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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. Source

Zaman M.,Ballance Agri Nutrients Ltd New Zealand | Zaman S.,University of Canterbury | Quin B.F.,Quin Environmentals NZ Ltd | Kurepin L.V.,University of Western Ontario | And 3 more authors.
Journal of Soil Science and Plant Nutrition | Year: 2014

A one year field experiment was conducted to assess the efficiency of urea fertilizer applied to pasture near Lincoln University, New Zealand. Urea with or without (±) molybdenum (Mo) were applied to field plot, with a urease inhibitor [N-(n-butyl) thiophosphoric triamide (nBTPT), nBTPT + elemental sulphur (S), and nitrification inhibitor dicyandiamide (DCD) + nBTPT defined as a double inhibitor (DI) in spring 2005. Mo was sprayed at the rate of 50 g Mo/ha/yr once. Urea ± various inhibitor and S treatments were broadcast at a rate of 30 kg N/ha 5 times over one year. The Mo alone treatment increased pasture dry matter (PDM) yield by 8.9%. Molybdenum, when applied together with urea+nBTPT+S, urea+nBTPT and urea alone, caused an initial depression in PDM yield by 14.2, 13 and 5.6% respectively. However, these depressions in yield disappeared from the second pasture cut. Over a one year period, Mo applied with urea+nBTPT, urea+DI and urea+nBTPT+S produced 18179, 16716 and 18253 kg DM ha-1 respectively, compared to 16171 kg ha-1 for urea+Mo. Pastures which received no Mo, but were treated with urea+nBTPT+S, or urea+nBTPT produced 18982 and 18276 kg DM ha-1 respectively, compared to 16363 kg ha-1 for urea alone, giving an increase of 16% and 12% over urea alone. Pastures receiving Mo, together with urea+nBTPT or urea+nBTPT+S, also showed improvement in N uptake and N recovery, compared to urea alone. Applying urea with nBTPT and S have the most potential to improve urea efficiency. Source

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. Source

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. Source

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. Source

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