61. Nitrous oxide emissions from fertilised UK arable soils: fluxes, emission factors and mitigation

• Authors:
  • Balshaw, H.
  • Williams, J. R.
  • Whitmore, A. P.
  • Ashton, R. W.
  • Webster, C.
  • Scott, T.
  • Cardenas, L.
  • Rees, R. M.
  • Topp, C. F. E.
  • Cloy, J. M.
  • Hinton, N.
  • Bell, M. J.
  • Paine, F.
  • Goulding, K. W. T.
  • Chadwick, D. R.
• Source: Article
• Volume: 212
• Year: 2015
• Summary: Cultivated agricultural soils are the largest anthropogenic source of nitrous oxide (N 2O), a greenhouse gas approx. 298 times stronger than carbon dioxide. As agricultural land covers 40-50% of the earth's surface agricultural N 2O emissions could significantly influence future climate. The timing, amount and form of manufactured nitrogen (N) fertiliser applied to soils are major controls on N 2O emission magnitude, and various methods are being investigated to quantify and reduce these emissions. A lack of measured N 2O emission factors (EFs) means that most countries report N 2O emissions using the IPCC's Tier 1 methodology, where an EF of 1% is applied to mineral soils, regardless of soil type, climate, or location. The aim of this research was to generate evidence from experiments to contribute to improving the UK's N 2O agricultural inventory, by determining whether N 2O EFs should vary across soil types and agroclimatic zones. Mitigation methods were also investigated, including assessing the impact of the nitrification inhibitor (NI) dicyandiamide (DCD), the application of more frequent smaller doses of fertiliser, and the impact of different rates and forms of manufactured N fertiliser. Nitrous oxide emissions were measured at one cropland site in Scotland and two in England for 12 months in 2011/2012, along with soil and environmental variables. Crop yield was also measured, and emission intensities were calculated for the contrasting fertiliser treatments. The greatest mean annual cumulative emissions from a range of ammonium nitrate (AN) fertiliser rates were measured at the Scottish site (2301 g N 2O-N ha -1), which experienced 822 mm rainfall compared to 418 mm and 472 mm at the English sites, where cumulative annual emissions were lower (929 and 1152 g N 2O-N ha -1, respectively). Climate and soil mineral N influenced N 2O emissions, with a combination of factors required to occur simultaneously to generate the greatest fluxes. Emissions were related to fertiliser N rate; however the trend was not linear. EFs for AN treatments varied between sites, but at both English sites were much lower than the 1% value used by the IPCC, and as low as 0.20%. DCD reduced AN- and urea-generated N 2O emissions and yield-scaled emissions at all sites. AN application in more frequent smaller doses reduced emissions at all sites, however, the type of fertiliser (AN or urea) had no impact. A significant difference in mean annual cumulative emissions between sites reflected differences in rainfall, and suggests that location specific or rainfall driven emission estimates could be considered.

62. Nitrous oxide emissions and nitrate leaching in an organic and a conventional cropping system (Seine basin, France)

• Authors:
  • Grehan, E.
  • Tournebize, J.
  • Billen, G.
  • Garnier, J.
  • Benoit, M.
  • Bruno, M.
• Source: Article
• Volume: 213
• Year: 2015
• Summary: Agricultural activities can lead to nitrogen losses in the environment, particularly nitrate (NO 3-) leaching and nitrous oxide (N 2O) emissions. This study aims to measure N losses from organic farming (OF) and conventional farming (CF) arable cropping systems, both adopted in a single farm, located on the same drained loamy soil in the Seine basin, in the North of France. Leaching was measured with ceramic cups and N 2O emissions with automatic and manual chambers over the 2011-2014 period. Manual chambers showed the same trend as automatic chambers but underestimated small variations and overestimated peak emissions. On average, N 2O emissions were lower in OF (0.650.64 kg N ha -1 yr -1) than in CF fields (0.950.77 kg N ha -1 yr -1). The mean amount of N leached was 13.3 kg N ha -1 yr -1 in the OF system during the 8-crops rotation (alfalfa 1, alfalfa 2, wheat, green bean, wheat, faba bean, wheat, flax) and 18.4 kg N ha -1 yr -1 in the CF system for a 3-crops CF rotation (legume, wheat, wheat), corresponding to 9 and 10% of total N inputs, respectively. Leached N and N 2O emissions expressed per unit of protein-N harvested were slightly higher in CF (0.11 kg NO 3-N kg -1 N yr -1 and 5.4 N 2O-N kg -1 N yr -1, respectively) than in OF systems (0.10 kg NO 3-N kg -1 N yr -1 and 4.7 g N 2O-N kg -1 N yr -1, respectively). These results show a relative lower environmental impact of OF practices compared to CF practices (-30% area-scaled and -12% yield-scaled for leaching and N 2O emissions), with further margins of progress in both systems, including a better management of fertilisers, legumes and catch-crops.

63. Spatio-temporal drivers of soil and ecosystem carbon fluxes at field scale in an upland grassland in Germany

• Authors:
  • Baatz, R.
  • Schmidt, M.
  • Hebel, C. V.
  • Schirrmann, M.
  • Borchard, N.
  • Firbank, L.
  • Vereecken, H.
  • Herbst, M.
• Source: Article
• Volume: 211
• Year: 2015
• Summary: Ecosystem carbon (C) fluxes in terrestrial ecosystems are affected by varying environmental conditions (e.g., soil heterogeneity and weather) and land management. However, the interactions between soil respiration ( Rs) and net ecosystem exchange (NEE) and their spatio-temporal dependence on environmental conditions and land management at field scale is not well understood. We performed repeated C flux measurement at 21 sites during the 2013 growing season in a temperate upland grassland in Germany, which was fertilized and cut three times according to the agricultural practice typical of the region. Repeated measurements included determination of NEE, Rs, leaf area index (LAI), meteorological conditions as well as physical and chemical soil properties. Temporal variability of Rs was controlled by air temperature, while LAI influenced the temporal variability of NEE. The three grass cuts reduced LAI and affected NEE markedly. More than 50% of NEE variability was explained by defoliation at field scale. Additionally, soil heterogeneity affected NEE, but to a lower extent (>30%), while Rs remained unaffected. We conclude that grassland management (i.e., repeated defoliation) and soil heterogeneity affects the spatio-temporal variability of NEE at field scale.

64. Local natures? Climate change, beliefs, facts and norms

• Authors:
  • Calder, G.
• Source: Climatic Change
• Volume: 133
• Issue: 3
• Year: 2015
• Summary: It is banal to say that different beliefs provide the basis for different conceptions of the good and diverse ways of life, the protection of which will seem to many to be paramount as a matter of justice. But what happens when those beliefs are about global processes of the magnitude of those involved in climate change, with the scale of their implications? How, and to what extent, should the diversity of local beliefs about factors relevant to climate change be factored into a normative response to the challenges it poses? This article is framed in response to the companion piece 'Local perceptions in climate change debates', which presents detailed contrasts between such beliefs in Peru and the South Tyrol. Focusing on perceptions of the nature/culture relationship as an example, I contrast 'globalist' and 'localist' normative responses to evidence of such diversity in belief. Both are limited, to the extent that they dwell on the fair treatment of beliefs. I argue that normatively speaking, what is crucial is not accommodating diversity in belief - as if beliefs about the factors implicated in climate change were on a par with other beliefs about the nature of the good - but acknowledging the requirement to make 'thick' commitments about which such beliefs are most adequate. Alongside their fascinating contributions in other respects, anthropological findings can be crucial in this one. They will help furnish the kind of understanding of human/nature relations on which a political philosophy of climate change must depend.

65. Vegetated canals mitigate nitrogen surplus in agricultural watersheds.

• Authors:
  • Vincenzi, F.
  • Racchetti, E.
  • Soana, E.
  • Castaldelli, G.
  • Fano, E.
  • Bartoli, M.
• Source: Agriculture, Ecosystems & Environment
• Volume: 212
• Year: 2015
• Summary: Within irrigated agricultural watersheds, canal networks may play a crucial role as nitrogen (N) sink. This is due to the intertwined action of macrophytes and microbial communities occurring in the dense net of small watercourses. We hypothesize that vegetated canals may buffer relevant fractions of excess N from agriculture via microbial denitrification, and that vegetation provides multiple interfaces that greatly support the activity of bacteria. To test these hypotheses, we measured net dinitrogen (N 2) fluxes in bare sediments and at the reach-scale in vegetated ditches. As study areas we selected canals subjected to diffuse N pollution, laying in a lowland sub-basin of the Po River (northern Italy). Denitrification was evaluated on the basis of changes in dissolved N 2:Ar, measured by Membrane Inlet Mass Spectrometry. Complementary data were obtained via upstream-downstream inorganic N balances and intact core incubations targeting sedimentary N fluxes. Denitrification was the major pathway for N removal, with rates at the reach-scale (5-25 mmol N m -2 d -1) up to one order of magnitude higher than in sediment alone (3-7 mmol N m -2 d -1). Results highlighted that N uptake by macrophyte stands was quantitatively small; however, aquatic vegetation provided multiple interfaces for microbial growth and N-related processes. Our data suggest that 1 ha of vegetated canal may remove between 150 and 560 kg N yr -1. In the study area, an average canal density of ~0.05 linear km ha -1 of agricultural land has the potential to buffer 5-17% of the excess N from agriculture (~60 kg N ha -1 yr -1). The results of this study suggest the central role of emergent vegetation in promoting microbial N-transformation and canal self-depuration. Innovative management of the canal networks should couple hydraulic needs with the maintenance of emergent vegetation.

66. Impact of biochar addition on the physical and hydraulic properties of a clay soil

• Authors:
  • Ventrella, D.
  • Palumbo, A.
  • Niedda, M.
  • Giglio, L.
  • Castellini, M.
• Source: Soil and Tillage Research
• Volume: 154
• Year: 2015
• Summary: Biochar represents a soil conditioner that can change the physical and hydraulic properties of the soil. To date, little information is available about the biochar-induced changes on physical and hydraulic properties of fine textured soils. Therefore, an evaluation of its effects before the field use is advisable. The main objective of this investigation was to evaluate the impact of biochar addition on saturated (Kfs) and unsaturated (K(h)) hydraulic conductivity, water retention, capacitive indicators such as macroporosity (Pmac), air capacity (AC), plant available water (PAWC) and relative field capacity (RFC, equal to the ratio between field capacity and saturated soil water content), dry bulk density (ρb) of a repacked clay soil. Biochar effects on simulated wheat yields were also evaluated using the DSSAT model. Five levels of amendments (0-5-10-20-30g biochar per kg-1 soil) were used and the soil columns remained in the field for about 30 months until undisturbed soil conditions were reached. No significant differences of the Kfs values were detected between amended and unamended soils and the ratio between Kfs values was, on average, equal to a factor of 1.01-0.93-0.98-1.25 (respectively for C5-C10-C20-C30). In the same way, biochar did not affect appreciably the K(h) values. Depending on the applied pressure head or the biochar concentration, the differences were within a factor of 0.83-0.39. On the contrary, significant increases of soil water retention were detected close to water saturation (0 values was, on average, equal to a factor of 1.01-0.93-0.98-1.25 (respectively for C5-C10-C20-C30). In the same way, biochar did not affect appreciably the K(h) values. Depending on the applied pressure head or the biochar concentration, the differences were within a factor of 0.83-0.39. On the contrary, significant increases of soil water retention were detected close to water saturation (0 values was, on average, equal to a factor of 1.01-0.93-0.98-1.25 (respectively for C5-C10-C20-C30). In the same way, biochar did not affect appreciably the K(h) values. Depending on the applied pressure head or the biochar concentration, the differences were within a factor of 0.83-0.39. On the contrary, significant increases of soil water retention were detected close to water saturation (0b values, our results confirm that small decreases in bulk density (on average, 0.014gcm-3) may result in appreciable modifications in soil water retention close to water saturation. The simulations carried out with DSSAT suggested that a moderate addition of biochar to a clay soil (not higher than 10gkg-1) has the potential to increase the production of durum wheat (mean increase±standard deviation, 236±126kgha-1). These findings will have to be verified under field conditions. © 2015 Elsevier B.V.

67. Soil Attributes and C and N Variation in Histosols Under Different Agricultural Usages in the State of Rio De Janeiro, Brazil

• Authors:
  • Pessim de Oliveira, A.
  • Pereira, M.
  • Cunha dos Anjos, L.
  • Zuchello, F.
  • Chaves Soares, P.
• Source: Agriculture Sciences
• Volume: 31
• Issue: 5
• Year: 2015
• Summary: Histosols are a natural reservoir of C in the soil, and their drainage followed by other farming practices leads to subsidence and soil organic matter transformations. The objective of this study was to evaluate the influence of use and management of Histosols, by means of: characterizing chemical and physical properties, and the content of SOM and humic fractions; and quantifying C and N stocks. In addition, to obtain preliminary data on greenhouse gas emissions (CO2, N2O) in Histosol areas with different agricultural practices. Three areas were selected with similar soil and environment, two in Macae municipality, under pasture, and with bean annual crop rotation, and the third in Santa Cruz, Rio de Janeiro city, cultivated with cassava (Manihot esculenta). The attributes evaluated were: physical - bulk density (BD), particle density (Dp), organic matter density (OMD), mineral matter (MM), mineral residue (MR), aggregate stability; and chemical - pH, exchangeable cations, soil organic matter (SOM), carbon in the humin (HUM-C), humic acid (HAF-C) and fulvic acid (FAF-C) fractions; stocks of C and N; and flux of CO2 and N2O. In general, the area cultivated with cassava had the highest values for exchangeable cations, as a result of fertilizer and soil management practices. The cassava site showed the highest values of BD and Dp; total volume of pores; MM, MR and OMD and higher degree of transformation of SOM; indicating higher alteration of Histosols properties under this usage. In all sites, the C levels indicated dominance of humin fraction. The SOM and C and N stocks were highest in the pasture, indicating preservation of organic matter, with values from 115.92 to 99.35Mg ha(-1) of C e 8.35 to 4.45 Mg ha(-1) for N. The values of CO2-C flux were within the range proposed by the IPCC, where the highest emission was 0.09 Mg CO2 ha(-1) day(-1) in the pasture site. The values of N2O-N flux were lower than proposed by the IPCC, with the highest value (270 g N2O-N m(-2) day(-1)) in the area under beans (crop rotation). In general, the multivariate analyses discriminated the sites and the pasture was the usage that least affected the Histosols properties.

68. Designing innovative productive cropping systems with quantified and ambitious environmental goals

• Authors:
  • Colnenne-David,Caroline
  • Dore,Thierry
• Source: Renewable Agriculture and Food Systems
• Volume: 30
• Issue: 6
• Year: 2015
• Summary: Agriculture must face a number of very pressing environmental issues. We used the prototyping method to design three innovative cropping systems, each satisfying three ambitious goals simultaneously: (1) overcoming a major environmental constraint, which represents a major break regarding objectives to be reached in current cropping systems (differing between systems: a ban on all pesticides but with chemical nitrogen (N) fertilizer permitted; reducing fossil energy consumption by 50%; or decreasing greenhouse gas (GHG) emissions by 50%), (2) meeting a wide range of environmental criteria and (3) maximizing yields, given the major constraint and environmental targets. A fourth cropping system was designed, in which the environmental and yield targets were achieved with no major constraint (the productive high environmental performance cropping system (PHEP) system). The performances of these innovative cropping systems were compared to a conventional system in the Ile-de-France region. We used a three-step prototyping method: (1) new cropping systems were designed on the basis of scientific and expert knowledge, (2) these system prototypes were assessed with tools and a model (ex ante assessment) adjusted to the set of constraints and targets, with optimization by an iterative process until the criteria were satisfied and (3) evaluation in a long-term field experiment (ex post assessment), which is currently underway. We describe only the first two steps here, together with the results of the prototypes assessment with tools and a model. The pesticide, energy and GHG constraints were fulfilled. All these innovative systems satisfied environmental criteria in terms of nitrogen and phosphorus management, pesticide use, energy consumption and crop diversity. For the pesticide-free system, the soil organic matter indicator was lower than expected due to frequent plowing (every 2 years) and yields were 20-50% lower than for the PHEP system, depending on the crop considered. We focus our discussions on the design methodology and the availability of scientific knowledge and tools for projects of this type.

69. Soil physical quality in contrasting tillage systems in organic and conventional farming

• Authors:
  • Crittenden,S. J.
  • Poot,N.
  • Heinen,M.
  • van Balen,D. J. M.
  • Pulleman,M. M.
• Source: Soil and Tillage Research
• Volume: 154
• Year: 2015
• Summary: Reduced tillage can improve soil physical quality relative to mouldboard ploughing by lessening soil disturbance, leaving organic matter at the soil surface, and stimulating soil biological activity. In organic farming, continuous ploughing may negate benefits to soil structure and function from increased use of manures and more diverse crop rotations, which are particularly important components of organic farming. The current study examined soil physical quality (i.e., properties and functioning) of a 4-year old reduced tillage system under organic and conventional farming with crop rotations that included root crops. Reduced tillage was compared to conventional mouldboard ploughing (MP) in 2 organic fields at different points of the same crop rotation (Org A and Org B) and 1 conventional field (Conv A). Reduced tillage consisted of non-inversion tillage (NIT) to 18-23. cm depth whereas MP was characterised by annual mouldboard ploughing to 23-25. cm depth. NIT improved soil water retention in Org B but had no effect in Org A. NIT increased soil aggregate stability at 10-20. cm depth compared to MP in all fields, and additionally at 0-10. cm in Conv A. Penetration resistance was higher in NIT in all fields. Furthermore, soil organic matter content was higher in NIT than MP at 0-10. cm depth in all fields and at 10-20. cm in Org B and Conv A. NIT increased carbon stocks in Org B but not in Org A. NIT statistically increased crop yields in spring wheat/faba bean mixture in Org A, and there was no yield penalty from NIT in Org B spring wheat nor Conv A sugar beet. In contrast, field-saturated hydraulic conductivity in all fields in autumn was lower in NIT. Differences in crop (i.e., phase of rotation) and associated organic inputs between Org A and B likely accounted for the differences in effects of tillage system. Overall, the NIT system improved or imposed no penalty on soil physical quality (except field-saturated hydraulic conductivity) and improved or imposed no penalty on crop yields and could therefore be considered as a viable alternative for farmers. © 2015 Elsevier B.V..

70. The fate of urea nitrogen applied to a vegetable crop rotation system

• Authors:
  • Chen, D.
  • Weng, B.
  • Zhang, J.
  • Zheng, X.
  • Hu, X.
  • Zhang, Y.
  • Li, S.
  • Ding, H.
• Source: Nutrient Cycling in Agroecosystems
• Volume: 103
• Issue: 3
• Year: 2015
• Summary: To investigate the fate of urea nitrogen (N) applied to vegetable fields, three N rates, N0 (0 kg N/ha), N1(225 or 240 kg N/ha) and N2 (450 or 480 kg N/ha) were applied to a rotation system. Nitrogen fertilizer recovery (NFR), N residue in soil, and N losses were measured in situ. Higher N application rates resulted in lower NFR, and increased N residues in soil and losses. The NFR, Chinese cabbage, and eggplant were different in the N1 and N2 groups (P < 0.01). The ratios of N fertilizer residue at 0-60 cm deep ranged from 30.2 to 41.1 % (N1), and 33.1 to 57.7 % (N2). The N loss ratios were only 6.6 % (N1) and 11.9 % (N2), because of the lower precipitation rates and temperatures characteristic of its growing season; meanwhile, N losses were 31.1 and 37.4 % in cayenne pepper, and 24.1 and 29.2 % in eggplants in the N1 and N2 treatments, respectively. The main pathways of N loss were leaching, followed by gaseous losses; these were major pathways of N loss in seasons with lower precipitation rates. NH3 volatilization was correlated with soil temperature (P < 0.01), and N2O emissions were correlated with soil moisture in the N1 treatment and with soil NH4 (+)-N concentration in the N2 treatment (P < 0.01). Denitrification rates were correlated with soil moisture in the N0 and N1 treatments, and with NO3 (-)-N content in the N2 treatment (P < 0.01). Finally, loss due to runoff was correlated with precipitation (P < 0.01).