Wetlands can either be net sinks or net sources of greenhouse gases (GHGs), depending on the mean annual water level and other factors like average annual temperature, vegetation development, and land use. Whereas drained and agriculturally used peatlands tend to be carbon dioxide (CO₂) and nitrous oxide (N₂O) sources but methane (CH₄) sinks, restored (i.e. rewetted) peatlands rather incorporate CO₂, tend to be N₂O neutral and release CH₄. One of the aims of peatland restoration is to decrease their global warming potential (GWP) by reducing GHG emissions. <br><br> We estimated the greenhouse gas exchange of a peat bog restoration sequence over a period of 2 yr (1 July 2007–30 June 2009) in an Atlantic raised bog in northwest Germany. We set up three study sites representing different land use intensities: intensive grassland (deeply drained, mineral fertilizer, cattle manure and 4–5 cuts per year); extensive grassland (rewetted, no fertilizer or manure, up to 1 cutting per year); near-natural peat bog (almost no anthropogenic influence). Daily and annual greenhouse gas exchange was estimated based on closed-chamber measurements. CH₄ and N₂O fluxes were recorded bi-weekly, and net ecosystem exchange (NEE) measurements were carried out every 3–4 weeks. Annual sums of CH₄ and N₂O fluxes were estimated by linear interpolation while NEE was modelled. <br><br> Regarding GWP, the intensive grassland site emitted 564 ± 255 g CO₂–C equivalents m⁻² yr⁻¹ and 850 ± 238 g CO₂–C equivalents m⁻² yr⁻¹ in the first (2007/2008) and the second (2008/2009) measuring year, respectively. The GWP of the extensive grassland amounted to −129 ± 231 g CO₂–C equivalents m⁻² yr⁻¹ and 94 ± 200 g CO₂–C equivalents m⁻² yr⁻¹, while it added up to 45 ± 117 g CO₂–C equivalents m⁻² yr⁻¹ and −101 ± 93 g CO₂–C equivalents m⁻² yr⁻¹ in 2007/08 and 2008/09 for the near-natural site. In contrast, in calendar year 2008 GWP aggregated to 441 ± 201 g CO₂–C equivalents m⁻² yr⁻¹, 14 ± 162 g CO₂–C equivalents m⁻² yr⁻¹ and 31 ± 75 g CO₂–C equivalents m⁻² yr⁻¹ for the intensive grassland, extensive grassland, and near-natural site, respectively. <br><br> Despite inter-annual variability, rew...

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In agricultural soils, macroporosity and hydraulic properties are influenced by tillage practices. The objective of this study was to characterize macroporosity and surface soil hydraulic properties in two soils of different texture (Lietzen: sandy loam–Humic Dystrudept; Adenstedt: silt loam; Typic Hapludoll) under conventional (CT) and conservational (RT) tillage systems. Soil hydraulic conductivity was assessed in situ by ponded infiltration with single rings (n = 70) and tension infiltration by means of a “closed‐top” hood infiltrometer (HIF; n = 48). Macroporosity (pore diameters >1 mm) was estimated from differences in infiltration at saturation and at −3 cm H2O soil matric potential. Mean saturated hydraulic conductivity (Ks) for Lietzen was 3.1 × 10−5 m s−1 and for Adenstedt was 4.3 × 10−5 m s−1 These values are by one order of magnitude higher than values estimated from soil texture. This implies that soil structure has a dominant influence on hydraulic conductivity. Mean values of macroporosity were 0.005% for Lietzen and 0.018% for Adenstedt (using the method of Watson and Luxmoore). The respective values were 0.0008 and 0.0013% when the method of Bodhinayake et al. was used. For Adenstedt, RT showed higher macroporosity than CT (not significant at P < 0.05 for n = 12). Such treatment‐induced differences were less developed for Lietzen. The Ks values measured with the ponded ring infiltrometer (RIF) at the sandy Lietzen site were higher than the corresponding values measured with the tension infiltrometer. These differences may be caused by subcritical soil water repellency (i.e., contact angles of the soil‐water‐air interface below 90°), although further factors could also be important (e.g., air entrapment, differences in water saturation, geometry of infiltration devices).

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The “phosphorus index” (PI) is a semiquantitative tool to assess the risk of P loss from fields to surface waters, which is based on simple arithmetic computations of source (soil test phosphorus (STP), P applications as manure and fertilizer, plant residues) and transport factors (erosion, surface runoff, subsurface drainage, connectivity). Work done since the 1990s in the U.S.A. and several European countries has shown that this approach is capable of delineating critical source areas for P export within a watershed. It is intended to adopt such a PI tool in Germany as well. However, there is no “standard” PI, and the variety of P indices is confusing, since each state and country has developed its own version to account for special regional conditions which are important for P loss. This paper reviews the factors of P loss which are taken into account in P indices and different modifications of P indices according to their components and structural approach. The literature concerning single source and transport factors of P loss is overwhelming, and a structured selection is given in this review. Most P indices can be classed into one of three groups: 1. additive approach, 2. multiplicative approach, and 3. multiplicative‐additive approach. For Germany, it is suggested that specific factors of P loss are incorporated into the basic backbone of a Pennsylvania‐style PI. Realization of the factors could be adopted from existing Scandinavian P indices or from other research results.