• Authors:
    • Marshall, A.
    • Mills, A.
    • Moot, D.
    • Edwards, G.
  • Source: Proceedings of the New Zealand Grassland Association
  • Volume: 69
  • Year: 2007
  • Summary: Lucerne sown immediately or after different forage crop sequences was investigated as a pasture option for post forestry conversion. In this experiment superphosphate and lime were applied in March 2005 before final seedbed preparation and establishment of seven cropping sequences; (1) lucerne sown in April 2005; (2-5) greenfeed cereals (oats or triticale) sown in April 2005 followed by lucerne in October 2005 with or without a rape cover crop; (6-7) winter fallow followed by glyphosate presowing in October 2005 or March 2006. After all crop sequences, lucerne was successfully established and provided 100% control of woody and annual weeds. Average lucerne dry matter (DM) yield was ~7.1 t DM/ha/yr for crops after a cereal. The last crop established also contained no woody weeds but produced 10.0 t DM/ha less over the 2 years due to the long (12 month) fallow. Lucerne sown in April 2005 had to be reestablished the following October. Thus, provided soil temperatures were adequate, lucerne was successfully spring and autumn sown after plantation forests. Lucerne offers flexibility for grazing or conserving in commercial conversions where internal fences and stock water supply are often, initially, inadequate for intensive pasture management.
  • Authors:
    • Sherlock, R. R.
    • Cameron, K. C.
    • Di, H. J.
  • Source: Soil Use and Management
  • Volume: 23
  • Issue: 1
  • Year: 2007
  • Summary: Nitrous oxide (N2O) is a potent greenhouse gas and, in New Zealand, about one-third of the total greenhouse gas emissions from the agricultural sector are of N2O, mostly derived from animal excreta in grazed pasture soils. The aim of this study was to determine the effectiveness of a nitrification inhibitor, dicyandiamide (DCD), in reducing N2O emissions from animal urine patches in four different soils located in different regions of New Zealand with different soil, climatic and management conditions. The four soils are Templeton fine sandy loam and Lismore stony silt loam in Canterbury in the South Island, Horotiu silt loam in the Waikato region and Taupo pumice sand near Lake Taupo, both in the North Island. Results showed that the application of a fine-particle suspension nitrification inhibitor, DCD, to grazed pasture soils was very effective in reducing N2O emissions in all four different soils. Total N2O emissions (over 69-137 days) from animal urine patches ranged from 1 to 20.9 kg N2O-N ha-1 without DCD. These were reduced to 0.31-5.7 kg N2O-N ha-1 by the use of DCD, representing 61-73% reductions (with an average of 70% reduction). The N2O-N emission factor from animal urine N, EF3, was reduced from an average of 0.9 to 0.3% by the use of DCD. These results demonstrate the potential of using nitrification inhibitors to mitigate N2O emissions in a wide range of grazed pasture soils under different climatic and management conditions.
  • Authors:
    • Sherlock, R. R.
    • Kelliher, F. M.
    • Buckthought, L. E.
    • Clough, T. J.
  • Source: Global Change Biology
  • Volume: 13
  • Year: 2007
  • Summary: There is uncertainty in the estimates of indirect nitrous oxide (N2O) emissions as defined by the Intergovernmental Panel on Climate Change (IPCC). The uncertainty is due to the challenge and dearth of in situ measurements. Recent work in a subtropical stream system has shown the potential for diurnal variability to influence the downstream N transfer, N form, and estimates of in-stream N2O production. Studies in temperate stream systems have also shown diurnal changes in stream chemistry. The objectives of this study were to measure N2O fluxes and dissolved N2O concentrations from a spring-fed temperate river to determine if diurnal cycles were occurring. The study was performed during a 72 h period, over a 180m reach, using headspace chamber methodology. Significant diurnal cycles were observed in radiation, river temperature and chemistry including dissolved N2O-N concentrations. These data were used to further assess the IPCC methodology and experimental methodology used. River NO3-N and N2O-N concentrations averaged 3.0mg L-1 and 1.6 lgL-1, respectively, with N2O saturation reaching a maximum of 664%. The N2O-N fluxes, measured using chamber methodology, ranged from 52 to 140 lgm-2 h-1 while fluxes predicted using the dissolved N2O concentration ranged from 13 to 25 lgm-2 h-1. The headspace chamber methodology may have enhanced the measured N2O flux and this is discussed. Diurnal cycles in N2O% saturation were not large enough to influence downstream N transfer or N form with variability in measured N2O fluxes greater and more significant than diurnal variability in N2O% saturation. The measured N2O fluxes, extrapolated over the study reach area, represented only 6104 % of the NO3-N that passed through the study reach over a 72 h period. This is only 0.1% of the IPCC calculated flux.
  • Authors:
    • Hedley, M. J.
    • Bolan, N. S.
    • Saggar, S.
    • Bhandral, R.
  • Source: Soil & Tillage Research
  • Volume: 94
  • Issue: 2
  • Year: 2007
  • Summary: Animal trampling is one of the main factors responsible for soil compaction under grazed pastures. Soil compaction is known to change the physical properties of the soil thereby affecting the transformation of nitrogen (N) and the subsequent of release of N as nitrous oxide (N2O). The form of N source added to these compacted soils further affects N emissions. Here we determine the interactive effects of soil compaction and form of N sources (cattle urine and ammonium, nitrate and urea fertilizers) on the loss of N through N2O emission from grassland soil. Overall, soil compaction caused a seven-fold increase in the N2O flux, the total N2O fluxes for the entire experimental period ranged from 2.62 to 61.74 kg N2O-N ha-1 for the compacted soil and 1.12 to 4.37 kg N2O-N ha-1 for the uncompacted soil. Among the N sources, the highest emissions were measured with nitrate application, emissions being 10 times more than those from other N sources for compacted soil, suggesting that the choice of N fertilizer can go a long way in mitigating N2O emissions in compacted grasslands.
  • Authors:
    • Paustian, K.
    • Lokupitiya, E.
  • Source: Journal of Environmental Quality
  • Volume: 35
  • Year: 2006
  • Summary: Parties to the United Nations Framework Convention on Climate Change (UNFCCC) are required to submit national greenhouse gas (GHG) inventories, together with information on methods used in estimating their emissions. Currently agricultural activities contribute a significant portion (approximately 20%) of global anthropogenic GHG emissions, and agricultural soils have been identified as one of the main GHG source categories within the agricultural sector. However, compared to many other GHG sources, inventory methods for soils are relatively more complex and have been implemented only to varying degrees among member countries. This review summarizes and evaluates the methods used by Annex 1 countries in estimating CO2 and N2O emissions in agricultural soils. While most countries utilize the Intergovernmental Panel on Climate Change (IPCC) default methodology, several Annex 1 countries are developing more advanced methods that are tailored for specific country circumstances. Based on the latest national inventory reporting, about 56% of the Annex 1 countries use IPCC Tier 1 methods, about 26% use Tier 2 methods, and about 18% do not estimate or report N2O emissions from agricultural soils. More than 65% of the countries do not report CO2 emissions from the cultivation of mineral soils, organic soils, or liming, and only a handful of countries have used country-specific, Tier 3 methods. Tier 3 methods usually involve process-based models and detailed, geographically specific activity data. Such methods can provide more robust, accurate estimates of emissions and removals but require greater diligence in documentation, transparency, and uncertainty assessment to ensure comparability between countries. Availability of detailed, spatially explicit activity data is a major constraint to implementing higher tiered methods in many countries.
  • Authors:
    • Nowicki, B. L.
    • Leonard, R.
    • Sherlock, R. R.
    • Bertram, J. E.
    • Clough, T. J.
  • Source: Global Change Biology
  • Volume: 12
  • Issue: 2
  • Year: 2006
  • Summary: There is considerable uncertainty in the estimates of indirect N2O emissions as defined by the intergovernmental panel on climate change's (IPCC) methodology. Direct measurements of N2O yields and fluxes in aquatic river environments are sparse and more data are required to determine the role that rivers play in the global N2O budget. The objectives of this research were to measure the N2O fluxes from a spring-fed river, relate these fluxes to the dissolved N2O concentrations and NO3-N loading of the river, and to try and define the indirect emission factor (EF5-r) for the river. Gas bubble ebullition was observed at the river source with bubbles containing 7.9 lLN2OL-1. River NO3-N and dissolved N2O concentrations ranged from 2.5 to 5.3mg L-1 and 0.4 to 1.9 lgN2O-NL-1, respectively, with N2O saturation reaching 404%. Floating headspace chambers were used to sample N2O fluxes. N2O-N fluxes were significantly related to dissolved N2O-N concentrations (r2 = 530.6) but not to NO3-N concentrations. The N2O-N fluxes ranged from 38-501 microg m-2 h-1 , averaging 171 lgm-2 h-1( SD 85) overall. The measured N2O-N fluxes equated to an EF5-r of only 6.6% of that calculated using the IPCC methodology, and this itself was considered to be an overestimate because of the degassing of antecedent dissolved N2O present in the groundwater that fed the river.
  • Authors:
    • Di, H. J.
    • Stewart, A.
    • Condron, L. M.
    • Stark, C.
    • O'Callaghan, M.
  • Source: New Zealand Journal of Crop and Horticultural Science
  • Volume: 34
  • Issue: 3
  • Year: 2006
  • Summary: Farming practices can have significant effects on important soil processes, including nitrogen (N) dynamics and nitrate leaching. A lysimeter experiment was conducted to determine differences in N leaching resulting from past and current crop management practices. Intact monolith lysimeters (50cm diam. x 70cm deep) were taken from sites of the same soil type that had either been under long-term organic or conventional crop management. These were then managed according to established organic and conventional practices over 2% years using the same crop rotation (barley (Hordeum vulgare L.), maize (Zea mays L.), rape (Brassica napus L. ssp. oleifera) plus a lupin green manure (Lupinus angustifolius L.)) and two fertiliser regimes, resulting in four treatments based on soil management history and current fertilisation strategy. Dry matter yield of each crop was determined after harvest and leachates were collected after significant rainfall events and analysed for total mineral N concentrations. Mineral fertilisation had a clear positive effect on yields of the first crop, whereas there were no considerable differences between treatments for the last crop owing to a significant positive effect of green manure incorporation on yields. Although there was a trend of lower mineral N leaching from organically fertilised soils (organic management: 24.2 kg N ha(-1); conventional management: 28.6), differences in N losses were not statistically significant between treatments. This shows that under the experimental conditions, leaching losses and crop yields were more strongly influenced by crop rotation and green manuring than by the presence or absence of mineral fertilisation. Overall, the study highlights the benefits of including a green manure in the crop rotation of any farming system.
  • Authors:
    • Kenny, S. N.
    • O'Brien, G. B.
    • Ward, G. N.
    • Jacobs, J. L.
    • Chapman, D. F.
    • Beca, D.
    • McKenzie, F. R.
  • Source: Proceedings of the New Zealand Grassland Association
  • Volume: 68
  • Year: 2006
  • Summary: Continued improvements in home grown forage consumption are needed to support the long-term profitability of the dairy industry in southern Australia. Most home grown forage currently comes from perennial ryegrass pastures, which have significant limitations in the southern Australia environment. These limitations threaten future productivity gains, and we therefore consider opportunities for using other plant species. Data on the production of alternative perennial grasses, brassica summer crops, C4 summer crops and winter cereals grown for whole-crop silage are limited and generally show large variation in yields between sites and years. Simulation models suggest that, once the base ryegrass pasture is well-utilised, incorporating complementary forages can return $70-$100/ha extra operating profit for every additional tonne of home grown forage DM consumed per ha. Double cropping (winter cereal or annual ryegrass followed by a summer crop of turnips or maize) and summer-active pastures such as tall fescue show particular promise. Further information is required on how to integrate these forages into whole farm feeding systems to realise the additional profit with manageable business and environmental risk.
  • Authors:
    • Darwin, R.
  • Source: Climatic Changer
  • Volume: 66
  • Issue: 1-2
  • Year: 2004
  • Authors:
    • Luo, J.
    • Hedley, C. B.
    • Bhandral, R.
    • Bolan, N. S.
    • Saggar, S.
  • Source: New Zealand Journal of Agricultural Research
  • Volume: 47
  • Issue: 4
  • Year: 2004
  • Summary: The agricultural sector in New Zealand is the major contributor to ammonia (NH3), nitrous oxide (N2O), and methane (CH4) emissions to the atmosphere. These gases cause environmental degradation through their effects on soil acidification, eutrophication, and stratospheric ozone depletion. With its strong agricultural base and relatively low level of heavy industrial activity, New Zealand is unique in having a greenhouse gas emissions inventory dominated by the agricultural trace gases, CH4 and N2O, instead of carbon dioxide which dominates in most other countries. About 96% of this anthropogenic CH4 is emitted by ruminant animals as a by-product during the process of enteric fermentation. Methane is also produced by anaerobic fermentation of animal manure and many other organic substrates.