching by 58% and 43%, respectively since the leaching events occurred during the time when these inhibitors were effective (1-2 weeks for nBTPT and 4-6 weeks for DCD). Neither the DI nor DCD had any such significant effect on NO 3 - leaching losses after their spring application because the leaching events occurred 3-5 months after inhibitor application, which was beyond the time that these inhibitors could be effective. Pasture productivity was only significantly increased by the DI after autumn application, but no significant trend was observed after spring application. These results suggest that DI applied in solid form prior to grazing has the most potential to reduce the 3 key N losses in grazed pastoral system; and it therefore warrants further research to improve its longevity to control N losses for a longer period. © 2012 Elsevier B.V.


Dawar K.,University of Canterbury | Zaman M.,Ballance Agri Nutrients Ltd New Zealand | Rowarth J.S.,Massey University | Blennerhassett J.,Ballance Agri Nutrients Ltd New Zealand | Turnbull M.H.,University of Canterbury
Agriculture, Ecosystems and Environment | Year: 2011

A field lysimeter/mini plot experiment was established in a silt loam soil near Lincoln, New Zealand, to investigate the effectiveness of urea fertilizer in fine particle application (FPA), with or without the urease inhibitor N-(n-butyl) thiophosphoric triamide (NBPT - "Agrotain"), in decreasing nitrogen (N) losses and improving N uptake efficiency. The five treatments were: control (no N) and 15N-labelled urea, with or without NBPT, applied to lysimeters or mini plots (unlabelled urea), either in granular form to the soil surface or in FPA form (through a spray) at a rate equivalent to 100 kgNha-1. Gaseous emissions of ammonia (NH 3) and nitrous oxide (N 2O), nitrate (NO 3 -) leaching, herbage dry-matter (DM) production, N-response efficiency, total N uptake and total recovery of applied 15N in the plant and soil varied with urea application method and with addition of NBPT. Urea with NBPT, applied in granular or FPA form, was more effective than in application without NBPT: N 2O emissions were reduced by 7-12%, NH 3 emissions by 65-69% and NO 3 - leaching losses by 36-55% compared with granular urea. Urea alone and with NBPT, applied in FPA form increased herbageDMproduction by 27% and 38%, respectively. TheN response efficiency increased from 10 kgDMkg-1 of applied N with granular urea to 19 kgDMkg-1 with FPA urea and to 23 kgDMkg-1 with FPA urea plus NBPT. Urea applied in FPA form resulted in significantly (P < 0.05) higher 15N recovery in the shoots compared with granular treatments and this was improved further when urea in FPA form was applied with NBPT. These results suggest that applying urea with NBPT in FPA form has potential as a management tool in mitigating N losses, improving N-response efficiency and increasing herbage DM production in intensive grassland systems. © 2011 Elsevier B.V.


Zaman M.,Ballance Agri Nutrients Ltd New Zealand | Zaman S.,University of Canterbury | Nguyen M.L.,International Atomic Energy Agency | Smith T.J.,Ballance Agri Nutrients Ltd New Zealand | Nawaz S.,Gomal University
Science of the Total Environment | Year: 2013

This field study evaluated the effects of applying a combination of urease (UI) and nitrification inhibitors (NI) on ammonia (NH3) and nitrous oxide (N2O) emission from urine patches, using zeolite, single superphosphate (SSP) and urea fertilizer as a carrier. The trial was conducted on a Typic Haplustepts silt loam soil, near Lincoln, Canterbury, New Zealand during 2009-11. The treatments in 2009 included: a control (no urine or inhibitor), urine alone at 600kgNha-1, and urine with either double inhibitor (DI) a mixture (1:7 ratio w/w) of UI (N-(n-butyl) thiophosphoric triamide (nBTPT - trade name Agrotain®sss) and NI, dicyandiamide (DCD) or DCD alone at 10kgha-1 using zeolite and SSP as carriers. In 2010 trials, both zeolite and urea were used as carriers for DI and DCD. DI-zeolite and DI-urea were equally effective and reduced the average NH3 losses from applied urine over two years by 34.6% in autumn and 40% in spring respectively. The nBTPT in DI-SSP was decomposed by the free acid produced during its dissolution and therefore increased NH3 emission as does DCD alone. DCD consistently increased NH3 emissions by 39% and 15.6% in autumn and spring respectively. Spring application resulted in NH3-N losses of 16.9% as a percentage of the total N applied compared to 8.4% in autumn. Over the two years, the DI reduced N2O emissions by 53% in autumn and 46% in spring over urine alone treatment; the equivalent reductions for DCD were 42% and 39% for autumn and spring, respectively. These results suggest that applying DI in autumn and spring using zeolite or urea carrier five days prior to grazing has the most potential to reduce NH3 and N2O losses from specific urination event than using DCD alone; and therefore warrants further research to improve its longevity. © 2013 Elsevier B.V.


Dawar K.,University of Canterbury | Zaman M.,Ballance Agri Nutrients Ltd New Zealand | Rowarth J.S.,Massey University | Turnbull M.H.,University of Canterbury
Soil Science and Plant Nutrition | Year: 2015

Two glasshouse-based studies investigated the impact of urea with urease inhibitor N-(n-butyl) thiopho- sphoric triamide (nBTPT — ‘‘Agrotain’’) applied in fine particle application (FPA) or in granular forms, on nitrogen (N) uptake in ryegrass (Lolium perenne L.). Ryegrass was grown from seed in topsoil collected from a pasture site near Lincoln, New Zealand. Fertilizer treatments were applied, either in FPA or in granular form, at a rate equivalent to 25 kg N ha1. Herbage was harvested 42 days after fertilizer application to assess dry matter (DM) production and N uptake. In a separate pot experiment,15N labelled urea (10 atom %), with or without Agrotain, was applied to ryegrass at 25 kg N ha1either to the shoots and leaves only or to the soil surface. After 4 hours, 8 hours, 1, 2, 3, 5, 10 and 21 days, pots were destructively sampled to determine urea hydrolysis, herbage DM and15N uptake. In both experiments, herbage DM yield and N uptake were significantly higher in the FPA treatments than in those receiving granular application. Urea applied with Agrotain in FPA form increased the N-response efficiency (N-RE) by 31% and 96%, respectively, compared with FPA urea or granular urea. N-response efficiency following addition of Agrotain- treated urea in FPA form was even higher than that following addition of other forms of ammonium (NH4) and nitrate (NO3) based fertilizers. Nitrate reductase activity was significantly affected by the added fertilizer treatments and generally decreased with time. Tissue amino acids and NH4and NO3contents were not significantly influenced by any fertilizer treatment. Results from the15N experiment support the hypothesis that Agrotain treatment improved the N-RE of urea applied in FPA form due to a delayed hydrolysis of urea on the leaves and in the soil, thus providing herbage an opportunity to absorb the added urea directly through leaves, cuticles and roots. We conclude that applying urea with Agrotain by FPA method has the potential to increase N-RE further than either granular urea or FPA urea alone © 2012 Japanese Society of Soil Science and Plant Nutrition.


PubMed | University of Western Ontario, University of Calgary and Ballance Agri Nutrients Ltd New Zealand
Type: Journal Article | Journal: Journal of the science of food and agriculture | Year: 2015

Crop yield, vegetative or reproductive, depends on access to an adequate supply of essential mineral nutrients. At the same time, a crop plants growth and development, and thus yield, also depend on in situ production of plant hormones. Thus optimizing mineral nutrition and providing supplemental hormones are two mechanisms for gaining appreciable yield increases. Optimizing the mineral nutrient supply is a common and accepted agricultural practice, but the co-application of nitrogen-based fertilizers with plant hormones or plant growth regulators is relatively uncommon. Our review discusses possible uses of plant hormones (gibberellins, auxins, cytokinins, abscisic acid and ethylene) and specific growth regulators (glycine betaine and polyamines) to enhance and optimize crop yield when co-applied with nitrogen-based fertilizers. We conclude that use of growth-active gibberellins, together with a nitrogen-based fertilizer, can result in appreciable and significant additive increases in shoot dry biomass of crops, including forage crops growing under low-temperature conditions. There may also be a potential for use of an auxin or cytokinin, together with a nitrogen-based fertilizer, for obtaining additive increases in dry shoot biomass and/or reproductive yield. Further research, though, is needed to determine the potential of co-application of nitrogen-based fertilizers with abscisic acid, ethylene and other growth regulators.


Zaman M.,International Atomic Energy Agency | Kurepin L.V.,University of Western Ontario | Catto W.,Ballance Agri Nutrients Ltd New Zealand | Pharis R.P.,University of Calgary
Journal of the Science of Food and Agriculture | Year: 2016

Fertilisation of established perennial ryegrass forage pastures with nitrogen (N)-based fertilisers is currently the most common practice used on farms to increase pasture forage biomass yield. However, over-fertilisation can lead to undesired environmental impacts, including nitrate leaching into waterways and increased gaseous emissions of ammonia and nitrous oxide to the atmosphere. Additionally, there is growing interest from pastoral farmers to adopt methods for increasing pasture dry matter yield which use 'natural', environmentally safe plant growth stimulators, together with N-based fertilisers. Such plant growth stimulators include plant hormones and plant growth promotive microorganisms such as bacteria and fungi ('biostimulators', which may produce plant growth-inducing hormones), as well as extracts of seaweed (marine algae). This review presents examples and discusses current uses of plant hormones and biostimulators, applied alone or together with N-based fertilisers, to enhance shoot dry matter yield of forage pasture species, with an emphasis on perennial ryegrass. © 2015 Society of Chemical Industry © 2016 Society of Chemical Industry.


PubMed | International Atomic Energy Agency, University of Western Ontario, Ballance Agri Nutrients Ltd New Zealand and University of Calgary
Type: Journal Article | Journal: Journal of the science of food and agriculture | Year: 2016

Fertilisation of established perennial ryegrass forage pastures with nitrogen (N)-based fertilisers is currently the most common practice used on farms to increase pasture forage biomass yield. However, over-fertilisation can lead to undesired environmental impacts, including nitrate leaching into waterways and increased gaseous emissions of ammonia and nitrous oxide to the atmosphere. Additionally, there is growing interest from pastoral farmers to adopt methods for increasing pasture dry matter yield which use natural, environmentally safe plant growth stimulators, together with N-based fertilisers. Such plant growth stimulators include plant hormones and plant growth promotive microorganisms such as bacteria and fungi (biostimulators, which may produce plant growth-inducing hormones), as well as extracts of seaweed (marine algae). This review presents examples and discusses current uses of plant hormones and biostimulators, applied alone or together with N-based fertilisers, to enhance shoot dry matter yield of forage pasture species, with an emphasis on perennial ryegrass.

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