Hamilton, New Zealand
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McDowell R.W.,Agresearch Ltd. | Littlejohn R.P.,Agresearch Ltd. | Blennerhassett J.D.,Summit Quinphos NZ Ltd
Soil Use and Management | Year: 2010

Two catchments were used to test the hypothesis that using reactive phosphate rock (RPR), a low water soluble fertilizer, instead of superphosphate, could decrease phosphorus (P) export in streams. The sheep-grazed catchments, each ca. 12 ha in size, received 20-25 kg P/ha either as RPR or superphosphate for 3 yr. Filterable (<0.45 μm) reactive P (FRP) and total P (TP) in stream samples were then compared against two subsequent years when both catchments received 20 kg P/ha as superphosphate. On average, during the 5-yr study, loads of FRP and TP in stream flow were low (110 g FRP/ha and 358 g TP/ha), typical of dry sheep-grazed hill country. However, FRP (58%) and TP (38%) in stream flow were significantly less when RPR was applied instead of superphosphate. Where appropriate climatic and soil conditions exist to maintain agronomic targets, RPR could be used to decrease P export in streams. © 2010 The Authors. Journal compilation © 2010 British Society of Soil Science.

Zaman M.,Summit Quinphos NZ Ltd | Nguyen M.L.,International Atomic Energy Agency
Agriculture, Ecosystems and Environment | Year: 2010

To understand the effect of soil amendments (i.e. lime or zeolite) on nitrous oxide (N2O) and dinitrogen (N2) emissions from pastoral soil, a field experiment was conducted using Topehaehae silt loam soil (Aeric Haplaquent) in a dairy catchment area at Toenepi, Hamilton, New Zealand during late September-November 2003. Field plots were treated with 2 N sources: cow urine or potassium nitrate (KNO3) each applied at 200 kg N ha-1 rate with and without added lime or zeolite (clinoptilonite). The control (no N) plots also received lime or zeolite. Each treatment had 3 replicates. Nitrous oxide and N2 emissions were measured periodically from field plots by taking intact soil cores, followed by incubating them in 1 L gas jars with or without acetylene (C2H2) under field conditions. Soil samples were also taken to determine soil pH and changes in soil ammonium (NH4+) and nitrate (NO3-) concentrations. Total N2O emission was significantly higher from urine treated soils (7622 g N2O-N ha-1) than from KNO3 treated soil (3479 g N2O-N ha-1) probably because of N2O production by both nitrifier-denitrification and denitrification in the former. Zeolite significantly reduced total N2O emissions by 11% from urine treated soils probably because of NH4+ sorption by zeolite; while it had no such effect on N2O emission in KNO3 treated soils. Lime did not have any effect on N2O emission in either urine or KNO3 treated soils. Total N2 emission was significantly higher from urine treated soil (1486 g N2O-N ha-1) than from KNO3 treated soil (795 g N2O-N ha-1). Lime increased N2 emissions by 11%, 6% and 101% in urine, KNO3 treated soils and in the control, respectively; while zeolite had no such effect. N2O:N2 ratios were higher for urine treated soils followed by KNO3 treated soils; while the lowest N2O:N2 ratios were observed in no N treatments. Lime lowered N2O:N2 ratios in urine treated soils and in the control treatment (no N), but had no such effect in KNO3 treated soils. Changes in soil mineral N suggest low soil NH4+ and reduced nitrification with zeolite in urine treated soil, while no such effect was observed in KNO3 treated soils. Lime increased soil pH in all treatments. Lime applied with urine increased both soil NH4+ and NO3- concentrations but no such trend was seen in KNO3 treated soil. The results indicate that zeolite reduced N2O emission while lime increased N2 emissions and lowered N2O:N2 ratios during a short-term field experiment therefore long-term field studies are required to assess zeolite life cycle and its potentials as a mitigating tool for N2O emissions from urine patches in grazed pasture system. © 2009 Elsevier B.V. All rights reserved.

Giltrap D.L.,Landcare Research | Singh J.,Landcare Research | Singh J.,Massey University | Saggar S.,Landcare Research | Zaman M.,Summit Quinphos NZ Ltd.
Agriculture, Ecosystems and Environment | Year: 2010

New Zealand's grazed pastures receive large quantities of nitrogen (N) inputs from animal excreta and chemical fertilisers. While N promotes pasture growth, surplus N can cause environmental problems by leaching into waterways or by nitrifying and denitrifying to form the greenhouse gas, nitrous oxide (N2O). Various approaches have been attempted to mitigate the economic and environmental impacts of N losses. One such approach is the use of nitrification inhibitors (NIs). The value of these inhibitors in mitigating N losses in grazed pasture partly depends on their rate of biodegradation and persistence in soils. A simplified model of nitrification inhibition was used with the process-based NZ-DNDC model to investigate the effect of NI dicyandiamide (DCD) on transformations of N to nitrate (NO3-) and subsequent reduction to N2O in a grazed pasture system receiving cow urine at application rate of 600 kg N/ha. The modelled N2O emissions with and without DCD application were comparable to the field measurements on Tokomaru silt loam soil, assuming that the effect of the DCD was to decrease the nitrification rate by about 70%. An attempt was also made to simulate the effect of the biological degradation of DCD by exponentially decreasing the inhibitor effectiveness with time. However, this did not improve the fit of the modelled N2O emissions over the 50-day measurement period. Further refinements including the effects of soil type, and changes in NI concentration throughout the soil profile over time and its subsequent effect on N transformations will be developed as more experimental data become available. © 2009 Elsevier B.V. All rights reserved.

Minimizing nitrogen (N) losses via ammonia (NH3) and nitrous oxide (N2O) emissions into the atmosphere and nitrate (NO3-) leaching into surface and ground waters from intensively grazed pastures is essential for environmental protection worldwide. Applying urease inhibitor such as N-(n-butyl) thiophosphoric triamide (nBPT) or (Agrotain) and nitrification inhibitor dicyandiamide (DCD) to grazed pastures has the potential to mitigate such N losses. A lysimeter/mini plot experiment, using Paparua silt loam soil near Lincoln, Canterbury New Zealand, was conducted to quantify these N losses during May 2007 to July 2008. The nine treatments were: cow urine only applied at an equivalent rate of 600 kg N ha-1, urine + DCD at 5 kg ha-1, urine + DCD at 7 kg ha-1, urine + DCD at 10 kg ha-1, urine + double inhibitor (DI), i.e. both Agrotain and DCD applied at 1 L ha-1 and 7 kg ha-1, respectively (or 1:7 of v/w basis), urine + DI (1:10), urine + DI (2:7), urine + DI (2:10) and the control (no urine). These treatments were randomly applied to one set of lysimeters or mini plots in May as autumn and then to another set of lysimeters or mini plots in August as spring applications. Additional nine lysimeters received DCD only at rates equivalent to 5, 7 and 10 kg ha-1 in autumn to see if DCD has any effect on NO3- leaching and pasture production and N uptake from non-urine patches in autumn. Gaseous emissions of NH3 and N2O, NO3- leaching and pasture production and N uptake varied with the types and rates of the applied inhibitors during the two seasons. DCD applied at 7 and 10 kg ha-1 rates with urine was more effective than its lower rate of 5 kg ha-1 and reduced N2O emissions by 37-53% (autumn) and 47% (spring), NO3- leaching losses by 57-55% (autumn) and 26-10% (spring) compared with urine alone. However DCD increased NH3 emissions by 41% and 18% compared with urine alone treatment after autumn and spring, respectively. DCD applied at higher rates also increased pasture dry matter by 9% and 12% and N uptake by 12% and 6% after autumn and spring applications, respectively. However DCD applied at different rates without urine in autumn had no such effect on either NO3- leaching or pasture dry matter yield or N uptake. The DI at 1:7 ratio was more effective than the higher rates of DI and DCD in reducing losses of NH3 (48% and 51%), N2O (55% and 63%) and NO3- leaching (56% and 42%) as well as increasing pasture production (13% and 17%) and N uptake (7% and 18%) compared with urine alone treatment in autumn and spring, respectively. These results suggest that applying Agrotain + DCD at a ratio of 1:7 (v/w) may provide the best option for both mitigating N losses and improving pasture production in intensively grazed systems. © 2009 Elsevier B.V. All rights reserved.

Dawar K.,University of Canterbury | Zaman M.,Ballance Agri Nutrients Ltd | Rowarth J.S.,Massey University | Blennerhassett J.,Summit Quinphos NZ Ltd | Turnbull M.H.,University of Canterbury
Biology and Fertility of Soils | Year: 2011

A glasshouse-based study was conducted to investigate the effect of urease inhibitor N-(n-butyl) thiophosphoric triamide ('Agrotain') and irrigation on urea hydrolysis and its movement in a Typic Haplustept silt loam soil (in 72 repacked soil cores). Half (36) of these cores were adjusted to soil moisture contents of 80% field capacity (FC) and the remaining 36 cores to 50% FC. Granular urea with or without Agrotain was applied at a rate equivalent to 100 kg N ha-1. There were three replicates to these two sets of soil cores. After 1 day of treatment application, soil cores of the 50% FC were adjusted to 80% FC by applying surface irrigation. Twelve pots were destructively sampled at each day after 1, 2, 3, 4, 7 and 10 days of treatment application to determine urea hydrolysis and its lateral and vertical movement in different soil layers. Agrotain-treated urea delayed urea hydrolysis during the first 7 days after its application. This delay in urea hydrolysis caused by Agrotain enabled added urea, which is uncharged, to move away from the surface soil layer to the sub-surface soil layer both vertically and laterally. In contrast, most urea hydrolysed to soil NH4+ within 2 days of its application. Irrigation after 1 day resulted in further urea movement both laterally and vertically from the surface soil layer (0-10 mm) to the sub-soil layer (30-50 mm) in Agrotain-treated urea. These results suggest that Agrotain delayed urea hydrolysis and allowed more time for rainfall or irrigation to move added urea from the surface layer to sub-soil layers where it is likely to make good contact with plant roots. This distribution of urea in the rooting zone has the potential to enhance N use efficiency and minimize N losses associated with ammonia volatilization from surface-applied urea. © 2010 Springer-Verlag.

Dawar K.,University of Canterbury | Zaman M.,Summit Quinphos NZ Ltd | Rowarth J.S.,Massey University | Blennerhassett J.,Summit Quinphos NZ Ltd | Turnbull M.H.,University of Canterbury
Crop and Pasture Science | Year: 2010

Improving nitrogen (N)-use efficiency of applied urea is critical to maximise its uptake and decrease environmental impact. Two glasshouse-based studies were conducted to investigate the potential of incorporating urea fertiliser with urease inhibitor (N-(n-butyl) thiophosphoric triamide (NBPT) or 'Agrotain') to enhance fertiliser N uptake efficiency. Topsoil (00.075m, Typic Haplustepts silt loam) from a pasture site near Lincoln, Canterbury, New Zealand, was collected and ryegrass (Lolium perenne L.) was grown from seed in standard plant trays maintained at soil moisture contents of 7580% field capacity. Urea, Agrotain-treated urea, ammonium nitrate, ammonium sulfate, or sodium nitrate, were applied in granular form at rates equivalent to 25 or 50kgN/ha with 4 replicates. Herbage was harvested 21 and 42 days after application of treatments to assess dry matter (DM) production, N uptake, leaf amino acid, ammonium (NH4+) and nitrate (NO 3-) concentrations, and nitrate reductase activity (NRA). In a separate pot experiment, granular 15N urea (10 atom%) with or without Agrotain was applied to ryegrass at 25kgN/ha. At 0.5, 1, 2, 3, 5, 10, and 21 days after treatment application, 3 pots per treatment were destructively sampled to determine urea hydrolysis, herbage DM, and 15N uptake. In both experiments, Agrotain-treated urea improved bio-availability of added N and resulted in significantly higher herbage DM yield and N uptake than urea alone or other forms of N fertilisers. Agrotain-treated urea applied at 25kgN/ha increased N response by 66% compared with urea alone (and by greater proportions compared with the other fertiliser forms). Agrotain-treated urea applied at 25kgN/ha produced significantly higher uptake efficiency (13g DM/g of applied N) than at 50kgN/ha (5g DM/g of applied N). Tissue amino acids, NH 4+ and NO3- contents, and NRA were not significantly influenced by any type of fertiliser. Results from the 15N experiment support the suggestion that a delay in urea hydrolysis by Agrotain provided an opportunity for direct plant uptake of an increased proportion of the applied urea-N than in the case of urea alone. Treating urea with Agrotain thus has the potential to increase N-use efficiency and herbage production. © 2010 CSIRO.

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