• Authors:
    • Larsen, S. E.
    • Kristensen, K.
    • Elsgard, L.
    • Blicher-Mathiesen, G.
    • Schäfer, C. -M
    • Hoffmann, C. C.
    • Petersen, S. O.
    • Torp, S. B.
    • Greve, M. H.
  • Source: Biogeosciences
  • Volume: 9
  • Issue: 1
  • Year: 2012
  • Summary: The use of organic soils by agriculture involves drainage and tillage, and the resulting increase in C and N turnover can significantly affect their greenhouse gas balance. This study estimated annual fluxes of CH4 and N2O, and ecosystem respiration (R-eco), from eight organic soils managed by agriculture. The sites were located in three regions representing different landscape types and climatic conditions, and three land use categories were covered (arable crops, AR, grass in rotation, RG, and permanent grass, PG). The normal management at each site was followed, except that no N inputs occurred during the monitoring period from August 2008 to October 2009. The stratified sampling strategy further included six sampling points in three blocks at each site. Environmental variables (precipitation, PAR, air and soil temperature, soil moisture, groundwater level) were monitored continuously and during sampling campaigns, where also groundwater samples were taken for analysis. Gaseous fluxes were monitored on a three-weekly basis, giving 51, 49 and 38 field campaigns for land use categories AR, PG and RG, respectively. Climatic conditions in each region during monitoring were representative as compared to 20-yr averages. Peat layers were shallow, typically 0.5 to 1 m, and with a pH of 4 to 5. At six sites annual emissions of N2O were in the range 3 to 24 kg N2O-N ha(-1), but at two arable sites (spring barley, potato) net emissions of 38 and 61 kg N2O-N ha(-1) were recorded. The two high-emitting sites were characterized by fluctuating groundwater, low soil pH and elevated groundwater SO42- concentrations. Annual fluxes of CH4 were generally small, as expected, ranging from 2 to 4 kg CH4 ha(-1). However, two permanent grasslands had tussocks of Juncus effusus L. (soft rush) in sampling points that were consistent sources of CH4 throughout the year. Emission factors for organic soils in rotation and with permanent grass, respectively, were estimated to be 0.011 and 0.47 gm(-2) for CH4, and 2.5 and 0.5 gm(-2) for N2O. This first documentation of CH4 and N2O emissions from managed organic soils in Denmark confirms the levels and wide ranges of emissions previously reported for the Nordic countries. However, the stratified experimental design also identified links between gaseous emissions and site-specific conditions with respect to soil, groundwater and vegetation which point to areas of future research that may account for part of the variability and hence lead to improved emission factors or models.
  • Authors:
    • Plieninger, T.
  • Source: Applied Geography
  • Volume: 32
  • Issue: 2
  • Year: 2012
  • Summary: This study explores the potential of historical maps to detect, measure and monitor changes of trees outside forests. The main goal is to assess local-level changes of scattered trees and orchards and their land-use determinants in two areas in Southern Germany between 1901/1905 and 2009. Firstly, overall landscape changes are recorded. Secondly, the spatial-temporal trajectories of scattered trees and their land-use determinants are identified. Thirdly, changes in quantity and fragmentation patterns of traditional orchards are analyzed in their relationship to overall land-cover change. The results confirm major losses in scattered trees, mainly due to urbanization, agricultural intensification, and land abandonment. They further reveal that, while orchards have persisted in total area, they have undergone critical changes toward a simplified landscape structure and loss of the traditional land-use mosaic, which is a characterizing feature of high nature value landscapes. Multi-temporal assessment showed that most trends have been continuous and did not change directions over time, but rather accelerated during periods of rapid change (most dramatically in the 1950-1990 period). The case of orchards and scattered trees illustrates a major problem of cultural landscapes in Europe: Semi-natural landscape features of high nature value are threatened by both intensification and abandonment of land uses. This makes their conservation a potentially costly enterprise, as both opportunity costs for lost alternative land uses and for conservation management costs arise. (C) 2011 Elsevier Ltd. All rights reserved.
  • Authors:
    • Oliveira, E. B. de
    • Moraes, A. de
    • Pelissari, A.
    • Reis, E. F. dos
    • Ruaro, L.
  • Source: Pesquisa Agropecuária Brasileira
  • Volume: 47
  • Issue: 4
  • Year: 2012
  • Summary: The objective of this work was to assess the effect of soil management systems and winter cover crops on the number of propagules of Fusarium spp. in soil, the incidence of sudden death syndrome (SDS), and the productivity of the soybean cultivars CD 206 and FT Fenix. Two experiments were carried out in the 2006/2007 and 2007/2008 crop years. The experimental design was a randomized complete block in a split-split plot arrangement, with three replicates. Two soil tillage systems were evaluated: no-tillage and plowed soil at a depth of 25 cm. The soil covers used were: black oat, with two planting densities; black oat+vetch; ryegrass; and fallow. The incidence of the disease in the 2006/2007 crop year in the cultivar FT Fenix was lower than in CD 206. In the 2007/2008 crop, there was no significant difference. There was an increase in productivity, of 125 kg ha -1, in the plowed treatment, when compared to no-tillage. The cover with black oat+vetch showed a higher number of propagules of Fusarium spp. in soil in the 2006/2007 crop year. However, in the second year, this difference was not observed. The soil management systems and winter cover crops used do not influence the incidence of SDS in soybean cultivars or the number of Fusarium spp. propagules in soil. The plowed system provides an increase in soybean yield in the second year of management.
  • Authors:
    • Cai, L.
    • Padovan, B.
    • Lee, B.
    • Ren, Y. L.
  • Source: Pest Management Science
  • Volume: 68
  • Issue: 2
  • Year: 2012
  • Summary: BACKGROUND: Methyl bromide is being phased out for use on stored commodities, as it is listed as an ozone-depleting substance, and phosphine is the fumigant widely used on grains. However, phosphine resistance occurs worldwide, and phosphine fumigation requires a long exposure period and temperatures of > 15 degrees C. There is an urgent requirement for the development of a fumigant that kills insects quickly and for phosphine resistance management. This paper reports on a new fumigant formulation of 95% ethyl formate plus 5% methyl isothiocyanate as an alternative fumigant for stored grains. RESULTS: The formulation is stable for at least 4 months of storage at 45 degrees C. A laboratory bioassaywith the formulation showed that it controlled all stages of Sitophilusoryzae (L.), Sitophilusgranarius (L.), Tribolium castaneum (Herbst), Rhyzopertha dominica (F.), Trogoderma variabile Ballion and Callosobruchus maculatus (Fabricius) in infestedwheat, barley, oats and peas at 80 mg L-1 for 5 days, and in canola at both 40mg L-1 for 5 days and 80mg L-1 for 2 days at 25 +/- 2 degrees C. After an 8-14 day holding period, residues of ethyl formate and methyl isothiocyanate in wheat, barley, peas and canola were below the experimental permit levels of 1.0 and 0.1 mg kg(-1). However, fumigated oats needed an 18 day holding period. CONCLUSIONS: The findings suggest that the ethyl formate plusmethyl isothiocyanate formulation has potential as a fumigant for the control of stored-grain insect pests in various commodities. (C) 2011 Society of Chemical Industry
  • Authors:
    • Oehler, F.
    • Ferchaud, F.
    • Durand, P.
    • Salmon-Monviola, J.
    • Sorel, L.
  • Source: Computers and Electronics in Agriculture
  • Volume: 81
  • Issue: February
  • Year: 2012
  • Summary: Assessing the environmental impacts of agricultural practices at the catchment scale increasingly involves the use of spatially distributed models that include cropping systems as input. Use of these models for diagnosis and evaluation requires large datasets at large spatial and temporal scales. The description of spatial dynamics of cropping systems at a fine resolution (i.e. field level) is particularly needed. As these data are scarce or not available, our objective was to propose a model that first reconstructs spatial dynamics of past cropping systems from available data, and second constructs alternative spatial cropping systems, corresponding to agricultural practice scenarios. Classification systems for farms and fertilisation practices were defined to classify farm-level organisation for crop-succession and crop management strategies, in particular nitrogen fertilisation. Winter cover crops and multiple strategies per crop at the farm level can be represented with this model. Cropping systems are modelled in three steps: we modelled crop cover succession in summer with Markov chains based on empirical data and in winter with rules based on expert agronomic knowledge: lastly a Knapsack-based algorithm was used to allocate a crop management system to fields with constraints on several crop management strategies per crop type. Results of a case study performed on the Fremeur catchment (western France) show that this model respects the main constraints for cropping system modelling to assess agricultural practices at the catchment scale. From a scenario discussed with stakeholders and regional authorities characterised by stable areas of summer crops, the decrease in bare soil area in winter and overall reduction in total nitrogen fertilisation for different types of crops and farms we demonstrate the model's ability to simulate coherent cropping systems. Thus, if faced with a lack of data or knowledge about the local factors that drive changes in cropping systems, the model can construct the spatial dynamics of cropping systems, which can be used as input to distributed nitrate transfer models to assess agricultural practices at the catchment scale. (C) 2011 Elsevier B.V. All rights reserved.
  • Authors:
    • Merckx, R.
    • Vanuytrecht, E.
    • Clymans, W.
    • Langhans, C.
    • Diels, J.
    • Govers, G.
    • Van den Putte, A.
    • Raes, D.
  • Source: Soil & Tillage Research
  • Volume: 122
  • Year: 2012
  • Summary: One of the most frequently used techniques to combat soil erosion on agricultural fields is conservation agriculture (CA). Conservation tillage techniques (CT), together with residue management and rotation are the pillars of CA. Studies have shown that CT can indeed be very effective in combating soil erosion. While several studies have demonstrated how CT may affect (the distribution of) carbon in the soil and documented compaction risks under CT, much less information is available with respect to the potential effects of CT on within-soil water movement and nutrient status. We therefore investigated the effect of superficial (0.15-0.2 m depth) and deep (0.3-0.4 m depth) CT on soil properties of agricultural silt loam soils in Belgium. From 2008 to 2010, we analyzed the effect of CT on water content, hydraulic conductivity, penetration resistance, bulk density, organic carbon and nitrate content of the soil. At the same time the effect of CT on root growth and crop yield was analyzed. We found that soil structural differences between conventional mouldboard ploughing and deep CT tended to be very small and did not have any effect on root growth and/or crop yield. Furthermore, we were not able to detect any significant difference between the different implements used in CT. The application of superficial CT however, led to an increase in penetration resistance in the upper soil layer hindering vertical soil water movement and root growth on one trial field. Crop yield was not affected due to a sufficient water and nutrient supply. Effects of deep CT on water availability and water movement were very limited and suggest that deep CT may slightly improve water availability only during dry summer periods. Total carbon content was not affected by CT, but its distribution through the plough layer changed whereby the carbon content in the upper few centimetres of soil increased while a decrease was noted at greater depths. The reduction of the nitrate content observed in deeper soil layers indicates that reduced tillage did not lead to increased nitrate leaching and may even help to reduce this problem if adequate catch crops are planted. We conclude that, on the Belgian silt loam soils, deep CT can be practiced whereby good soil functioning can be ensured. As crop yields were also similar, deep CT is a viable alternative that may contribute to soil protection. The use of superficial CT cannot be recommended due to a compaction risk. (c) 2012 Elsevier B.V. All rights reserved.
  • Authors:
    • McDonnell, K.
    • Grant, J.
    • Finnan, J.
    • Ryan, D.
    • Fagan, C.
    • Galbally, P.
  • Source: Journal of Environmental Quality
  • Volume: 41
  • Issue: 1
  • Year: 2012
  • Summary: It is necessary to determine the risk of water pollution arising from amendment of organic by-products (OBs) to energy crops under Irish conditions. Therefore, the impact of landspreading two OBs on the quality of groundwater underlying plantations of Miscanthus * giganteus was assessed. Municipal biosolids and distillery effluent (DE) were spread annually (for 4 yr) on six 0.117-ha treatment plots at rates of 100, 50, and 0%. The 100% rate represented a maximum P load of 15 t ha -1 as per Irish EPA regulation. Groundwater was sampled for 25 mo and tested for pH, electrical conductivity, NO 3-, orthophosphate (PO 43-), total soluble P, K +, Cu, Cd, Cr, Pb, Ni, and Zn. Assessment of quality was based on comparison with Irish groundwater threshold values (GTVs). The study was limited to within-plot using a "well bottom" approach and did not investigate movement of groundwater plumes or vectors of percolation through the soil profile. Mean groundwater concentrations did not exceed GTVs during the sampling period for any species, with the exception of groundwater PO 43- in the 100% DE plot, which was almost double the GTV of 0.035 mg L -1. There was no significant build-up of nutrients or heavy metals in groundwater (or soil) for any plot. Excessive PO 43- in the 100% DE plot groundwater is likely due to high background soil P, soil characteristics, and the occurrence of macropore/soil pore flow. These factors (particularly background soil P) should be assessed when determining suitable sites for land-spreading OBs.
  • Authors:
    • Southway, S.
    • Simper, J.
    • Birkett, T.
    • Moreby, S.
    • Oaten, H.
    • Holland, J. M.
    • Smith, B. M.
  • Source: Agriculture Ecosystems and Environment
  • Volume: 155
  • Year: 2012
  • Summary: The impact of two predatory guilds, epigeal and aerial natural enemies, on levels of cereal aphid control in winter wheat was examined on farms with contrasting proportions of grass margins, one of the most popular agri-environment options in England. In year 1, by 14 d after inoculation the aerial natural enemies alone had caused substantial reductions (88%) in numbers of cereal aphids compared to where no natural enemies were present. In contrast, epigeal predators achieved a 31% reduction, although this reached 88% after 28 d. In year 2, both aerial and epigeal natural enemies achieved over 87% control after 14 d. Aerial natural enemies were largely comprised of predatory Diptera and Linyphiidae (Araneae). Levels of control were positively related to the proportion of linear grass margins within 250, 500 and 750 m radii of the study arenas. There was weaker evidence that hedgerows decreased aphid control by epigeal predators. This study demonstrated that an agri-environment option can be used to improve an ecosystem service on arable farmland.
  • Authors:
    • Krumhardt, K. M.
    • Kaplan, J. O.
    • Zimmermann, N. E.
  • Source: Global Change Biology
  • Volume: 18
  • Issue: 3
  • Year: 2012
  • Summary: The long residence time of carbon in forests and soils means that both the current state and future behavior of the terrestrial biosphere are influenced by past variability in climate and anthropogenic land use. Over the last half-millennium, European terrestrial ecosystems were affected by the cool temperatures of the Little Ice Age, rising CO 2 concentrations, and human induced deforestation and land abandonment. To quantify the importance of these processes, we performed a series of simulations with the LPJ dynamic vegetation model driven by reconstructed climate, land use, and CO 2 concentrations. Although land use change was the major control on the carbon inventory of Europe over the last 500 years, the current state of the terrestrial biosphere is largely controlled by land use change during the past century. Between 1500 and 2000, climate variability led to temporary sequestration events of up to 3 Pg, whereas increasing atmospheric CO 2 concentrations during the 20th century led to an increase in carbon storage of up to 15 Pg. Anthropogenic land use caused between 25 Pg of carbon emissions and 5 Pg of uptake over the same time period, depending on the historical and spatial pattern of past land use and the timing of the reversal from deforestation to afforestation during the last two centuries. None of the currently existing anthropogenic land use change datasets adequately capture the timing of the forest transition in most European countries as recorded in historical observations. Despite considerable uncertainty, our scenarios indicate that with limited management, extant European forests have the potential to absorb between 5 and 12 Pg of carbon at the present day.
  • Authors:
    • Moyo, B. H.
    • Chirwa, P. W.
    • Khumalo, S.
    • Syampungani, S.
  • Source: Agriculture Ecosystems and Environment
  • Volume: 157
  • Year: 2012
  • Summary: This paper reviews the agroecosystems and agricultural biodiversity in Southern Africa and highlights the importance of the agricultural landscape in biodiversity conservation and the important role that the traditional farming systems play in conserving biodiversity. The review established that agrobiodiversity is of great importance to both small scale and large commercial farmers in Southern Africa through its provision of ecosystem services. The paper also highlights the significant loss of agrobiodiversity as a result of human population pressure and the transition from traditional mixed farming systems which is characterized with high agrobiodiversity, to modern monoculture farming resulting in decline of species diversity. Although concerted efforts are being made to promote the sustainable use and management of this agrobiodiversity, there need to have a multi-stakeholder approach so that conservation efforts are successful, a role that is currently played by the SADC Plant Genetic Resources Centre in Southern African conservation of agrobiodiversity.