Charmley E.,CSIRO |
Williams S.R.O.,Jobs Transport and Resources |
Moate P.J.,Jobs Transport and Resources |
Hegarty R.S.,University of New England of Australia |
And 6 more authors.
Animal Production Science | Year: 2016
The methods for estimating methane emissions from cattle as used in the Australian national inventory are based on older data that have now been superseded by a large amount of more recent data. Recent data suggested that the current inventory emissions estimates can be improved. To address this issue, a total of 1034 individual animal records of daily methane production (MP) was used to reassess the relationship between MP and each of dry matter intake (DMI) and gross energy intake (GEI). Data were restricted to trials conducted in the past 10 years using open-circuit respiration chambers, with cattle fed forage-based diets (forage >70%). Results from diets considered to inhibit methanogenesis were omitted from the dataset. Records were obtained from dairy cattle fed temperate forages (220 records), beef cattle fed temperate forages (680 records) and beef cattle fed tropical forages (133 records). Relationships were very similar for all three production categories and single relationships for MP on a DMI or GEI basis were proposed for national inventory purposes. These relationships were MP (g/day) ≤ 20.7 (±0.28) × DMI (kg/day) (R2 ≤ 0.92, P < 0.001) and MP (MJ/day) ≤ 0.063 (±0.008) × GEI (MJ/day) (R2 ≤ 0.93, P < 0.001). If the revised MP (g/day) approach is used to calculate Australia's national inventory, it will reduce estimates of emissions of forage-fed cattle by 24%. Assuming a global warming potential of 25 for methane, this represents a 12.6 Mt CO2-e reduction in calculated annual emissions from Australian cattle. © CSIRO 2016.
Liu D.L.,Australian Department of Primary Industries and Fisheries |
Liu D.L.,Charles Sturt University |
O'Leary G.J.,Jobs Transport and Resources |
Ma Y.,Australian Department of Primary Industries and Fisheries |
And 10 more authors.
Geoderma | Year: 2016
The level of soil organic carbon (SOC) that is attained under agriculture largely depends upon rates of carbon input and its decomposition under various agronomic practises such as stubble (crop residue) management and fertiliser application. In this study, we used the APSIM-Wheat and APSIM-Agpasture models to simulate changes in SOC in a range of crop and pasture management systems across nine locations in eastern Australia. We explored the extent to which various crop and pasture management options affect changes in SOC from a sub-tropical to a temperate environment. Specifically, we examined how nitrogen fertilisation, stubble management and stocking rate affect SOC and what strategies might be employed by farmers to increase SOC sequestration across eastern Australia. We modelled a continuous cropping regime, a continuously grazed pasture and a mixed cropping and pasture rotation. Under continuous cropping higher nitrogen application and higher amounts of stubble incorporation increased the SOC levels at all locations. At Roma, the northern-most site, there was little additional gain in SOC from increasing N above 70kgNha-1 whereas most other sites showed benefits above 70kgNha-1. The biggest factor in boosting SOC under cropping was the level of stubble incorporation. At all but one site, continuously grazed pasture generally resulted in SOC increases over the 60years. However, increasing stocking rate decreased the rates of SOC changes at all sites. Crop-pasture rotations show that the impacts of even 4years of pasture is likely to be significant in reducing declining SOC at low nitrogen application during cropping phases. N fertilisation and stubble incorporation reduced the impact of stocking rate by reducing the decline in SOC. The difference in SOC changes between nine sites across eastern Australia was largely described by mean temperature and rainfall but high temperature strongly interacted with management practises (stocking rate, N application and residue incorporation) to reduce the sequestration of C despite favourable rainfall. Our results indicate that a mean annual temperature higher than about 20°C can switch a soil from net sink into a net source of atmospheric CO2 if other factors affecting soil carbon changes such as stubble incorporation, stocking rate and site rainfall are constant. © 2015 Elsevier B.V.
Buchner P.,Rothamsted Research |
Tausz M.,University of Melbourne |
Ford R.,University of Melbourne |
Leo A.,University of Melbourne |
And 3 more authors.
Plant Science | Year: 2015
Projected climatic impacts on crop yield and quality, and increased demands for production, require targeted research to optimise nutrition of crop plants. For wheat, post-anthesis carbon and nitrogen remobilisation from vegetative plant parts and translocation to grains directly affects grain carbon (C), nitrogen (N) and protein levels. We analysed the influence of increased atmospheric CO2 on the expression of genes involved in senescence, leaf carbohydrate and nitrogen metabolism and assimilate transport in wheat under field conditions (Australian Grains Free Air CO2 Enrichment; AGFACE) over a time course from anthesis to maturity, the key period for grain filling. Wheat grown under CO2 enrichment had lower N concentrations and a tendency towards greater C/N ratios. A general acceleration of the senescence process by elevated CO2 was not confirmed. The expression patterns of genes involved in carbohydrate metabolism, nitrate reduction and metabolite transport differed between CO2 treatments, and this CO2 effect was different between pre-senescence and during senescence. The results suggest up-regulation of N remobilisation and down-regulation of C remobilisation during senescence under elevated CO2, which is consistent with greater grain N-sink strength of developing grains. © 2015.
Hunter T.E.,University of Melbourne |
Suster D.,Jobs Transport and Resources |
DiGiacomo K.,University of Melbourne |
Dunshea F.R.,University of Melbourne |
And 3 more authors.
Small Ruminant Research | Year: 2015
The introduction of East Friesian (EF) genetics into commercial sheep milking herds has the potential to improve milk yield and offer a robust dam for meat lamb production systems. This study was conducted to measure the milk production, feed intake and longitudinal changes in body composition of EF×Romney (EFR) and Border Leicester×Merino (BLM) ewes over the first nine weeks of lactation. Sixteen seconds parity single-bearing EFR (n =8) and BLM (n =8) ewes that had been mated to a purebred EF ram were housed in individual pens from 2 weeks prior to, and until 9 weeks after, lambing and fed a commercial pelleted diet with additional chaff. Milk yield was measured twice a week using the four-hour milking interval technique after injection of oxytocin and body composition was determined by dual energy X-ray absorptiometry (DXA) at 1, 3, 5 and 9 weeks of lactation. Potential milk production was higher in EFR than BLM ewes (2.57 vs. 1.92kg/d, P =0.028) and declined as lactation advanced. Similarly, the yields of milk fat (P =0.015), protein (P =0.018) and lactose (P =0.062) were all higher in EFR than BLM ewes and declined as lactation advanced. Energy intake increased over the first 4 weeks of the study, before reaching a plateau for the remaining 5 weeks of the study. However, there was no significant difference in energy intake or energy balance between EFR and BLM ewes. Changes in tissue energy between DXA scans were highly correlated (R 2 =0.51, P <0.001) to average estimated energy balance over the same periods. There was no effect of breed on birth weight of lambs nor was there any effect of dam breed on average daily gain of lambs. In conclusion, EFR ewes have greater potential milk yield than BLM ewes but this was not realized as an increased average daily gain in the single lambs possibly due to insufficient milking pressure failing to produce a difference in actual milk yield. It is likely that this difference would be expressed in response to a greater milking demand (i.e. from a milking machine or twin/triplet lambs). The EFR ewes ate more than BLM ewes during lactation and mobilized less fat than BLM ewes to maintain similar nursing lamb growth. However, a greater milking demand of twins or triplets may allow the greater potential milk yield of EFR to be expressed. Alternatively, machine milking EFR would most likely allow the expression of their full milking potential. Finally, DXA was able to predict body tissue mobilization and accretion in lactating ewes and these changes in body composition were related to estimated energy balance indicating that DXA can be used to serially determine body composition in lactating sheep. © 2015 Elsevier B.V..
Morris M.R.,Jobs Transport and Resources |
Hussain A.,Jobs Transport and Resources |
Gillies M.H.,University of Southern Queensland |
O'Halloran N.J.,Jobs Transport and Resources
Agricultural Water Management | Year: 2015
Modernisation of regional water delivery infrastructure can provide irrigators using border irrigation systems with the option to apply water to border irrigation bays at much higher inflow rates. Substantial improvements in irrigation performance have been claimed by proponents of higher bay inflow rates, leading to large investments in farm infrastructure. In this work, measurements made on bays irrigated at different inflow rates on a range of soil types, crops and irrigation deficits did not demonstrate substantial differences in irrigation performance. Assessments made using a surface irrigation model fitted to the measured irrigations also showed limited differences in feasible irrigation performance related to inflow rates. Extrapolating irrigation performance over feasible inflow rates and durations revealed that equivalent performance could be achieved with inflow rates ranging from 2 to 7Ls-1m-1 provided that appropriate inflow durations were adopted. An analysis involving modest variations of ±5% in inflow rate and ±5mm in the estimate of irrigation requirement produced substantial uncertainties in irrigation performance, suggesting that attempts by irrigators to consistently achieve more precise irrigation performance targets may not be feasible. Improved understanding of the role of uncertainty in border irrigation systems, models and measures of irrigation performance would provide a useful basis for improving border irrigations. © 2015 Elsevier B.V.
Belyaeva O.N.,Jobs Transport and Resources |
Officer S.J.,Jobs Transport and Resources |
Armstrong R.D.,La Trobe University |
Harris R.H.,Jobs Transport and Resources |
And 4 more authors.
Soil Research | Year: 2016
Conversion of long-term pasture to cropping was investigated for its effects on nitrous oxide (N2O) emissions in a 2-year field experiment in the high-rainfall zone of south-western Victoria. Early termination (pasture terminated 6 months before sowing) followed by winter (ETw) and spring (ETs) crops and late termination (pasture terminated 1 month before sowing) followed by a winter crop (LTw) were compared with continuous, mown pasture (MP). Emissions of N2O were measured with an automated gas sampling and analysing system. Emissions from MP were the lowest throughout the study, resulting in annual losses of 0.13kg N2O-N ha-1 in the first and the second years of the experiment. N2O-N loss was 0.6kgha-1 from treatments without fallow in both years (LTw in 2013 and ETs in 2014). In the first year, annual losses from previous fallow in ETw and ETs plots were 7.1 and 3.6kg N2O-N ha-1, respectively. Higher annual N2O losses from treatments with fallow periods continued in the second year of the study and were 2.0 and 1.3kg N2O-N ha-1 from ETw and LTw treatments, respectively. High emissions were associated with N mineralisation and the accumulation of NO3-N in the soil during the extensive fallow period after early pasture termination or wheat harvest. Soil water content was a key factor influencing the temporal fluctuations in N2O emissions. Low emissions occurred when water-filled pore space was <30%, whereas high emissions occurred when it was >65%, suggesting that denitrification was the major source of N2O emission. Crop grain yield was not affected by the duration of fallow (and therefore timing of pasture termination) in the first year, but was lower (P<0.05) in the treatment without fallow in the second year. Terminating pasture late rather than early, thus reducing the length of the fallow period, is a practical way of reducing N2O emissions from mixed pasture-cropping systems. © CSIRO 2016.
Robertson F.,Jobs Transport and Resources |
Crawford D.,Jobs Transport and Resources |
Partington D.,Jobs Transport and Resources |
Oliver I.,Jobs Transport and Resources |
And 8 more authors.
Soil Research | Year: 2016
Increasing soil organic carbon (SOC) storage in agricultural soils through changes to management may help to mitigate rising greenhouse gas emissions and sustain agricultural productivity and environmental conditions. However, in order to improve assessment of the potential for increasing SOC storage in the agricultural lands of Victoria, Australia, further information is required on current SOC levels and how they are related to environmental conditions, soil properties and agricultural management. Therefore, we measured stocks of SOC at 615 sites in pasture and cropping systems in Victoria, encompassing eight regions, five soil orders and four management classes (continuous cropping, crop-pasture rotation, sheep or beef pasture, and dairy pasture), and explored relationships between the C stocks and environment, soil and management. The results showed an extremely wide range in SOC, from 2 to 239tC/ha (0-30cm). Most of this variation was attributable to climate; almost 80% of the variation in SOC stock was related to annual rainfall or vapour pressure deficit (i.e. humidity). Texture-related soil properties accounted for a small, additional amount of variation in SOC. After accounting for climate, differences in SOC between management classes were small and often not significant. Management practices such as stubble retention, minimum cultivation, perennial pasture species, rotational grazing and fertiliser inputs were not significantly related to SOC stock. The relationships between SOC and environment, soil and management were scale-dependent. Within individual regions, the apparent influence of climate and soil properties on SOC stock varied, and in some regions, much of the variation in SOC stock remained unexplained. The results suggest that, across Victoria, there is a general hierarchy of influence on SOC stock: climate>soil properties>management class>management practices. Journal compilation. © CSIRO 2016.