• Authors:
    • Duijnisveld, W. H. M.
    • Flessa, H.
    • Böttcher, J.
    • von der Heide, C.
    • Well, R.
    • Weymann, D.
  • Source: Nutrient Cycling in Agroecosystems
  • Volume: 85
  • Issue: 3
  • Year: 2009
  • Summary: Production and accumulation of the major greenhouse gas nitrous oxide (N2O) in surface groundwater might contribute to N2O emissions to the atmosphere. We report on a 15 Ntracer study conducted in the Fuhrberger Feld aquifer in northern Germany. A K15NO3 tracer solution (60 atom%) was applied to the surface groundwater on an 8 m2 measuring plot using 45 injection points in order to stimulate production of 15 N2O by denitrification and to detect its contribution to emissions at the soil surface. Samples from the surface groundwater, from the unsaturated zone and at the soil surface were collected in regular intervals over a 72-days period. Total N2O fluxes at the soil surface were low and in a range between -7.6 and 29.1 lg N2O-N m-2h-1.15 N enrichment of N2O decreased considerably upwards in the profile. In the surface groundwater, we found a 15N enrichment of N2O between 13 and 42 atom%. In contrast, 15N enrichment of N2O in flux chambers at the soil surface was very low, but a detectable 15N enrichment was found at all sampling events. Fluxes of groundwater-derived 15N-N2O were very low and ranged between 0.0002 and 0.0018 kg N2O-N ha-1 year-1, indicating that indirect N2O emissions from the surface groundwater of the Fuhrberger Feld aquifer occurring via upward diffusion are hardly significant. Due to these observations we concluded that N2O dynamics at the soil-atmosphere interface is predominantly governed by topsoil parameters. However, highest 15 N enrichments of N2O throughout the profile were obtained in the course of a rapid drawdown of the groundwater table. We assume that such fluctuations may enhance diffusive N2O fluxes from the surface groundwater to the atmosphere for a short time.
  • Authors:
    • Kelly,K.
    • Graham,J.
    • Biswas,W. K.
    • John,M. B.
  • Source: 6th Australian Conference on Life Cycle Assessment
  • Year: 2009
  • Authors:
    • Eckard, R.
    • Henry, B.
  • Source: Tropical Grasslands
  • Volume: 43
  • Year: 2009
  • Summary: Agriculture is responsible for a significant proportion of total anthropogenic greenhouse gas emissions (perhaps 18% globally), and therefore has the potential to contribute to efforts to reduce emissions as a means of minimising the risk of dangerous climate change. The largest contributions to emissions are attributed to ruminant methane production and nitrous oxide from animal waste and fertilised soils. Further, livestock, including ruminants, are an important component of global and Australian food production and there is a growing demand for animal protein sources. At the same time as governments and the community strengthen objectives to reduce greenhouse gas emissions, there are growing concerns about global food security. This paper provides an overview of a number of options for reducing methane and nitrous oxide emissions from ruminant production systems in Australia, while maintaining productivity to contribute to both objectives. Options include strategies for feed modification, animal breeding and herd management, rumen manipulation and animal waste and fertiliser management. Using currently available strategies, some reductions in emissions can be achieved, but practical commercially available techniques for significant reductions in methane emissions, particularly from extensive livestock production systems, will require greater time and resource investment. Decreases in the levels of emissions from these ruminant systems (i.e., the amount of emissions per unit of product such as meat) have already been achieved. However, the technology has not yet been developed for eliminating production of methane from the rumen of cattle and sheep digesting the cellulose and lignin-rich grasses that make up a large part of the diet of animals grazing natural pastures, particularly in arid and semi-arid grazing lands. Nevertheless, the abatement that can be achieved will contribute significantly towards reaching greenhouse gas emissions reduction targets
  • Authors:
    • Graham, J.
    • Phelan, A.
    • Kelly, K. B.
    • Officer, S. J.
  • Source: Climate Change and Resources
  • Year: 2009
  • Authors:
    • Smith, K. A.
    • Edwards, A. C.
    • Reay, D. S.
  • Source: Agriculture, Ecosystems & Environment
  • Volume: 133
  • Issue: 3-4
  • Year: 2009
  • Summary: Direct and indirect nitrous oxide (N2O) emissions and leaching losses from an intensively managed grazed pasture in the Ythan catchment, Aberdeenshire, UK, were measured and compared over a 17-month period. Simultaneous measurements of farm-wide leaching losses of N2O were also made and catchment-wide fluxes were estimated from existing N leaching data. The relative importance of direct and indirect N2O fluxes at the field, farm and catchment scale was then assessed. At the field scale we found that direct N2O emissions were low (1.2 kg N ha-1 year-1, 0.6% of N input) with indirect N2O emissions via drainage waters comprising a significant proportion (25%) of total N2O emissions. At the whole-farmscale, the N2O-N emission factor (0.003) for leached NO3-N (EF5-g) was in line with the IPCC's recent downward revision. At the catchment scale, a direct N2O flux of 1.9 kg N ha-1 year-1 and an indirect flux of 0.06 kg N2O-N ha-1 year-1 were estimated. This study lends further support to the recent downward revision of the IPCC emission factor for N2O arising from leached N in surface and ground waters (EF5-g) and highlights the need for multiple point sampling to ensure that the importance of indirect N2O losses via drainage waters is not misrepresented at the farm and catchment scales.
  • Authors:
    • Bol, R.
    • Krull, E.
    • Lopez-Capel, E.
    • Sohi, S.
  • Source: CSIRO Land and Water Science Report
  • Year: 2009
  • Authors:
    • Institute for the Study of Earth, Oceans and Space
  • Year: 2009
  • Summary: The DNDC model is a process-base model of carbon (C) and nitrogen (N) biogeochemistry in agricultural ecosystems. This document describes how to use the PC Windows versions of the DNDC model for predicting crop yield, C sequestration, nitrate leaching loss, and emissions of C and N gases in agroecosystems. Part I provides a brief description of the model structure with relevant scientific basis. Part II describes how to install the model. Part III and IV demonstrate how to conduct simulations with the site and regional versions of DNDC, respectively. Part V provides basic information for uncertainty analysis with DNDC. Part VI contains six case studies demonstrating the input procedures for simulating crop yield, soil C dynamics, nitrate leaching loss, and trace gas emissions. A list of relevant publications is included in Part VII. These publications provide more information about the scientific background and applications of DNDC far beyond this User's Guide. DNDC9.3 can run in two modes: site or regional. By selecting the mode, the users will open a corresponding interface to manage their input information for the modeled site or region.
  • Authors:
    • Baraibar, B.
    • Westerman, P. R.
    • Recasens, J.
  • Source: Journal of Applied Ecology
  • Volume: 46
  • Issue: 2
  • Year: 2009
  • Summary: Agricultural intensification can cause a huge increase in productivity. However, associated costs in terms of reduced, self-regulation and increased reliance on external inputs for the control of pests, diseases and weeds are seldom taken into account or acknowledged. A pro-active approach in which ecosystems services are documented and potential effects of changes in agricultural practices evaluated may lead to more informed decisions prior to implementation. We investigated the effects of management of cereal production in a semi-arid region on weed seed mortality caused by predators. Seed losses have a greater impact on weed population size than any other life cycle process and should therefore be of significance for natural weed control. We hypothesized that the conversion from rain-fed to irrigated production should lead to reduced and the adoption of no-till techniques to increased seed predation. Seed removal and seed predator populations were monitored in irrigated (N = 3) and rain-fed cereal fields (N = 6) and field margins. Of the dryland fields half was conventionally tilled and the other half no-till. Seed removal (g g(-1) 2-days(-1)) was followed from April 2007 until June 2008, using Petri-dishes and exclosure cages. Populations of harvester ants were estimated by direct nest counts; rodent populations by Sherman live traps. Seed removal in dryland cereals, mainly by harvester ants Messor barbarus was high from mid April to mid October, and should cause a strong weed suppressive effect. Seed removal in irrigated cereals, mainly by granivorous rodents Mus spretus, was low. Seed removal was higher in no-till than in conventional fields and corresponded to differences in harvester ant nest densities. Synthesis and applications. Our results show that tillage and irrigation in a semi-arid cereal production system results in a reduction and total annihilation of granivorous harvester ants, respectively. The concurrent decline in weed seed mortality could lead to increased herbicide use and dependency. In particular, in areas where economic margins are small or the environmental costs of tillage and irrigation high, the increased costs of chemical weed control may exceed the benefits. Here, preserving biodiversity to enhance natural weed control is a viable alternative to agricultural intensification.
  • Authors:
    • Holloway, S.
    • Smith, G.
    • Ravenscroft, N.
    • Henderson, I. G.
  • Source: Agriculture, Ecosystems & Environment
  • Volume: 129
  • Issue: 1-3
  • Year: 2009
  • Summary: This 6-year experimental study measured the response of bird populations and abundance to combinations of mixed cropping and low pesticide regimes associated with a commercial crop rotation. The results show a rapid and sustained population increase among a wide range of bird species, in contrast to local regional trends for the same species. Seventy percent of the increase occurred within the first 3 years of the experiment, with species of high conservation concern, and those monitored as environmental indicators on lowland farmland in the UK, increasing on average, by 30% and 20% respectively (reaching respective peaks of 44% and 33% after 4 years). For some individual species, the increase was higher still, i.e., 300% (1-4 pairs) for grey partridge (Perdix perdix) and 46% (13-19 pairs) for skylarks (Alauda arvensis) in peak years. The results demonstrate that bird species typical of lowland arable farmland in the UK are responsive to suitable farm-scale changes in habitat and food provision (roughly, manipulation within less than 1-km2). They show that the carrying capacity of modern, commercially viable, arable farmland can be increased significantly for birds, in this case, mainly by using crops mosaics to create habitats alongside the appropriate use of herbicides on non-cropped habitats.
  • Authors:
    • Suleau, M.
    • Heinesch, B.
    • Dufranne, D.
    • Bodson, B.
    • Moureaux, C.
    • Aubinet, M.
    • Vancutsem, F.
    • Vilret, A.
  • Source: Agricultural & Forest Meteorology
  • Volume: 149
  • Issue: 3/4
  • Year: 2009
  • Summary: A crop managed in a traditional way was monitored over a complete sugar beet/winter wheat/potato/winter wheat rotation cycle from 2004 to 2008. Eddy covariance, automatic and manual soil chamber, leaf diffusion and biomass measurements were performed continuously in order to obtain the daily and seasonal Net Ecosystem Exchange (NEE), Gross Primary Productivity (GPP), Total Ecosystem Respiration (TER), Net Primary Productivity (NPP), autotrophic respiration, heterotrophic respiration and Net Biome Production (NBP). The results showed that GPP and TER were subjected to important inter-annual variability due to differences between crops and to climate variability. A significant impact of intercrop assimilation and of some farmer interventions was also detected and quantified. Notably, the impact of ploughing was found to be limited in intensity (1-2 mol m -2 s -1) and duration (not more than 1 day). Seasonal budgets showed that, during cropping periods, the TER/GPP ratio varied between 40 and 60% and that TER was dominated mainly by the autotrophic component (65% of TER and more). Autotrophic respiration was closely related to GPP during the growth period. The whole cycle budget showed that NEE was negative and the rotation behaved as a sink of 1.59 kgC m -2 over the 4-year rotation. However, if exports are deducted from the budget, the crop became a small source of 0.22 (0.14) kgC m -2. The main causes of uncertainty with these results were due to biomass samplings and eddy covariance measurements (mainly, uncertainties about the u* threshold determination). The positive NBP also suggested that the crop soil carbon content decreased. This could be explained by the crop management, as neither farmyard manure nor slurry had been applied to the crop for more than 10 years and because cereal straw had been systematically exported for livestock. The results were also strongly influenced by the particular climatic conditions in 2007 (mild winter, and dry spring) that increased the fraction of biomass returned to the soil at the expense of harvested biomass, and therefore mitigated the source intensity. If 2007 had been a 'normal' year, this intensity would have been twice as great. This suggests that, in general, the rotation behaved as a small carbon source, which accords with similar studies based on multi-year eddy covariance measurements and export assessment and with modelling or inventory studies analysing the evolution of crop soil organic carbon (SOC) on a decennial scale.