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Item Plantain-mixed pasture collected in different climatic seasons produced less methane and ammonia than ryegrass–white clover pasture in vitro(CSIRO Publishing, 2025-06-23) Sivanandarajah K; Donaghy D; Molano G; Horne D; Kemp P; Navarrete S; Ramilan T; Pacheco D; Jonker AContext Plantain (PL) is recognised for reducing nitrate leaching and nitrous oxide emissions in pastoral systems. Evidence has shown that cows fed pure PL produced less methane (CH4) than cows fed ryegrass. However, it is unclear if the CH4 reduction can be achieved with PL in mixed pasture. Aim The study evaluated the in vitro rumen fermentation profiles of ryegrass–white clover (RWC) and medium-level PL (PLM, containing ~40% PL) pasture collected during different climatic seasons, to determine whether this inclusion level influences CH4 and rumen ammonia (NH3) production. Methods Substrates were selected from samples with various proportions of PL. Samples were categorised into three climatic seasons (i.e. spring, summer and autumn) and two pasture types (PLM and RWC). Representative samples for these scenarios were tested in an automated in vitro rumen batch culture system for gas, CH4 (mL/g DM) and NH3 (mM/g DM) production. Key results In summer samples, PLM produced approximately 8%, 14% and 19% less CH4 at 12 h, 24 h and potential CH4 production (PCH4), respectively. Although gas production (GP) was similar at 12 and 24 h, PLM had 13% lower potential GP than RWC (P < 0.05). In spring samples, PLM had approximately 11% greater GP and CH4 production at 12 h. For the autumn samples, GP and CH4 production were similar between PLM and RWC (P > 0.05). Net NH3 production from PLM substrates was significantly lower in spring (27%) and autumn (17%) samples, with no differences in summer, despite higher crude protein levels in the selected PLM. Conclusions Compared with RWC, PLM changed rumen fermentation parameters that could translate to potential environmental benefits: PLM produced less net NH3 in spring and autumn samples (27% and 17%, respectively), and up to 19% less CH4 production in summer samples. Implications Incorporating ~40% PL into RWC pasture showed a promising reduction of CH4 emissions and nitrogen losses in vitro. If the in vitro results translate to cows grazing pasture, this could offer greater environmental benefits with minimal input costs. In vitro results suggest that PLM’s potential to mitigate CH4 emissions can be influenced by seasonal variations in pasture quality compared with RWC. However, further animal studies are needed to fully comprehend the CH4 mitigation potential of this forage.Item Evaluation of methane prediction equations for Australian feedlot cattle fed barley and wheat-based diets(CSIRO Publishing, Clayton, Victoria, Australia, 2025-03-13) Almeida AK; McMeniman JP; Van der Saag MR; Cowley FC; Dougherty JContext. Accurately predicting baseline methane (CH4) emissions from beef cattle is of utmost importance for the beef industry and governments alike. It serves as a vital component for accounting as part of national GHG inventories and enables the development and implementation of greenhouse gas (GHG) mitigation strategies. Aims. The aim of this study was to evaluate equations in the literature for predicting CH4 emissions of beef cattle when fed barley and wheat-based diets typical of the Australian feedlot industry. Then, propose the best prediction equation to accurately reflect CH4 emissions of feedlot cattle under Australian conditions. Methods. As part of the project, a large database of methane measurements performed in respiratory calorimeters taken from beef cattle fed a range of feedlot diets was assembled. The dataset included a wide range of factors that are known to impact CH4 production, such as dry matter intake (DMI), ether extract (EE), crude protein (CP), and cell wall components, amongst others. The database contained 713 individual measurements, from 175 animals and 12 studies. Key results. The equation currently utilised by the Australian National Inventory Report had poor accuracy, with mean bias overprediction of 115 g/day (P < 0.01), along with significant linear bias (P < 0.01) and poor precision (r2 = 0.05). The mean bias was 144% of average observed CH4 production. All evaluated equations lacked accuracy and precision in predicting CH4 emissions for the diets fed in this study. Roughage concentrations (DM basis) ranged from 5.54 to 43.0% with a mean of 20.5 ± 11.1%. Given these findings, two specific equations were developed, (1) a CH4 yield equation based on DMI: CH4 (g/day) = 9.89 ± 1.54 × DMI (n = 384; P < 0.01; root mean square error (RMSE) = 32.6 g/day; r2 = 0.85); and (2) an equation based on DMI, neutral detergent fibre (NDF) and EE: CH4 (g/day) = 5.11 ± 1.58 × DMI − 4.00 ± 0.821 × EE + 2.26 ± 0.125 × NDF (n = 384; P < 0.05; RMSE = 22.2 g/day; r2 = 0.91). When validated, the second equation yielded a mean bias of 6.10 g overprediction, with no linear bias, and better fit than any of the literature equations. Conclusions. Based on a thorough model evaluation, our findings support the need to revise current methods to predict CH4 for barley and wheat-based diets. Implications. This study contributes to developing accurate estimations of enteric CH4 emissions for cattle fed barley and wheat-based diets.Item Assessment of biogeochemical transformation of nitrate in shallow groundwater in the agricultural landscape : a thesis presented in partial fulfilment of the requirements for the degree of Master of Science in Soil Science at Massey University, Manawatu, New Zealand(Massey University, 2019) Gonzalez Moreno, Marcela AngelicaIn groundwaters, denitrification or subsurface denitrification (SD) has been identified as a key attenuation process. Where leached nitrate (NO₃⁻) can be reduced to dinitrogen (N₂ — a harmless gas), offering an ecosystem service in terms of reducing water pollution. However, partial denitrification (PD) can release nitrous oxide (N₂ — a greenhouse gas), resulting in a pollution swap from liquid to gaseous pollution and adding to greenhouse gas emission. There is very limited information available about occurrence, characteristics and dynamics of subsurface denitrification in shallow groundwaters across New Zealand agricultural catchments. We studied 6 pastoral farms (DF 1, 2, 3; SC 1, 2, 3; ARM 1, 2, 3; CAM 1, 3; SR 1, 2, 3; BUR 1, 2 and 3) located in various hydrogeological settings in the Manawatu and Rangitikei Rivers catchments, in the lower North Island of New Zealand. We collected 7 sets of monthly groundwater observations at 17 piezometers from March to September 2018 to characterize the groundwater monthly chemical variations. The collected groundwater samples were analyzed for groundwater redox status, including dissolved oxygen (DO), oxidation-reduction potential, pH, NO₃⁻-N, iron (Fe²⁺), manganese (Mn²⁺) and sulphate (SO₄²⁻). We also conducted a set of push-and-pull tests to gain insights into dynamics of subsurface denitrification occurring in the groundwater samples at the study sites. We quantified changes in concentration of NO₃⁻-N, Br⁻ (tracer), dissolved N₂O-N and excess N₂ during the push-and-pull tests. Our results suggested a spatially variable groundwater redox conditions and SD occurring across the study sites. The piezometers DF 2, 3; SC 1, 2; CAM 3; ARM 1, 2 and 3 showed anoxic redox status. Only the piezometers SC 3 and CAM 1 presented mixed redox condition. While the piezometers DF 1; SR 1, 2, 3; BUR 1, 2 and 3 indicated oxic conditions with some variability over the study. Nitrate is being reduced in the anoxic piezometers DF 2, 3; SC 1, 3; ARM 1, 2, 3 and CAM 3, showing no NO₃⁻-N accumulation (< 0.5 mg L⁻¹). One of the piezometers with mixed redox condition (CAM 1) showed NO₃⁻-N accumulation (> 6 mg L⁻¹) while the piezometer SC 3 showed variability in NO₃⁻-N accumulation ranging from 0.02 mg L⁻¹ to 22.56 mg L⁻¹. The oxic piezometers SR 1, 2, 3; BUR 1, 2 and 3 showed NO₃⁻-N accumulation (> 3 mg L⁻¹) except for piezometer DF 1 that showed variability in NO₃⁻-N concentrations ranging from 0.01 mg L⁻¹ to 3.75 mg L⁻¹ over the study. The concentrations of the electron donors Fe²⁺ and Mn²⁺ were found to be suitable for SD on anoxic piezometers DF 2, 3; SC 1, 2; CAM 3 and ARM 1, 2, 3 (> 1 mg L⁻¹ and > 0.05 mg L⁻¹ respectively). The piezometers with mixed redox status SC 3 and CAM 1 ranged just over the redox threshold for identifying redox processes (0.1 – 1.0 mg L⁻¹ and > 0.05 mg L⁻¹ respectively). In general, the piezometer with oxic redox status (DF 1, SR 1, 2, 3 and BUR 1, 2, 3) showed [Fe²⁺] and [Mn²⁺] below the threshold for identifying redox processes (< 0.1 mg L⁻¹ and < 0.05 mg L⁻¹ respectively) and not suitable to support SD. The dominant terminal product of SD, whether was complete denitrification (N₂ — as end product) or partial SD (N₂O — as end product) spatially varied according to the redox status of the groundwater. Push-pull test results showed an increase in excess N₂ and N₂O-N concentrations at DF 3, ARM 3, CAM 3, BUR 3. The push-pull test conducted at SR 3 and SC 3 showed inconclusive results. Piezometers CAM 3 and ARM 3 showed the highest suitable conditions for SD followed by DF 3. Piezometer BUR 3 showed the highest partial SD rate. Therefore BUR 3 is considered in general, the less suitable piezometer for SD. Our observations highlight the influence of different hydrogeological settings on spatial variability of partial (pollution swamp) or complete (ecosystem service) SD in shallow groundwaters. A better understanding and quantification of spatial and temporal variability of SD process will support information, design and formulation of targeted and effective management measures for sustainable agricultural production while protecting soil, water and air quality.Item The potential reduction of carbon dioxide (CO2) emissions from gas flaring in Nigeria’s oil and gas industry through alternative productive use(MDPI, 23/11/2016) Otene IJJ; Murray PE; Enongene KE; Levy, JK; Yu, PGlobally, climate change and its adverse effects on the human population and the environment has necessitated significant research on the sustainable use of natural resources. Gas flaring in Nigeria’s oil and gas industry causes environmental and health hazards and to a large extent, culminates in yearly loss of the Nation’s revenue. The aim of the study is to highlight the potentials of converting flared gas from the Nigerian oil and gas industry to compressed natural gas (CNG) which could be an alternative fuel for the 220 Lagos Bus Rapid Transit (BRT-Lite) while reducing CO2 emissions. In addition, the study provided an overview of gas flaring in the oil and gas industry and energy utilisation in some selected sectors in the country. The Long-range Energy Alternative Planning System (LEAP) software was employed to model the energy demand and carbon dioxide emissions from the BRT-Lite by creating a current scenario and projections to the year 2030. The use of CNG as an alternative fuel for Lagos BRT-Lite will significantly reduce CO2 emissions in Nigeria’s oil and gas industry. Other utilization options for flared gas from this industry includes: Liquefied Natural Gas (LNG), Liquefied Petroleum Gas (LPG), and power generationItem C3 and C4 grass species: who can reduce soil nitrous oxide emissions in a continental arid region?(MDPI AG, 8/09/2020) Ning J; He XZ; Hou FIn order to relieve grazing pressure, drought-tolerant grass species are widely cultivated in arid regions. However, soil N emission is largely neglected while pursuing forage yield. We carried out a randomized block study to investigate whether and how the C3 and C4 grass species differ in soil N emission in a typical salinized field with temperate continental arid climate in the northwest inland regions, China. We quantified soil N2O flux from two C3 (barley and rye) and two C4 grass species [corngrass and sorghum hybrid sudangrass (SHS)] in fields during the growing season (from May to September) by using the static box method, and then determined the relationships between soil N2O fluxes and forage yield and soil properties. Results show that soil available nitrogen, soil temperature, pH, soil organic carbon, and total nitrogen were correlated, but soil water was anti-correlated with soil N2O fluxes. In addition, N2O flux increased significantly faster with soil temperature in C4 than in C3 grass fields. Although the lower total N2O emission fluxes were detected for C3 species, the lower yield-scaled N2O was detected for C4 species. Our study provided insights into the determination of grass species and the understanding of mechanisms regulating N2O fluxes in C3 and C4 species in the continental arid regions.
