• Authors:
    • Don, A.
    • Poeplau, C.
  • Source: GEODERMA
  • Volume: 192
  • Year: 2013
  • Summary: Land-use changes (WC) influence the balance of soil organic carbon (SOC) and hence may cause CO2 emissions or sequestration. In Europe there is a side by side of LUC types that lead to SOC loss or SOC accumulation. However, there is a lack of studies covering all major LUC types to investigate qualitative and quantitative LUC effects on SOC. In this study we sampled 24 paired sites in Europe to a depth of 80 cm, covering a wide range of pedo-climatic conditions and comprising the major European LUC types cropland to grassland, grassland to cropland, cropland to forest and grassland to forest To assess qualitative changes and the sensitivity of different functional SOC pools with distinct turnover times, we conducted a fractionation to isolate five different fractions of SOC. The mean SOC stock changes after LUC were 18 +/- 11 Mg ha(-1) (cropland to grassland), 21 +/- 13 Mg ha(-1) (cropland to forest), -19 +/- 7 Mg ha(-1) (grassland to cropland) and 10 +/- 7 Mg ha(-1) (grassland to forest) with the main changes occurring in the topsoil (0-30 cm depth). However, subsoil carbon stocks ( >30 cm depth) were also affected by LUC, at 19 out of 24 sites in the same direction as the topsoil. LUC promoting subsoil SOC accumulation might be a sustainable C sink Particulate organic matter (POM) was found to be most sensitive to LUC After cropland afforestation. POM accounted for 50% (9.1 +/- 2.3 Mg ha(-1)) of the sequestered carbon in 0-30 cm: after grassland afforestation POM increased on average by 5 +/- 23 Mg ha(-1), while all other fractions depleted. Thus, afforestations shift SOC from stable to labile pools. The resistant fraction comprising the so-called inert carbon was found to be only slightly less sensitive than the total SOC pool, suggesting that an inert carbon pool was not chemically extracted with NaOCl oxidation, if there is any inert carbon.
  • Authors:
    • Clothier, B. E.
    • Jun, G. I.
    • Young, I.
    • Huh, K. Y.
    • Kim, I.
    • Mueller, K.
    • Deurer, M.
  • Source: GEODERMA
  • Volume: 183
  • Year: 2012
  • Summary: In an organic apple (Malus domestica Borkh., Braeburn on MM.106 rootstock) orchard in New Zealand we observed that the soil's carbon concentration in 0-0.1 m depth directly below a wheel-track in the grassed alley-way was significantly higher than under the grassed tree-row. By using a literature review and direct measurements, we systematically exclude two explanations for the possible accumulation of soil carbon under the wheel-track. Firstly, we discard the possibility of higher carbon inputs to the wheel-track compared to the tree-row area. The tree-row received more carbon inputs by the regular application of compost, and the growth of roots was not impeded by compaction. Secondly, we directly measured the monthly dynamics of microbial biomass and respiration rates per unit of soil carbon over a year, and based on 3D X-ray computed tomography (CT) images we modelled the gas exchange close to water saturation. A restricted gas exchange under wet conditions would be an indication that soil carbon mineralization is reduced under wet conditions. We found that both the microbial carbon decomposition dynamics and the gas exchange under wet conditions were similar in the tree-row and under the wheel-track. The most probable explanation for the enhanced carbon sequestration under the wheel-track is a reduction in carbon losses. The water infiltration rates into the wheel-tracks were significantly smaller than in the tree-row. This means that the carbon loss with water flow in the form of dissolved carbon is probably smaller under the wheel-track Additionally, a reduction in meso- and macro-faunal activities exporting particulate organic matter from the soil volume is probable under minor compaction. We conclude that a minor compaction like under a wheel-track can be a physical protection mechanism for soil carbon. (C) 2012 Published by Elsevier B.V.
  • Authors:
    • Condron, L. M.
    • Almond, P. C.
    • Eger, A.
  • Source: Geoderma
  • Volume: 189
  • Year: 2012
  • Summary: Although the importance of dust deposition as an integral component of terrestrial biogeochemical cycles is well-recognised, few studies have directly addressed pedogenic processes associated with dust deposition on the land surface itself, and if so, mainly as relict features. This work addresses this gap by looking at the pedogenic response to an active loess flux gradient in a super-humid, strong weathering environment on the west coast of New Zealand's South Island. Along the gradient, seven soil pits were examined for a range of soil physical (colour, texture, bulk density, structure, roots) and chemical properties (pH, F-o, Fe-d, Al-o, soil organic carbon) measured to a depth of 50 cm to capture the transitional changes arising from minimal to maximal loess deposition rates. Maximal deposition rate was estimated to be 28.4 g m(-2) y(-1). Along the gradient towards the highest deposition rate, loess-free, sandy Spodosols changed to increasingly more finely-textured soils, ultimately featuring a two-fold increase of silt. The pedogenic oxides F-o, Fe-d and Al-o gradually increased each by 50% and soil organic carbon by 60%. These increases were facilitated by continuous accession of loess. The loess mixed with organic matter at the surface and became increasingly weathered and leached with the time that it had spent undergoing eluviation. Subsequently, the loess increments were buried within the subsoil as part of an upwardly thickening spodic horizon (upbuilding pedogenesis). Because of the high deposition rates under maximum loess flux, Spodosol formation became ultimately retarded and an Inceptisol formed because loess supply overwhelmed topsoil leaching. Having also an illuvial subsoil horizon, this Inceptisol showed the strongest chemical indicators for podzolisation of the gradient. Soil data from supplementary sites suggested that more developed soils required lower loess fluxes to retard further pedogenic differentiation than younger soils. The existence of a loess gradient that is capable of forming distinctive deposits in a super-humid environment gives evidence that not only dry/arid climates (e.g. during glacials) are potentially suitable for the formation of aeolian substrates (loess). The study indicates enhanced soil organic carbon storage in soils as a result of loess deposition and concomitant pedogenesis. (c) 2012 Elsevier By. All rights reserved.
  • Authors:
    • Baisden, W. T.
    • Schipper, L. A.
    • Dymond, J. R.
    • Stevenson, B. A.
    • Parfitt, R. L.
    • Ballantine, D. J.
  • Source: New Zealand Journal of Agricultural Research
  • Volume: 55
  • Issue: 3
  • Year: 2012
  • Summary: Reactive nitrogen (N) is increasingly added to the New Zealand environment because of increased sales of N fertilizer and increased human population. The Greenhouse Gas Inventory now reports in detail on changes for N losses from grazing animals from 1990 to 2010. Using animal numbers, we made assessments of N inputs and outputs for the 16 regions of New Zealand for 1990, 2001 and 2010 to assess temporal trends. Fertilizer sales have increased from 46 Gg N in 1990 to 329 Gg N in 2010, which leads to reduced biological N fixation by pastures. The import of oil-palm kernel has increased from zero to about 28 Gg N in 2010. Total N inputs are estimated to have increased from 689 Gg to 951 Gg N. The outputs of produce, leachate, gasses and sediment have increased from 771 to 866 Gg N; outputs to rivers may increase further if increases in outputs lag behind increases in inputs. Many of the inputs and outputs are well constrained because animal numbers have been used rather than land area, but uncertainties do exist for specific land-use classes. For example, the area of lifestyle blocks is approaching 800,000 ha and there is uncertainty regarding N inputs and outputs in this land use. There are also uncertainties in the amount of N fixation, the N loss by leaching in any one year, the amounts and fate of dissolved organic N, and the N content of eroded sediment. These uncertainties need to be resolved so that the amount of N stored in soils can be assessed. It seems likely that the N concentration of soils under dairying is increasing relative to the carbon concentration (i.e. soil C/N ratios are declining) but there is conflicting evidence as to whether the total N (and C) in these soils is increasing or decreasing.
  • Authors:
    • Samarasinghe, S.
    • Safa, M.
  • Source: Environmental Pollution
  • Volume: 171
  • Issue: December
  • Year: 2012
  • Summary: This review paper concentrates on carbon dioxide emissions, discussing its agricultural sources and the possibilities for minimizing emissions from these sources in wheat production in Canterbury, New Zealand. This study was conducted over 35,300 ha of irrigated and dryland wheat fields in Canterbury. Total CO2 emissions were 1032 kg CO2/ha in wheat production. Around 52% of the total CO2 emissions were released from fertilizer use and around 20% were released from fuel used in wheat production. Nitrogen fertilizers were responsible for 48% (499 kg CO2/ha) of CO2 emissions. The link between nitrogen consumption, CO2 emissions and crop production showed that reducing the CO2 emissions would decrease crop production and net financial benefits to farmers. (C) 2012 Elsevier Ltd. All rights reserved.
  • Authors:
    • Cook, F.
    • Francis, G.
    • Close, M.
    • Dann, R.
    • Waterland, H.
    • Thomas, S.
  • Source: Soil Science Society of America Journal
  • Volume: 76
  • Issue: 4
  • Year: 2012
  • Summary: Subsoil denitrification is a potential sink for leached nitrate (NO3-) that may otherwise contaminate ground water. A field trial was undertaken to assess the importance of subsoil denitrification and to examine the role of leached NO3- on subsurface nitrous oxide (N2O) (a potent greenhouse gas) dynamics. We monitored NO3-, Br-, N2O, CO2, and O-2 concentrations in alluvial vadose materials to a depth of 7 m over a 32-mo period following the application of N (400 kg ha(-1) as NH4NO3) and Br- to potatoes (Solanum tuberosum L.) followed by a second application (400 kg ha(-1) as NH4NO3) to ryegrass (Lolium multiflorum Lam.) 24 mo later. Our sampling system consisted of an array of ceramic cups and permeable silicone tubing chambers to sample soil solution and gases. Following rainfall and irrigation, subsoil N2O concentrations increased rapidly. Within days of NO3- leaching below 1 m, high concentrations of NO3-, Br-, and N2O were observed at 7-m depth. Based on N to Br- ratios, and NO3- leaching estimates from drainage amounts and leachate NO3- concentrations, 5 to 10% of the fertilizer and soil N was denitrified. Based on N2O flux estimates and NO3--N/Br- ratios, almost all of the net N2O production occurred in the subsoil above the gravel material (1-m depth). In the gravel matrix the NO3--N/Br- ratio did not change indicating a low capacity to attenuate NO3-.
  • Authors:
    • Allen, R. B.
    • Mason, N. W. H.
    • Hall, G. M. J.
    • Burrows, L. E.
    • Carswell, F. E.
  • Source: New Zealand Journal of Ecology
  • Volume: 36
  • Issue: 2
  • Year: 2012
  • Summary: Natural regeneration of new forests has significant potential to mitigate greenhouse gas emissions, but how strong is the potential biodiversity co-benefit? We quantified carbon accumulation and biodiversity gain during secondary succession of two New Zealand lowland forests. The rate of carbon sequestration was the same for the kanuka-red beech succession as for the coastal broadleaved succession (c. 2.3 Mg C ha(-1) year(-1)) over the first 50 years of succession. Mean above-ground carbon stocks were 148 +/- 13 Mg C ha(-1) for kanuka-red beech forests and 145 +/- 19 Mg C ha(-1) for tall coastal broadleaved forests after at least 50 years of succession. Biodiversity gain was investigated through the quantification of 'ecological integrity', which comprises dominance by indigenous species, occupancy of indigenous species or a group of species fulfilling a particular ecological role, and gain in representation of lowland forests within each ecological region. All components of ecological integrity increased with carbon accumulation for both successions. In addition, above-ground carbon stocks were correlated with the Shannon and Simpson diversity indices and species richness for both successions, suggesting that conventional metrics of diversity also show biodiversity gain with above-ground carbon during succession of recently non-forested lands to secondary forest.
  • Authors:
    • Clark, H.
    • Molano, G.
    • Muetzel, S.
    • Hoskin, S.
    • Sun, X.
  • Source: Animal Feed Science and Technology
  • Volume: 166/167
  • Year: 2011
  • Summary: Published reports of CH 4 yields as g CH 4/kg dry matter (DM) intake suggest that emissions from sheep fed fresh forage chicory ( Cichorium intybus) are about 30% lower than from those fed fresh ryegrass. In this study, 2 year old wethers (16; 543.8 kg liveweight) were fed either mature chicory or perennial ryegrass at 1.3 times maintenance metabolisable energy requirements in the late spring/early summer of 2009. Methane emissions were determined using individual animal respiration chambers. Feeds differed in their chemical composition with chicory containing 856 g/kg organic matter (OM), 117 g/kg crude protein (CP) and 281 g/kg neutral detergent fibre (aNDF), whereas ryegrass contained 916 g/kg OM, 85 g/kg CP and 499 g/kg aNDF. The DM intake was similar for both forages at 0.76 kg/d, and CH 4 yields did not differ between forages being 22.8 and 23.8 g CH 4/kg DM intake for chicory and ryegrass, respectively. In vitro incubations of chicory and perennial ryegrass in the vegetative or mature states had similar CH 4 yields. Despite large differences in chemical composition, especially aNDF, chicory and ryegrass had similar CH 4 yields in vitro and in vivo. Chicory is not a viable alternative to perennial ryegrass for mitigating CH 4 in pastoral based sheep production systems.
  • Authors:
    • Pan, G.
    • Ogle, S.
    • Siebner, C.
    • McConkey, B.
    • Katterer, T.
    • Grace, P. R.
    • Goidts, E.
    • Etchevers, J.
    • Dodd, M.
    • Cerri, C. E. P.
    • Andren, O.
    • Paustian, K.
    • vanWesemael, B.
  • Source: Plant and Soil
  • Volume: 338
  • Issue: 1-2
  • Year: 2011
  • Summary: As regional and continental carbon balances of terrestrial ecosystems become available, it becomes clear that the soils are the largest source of uncertainty. Repeated inventories of soil organic carbon (SOC) organized in soil monitoring networks (SMN) are being implemented in a number of countries. This paper reviews the concepts and design of SMNs in ten countries, and discusses the contribution of such networks to reducing the uncertainty of soil carbon balances. Some SMNs are designed to estimate country-specific land use or management effects on SOC stocks, while others collect soil carbon and ancillary data to provide a nationally consistent assessment of soil carbon condition across the major land-use/soil type combinations. The former use a single sampling campaign of paired sites, while for the latter both systematic (usually grid based) and stratified repeated sampling campaigns (5-10 years interval) are used with densities of one site per 10-1,040 km2. For paired sites, multiple samples at each site are taken in order to allow statistical analysis, while for the single sites, composite samples are taken. In both cases, fixed depth increments together with samples for bulk density and stone content are recommended. Samples should be archived to allow for re-measurement purposes using updated techniques. Information on land management, and where possible, land use history should be systematically recorded for each site. A case study of the agricultural frontier in Brazil is presented in which land use effect factors are calculated in order to quantify the CO2 fluxes from national land use/management conversion matrices. Process-based SOC models can be run for the individual points of the SMN, provided detailed land management records are available. These studies are still rare, as most SMNs have been implemented recently or are in progress. Examples from the USA and Belgium show that uncertainties in SOC change range from 1.6-6.5 Mg C ha-1 for the prediction of SOC stock changes on individual sites to 11.72 Mg C ha-1 or 34% of the median SOC change for soil/land use/climate units. For national SOC monitoring, stratified sampling sites appears to be the most straightforward attribution of SOC values to units with similar soil/land use/climate conditions (i. e. a spatially implicit upscaling approach).
  • Authors:
    • Cromey, M.
    • McKay, A.
    • Harrow, S.
    • Butler, R.
    • Bithell, S.
  • Source: Annals of Applied Biology
  • Volume: 159
  • Issue: 2
  • Year: 2011
  • Summary: Two field trials were conducted to investigate different herbage grasses and cereals for their susceptibility to the disease take-all, for their impact on concentrations of the pathogen, Gaeumannomyces graminis var. tritici ( Ggt), in soil and for their effect on development of take-all in a subsequent wheat crop. In the herbage grass trial, Bromus willdenowii was highly susceptible to Ggt, produced the greatest post-senescence Ggt concentrations in soil and highest incidence of take-all in following wheat crop. Lolium perenne, Lolium multiflorum and Festuca arundinacea supported low Ggt soil concentrations and fallow the least. The relationship between susceptibility to Ggt and post-senescence concentrations in soil differed between pasture grasses and cereals. In a trial in which Ggt was added to half the plots and where wheat, barley, triticale, rye or fallow were compared, the susceptibility of the cereals to take-all was not clearly linked to post-harvest soil Ggt concentrations. In particular, triticale and rye had low and negligible take-all infection respectively, but greater post-harvest soil Ggt concentrations than barley or wheat. This indicates that low Ggt concentrations on roots may build up during crop senescence on some cereals. Soil Ggt concentrations were greater following harvest in inoculated plots sown to cereals, but in the second year there was more take-all in the previously non-inoculated than inoculated plots. Thus, the grass and cereal species differed in susceptibility to take-all, in their impact on Ggt multiplication and in associated take-all severity in following wheat crop.