Centre for Soil and Environmental Research
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Item Effect of soil moisture status and animal treading on N₂O emissions and the effectiveness of a nitrification inhibitor mitigation technology(New South Wales Department of Primary Industry, 2013-09) Di, Hong J.; Cameron, Keith C.; Ball, B.; Podolyan, Andriy; He, J.; Michalk, D. L.; Millar, G. D.; Badgery, W. B.; Broadfoot, K. M.Nitrous oxide (N₂O) is a potent greenhouse gas with a long term global warming potential about 298 times that of carbon dioxide (CO₂). In grazed grassland, most of the N₂O is emitted from nitrogen (N) excreted by the grazing animal, particularly in the animal urine. When the soil is wet, such as that in winter grazing conditions, animal grazing can cause soil structural damage, leading to soil compaction. The combination of a wet soil plus soil compaction is particularly conducive for N₂O production. A nitrification inhibitor technology using dicyandiamide (DCD) has been developed to reduce N₂O emissions from grazed grassland (Di and Cameron 2002; 2003). However, the efficacy of this technology under wet and compact soil conditions has not been well studied. The objectives of this study were to determine: (1) The impact of soil moisture content on the abundance of ammonia oxidizers and N₂O emissions; (2) the impact of animal treading on N₂O emissions; and (3) The effectiveness of the nitrification inhibitor DCD in reducing N₂O emissions, as affected by soil moisture status and animal treading.Item Urine patch area coverage of an intensively stocked dairy pasture(Lincoln University., 2010-08) Moir, James L.; Cameron, Keith C.; Di, Hong J.; Fertsak, UlrikeThe objective of this study was to develop a new method to quantify seasonal and annual urine patch area coverage under an intensive dairy farming system.Item 15N and 18O values of soil emitted N2O from a New Zealand pasture amended with lactose-depleted dairy factory effluent and urea - preliminary results(Lincoln University. Centre for Soil and Environmental Quality) Ford, Christopher I.; Bol, R.; Clough, Timothy J.; Sherlock, Robert R.; Di, Hong J.; Cameron, Keith C.The study presents some preliminary data of the influence of LD-DFE on the 18O and 15N values of N2O from a New Zealand pasture soil.Item The spatial distribution and area coverage of urine depositions in grazed pastures in NZ(Lincoln University., 2006) Moir, James; Fertsak, Ulrike; Cameron, Keith; Di, HongIn grazed pasture systems, grazing animals deposit urine and dung causing high nutrient loading to a relatively small proportion of the total grazed area. The majority of ingested nitrogen (N) is excreted in urine, and high N loading in the urine patch is of particular environmental concern because of the potential for leaching of soil nitrate N from the patch and the subsequent potential degradation of ground and surface water quality. Animal stocking rate and stock type are key factors driving the quantity of nutrient, especially N, which may be deposited as urine and dung to pasture soils. Therefore the total paddock area receiving urine deposits in any time period is critical to the understanding of nutrient cycling and nutrient loss in grazed pasture systems. Some theoretical estimates of this critical area coverage value have been made by researchers, but quantitative field spatial data is scarce and seasonal components have often been ignored in earlier estimates. Consequently, much variability and uncertainty still surrounds the current estimate of annual urine patch area coverage in grazed pasture systems, and how area coverage varies with different stocking rates and stock type. A new method using global positioning system (GPS) and geographic information system (GIS) technology was developed and successfully used to quantify the spatial distribution and area coverage of urine patches deposited by grazing animals. Accurate measurements of urine patches over a period of twelve months were made for two farm types, which are typical of New Zealand grazed pasture systems: (i) an irrigated dairy farm and (ii) a sheep and beef hill country farm. At two field sites urine patch areas were visually identified from the enhanced pasture growth in those areas and their area and spatial location recorded with GPS at regular time intervals. The GPS data was analysed in a GIS system. These data were then used to calculate seasonal and annual urine patch coverage in the paddocks on an area basis. On the dairy farm at an effective stocking rate of 3.5 cows ha-1 (c. 32 standard stock units [ssu] ha-1) the observed annual urine patch area coverage was 22%. The mean urine patch radius was 30.5 cm. Mean urine patch radius ranged from 27 to 35 cm between seasons. The observed average urine patch area was 0.28 m2. Urine patch coverage was shown to increase with increased stocking rate (cows ha-1 or cow grazing days). For the sheep and beef farm at an effective stocking rate of 15.1 ssu ha-1 the observed annual urine patch area coverage was 16.8% for the study paddock. Average urine patch coverage was 19.3% and 14.3 % on flat areas (0 – 3°) and hill slopes (7 – 15°) respectively. This result confirms that a higher grazing pressure occurred on flat areas than on hill slopes. For the observed one-year period, the mean urine patch radius was 25 cm. Mean urine patch radius ranged from 19 to 29 cm between seasons. The observed average urine patch area was 0.19 m2. This study has successfully used GPS and GIS technology to make initial measurements of the spatial distribution and area coverage of urine depositions in grazed dairy and sheep and beef pastures in New Zealand. Field measurements for this study are ongoing.Item Verification of the implementation of CWM1 in the HYDRUS Wetland Module(Lincoln University, 2013) Palfy, Tamas GaborThe Constructed Wetland Model N°1 (CWM1) is a numerical biokinetic model describing microbial transformation and degradation processes in subsurface flow constructed wetlands. In this master thesis the CWM1 implementation in the HYDRUS wetland module was verified using data from previously conducted controlled environment column experiments. These twenty day long batch experiments used synthetic wastewater and three different plant species (Carex rostrata Stokes, Schoenoplectus acutus Muhl. Ex Bigelow and Typha latifolia L.) in addition to unplanted replicates at four different temperatures. The minimum number of adjusted parameters between the sixteen simulated columns was targeted, and it was found that: (1) initial bacterium concentrations, (2) initial adsorbed ammonia nitrogen concentrations, and (3) root oxygen loss rate for each simulation inevitably needed to be set separately. For all other parameters the same values have been used. Some biokinetic parameters had to be adapted during calibration to match measured data. This was required to allow anaerobic, anoxic and aerobic processes to run parallel and explained by the local effect of root zone re-aeration. The simulation results were evaluated by conventional visual and numerical and a new goodness of fit analysis method, deflection analysis. The new method was introduced to compare simulations to measured data with standard deviation. Simulated contaminant concentrations had a very good fit to measured values of NH₄-N and SO₄-S and a reasonable good fit to measured values of COD versus time.