ALBERT

Notes: Andalusite porphyroblasts are totally pseudomorphosed by margarite–paragonite aggregates in aluminous pelites containing the peak mineral assemblage andalusite, chlorite, chloritoid, margarite, paragonite, quartz ± garnet, in a NW Iberia contact area. Equilibria at low P–T are investigated using new KFMASH and (mainly) MnCNKFMASH grids constructed with Thermocalc 3.21. P–T and T–X pseudosections with phase modal volume isopleths are constructed for compositions relatively richer and poorer in andalusite to model the assemblages in an andalusite-bearing rock that contains a thin andalusite-rich band (ARB) during retrogression. Their compositions, prior to retrogression, are used in the modelling, and have been retrieved by restoring the pseudomorph-forming elements into the current-depleted matrix, except for Al2O3 which is assumed to be immobile. Compositional differences between the thin band and the rest of the rock have not resulted in differences in andalusite porphyroblast retrogression. The absence of chloritoid resorbtion implies either a pressure increase at constant reacting-system composition, or that its composition changed during retrogression at constant pressure, by becoming enriched in the progressively replaced andalusite porphyroblasts. T–X pseudosections at 1 kbar model this latter process using as end-members in X, first, the restored original rock and ARB compositions, and, then the same process, taking into account the change in composition of both as retrogression proceeded. The MnNCKFMASH pseudosections of rocks with different Al contents facilitate making further deductions on the rock-composition control of the resulting assemblages upon retrogression. Andalusite eventually disappears in relatively Al-poor rocks, resulting, as in this study, in a rock formed by chloritoid–chlorite as the only FM minerals, plus margarite–paragonite pseudomorphs of andalusite. In rocks richer in Al, chlorite would progressively disappear and a kyanite/andalusite–chloritoid assemblage would eventually be stable at retrograde conditions. The Al-silicate, stable during retrogression in Al-rich rocks, indicates pressure conditions and hence the tectonic context under which retrogression took place.

Notes: In statistically optimised P–T estimation, the contributions to overall uncertainty from different sources are represented by ellipses. One source, for a diffusion-controlled reaction at non-equilibrium, is diffusion modelling of the reaction texture. This modelling is used to estimate ratios, Q, between free-energy differences, ΔG, of reactions among mineral end-members, to replace the equilibrium condition ΔG = 0. The associated uncertainty is compared with those already inherent in the equilibrium case (from end-member data, activity models and mineral compositions). A compact matrix formulation is introduced for activity coefficients, and their partial derivatives governing error propagation. The non-equilibrium example studied is a corona reaction with the assemblage Grt–Opx–Cpx–Pl–Qtz. Two garnet compositions are used, from opposite sides of the corona. In one of them, affected by post-reaction Fe, Mg exchange with pyroxene, the problem of reconstructing the original composition is overcome by direct use of ratios between chemical-potential differences, given by the diffusion modelling. The number of geothermobarometers in the optimisation is limited by near-degeneracies. Their weightings are affected by strong correlations among Q ratios. Uncertainty from diffusion modelling is not large in comparison with other sources. Overall precision is limited mainly by uncertainties in activity models. Hypothetical equilibrium P–T are also estimated for both garnet compositions. By this approach, departure from equilibrium can be measured, with statistical uncertainties. For the example, the result for difference from equilibrium pressure is 1.2 ± 0.7 kbar.

Notes: This paper characterizes the metamorphic thermal structure of the Higo Metamorphic Complex (HMC) and presents the results of a numerical simulation of a geotherm with melt migration and solidification. Reconstruction of the geological and metamorphic structure shows that the HMC initially had a simple thermal structure where metamorphic temperatures and pressures increased towards apparent lower structural levels. Subsequently, this initial thermal structure has been collapsed by E–W and NNE–SSW trending high-angle faults. Pressure and temperature conditions using the analysis of mineral assemblages and thermobarometry define a metamorphic field P–T array that may be divided into two segments: the array at apparent higher structural levels has a low-dP/dT slope, whereas that at apparent lower structural levels has a high-dP/dT slope. This composite array cannot be explained by heat conduction in subsolidus rocks alone. Migmatite is exposed pervasively at apparent lower structural levels, but large syn-metamorphic plutons are absent at the levels exposed in the HMC. Transport and solidification of melt within migmatite is a potential mechanism to generate the composite array. Thermal modelling of a geotherm with melt migration and solidification shows that the composite thermal structure may be formed by a change of the dominant heat transfer from an advective regime to a conduction regime with decreasing depth. The model also predicts that strata beneath the crossing point will consist of high-grade solid metamorphic rocks and solidified melt products, such as migmatite. This prediction is consistent with the observation that migmatite was associated with the very high-dP/dT slope. The melt migration model is able to generate the very high-dP/dT segment due to the high rate of heat transfer by advection.

Notes: Sapphirine, coexisting with quartz, is an indicator mineral for ultrahigh-temperature metamorphism in aluminous rock compositions. Here a new activity-composition model for sapphirine is combined with the internally consistent thermodynamic dataset used by THERMOCALC, for calculations primarily in K2O-FeO-MgO-Al2O3-SiO2-H2O (KFMASH). A discrepancy between published experimentally derived FMAS grids and our calculations is understood with reference to H2O. Published FMAS grids effectively represent constant aH2O sections, thereby limiting their detailed use for the interpretation of mineral reaction textures in compositions with differing H2O.For the calculated KFMASH univariant reaction grid, sapphirine + quartz assemblages occur at P–T in excess of 6–7 kbar and 1005 °C. Sapphirine compositions and composition ranges are consistent with natural examples. However, as many univariant equilibria are typically not ‘seen’ by a specific bulk composition, the univariant reaction grid may reveal little about the detailed topology of multi-variant equilibria, and therefore is of limited use for interpreting the P–T evolution of mineral assemblages and reaction sequences. Calculated pseudosections, which quantify bulk composition and multi-variant equilibria, predict experimentally determined KFMASH mineral assemblages with consistent topology, and also indicate that sapphirine stabilizes at increasingly higher pressure and temperature as XMg increases. Although coexisting sapphirine and quartz can occur in relatively iron-rich rocks if the bulk chemistry is sufficiently aluminous, the P–T window of stability shrinks with decreasing XMg. An array of mineral assemblages and mineral reaction sequences from natural sapphirine + quartz and other rocks from Enderby Land, Antarctica, are reproducible with calculated pseudosections. That consistent phase diagram calculations involving sapphirine can be performed allows for a more thorough assessment of the metamorphic evolution of high-temperature granulite facies terranes than was previously possible. The establishment of a a-x model for sapphirine provides the basis for expansion to larger, more geologically realistic chemical systems (e.g. involving Fe3+).

Notes: Large garnet poikiloblasts hosted by leucosome in metapelitic gneiss from Broken Hill reflect complex mineral–melt relationships. The spatial relationship between the leucosomes and the garnet poikiloblasts implies that the growth of garnet was strongly linked to the production of melt. The apparent difficulty of garnet to nucleate a large number of grains during the prograde breakdown of coexisting biotite and sillimanite led to the spatial focussing of melting reactions around the few garnet nuclei that formed. Continued reaction of biotite and sillimanite required diffusion of elements from where minerals were reacting to sites of garnet growth. This diffusion was driven by chemical potential gradients between garnet-bearing and garnet-absent parts of the rock. As a consequence, melt and peritectic K-feldspar also preferentially formed around the garnet. The diffusion of elements led to the chemical partitioning of the rock within an overall context in which equilibrium may have been approached. Thus, the garnet-bearing leucosomes record in situ melt formation around garnet porphyroblasts rather than centimetre-scale physical melt migration and segregation. The near complete preservation of the high-grade assemblages in the mesosome and leucosome is consistent with substantial melt loss. Interconnected networks between garnet-rich leucosomes provide the most likely pathway for melt migration. Decimetre-scale, coarse-grained, garnet-poor leucosomes may represent areas of melt flux through a large-scale melt transfer network.

Notes: Book reviewed in this article: Trees, crops and soil fertility: concepts and research methods. By G. Schroth and F.I. Sinclair (Editors).

Notes: Abstract. Current tillage erosion models account for the influence of tillage direction in the magnitude of the soil transport coefficient. It is argued that a re-modelling of tillage erosion is preferable in which the influence of tillage direction is separated from the soil transport coefficient, which is a measure of tillage intensity. This has been achieved here by developing a two-dimensional tillage erosion model that incorporates tillage direction in the measure of slope and uses soil transport coefficients that are independent of tillage direction and based on relationships between transport and the slope in the direction that bisects tillage direction and the overturning direction. Mean tillage erosion, associated with a single pair of opposing tillage directions and pair of overturning directions, can be described by a two-dimensional diffusion-type equation if the dimensions are defined as the tillage direction and the direction perpendicular to tillage. Application of the model to a real-world case allows quantification of the potential soil conservation benefits associated with optimization of tillage direction. The scope for amelioration is related to the ratio between the coefficients for transport in the direction of tillage and perpendicular to tillage. As this ratio approaches unity, the potential for amelioration reduces towards zero. For the study site investigated, use of the experimentally derived ratio of 0.66 indicated that a 12% reduction in tillage erosion could be obtained by ploughing across the dominant field slope as compared to ploughing up and down the dominant slope. For an implement with a coefficient ratio of 0.2 the reduction in tillage erosion intensity, associated with optimizing the tillage direction, reaches 28%. Nevertheless, such benefits must be considered in the context of other management considerations. The tillage direction that minimizes erosion is associated with lateral slopes of 10°, or more, over 20% of the field. To the land-user this disadvantage may outweigh the soil conservation benefits.

Notes: Abstract. Efforts to understand the fate of organochlorine compounds in arable soil have concentrated on anthropogenic compounds, in spite of the fact that organochlorine compounds are both produced and mineralized in soil through natural processes. In order to understand the fate of chlorinated pesticides, it is necessary to take account of the natural chlorine cycle. The present study is a first attempt to illuminate the relationship between the natural chlorine cycle and agricultural practices. The concentration and storage of organic chlorine (Clorg) and chloride (Clinorg) were determined in topsoil of a paddy field compared to an adjacent afforested hill at a sampling site in the Meicun area, Anhui Province, China. The concentration of Clorg, as well as the chlorine-to-carbon ratio, was significantly lower in the paddy field samples than in the forest soil samples. A weak relationship between the concentration of Clorg and the organic carbon content was observed in the paddy field, in contrast to the observations made in the adjacent forest soil as well as those made in previous studies, which have suggested a positive correlation between organic carbon content and Clorg. The similarity between our results at the forest site and the previous studies, which have been carried out in temperate regions, suggests that it is the land use rather than the climate that makes the current paddy soil results different. Our results suggest that the contribution of Clorg to the paddy soil from above-ground litter and from production within the soil are small or negligible compared with the contribution from pesticide application and wet and dry deposition.

Notes: Abstract. Vineyards in Champagne, France are generally situated on slopes where the soils are subject to erosion. Therefore it is important to find a soil-surface management practice that protects the soil against water erosion. We assessed the potential of mulches or grass covers to stabilize soil aggregates in a calcareous sandy loam from a vineyard in Champagne after 9 years under different management systems. Four different treatments were studied: (i) a bluegrass (Poa pratensis) surface cover between the vine rows (GC) with bare soil under the vines (R); two organic mulches of (ii) coniferous (CB) or (iii) poplar (PB) bark that covered the entire soil surface, and (iv) bare soil between the rows as a control. The bark amendments were applied every 3 years at rates of 61 and 67 t ha−1 for the PB and CB treatments, respectively. The kinetics of soil disaggregation in water fitted a power law (A=K t−D), in which K was the fraction of water-stable 〉200 μm aggregates remaining after 1 hour of wet-sieving. In the 0–5 cm layer, aggregate stability was greater for GC (K=21.7), CB (K=15.2) and PB (K=13.6) than for the control (K=10.5) and R (K=11.8). In the 0–20 cm layer, CB also stabilized soil aggregates (K=14.0–15.0); but PB did not. Structural stability was more strongly related to total organic carbon (R2=0.64, P 〈0.001) than to microbial biomass carbon (R2=0.54, P〈0.001). A bluegrass cover enhanced structural stability in the 0–5 cm and 0–20 cm layers (K=14.2), probably because of intense root development and rhizodeposition enhancing microbially produced metabolites, such as carbohydrates. Establishing grass cover or applying bark mulch are effective agricultural practices that improve soil aggregate stability and thus should reduce soil erosion. The vegetative growth of the vines was greater on the soils amended with bark mulches and less on the grass covered soils compared with the control soil; however, no difference in wine quality was observed among the different treatments.

Notes: Abstract. Salt affected soil is one of the main problems decreasing the productivity of irrigated agriculture in the Mediterranean area. Simulation models in combination with geographical information systems (GISs) could be used to evaluate the risk of salinization at a regional scale. In this study, two logical models (Pla and Riverside) were combined in a GIS to evaluate the risk of soil salinity and sodicity in the irrigated agriculture of the Valencian Community, Spain. Simple models were chosen so that they could be used at a regional scale. Before running them in a GIS framework, a soil and irrigation water survey was conducted to validate the models with observed data. The Pla model fitted observed data better than Riverside guidelines, probably because parameters of water quality, soil and climate were considered by the Pla model. The resulting maps indicated that the soils most affected by salts are those located in the south of study area, owing to the arid climate, and those areas near the coast due to saline intrusion. Close to 42% of the irrigated area was predicted to be somewhat affected by salinization. The regional-scale soil salinity assessment presented here for the Valencian Community is the first to be made for this region and will be useful in targeting critical areas that may require special management.

Notes: Abstract. Over a 10-year period, runoff and soil erosion on the plots of the Woburn Erosion Reference Experiment were concentrated in periods with sparse vegetation cover: in winter after the late planting of cereals; in spring after the planting of beets; or when soils were bare after harvest. The mean event runoff of 1.32 mm from plots cultivated up-and-downslope was significantly greater (P〈0.05) than that from plots cultivated across-slope (0.82 mm). However, mean event soil loss was not significantly different between the two cultivation directions. No significant differences were found between minimal and standard cultivations. Mean event runoff from the across-slope/minimal tillage treatment combination (0.58 mm) was significantly less (P〈0.01) than from the up-and-downslope/minimal tillage (1.41 mm), up-and-downslope/standard tillage (1.24 mm), and across-slope/standard tillage (1.07 mm) treatment combinations. Runoff from the across-slope/standard treatment combination was significantly (P〈0.05) less than from the up-and-downslope/minimal tillage treatment. The across-slope/minimal tillage treatment combination had a significantly smaller (P〈0.05) event soil loss (67 kg ha−1) than the up-and-downslope/standard tillage (278 kg ha−1) and up-and-downslope/minimal tillage (245 kg ha−1) combinations. Crop yields were significantly (P〈0.05) higher on across-slope plots in 1988, 1996 and 1997 than on up-and-downslope plots, and were also higher (but not significantly) on the across-slope plots in 7 of the 8 remaining years. Minimal cultivation decreased yield compared with standard cultivation in one year only. We recommend that across-slope cultivation combined with minimal tillage be investigated at field scale to assess its suitability for incorporation into UK farming systems.

Notes: Abstract. Three successive crops of winter wheat were grown on a sandy loam to test the residual effect of long-term annual incorporation of spring barley straw at rates of 0, 4, 8 and 12 t ha−1, and ryegrass catch crops with or without additions of pig slurry. Soil receiving 4, 8 and 12 t ha−1 of straw annually for 18 years contained 12, 21 and 30% more carbon (C), respectively, than soil with straw removal, and soil C and nitrogen (N) contents increased linearly with straw rate. The soil retained 14% of the straw C and 37% of the straw N. Ryegrass catch-cropping for 10 years also increased soil C and N concentrations, whereas the effect of pig slurry was insignificant. Grain yield in the first wheat crop showed an average dry matter (DM) increase of 0.7 t ha−1 after treatment with 8 and 12 t straw ha−1. In the two subsequent wheat crops, grain yield increased by 0.2–0.3 t DM ha−1 after 8 and 12 t straw ha−1. No grain yield increases were found after 4 t straw ha−1 in any of the three years. Previous ryegrass catch crops increased yields of wheat grain, but effects in the third wheat crop were significant only where ryegrass had been combined with pig slurry. Straw incorporation increased the N offtake in the first wheat crop. In the second crop, only 8 and 12 t straw ha−1 improved wheat N offtake, while the N offtake in the third wheat crop was unaffected. Ryegrass catch crops increased N offtake in the first and second wheat crop. Again, a positive effect in the third crop was seen only when ryegrass was combined with slurry. Long-term, annual incorporation of straw and ryegrass catch crops provided a clear and relatively persistent increase in soil organic matter levels, whereas the positive effects on the yield of subsequent wheat crops were modest and transient.

Notes: Abstract. Net accumulation of organic nitrogen in soil is constrained by the amount of organic matter and its minimum C:N ratio. Our objective was to estimate the potential for New Zealand soils to continue accumulating nitrogen within the soil organic pool. We calculated total carbon and nitrogen in the top metre of 138 representative soil profiles from the New Zealand National Soils Database. Carbon in these mainly pasture soils was assumed to be at steady state. The maximum nitrogen storage capacity was estimated by calculating the amount of nitrogen stored under assumed minimum soil C:N ratios of either 9, 10 or 11. The storage capacity remaining was determined as the difference between the amount of nitrogen currently stored and the maximum storage capacity. The length of time before a soil profile will reach the maximum capacity for nitrogen storage was calculated assuming net accumulation of 20, 50 and 100 kg N ha−1 yr−1. A C:N ratio of 9 (giving most storage capacity) and a conservative accumulation rate of 20 kg N ha−1 yr−1 showed that 12% of these soils would be at maximum storage within 40 years. A C:N ratio of 10 and a storage rate of 50 kg N ha−1 yr−1 would result in 54% of the soils reaching maximum storage within the next 40 years. As the capacity for nitrogen storage in soils declines, nitrate leaching is likely to increase with associated risk to the environment.

Notes: Abstract. We studied the effects of red deer grazing and fence-line pacing on soil losses of contaminants (suspended sediment, Escherichia coli, phosphorus) and nitrogen species (ammonia, nitrate) via overland flow and soil physical properties (macroporosity, bulk density, saturated hydraulic conductivity, Ksat) soon after (1 day) and 6 weeks after grazing on a Pallic pastoral soil in southern New Zealand. Fence-line pacing decreased the soil volume occupied by water, macroporosity and Ksat, while increasing suspended sediment (to 0.226 g 100 mL−1), total P (to 2.0 mg L−1), mainly as particulate P (up to 90% of total P), and E. coli (to 3.52 log10 c.f.u. 100 mL−1) concentrations in overland flow at 1 day after grazing compared with soils from the rest of the paddock (0.148 g 100 mL−1, 0.86 mg L−1 and 2.86 log10 c.f.u. 100 mL−1, respectively). Although concentrations in overland flow were less at 6 weeks after grazing than at 1 day after grazing, losses of P, especially in fence-line soils, were still above recommended limits for surface water quality. Compared to P, losses of N species would be unlikely to have a significant impact on downstream water quality. Management strategies should be directed towards minimizing the occurrence of fence-line pacing to prevent contaminant loss and maintain water and soil quality.

Notes: Abstract. Agricultural practices in the UK have come under increased scrutiny since the heavy and widespread flooding of 2000 and 2001. Although the impact of land use on runoff and flood risk is of growing concern, there are few quantitative data available. A preliminary study was undertaken in the Nant Pontbren catchment, mid-Wales. Experimental tree shelterbelts were established in selected pastures of land used for sheep grazing. Water infiltration rates were up to 60 times higher in areas planted with young trees than in adjacent grazed pastures. This demonstrates that farm trees could represent a key landscape feature, reducing run-off even when only present as a small proportion of the land cover. This is likely to be just one of the environmental and economic benefits of planting trees to re-create a more diverse agricultural landscape.

Notes: Abstract. Nitrate is widely and mistakenly perceived to threaten human health by causing methaemoglobinaemia in infants and stomach cancer in adults, but it does cause environmental problems. Methaemoglobinaemia is a side-effect of gastroenteritis and is not caused by nitrate but by nitric oxide, which is produced in a defensive reaction stimulated by gastroenteritis. The latter may be caused by a bacterium or a virus. The association of methaemoglobinaemia with nitrate may have arisen because early cases of the condition were often associated with wells polluted with bacteria, and the same pollution increased the nitrate concentration. Four epidemiological studies sought a link between stomach cancer and nitrate but did not find one. The incidence of this cancer has also declined during the last 30 years, while nitrate concentrations in water have increased. Nitrate preserves, rather than threatens, health. It is reduced by microbes on the tongue to nitrite, which generates nitric oxide when acidified in an antibacterial defence mechanism vital to our well-being. This mechanism acts with great effectiveness in the stomach against Salmonella, Escherichia coli and other organisms that cause gastroenteritis. It also acts in our mouths against dental caries and even on our skin against fungal pathogens such as Tinea pedis (athlete's foot). This mechanism is the basis of the centuries-old practice of adding nitrate or nitrite to stored meat to protect against botulism, caused by the most lethal toxin known to mankind.

Notes: Abstract. Results from recent studies of peatland biogeochemistry suggest that appropriate soil water sampling techniques are required in order to advance our understanding of peatland soil systems. In a comparative field experiment, concentrations of inorganic solutes and dissolved organic carbon (DOC) were measured in soil water extracted at a depth of 10 cm beneath the surface of deep peat by three techniques: zero-tension (z-t) lysimeters, PTFE suction samplers, and polysulfone suction samplers. The majority of solute concentrations were broadly similar, but mean concentrations of silicon, DOC, iron and aluminium in water extracted by z-t lysimeters and PTFE samplers were in ratios of 1:5; 1:2; 1:5 and 1:3 respectively. Mean conductivity and concentrations of chloride and hydrogen ion were significantly larger in the z-t lysimeter samples, which had sodium, potassium and magnesium to chloride ratios that were very similar to local rainfall. The z-t lysimeters appeared to sample macropores preferentially, while the suction samplers collected micropore water.

Notes: Book reviewed in this article: Scaling methods in soil physics. By Y. Pachepsky, D.E. Radcliffe and H. Magdi Selim (Editors).

Notes: Abstract. Tendency to crust is a potentially useful index for assessing soil degradation and for assisting land use planning in South Africa. In this study, the influence of land use, geology and vegetation cover on the tendency of soil to form a surface crust was investigated in six vegetation types. Crusting at all sites was greater in exposed soils than soils under vegetation, as determined by infiltration rate, water dispersible clay and modulus of rupture. In Renosterveld, crusting was markedly greater in exposed soil than vegetation covered soil (mean infiltration 16 vs 44 mm h−1; dispersible clay 2.6 vs 2.2%; modulus of rupture 121 vs 64 kPa). Greater crusting in exposed soil was attributed to lower soluble salt and labile carbon (C) contents and an associated increase in the dispersion of clay. In Karoo, crusting of exposed, shale-derived soils was greater than that of exposed, dolerite-derived soils (infiltration 40 vs 83 mm h−1; dispersible clay 2 vs 1.2%), and a similar pattern was evident in Tall Grassveld (infiltration 18 vs 36 mm h−1; dispersible clay 1.2 vs 0.9%; modulus of rupture 31 vs 21 kPa). In Upland Grassland, cultivation of maize and rye enhanced crusting. In Thicket, crusting was greater in soils from open, degraded vegetation than intact, densely wooded sites (infiltration 19 vs 51 mm h−1; modulus of rupture 16 vs 34 kPa), probably due to lower content of soil C. In Bushveld, crusting was greater in annually burnt plots than unburnt plots (infiltration 109 vs 163 mm h−1; dispersible clay 0.9 vs 0.6% on granite-derived soils; and infiltration 56 vs 72 mm h−1; dispersible clay 1.5 vs 1.3% on basalt-derived soils). Greater crusting of soil from burnt plots was ascribed to a reduction in soil C and soluble salts as well as a greater exchangeable sodium percentage.

Notes: Abstract. The volcanic island of Lanzarote (Canary Islands, Spain) is one of the most arid parts of the European Union. During the eruptions of 1730–36, a third of the island was covered with lava and pyroclastic material. In areas under basaltic tephra, an agrosystem has been developed that allows a form of dry farming that has become a key component of the local economy. This article illustrates the effectiveness of the layer of natural tephra mulch in conserving soil and water.

Notes: Abstract. Land use change and land management practices affect the net emissions of the trace gases methane (CH4) and nitrous oxide (N2O), as well as carbon sources and sinks. Changes in CH4 and N2O emissions can substantially alter the overall greenhouse gas balance of a system. Drainage of peatlands for agriculture or forestry generally increases N2O emission as well as that of CO2, but also decreases CH4 emission. Intermittent drainage or late flooding of rice paddies can greatly diminish the seasonal emission of CH4 compared with continuous flooding. Changes in N2O emissions following land use change from forest or grassland to agriculture vary between climatic zones, and the net impact varies with time. In many soils, the increase in carbon sequestration by adopting no-till systems may be largely negated by associated increases in N2O emission. The promotion of carbon credits for the no-till system before we have better quantification of its net greenhouse gas balance is naïve. Applying nitrogen fertilizers to forests could increase the forest carbon sink, but may be accompanied by a net increase in N2O; conversely, adding lime to acid forest soils can decrease the N2O emission.

Notes: Abstract. This article examines some of the factors that influence the relative risk of Escherichia coli pollution of surface waters from grazing animals compared to cattle slurry application. Drainage water from pipe-drained plots grazed with sheep (16 sheep + lambs per hectare) from 29 May to 17 July 2002 had average E. coli counts of 11 c.f.u. mL−1 or 0.4% of estimated E. coli inputs over the grazing period. Drainage water from plots on the same site treated with cattle slurry (36 m3ha−1 on 29 May 2002) had lower average E. coli counts of 5 c.f.u. mL−1 or 0.03% of estimated faecal input. Sheep (16 lambs per hectare) grazing under cooler, moister conditions from 24 September to 3 December 2001 gave drainage water with much higher average E. coli counts of 282 c.f.u. mL−1 or 8.2% of estimated input, which is more than twice the average E. coli counts previously reported under such conditions (Vinten et al. 2002 Soil Use and Management 18, 1–9). Laboratory studies of runoff from soil slabs after slurry application showed that the mobility of E. coli in surface soil decreased with time, suggesting that increased attachment to soil or migration to ‘immobile’ water also provides at least part of the physical explanation for the relatively higher risk of pollution from grazing animals compared with slurry. Sampling for E. coli in field drainflow and in streamwater during a storm event in the predominantly dairy Cessnock Water catchment, Ayrshire, Scotland supported the hypothesis that E. coli transport is linked to grazing animals. For a 7-mm rainfall event, roughly 14% of the estimated daily input from grazing livestock was transported to the river, even though little slurry spreading had occurred in the catchment in the previous month. Spot sampling of field drains in grazed fields and silage fields in the same catchment also showed that grazing animals were the principal source of E. coli and faecal streptococci.

Notes: Abstract. Four management systems combining high and low livestock densities (0.7 and 1.4 livestock units ha−1) and different types of organic manure (slurry and straw based FYM) were applied to an organic dairy crop rotation (undersown barley – grass–clover – grass–clover – barley/pea – oats – fodder beet) between 1998 and 2001. The effects of the management systems on crop yields and nitrate leaching were measured. In all four years, nitrate leaching, as determined using ceramic suction cups, was higher in the three crops following ploughing of grass–clover than under the barley or grass–clover. Overall, no significant differences in nitrate leaching were observed between the management systems. However, the replacement of the winter wheat crop used in the earlier experimental period (1994–97) by spring oats with catch crops in both the preceding and succeeding winters reduced nitrate leaching compared with the earlier rotation. Increasing the livestock density, which increased manure application by c. 60 kg total N ha−1, increased crop yields by 7 and 9% on average for FYM and slurry, respectively. Yields were 3–5% lower where FYM was used instead of slurry. The experiment confirmed the overriding importance of grassland N management, particularly the cultivation of the ley, in organic dairy crop rotations.

Notes: Abstract. The effects of grazed, annual ryegrass pasture (annually tilled with a rotary cultivator) and permanent kikuyu pasture were compared with that of undisturbed native vegetation at four sites in the Tsitsikamma region, South Africa. Soil organic carbon content, aggregate stability, saturated hydraulic conductivity, air permeability, root length density and rooting depth were all less under ryegrass than kikuyu pasture. There was, however, no consistent effect of pasture-type on pore size distribution or penetrometer resistance. Differences in penetrometer resistance were most obvious in the 10–30 cm layer with subsurface compaction being evident at some sites under both types of pasture. This was attributed to the treading effects of grazing cattle plus formation of a compacted layer at the depth of tillage under ryegrass pastures. Subsoil tillage of a ryegrass pasture resulted in a substantial reduction in penetrometer resistance in the compacted 10–20 cm layer and increases in hydraulic conductivity, air permeability, root length density and rooting depth. We conclude that conversion from conventional to zero tillage is a potential way of improving the sustainability of annual pasture production and that the extent of subsoil compaction under both pasture types needs further investigation.

Notes: Abstract. Grassland is a major source of nitrous oxide (N2O) and methane (CH4) emissions in the UK, resulting from high rates of fertilizer application. We studied the effects of substituting mineral fertilizer by organic manures and a slow-release fertilizer in silage grass production on greenhouse gas emissions and soil mineral N content in a three-year field experiment. The organic manures investigated were sewage sludge pellets and composted sewage sludge (dry materials), and digested sewage sludge and cattle slurry (liquid materials). The organic manures produced N2O and carbon dioxide (CO2) consistently from time of application up to harvest. However, they mitigated N2O emissions by around 90% when aggregate emissions of 15.7 kg N ha−1 from NPK fertilizer were caused by a flux of up to 4.9 kg N ha−1 d−1 during the first 4 days after heavy rainfall subsequent to the NPK fertilizer application. CH4 was emitted only for 2 or 3 days after application of the liquid manures. CH4 and CO2 fluxes were not significantly mitigated. Composting and dried pellets were useful methods of conserving nutrients in organic wastes, enabling slow and sustained release of nitrogen. NPK slow-release fertilizer also maintained grass yields and was the most effective substitute for the conventional NPK fertilizer for mitigation of N2O fluxes.

Notes: Abstract. Calibration coefficients for a Diviner 2000 capacitance sensor were developed under laboratory conditions for soils of six textures. The calibration equations, derived by regression analysis, significantly (P 〈0.001) related Diviner 2000 measurements of scaled frequency (SF) with volumetric soil water content of the soil. In all cases the calibration accounted for 〉93% of the variation (R2 adjusted) with the volumetric water content of the soil.

Notes: Abstract. Fertilizer applications to agricultural land are a significant source of ammonia (NH3) emission to the atmosphere, accounting for approximately 10% of the total emissions from agriculture. Current estimates of emissions from fertilizer applications use ‘fixed’ emission factors. This paper describes a model in which the emission factors are expressed as a function of the important influencing variables: fertilizer type, soil pH, land use, application rate, rainfall and temperature. Total emission in 2002 for the UK were estimated by running the model for a ’standard UK‘ scenario, viz. 28.7 kt NH3-N, which compares well with the UK inventory estimate of 30.4 kt NH3-N. Differences exist in the estimates for specific fertilizer types, with the mean emission factor for urea applications to grassland, in particular, being lower by use of this model (13% compared with 23% of applied N for the UK inventory). Emission estimates were most sensitive to temperature and fertilizer type. Scenario testing showed that significant reductions in emission could be achieved by replacing urea with other forms of N fertilizer, by combining urea use with a urease inhibitor, or by modifying some management practices.

Notes: Abstract. In organic farming systems, fertilizing materials can be used when potassium (K) deficiency is shown, but such systems are dominantly nitrogen (N) limited and this is likely to affect crop utilization of K. The supply of K to grass/clover from a range of mineral and organically based K fertilizers and its interaction with N supply were studied in a greenhouse experiment. Sequential plant cuts were taken for yield and nutrient content determinations in crop and soil. Crop yields were limited by N: where N supply was increased either through the mineralization of N from organic materials (rapemeal, farmyard manure) or inorganic fertilizer, plant yields increased significantly. Grass/clover responded better to additional K where sufficient N was available. However, yield responses to K were generally small, even in the presence of adequate N. Of the different fertilizers, kali and MSL-K increased yields above those of the control by less than 5%, sylvinite, DKSI and farmyard manure by 10–20%, and rapemeal and potassium sulphate by more than 25%. In all treatments, K offtakes in the grass/clover were considerably greater than fertilizer K inputs. The grass/clover showed an increased uptake of Na where insufficient K was available. However, the Mg content of the grass/clover was not adversely affected by K fertilizer application. Organic farmers need to consider the soil K status, the rotational nutrient budget, the supply of all nutrients in fertilizing materials and nutrient interactions to achieve effective K management in organic farming systems.

Notes: Abstract. A laboratory experiment was designed to assess the impact of surface seal development on the hydrological response of a clay soil. The influence of surface sealing on vertical macropore flow and lateral throughflow was of particular interest. The extent and development of the surface seal in repacked lysimeters was designed to match that recorded over two growing seasons at a clay field site in Essex, and was not extensive enough to reduce significantly the infiltration capacity of the soil. Consequently, the hydrological response of the lysimeters was similar under sealed and unsealed conditions, with a more rapid wetting response under sealed conditions being attributed to the higher soil moisture content required to create the surface seal. Macropore flow was initiated at the A/B soil boundary of the lysimeters, in response to the development of a saturated layer. The rate of macropore and throughflow in the soil was dictated by rainfall intensity at the soil surface as this controlled the depth of water in the perched water table. Simulation of the tensiometer response in the lysimeters demonstrated that it was possible to attribute the rapid movement of water through the A horizon to water displacement processes alone, without recourse to preferential flow processes.

Notes: Abstract. The behaviour of potassium (K) in a range of arable soils was examined by plotting the change in exchangeable K of the topsoil (Δ Kex) at the end of a 3–5 year period against the K balance over the same period (fertilizer K applied minus offtake in crops, estimated from farmers' records of yield and straw removal). Based on the assumption that values for offtake per tonne of crop yield used for UK arable crops MAFF 2000) are valid averages, 10–50% of Δ Kex was explained by the balance, relationships being stronger on shallow/stony soils. Excess fertilizer tended to increase Kex and reduced fertilization decreased it, requiring between 1.2 and 5.4 kg K ha−1 for each mg L−1Δ Kex. However, merely to prevent Kex falling required an extra 20 kg K ha−1 yr−1 fertilizer on Chalk soils and soils formed in the overlying Tertiary and Quaternary deposits, despite clay contents 〉18%. Whereas, on older geological materials, medium soils needed no extra K and clays gained 17 kg K ha−1 yr−1. It is unlikely that the apparent losses on some soil types are anomalies due to greater crop K contents. Theory and the literature suggest leaching from the topsoil as a major factor; accumulation in the subsoil was not measured. Recommendations for K fertilization of UK soils might be improved by including loss or gain corrections for certain soil types.

Notes: Abstract. The saline–sodic soils of the dryland Songnen Plain in northeast China are only slowly permeable to fresh water because of their large content of montmorillinite clay and sodium bicarbonate. Use of slightly saline groundwater containing adequate dissolved calcium and magnesium for leaching and reclamation can potentially prevent dispersion of the clay soil particles during treatment. Amelioration was evaluated using shallow, mildly saline groundwater to irrigate sorghum–corn rotations in a two-year field experiment. After two growing seasons during which a total of 400 mm of leaching water was applied, in addition to some supplemental irrigation water, the average electrical conductivity (ECe) of the top 1.2 m of the soil profile decreased from 14.5±3.5 to 2.7±0.2 dS m−1, and the sodium absorption ratio (SARe) decreased from 35.3±4.1 to 10.1±2.5 (meq L−1)0.5. The soil physical properties were improved: infiltration rate with mildly saline groundwater increased from 12.1 to 42 mm h−1. Salinity changes in the top 1.2 m of soil layers after 700 mm of leaching produced no further improvement. Crop yields produced on plots undergoing amelioration increased by 64–562% compared with the rainfed control. The improved soil conditions after leaching resulted in 59–548% greater crop yields.

Notes: Abstract. Drainage water was sampled intensively during a four-year field experiment on a sandy loam soil subjected to four unreplicated tillage treatments: (1) harrowing with a springtine harrow, drilling; (2) direct drilling; (3) ploughing with light subsurface compaction, one pass with a PTO-driven rotary harrow, drilling; (4) ploughing, one pass with a springtine harrow, drilling. In all years, the losses of suspended matter with drainage water (0.1–4.3 kg ha−1 yr−1) were smaller by a factor of 1.9 or more from direct drilled plots than from plots subjected to the other tillage treatments, strongly suggesting that tillage increased the losses. Annual bromide losses were governed by the amount of drainage water rather than by the tillage treatments. However, after one drainage season, more bromide was left in the soil at 0–100 cm depth with ploughless tillage than with ploughing, thus indicating more bypass flow without ploughing. The study demonstrated very changeable patterns of suspended matter and bromide concentrations in drainage water sampled from large field plots, and questions the representativeness of drainage water samples for water reaching the subsoil or shallow groundwater.

Notes: Abstract. This article presents an inventory of digital soils data and supporting information available or publicized on the World Wide Web. The amount and quality of digital soil survey information at global, national, regional, and local scales is increasing dramatically. Some is freely available on-line, some is available on CD-ROM and only publicized, not distributed, on the Web. The world is completely mapped at small scale. Many regions are covered by medium-scale inventories, especially using the SOTER methodology. Large-scale digital data are limited to the USA, Canada, Australia and Europe, but there is discrepancy with respect to their philosophies of public access to foundation data such as soil maps. Remaining problems include the lack of metadata, limited interpetations for professionals who are not soil specialists, and geodesic incompatibility with other digital data. The frequent reorganization of websites leads, at best, to user frustration and, at worst, to the disappearance of information.

Notes: Abstract. A study was carried out to compare the impact of 6-year-old plantations of Prosopis juliflora (Swartz) D.C., Dalbergia sissoo Roxb. Ex. D.C. and Eucalyptus tereticornis Sm. on the physical and chemical properties of sodic soil in the Indo-Gangetic alluvial plains of Uttar Pradesh, India. Soil properties under the three tree species showed significant improvement through a reduction in the pH, electrical conductivity, exchangeable sodium percentage, CaCO3 and gypsum requirement, and by increase in organic C, total N, and available P and K. The six years of reclamation had achieved a marked reduction in exchangeable sodium (from 11.5 to 4.5 cmolc kg−1) to a depth of 1.5 m in the soil profile, whereas the levels of exchangeable calcium, magnesium and potassium had increased. There was also a significant reduction in soil bulk density (from 1.66 to 1.24 g cm−3) and increases in porosity, water holding capacity, field capacity, permeability and infiltration rate. The equilibrium infiltration rate after 455 min increased from 0.03 cm h−1 in the control to 0.13 cm h−1 under P juliflora and D. sissoo and 0.10 cm h−1 under E. tereticornis. It is concluded that salt-tolerant tree species have a significant impact on soil properties, which could help to rehabilitate the sodic wastelands in the region.

Notes: Abstract. Soil organic (SOC) and inorganic carbon (SIC) stocks of Kenya were determined using four different methods to provide baseline data. The assessments used an updated version of the 1:1 M soil and terrain database for the country. Estimates for national SOC stocks to 1 m depth ranged from 3452 to 3797 Tg C. The findings highlight the need for comprehensive databases of soil and terrain data of good quality that consider more than one representative profile per soil component. The 95% confidence limits for the median, area-weighted SOC content were largest in the humid highlands (15.4–15.7 kg C m−2) and smallest in the hot arid zone (4.4–4.5 kg C m−2). Conversely, for SIC these values were largest in the arid zone (4.3–4.5 kg C m−2) and smallest in high rainfall areas (〈0.1 kg C m−2). Many croplands in Kenya have been over-exploited, resulting in nutrient depletion and loss of organic matter. The SOC gains considered ecologically and technically feasible upon improved management of croplands were estimated at 5.8–9.7 Tg C over the next 25 years. This corresponds to an estimated annual mitigation potential of 5–9% of Kenya's CO2-C emissions from fossil fuels, cement manufacturing and land use change for 1990.

Notes: Book reviewed in this article: The role of erosion and sediment transport in nutrient and contaminant transfer. By M. Stone (Editor).

Notes: Abstract. Current tillage erosion models account for the influence of tillage direction in the magnitude of the soil (tillage) transport coefficient. It is argued here that this is counter-intuitive and causes significant problems in modelling tillage erosion in areas of complex terrain. This article examines whether a re-modelling of tillage erosion is possible that separates tillage direction (an interaction with the landform) from the soil transport coefficient (a measure of tillage intensity representing the combination of implement erosivity and soil erodibility). Experimental data for mouldboard ploughing upslope, downslope and cross-slope at Coombe Barton Farm, Devon are examined. Integration of data for all directions into a single relationship, which relates translocation in the direction of tillage to slope in the direction of tillage and translocation perpendicular to tillage to slope perpendicular to tillage, is not possible using previously published methods of analysis. However, when total translocation distance is regressed against the tangent of the slope at 45° to the tillage direction (bisecting the tillage direction and the direction of overturning) it is found that a single relationship can be used to describe tillage in all three directions. Therefore, this relationship is used to determine a single value of the soil transport coefficient (kfTa) for constant soil and implement conditions but different tillage directions. This redefinition of tillage is important both for true estimation of tillage erosion severity, the adirectional coefficient being 40% larger than the directional coefficient, and for modelling of tillage erosion in complex terrain. These improvements are vital when tillage erosion simulation is used to direct soil conservation strategies.

Notes: Abstract. In areas of intensive pig farming, fresh pig slurry is often applied annually to the same fields. Thus, to avoid nitrogen (N) losses correct fertilizer practice should take account of residual effects of slurry on the following crops. The residual effects of different rates of slurry applied during three years were evaluated in subsequent wheat crops. The experiment was conducted on an irrigated Mediterranean Typic Xerofluvent soil, where plots were left unfertilized or fertilized with 150 kg N ha−1 as ammonium nitrate. Grain yield and grain N uptake increased with slurry rates in both fertilized and unfertilized treatments. The increases in the unfertilized treatments were interpreted as a nitrogen effect of the previous 1996–98 slurry applications. The equivalent mineral N released from the pig slurry was underestimated by two existing decay-series approaches. Although decay-series are useful tools for estimating manure residual effects they should be adjusted for local conditions. A significant positive relationship was detected between apparent N use efficiency of the slurry and the total amount of applied organic N, which was interpreted as a specific residual effect rather than due to the N dose of previously applied pig slurry.

Notes: Abstract. Soil protection policies are being developed in many countries, particularly those in the European Union where pan-national regulatory frameworks now exist. We report an analysis of a survey of the views of a wide range of stakeholders in the soil resource of Scotland, including representatives of rural and urban land users, public bodies and authorities, non-governmental environmental organizations, and soil scientists based in Scotland. The four soil issues considered of particular importance were soil pollution, soil erosion, loss of soils to development, and loss of biodiversity. Comments were strongly polarized, either strongly promoting issues or indicating lack of awareness, on a set of topics: the loss of valued soils, loss of archaeological sites, and changes in terrestrial carbon store. It is argued that an integrated approach is required to implement any future soil protection strategies, and that special attention should be paid to monitoring long-term changes and to provision of soil survey data from urban areas.

Notes: Abstract. Soil carbon sequestration could meet at most about one-third of the current yearly increase in atmospheric CO2-carbon, but the duration of the effect would be limited, with significant impacts lasting only 20–50 years. Coupled with this limited duration, increases in population and per-capita energy demand mean that soil carbon sequestration could play only a minor role in closing the difference between predicted and target carbon emissions by 2100. However, if atmospheric CO2 concentrations are to be stabilized at reasonable levels (450–650 ppm), drastic reductions in carbon emissions will be required over the next 20–30 years. Given this, carbon sequestration should form a central role in any portfolio of measures to reduce atmospheric CO2 concentrations over this crucial period, while new energy technologies are developed and implemented. International agreements, such as the Kyoto Protocol, encourage soil carbon sequestration and could be used to formulate soil carbon sequestration polices. Such policies need to take account of other environmental impacts as well as political, economic and societal needs, so that they form part of a raft of measures encouraging sustainable development. Of the carbon sequestration options available, those of a ‘win–win’ nature, that is, those that increase carbon stocks at the same time as improving other aspects of the environment, and those that protect or enhance existing stocks (‘no regrets’ implementation) show the greatest promise in meeting these goals.

Notes: Abstract. Leaching of calcium (Ca), potassium (K) and magnesium (Mg) from urine patches in grazed grassland represents a significant loss of valuable nutrients. We studied the effect on cation loss of treating the soil with a nitrification inhibitor, dicyandiamide (DCD), which was used to reduce nitrate loss by leaching. The soil was a free-draining Lismore stony silt loam (Udic Haplustept loamy skeletal) and the pasture was a mixture of perennial ryegrass (Lolium perenne) and white clover (Trifolium repens). The treatment of the soil with DCD reduced Ca2+ leaching by the equivalent of 50%, from 213 to 107 kg Ca ha−1 yr−1 on a field scale. Potassium leaching was reduced by 65%, from 48 to 17 kg K ha−1 yr−1. Magnesium leaching was reduced by 52%, from 17 to 8 kg Mg ha−1 yr−1. We postulate that the reduced leaching loss of these cations was due to the decreased leaching loss of nitrate under the urine patches, and follows from their reduced requirement as counter ions in the drainage water. The treatment of grazed grassland with DCD thus not only decreases nitrate leaching and nitrous oxide emissions as reported previously, but also decreases the leaching loss of cation nutrients such as Ca2+, K+ and Mg2+.

Notes: Abstract. Physical, chemical and environmental consequences of land use change from cultivated land to desert grassland and vice-versa were monitored in the middle reaches of the Heihe River basin, which is one of the largest inland basins of arid northwest China. Levels of N and P in soils and surface waters and soil organic carbon were measured. After the first 3–5 years of cultivation the N and P contents of various former grassland soils, including mountain-meadow and plains-meadow grasslands, decreased significantly. After some 13 years of cultivation, soil nutrient content in former mountain meadow grasslands gradually stabilized, whereas those of desertified grassland, where cultivation had simply been abandoned, showed a notable decrease. Under these latter conditions, soil N and P were lost at a rate of 276 kg ha−1 and 360 kg ha−1, respectively, over the 13-year period. The transformation of grassland into cultivated land and that of cultivated land into desert grassland resulted in organic carbon emissions of 1.68 Tg C and 0.55 Tg C, respectively, over 13 years. Land use changes in the arid inland region clearly have a significant influence on the soil organic carbon pool and carbon cycle. Falls in soil N and P led to 63% and 34% mean enrichment of N and P, respectively, in downstream waters, thus posing a future environmental problem for the arid region of northwest China.

Notes: Abstract. The effects of especially frequent nitrogen (N) additions (from 1959 to 1986, totalling 860 kg N ha−1) and liming (in 1958 and 1980, totalling 6000 kg CaCO3 ha−1) on CH4 uptake by a boreal forest soil were studied in a stand of Norway spruce. Except for a forested reference plot, the stand was clear-cut in January 1993 and the following year one-half of each clear-cut plot was prepared by mounding. Fluxes of CH4 were measured with static chambers in the autumn before clear-cutting and during the following four summers. The average CH4 uptake during 1993–96 in the forested reference plot was 82 μg CH4 m−2 h−1(ranging from 10 to 147 units). In the first summer after clear-cutting, the cleared plot showed 42% lower CH4 uptake rate than the forested reference plot, but thereafter the difference became less pronounced. The short-term decrease in CH4 consumption after clear-cutting was associated with increases in soil NH4+ and NO3−concentrations. Mounding tended at first to stimulate CH4 uptake but later to inhibit it. Neither liming nor N-fertilization had significant effects on CH4 consumption. Our results suggest that over the long term, in N-limited upland boreal forest soils, N addition does not decrease CH4 uptake by the soil.

Notes: Abstract. In the extremely arid island of Fuerteventura (Canary Islands, Spain), a traditional water harvesting practice has evolved in slightly sloping areas, which receive runoff water from time to time. The system is particularly effective in the rehabilitation of saline–sodic soils where the improved fertility allows certain crops to be grown, which would not be possible without water harvesting. The influence of the water harvesting on soil fertility was investigated by comparing the properties of the cultivated soils receiving periodic runoff with those of natural control soils that did not receive runoff. The saline–sodic characteristics of the four uncultivated soils were absent from the four cultivated soils which, on average, contained only one quarter of the exchangeable sodium and more than twice the exchangeable calcium content. The clay and silt content of all four of the cultivated soils had been substantially enhanced relative to the control soils, by sediment contained in the runoff.

Notes: Abstract. On the volcanic soils of the uplands of the French West Indies, banana monocropping has been practised since about 1980, mostly with large inputs of chemicals and replanting every three to five years after ploughing. However, in Guadeloupe less intensive cropping systems with only few added chemicals are still being used. The effects of the intensive practices on the physical, chemical and biological attributes of soils were evaluated on 34 farmed fields, which were selected to include the diverse soils and management practices found in the uplands of South Basse-Terre. Management was classified into four groups to differentiate effects of fertilizers, nematicides and tillage over at least 10 years. The population of the parasitic nematode Radopholus similis was, on average, greater 3 months after the application of nematicides. Thus, the use of nematicides increases the dependency of yield on nematicides. Ploughing decreased soil organic matter in the 0–10 cm layer as well as microbial respiration and earthworm biomass, but increased banana root infestation by R. similis. Ploughing was also associated with a change in soil structure, as revealed by the decrease in soil water content at −1 kPa potential and the increased infiltration rate of water into the 0–10 cm layer. The use of fertilizers has advantages for the maintenance or increase of soil reserves of K. However, due to the decreasing of negative electrical charges in the lower layers of andosols, where pH remains low, the majority of the cations supplied by fertilizers, mainly potassium, are prone to leaching.

Notes: Abstract. Eulaliopsis binata is a perennial fibre-producing plant, which has a growing market in southern China and also has favourable effects on soil and water conservation. In the present study, three land use treatments, Eulaliopsis binata (EB), undisturbed natural grassland (NG) and orange grove (OG) were compared with respect to their effects upon a red soil after 20 years. Of these treatments, EB had the most favourable effects on soil physicochemical and biological properties and on soil microclimate. These properties were combined in a relative soil quality index (RSQI), which gave values in the order EB 〉 OG 〉 NG. Soil microbial numbers and enzyme activities were shown to be sensitive indicators of overall changes in soil properties.

Notes: Abstract. The number of outdoor pigs has increased greatly in England over the last two decades. It is known that runoff and soil erosion are likely to occur in such fields; however, the off-field impacts of runoff have not been addressed. A group of properties adjacent to fields of outdoor pigs near Culford, Suffolk, England was flooded at frequent intervals in 1998 and 1999. The factors that may have caused the flooding are examined. The floods were initiated and exacerbated because the soils in the fields were trampled by pigs and rutted by tractors, severely restricting the rates at which rain could infiltrate the soil, thereby promoting runoff. The runoff carried sediment, faeces and pathogens. To a home owner such flooding, or a high risk of flooding, is unacceptable. The results of a claim in the County Court arising from the floods are briefly described.

Notes: Abstract. Nitrogen (N) loss by leaching poses great challenges for N availability to crops as well as nitrate pollution of groundwater. Few studies address this issue with respect to the role of the subsoil in the deep and highly weathered savanna soils of the tropics, which exhibit different adsorption and drainage patterns to soils in temperate environments. In an Anionic Acrustox of the Brazilian savanna, the Cerrado, dynamics and budgets of applied N were studied in organic and inorganic soil pools of two maize (Zea mays L.) – soybean (Glycine max (L.) Merr.) rotations using 15N tracing. Labelled ammonium sulphate was applied at 10 kg N ha−1 (with 10 atom%15N excess) to both maize and soybean at the beginning of the cropping season. Amounts and isotopic composition of N were determined in above-ground biomass, soil, adsorbed mineral N, and in soil solution at 0.15, 0.3, 0.8, 1.2 and 2 m depths using suction lysimeters throughout one cropping season. The applied ammonium was rapidly nitrified or immobilized in soil organic matter, and recovery of applied ammonium in soil 2 weeks after application was negligible. Large amounts of nitrate were adsorbed in the subsoil (150–300 kg NO3−-N ha−1 per 2 m) matching total N uptake by the crops (130–400 kg N ha−1). Throughout one cropping season, more applied N (49–77%; determined by 15N tracers) was immobilized in soil organic matter than was present as adsorbed nitrate (2–3%). Most of the applied N (71–96% of 15N recovery) was found in the subsoil at 0.15–2 m depth. This coincided with an increase with depth of dissolved organic N as a proportion of total dissolved N (39–63%). Hydrophilic organic N was the dominant fraction of dissolved organic N and was, together with nitrate, the most important carrier for applied N. Most of this N (〉80%) was leached from the topsoil (0–0.15 m) during the first 30 days after application. Subsoil N retention as both adsorbed inorganic N, and especially soil organic N, was found to be of great importance in determining N losses, soil N depletion and the potential of nitrate contamination of groundwater.

Notes: Abstract. The effectiveness of sodium polyacrylate to increase soil water retention and to enhance growth of wheat under water deficit was evaluated. Water-holding capacity of the soils was considerably increased only when the soil was amended with the polymer at a rate 〈inlineGraphic alt="geqslant R: gt-or-equal, slanted" extraInfo="nonStandardEntity" href="urn:x-wiley:02660032:SUM207:ges" location="ges.gif"/〉3 g L−1. The effect on plant-available water was greater at soil matric potentials up to −1000 hPa. The biomass and grain yield of plants without water deficit were increased by the polymer amendment, but decreased under severe water deficit stress. The polymer had no significant affect on plant N, grain N or grain Na content.

Notes: Abstract. Long term fallow is no longer possible in densely populated tropical areas, but legume cover crops can help maintain soil fertility. Our work aimed to study changes in soil carbon in a sandy loam Ultisol in Benin, which involved a 12-year experiment on three maize cropping systems under manual tillage: traditional no-input cultivation (T), mineral fertilized cultivation (NPK), and association with Mucuna pruriens (M). The origin of soil carbon was also determined through the natural abundance of soil and biomass 13C. In T, NPK and M changes in soil carbon at 0–40 cm were −0.2, +0.2 and +1.3 t C ha−1 yr−1, with residue carbon amounting to 3.5, 6.4 and 10.0 t C ha−1 yr−1, respectively. After 12 years of experimentation, carbon originating from maize in litter-plus-soil (0–40 cm) represented less than 4% of both total carbon and overall maize residue carbon. In contrast, carbon originating from mucuna in litter-plus-soil represented more than 50% of both total carbon and overall mucuna residue carbon in M, possibly due to accelerated mineralization of native soil carbon (priming effect) and slow mulch decomposition. Carbon originating from weeds in litter-plus-soil represented c. 10% of both total carbon and overall weed residue carbon in T and NPK. Thus mucuna mulch was very effective in promoting carbon sequestration in the soil studied.

Notes: Abstract. A carbon emission inventory of the Brazilian agricultural sector was used to compare greenhouse gas emissions with estimated carbon offsets promoted by two main changes in agricultural management: the replacement of conventional tillage by no-tillage and the cessation of annual burning in sugar cane production. Using the IPCC revised 1996 guidelines for national greenhouse gas inventories, we estimate that 12.65 Mt C are emitted annually from agricultural land in Brazil. Ongoing conversion of conventionally tilled land to no-tillage currently accumulates 9 Mt C yr−1. Industrial by-products like alcohol and bagasse from sugar cane processing substitute fossil fuel for transportation and power generation offsetting 10 and 8 Mt C yr−1, respectively. An additional opportunity for 0.53 Mt C yr−1 sequestration is presented by avoiding burning before harvesting of sugar cane. These data show that there could be almost full compensation between sources and sinks/offsets in the agricultural carbon cycle. There is a great opportunity to achieve this mitigation benefit because the adoption of new technologies is increasing rapidly.

Notes: Abstract. Rainfall simulation experiments give an indication of the tendency of soils to crust or seal but are time-consuming and require several kilograms of soil per sample. We developed a laboratory infiltration method that is less time-consuming than rainfall simulation and uses less than 40 g of soil. The method involves the leaching of an agitated 1:5 soil/water suspension through a packed soil column, which simulates the crusting process. The preparation of a dispersed soil suspension is a key feature of the method as it simulates disturbance of a soil surface by rain. This laboratory infiltration method was performed on sandy, granite-derived soils from annually burnt as well as unburnt plots in the Kruger National Park, South Africa and gave results which correlated strongly with results from rainfall simulation experiments on the same soils. We suggest that this new method may be useful for assessing the effect of different land management practices on the tendency of soils to crust.

Notes: Abstract. Belgium's soil survey data collected between 1950 and 1970 (pre-Kyoto Protocol) contain more than 13 000 geo-referenced soil profile descriptions, which allow the computation of a spatially distributed baseline carbon content for incremental soil depths, based on soil/land-use combinations (landscape units) and multiple matching soil profile observations. The results show that the soil organic carbon (SOC) and soil inorganic carbon (SIOC) contents of many landscape units do not differ significantly. However, landscape units under forest and grassland tend to contain more carbon. The same is true for landscape units on poorly drained and/or clayey soils, podzols or anthropogenic soils. The change of the SOC in the upper 100 cm of mineral soil follows a logarithmic decline with increasing depth, useful for the extrapolation of SOC of surface layers to deeper layers. SIOC values are strongly related to the geological soil characteristics and increase linearly with depth. Integrating the mean SOC and SIOC content of landscape units over the Belgian territory results in a total soil carbon stock of 303 Mt C in the upper 100 cm layer. Ectorganic horizons contain 35 Mt C and mineral soil contains 245 Mt C in organic form and 23 Mt C in inorganic form. These results are shown to be consistent with an independent set of SOC measurements on 3134 surface samples.

Notes: Abstract. Land application of organic wastes can result in the accumulation of available soil phosphorus (P) and in an increase risk of eutrophication of surface and shallow groundwaters. We conducted laboratory experiments to examine the effect of waste application on the concentration of dissolved reactive phosphorus (DRP) in 1:5 soil to 0.005 m CaCl2 suspensions. Ten organic wastes, of which eight were mature composts, were applied to a P-rich Calcaric Fluvisol at rates ranging from 0 to 10% of soil by weight, and the difference in DRP concentration between suspensions containing waste and the untreated control (ΔDRP) was measured over a period of 300 days. In half of the suspensions of each waste–soil combination, 80 mg P (as KH2PO4) kg−1 soil was applied at day 14. Values of ΔDRP were generally positive, but a significant number of negative values were also recorded for some wastes and application rates, particularly at later sampling times if inorganic P had been added. Regression analyses revealed that ΔDRP (i) increased with increasing soluble reactive P at all times and (ii) increased in the short term, but decreased in the long term with increasing water soluble organic carbon in the waste. The fact that ΔDRP was sometimes negative for some waste types suggests that application of organic waste to soil does not necessarily increase eutrophication risks caused by soil P losses.

Notes: Abstract. The potential for soil organic carbon sequestration, energy savings and the reduction of the emission of greenhouse gases were investigated for a range of changes in the management of tilled land and managed grassland. These parameters were modelled on a regional basis, according to local soils and crop rotations in England, and avoided the use of soil related indices. The largest carbon sequestration and saving contribution possible comes from an increase in the proportion of permanent woodland, such that a 10% change in land use could amount to 9 Mt C yr−1 in the initial years (arable and grassland). Changes in arable management could make a significant contribution to an abatement strategy if carried out in concert with greater use of permanent conservation field margins, increased returns of crop residues and reduced tillage systems, contributing 1.3 Mt C yr−1 in the initial years. It should be noted, however, that true soil carbon sequestration would be only a minor component of this (125 kt C yr−1), the main part being savings on CO2 emissions from reduced energy use, and lower N2O emissions from reduced use of inorganic nitrogen fertilizer.

Notes: Abstract. After clear-felling of a first generation Chinese fir (Cunninghamia lanceolata) forest, mixed stands of Chinese fir and Michelia macclurei (a broadleaf tree) (MCM), pure M. macclurei stands (PMS) and pure Chinese fir stands (PCS) were established in 1983. The effects on soil were evaluated 20 years after planting by measuring physicochemical, microbiological and biochemical parameters. Both broadleaf monoculture and mixtures of broadleaf and conifer exerted a favourable effect on soil fertility. A soil quality index (SQI) decreased in the order: PMS (0.62) 〉 MCM (0.57) 〉 PCS (0.41). Improvement in soil quality, enhanced biological activity and forest productivity demonstrated that mixed stands are an effective measure to maintain sustainable forest productivity, as well as to control soil degradation under successive stands of Chinese fir. In addition, since the microbiological and biochemical parameters measured were sensitive to the forest management, they may be potential indicators for assessing the sustainability of different management systems. The results also showed that total organic carbon, cation exchange capacity and microbial biomass carbon are effective indicators of the improvement or deterioration of soil quality under forest.

Notes: Abstract. The repeated application of pig slurry to agricultural soils may result in an accumulation of salts and a risk of aquifer pollution due to nitrate leaching and salinization. Under Mediterranean conditions, a field experiment on a sandy loam soil (Typic Xerofluvent) was performed with maize (Zea mays) in 1998, 1999 and 2001 to study the effects of applying optimal (P1) and excessive rates (P3) of pig slurry on soil salinization, nitrate leaching and groundwater pollution. The rate of pig slurry was established considering the optimal N rate for maize in this soil (170, 162 and 176 kg N ha−1 for 1998, 1999 and 2001, respectively). Pig slurry treatments were compared to an optimal N rate supplied as urea (U) and a control treatment without N fertilizer (P0). The composition of the slurries showed great variability between years. Mean NO3− leaching losses from 1998 to 2001 were 329, 215, 173 and 78 kg N ha−1 for P3, P1, U and P0 treatments, respectively. The amount of total dissolved salts (TDS) added to the soil in slurry application between 1998 and 2001 was 2019 kg TDS ha−1 for the P1 treatment and 6058 kg TDS ha−1 for the P3 treatment. As a consequence, the electrical conductivity (EC) of the slurry-treated soils was greater than that of the control soil. The EC correlated significantly with the sodium concentration of the soil solution. Over the entire experimental period, 2653, 2202 and 2110 kg Na ha−1 entered the aquifer from the P3, P1 and P0 treatments, respectively. The P3 treatment did not significantly increase grain production in 1999 and 2001 compared with that achieved with the optimal N rate treatment (P1). This behaviour shows the importance of establishing application guidelines for pig slurry that will reduce the risk of soil and groundwater pollution.

Notes: Abstract. An airborne electromagnetic survey yields a three-dimensional map of ground electrical conductivity. The remotely sensed data are translated into salt load by field and laboratory calibration: drilling, measurement of borehole conductivity, electrical conductivity of 1:5 soil–water extracts (EC1:5) and chemical analysis of pore fluids. Using these field measurements, the conductivity map is calibrated by constraining model parameters within limits defined by the measured values. Once the airborne data is calibrated, we can derive a regional constant (Ksalt) by comparing total ground conductivity with the mass of salt measured in bore samples. Pore fluid chemistry provides a definitive measure of salt, but EC1:5 values may be used, provided that the procedure ensures complete dispersal of clay aggregates to release all the salt. Maps of salt load can be generated from the conductance (total conductivity) maps using a geographical information system. Without calibration, airborne electromagnetic surveying is misleading. Properly calibrated, it provides a detailed, semi-quantitative, three-dimensional map of the distribution of salt in the landscape: a prerequisite for the effective management of salinity. Salt appearing at the surface and in streams is the result of processes operating throughout entire catenas and groundwater flow systems. Across the southeastern catchments of the Murray–Darling Basin, we found that salt is stored predominantly in thick clay horizons within the regolith (encompassing the soil cover, weathered parent material and unlithified sediments down to unweathered basement). Coarse materials, for example in prior stream channels, may serve as conduits for salt transport to rivers and the land surface.

Notes: Abstract. Two field experiments were carried from 1999 to 2001 to assess the effectiveness of autumn, winter and spring application of straw-based farmyard manure (FYM). The soil was a sandy loam containing 106 g clay kg−1 situated in the temperate coastal climate of Denmark. The FYM was applied manually to experimental plots at a target rate of 300 kg N ha−1. The manure was incorporated by three initial tillage strategies (harrowing, rotavating or no-tillage) prior to ploughing. All combinations of tillage strategies were also carried out without manure application. Spring barley (Hordeum vulgare L.) was grown, followed by ryegrass (Lolium perenne L.). The results suggest that, as far as circumstances permit, FYM should be applied in spring to achieve the optimum use of nitrogen in the manure. Further, yield and nitrogen uptake did not benefit from harrowing or rotavating the manure before ploughing. When manure was not applied, soil tillage prior to ploughing did not significantly affect grain yield or nitrogen uptake.

Notes: Abstract. The in-field calibration of a dielectric probe to measure soil water content is described. The probe uses an access tube analogous to that of the neutron probe. The dielectric constant was measured at soil depths of 10, 20, 30, 40, 60 and 100 cm. Cores of soil were then taken from the face of pits dug 30 cm from the access tube and their soil water contents determined by oven drying. The dielectric constant values measured by the probe were calibrated against water contents from these cores. We found that sensor depth needed to be included to achieve a good calibration model that explained 72% of the variance. It is argued that depth needs to be included because of artefacts introduced during the installation of the access tube.

Notes: Abstract. A set of lysimeter based experiments was carried out during 2000/01 to evaluate the impact of soil type and grassland management on potassium (K) leaching. The effects of (1) four soil textures (sand, loam, loam over chalk and clay), (2) grazing and cutting (with farmyard manure application), and (3) K applied as inorganic fertilizer, dairy slurry or a mixture of both sources were tested. Total K losses in the clay soil were more than twice those in the sand soil (13 and 6 kg K ha−1, respectively) because of the development of preferential flow in the clay soil. They were also greater in the cut treatment than in the grazed treatment (82 and 51 kg K ha−1, respectively; P〈inlineGraphic alt="leqslant R: less-than-or-eq, slant" extraInfo="nonStandardEntity" href="urn:x-wiley:02660032:SUM182:les" location="les.gif"/〉 0.01), associated with a 63% increase of K concentration in the leachates from the former (6.7 ± 0.28 and 4.1 ± 0.22 mg K L−1 for cut and grazed, respectively; P〈inlineGraphic alt="leqslant R: less-than-or-eq, slant" extraInfo="nonStandardEntity" href="urn:x-wiley:02660032:SUM182:les" location="les.gif"/〉 0.01) because of the K input from the farmyard manure. The source of fertilizer did not affect total K losses or the average K concentration in the leachates (P 〉 0.05), but it changed the pattern of these over time.

Notes: Abstract. Coliforms such as Escherichia coli and E. coli O157 are present in faeces deposited on the ground by grazing livestock, which gives rise to environmental concerns about the consequences of their transport in soil water draining to rivers, lakes, groundwater, water supplies and bathing waters. Following a similar study in relation to slurry spreading (Soil Use and Management 2003; 19, 321–330), a two-stage approach was adopted to using the dual-porosity contaminant transport model macroto simulate processes by which E. coli microorganisms from grazing livestock (sheep) pass through the soil to receiving waters via field drains. First, model parameter values were selected to reproduce experimental measurements showing rapid flows of the organisms by macropore flow without trapping in smaller pores. However, because of the large number of parameters and likely experimental errors, the set of values chosen, although plausible, is not necessarily unique and so any predictions should be considered provisional pending validation. Second, a series of predictive simulations was carried out to test the influence of soil and weather conditions on losses to field drains during grazing. These showed that E. coli losses were influenced almost entirely by the soil water content at the time of grazing, rising to a high level during grazing in wet conditions, but low or zero under dry conditions. In contrast, rainfall at the time of grazing had almost no consistent effect, other than large losses on the occasional days with over 20 mm of rain. Overall losses for a period of grazing were generally small during summer, but rose to a high level if grazing continued into autumn, due to the increase in soil water content. This demonstrates that there would probably be substantial reductions in the environmental risks of water pollution by E. coli and other faecal microorganisms if continuous grazing were stopped around early September and replaced by grazing on dry days only.

Notes: Abstract. Temperate grasslands account for c. 20% of the land area in Europe. Carbon accumulation in grassland ecosystems occurs mostly below ground and changes in soil organic carbon stocks may result from land use changes (e.g. conversion of arable land to grassland) and grassland management. Grasslands also contribute to the biosphere–atmosphere exchange of non-CO2 radiatively active trace gases, with fluxes intimately linked to management practices. In this article, we discuss the current knowledge on carbon cycling and carbon sequestration opportunities in temperate grasslands. First, from a simple two-parameter exponential model fitted to literature data, we assess soil organic carbon fluxes resulting from land use change (e.g. between arable and grassland) and from grassland management. Second, we discuss carbon fluxes within the context of farming systems, including crop–grass rotations and farm manure applications. Third, using a grassland ecosystem model (PaSim), we provide estimates of the greenhouse gas balance, in CO2 equivalents, of pastures for a range of stocking rates and of N fertilizer applications. Finally, we consider carbon sequestration opportunities for France resulting from the restoration of grasslands and from the de-intensification of intensive livestock breeding systems. We emphasize major uncertainties concerning the magnitude and non-linearity of soil carbon stock changes in agricultural grasslands as well as the emissions of N2O from soil and of CH4 from grazing livestock.

Notes: Abstract. Field margins are a valuable resource in the farmed landscape, providing numerous environmental benefits. We present a preliminary analysis of the carbon mitigation potential of different field margin management options for Great Britain, calculated using data from long-term experiments and literature estimates. The carbon sequestration potential of the individual options investigated here varies from 0.1 to 2.4% of 1990 UK CO2-C emissions, or 0.7–20% of the Quantified Emission Limitation Reduction Commitment (QELRC). The scenarios investigated covered three possible margin widths and options for the management of margins at each width (viz. grass strips, hedgerows and tree strips). Scenarios involving margin widths of 2, 6 or 20 m would require approximately 2.3, 6.7 or 21.3% of the total arable area of Great Britain, respectively. Scenarios including tree strips offered the greatest potential for carbon sequestration, since large amounts would be accumulated in above-ground biomass in addition to that in soil. We also accounted for the possible impacts of changed land management on trace gas fluxes, which indicated that any scenario involving a change from arable to grass strip, hedgerow or tree strip would significantly reduce N2O emissions, and thus further increase carbon mitigation potential. There would also be considerable potential for including the scenarios investigated here with other strategies for the alternative management of UK arable land to identify optimal combinations. We assumed that it would take 50–100 years for soil carbon to reach a new equilibrium following a land use change. More detailed analyses need to be conducted to include environmental benefits, socioeconomic factors and the full system carbon balance.

Notes: Abstract. The Marrakech Accords allow biospheric carbon sinks and sources to be included in attempts to meet emission reduction targets for the first commitment period of the Kyoto Protocol. Forest management, cropland management, grazing land management and re-vegetation are allowable activities under Article 3.4 of the Kyoto Protocol. Soil carbon sinks and sources can therefore be included under these activities. The Kyoto Protocol states that sinks and sources of carbon should be accounted for ‘taking into account uncertainties, transparency in reporting, verifiability’. At its most stringent, verifiability would entail the sampling of each geo-referenced piece of land subject to an Article 3.4 activity at the beginning and end of a commitment period, using a sampling regime that gives adequate statistical power. Soil and vegetation samples and records would be archived and the data from each piece of land aggregated to produce a national figure. Separate methods would be required to deliver a second set of independent verification data. Such an undertaking at the national level would be prohibitively expensive. At its least stringent, verifiability would entail the reporting of areas under a given practice (without geo-referencing) and the use of default values for a carbon stock change for each practice, to infer a change for all areas under that practice. A definition of verifiability between these extremes would allow simple methods, such as those derived from IPCC default values for CO2 fluxes from soil, to be used for estimating changes in soil carbon. These may enable low-level verifiability to be achieved by most parties by the beginning of the first commitment period (2008–2012).

Notes: Abstract. This article explores the question of how scientific information can improve local agronomic management using concepts of uncertainty classification and uncertainty management. Information and data on local management of soil fertility based on a local classification system of soil quality were collected from a small watershed in Cauca (Colombia). The analyses suggest that farmers hold local knowledge about soils at two levels. The first is based on empirical observations and refers to local knowledge about soils and landscape, which shows that the classes identified in the local soil quality classification are consistent with results obtained using measured soil parameters. At the second level, farmers have some awareness of ecological processes and the appropriate use of relationships between key soil characteristics and management options. It is argued that local knowledge is not sufficient to cope with uncertainty introduced by a rapidly changing agriculture, including, for example, increasing land pressure, unpredictable market forces and climate change. We have suggested how scientific knowledge can contribute to the solution, based on an analysis that relates Cohen's (Heuristic reasoning about uncertainty: an artificial intelligence approach. Pitman London, 1985) and Rowe's (Risk Analysis 14, 743–750, 1994) uncertainty concepts to local knowledge.

Notes: Abstract. Over the last two decades, large gully control programmes have been established in Ethiopia. Based on detailed observations and measurements of 400 check dams in the highlands near Hagere Selam (Tigray, northern Ethiopian Highlands), the effectiveness of the check dam technique was assessed. In this study, catchment area, slope gradient, technical characteristics and the presence of smectite clays are the main factors controlling dam stability. Simple and logistic regression techniques were used to analyse the data. The frequent collapse of dams (39% after two years) is strongly associated with drainage area (A) and slope gradient of the soil surface near the gully (S), the product of these factors (S×A) being a proxy for runoff energy. Good functioning dams have a spillway, apron, concave plan form (when looking downslope) and are built at vertical intervals and with heights that result in a negative slope gradient of the line connecting the spillway and the foot of the upstream dam. Therefore, a reverse slope of this line is recommended. Furthermore, if large cracks are present in smectite-rich soils, the construction of check dams can lead to piping and concentrated flow bypassing the dam. Given that the collapse of some check dams seems inevitable where catchment areas are large or there are steep slopes, it is necessary to repair dams as soon as partial collapse starts and to complement this gully control technique with biological control measures.

Notes: Abstract. Field trials of vegetation modification were carried out to test the hypothesis that the management of key plant groups such as trees, perennial grasses and legumes would improve soil chemical properties in short-term fallows. Soil properties and plant production during a 4-year fallow period and millet yields after clearing were recorded at two sites representing dry and subhumid climates in Senegal, West Africa. During the four years of fallow, soil organic matter did not vary significantly at either site. A decrease in amounts of Olsen P, calcium and potassium in soil (0–10 cm depth) by 42–50% occurred at one site due to an effect of perennial grasses. The highest millet yields were measured in plots on which the largest amounts of biomass had been burnt after clear-cutting. These results confirmed that short-term fallows do not replenish soil organic matter and nutrient contents. The introduction of planted species did not arrest the decline in soil quality.

Notes: Abstract. A laboratory experiment was designed to assess the impact of surface seal development on herbicide loss from a clay soil. The influence of surface sealing on herbicide loss through vertical macropores and lateral throughflow pathways was of particular interest. Losses of the phenylurea herbicide, isoproturon, increased from 0.025% to 0.5% of the total applied under sealed compared with unsealed conditions, as a result of two different mechanisms. First, an increased flow rate through the A horizon under the wetter, sealed conditions resulted in earlier initiation of, and hence a greater volume of, throughflow containing isoproturon in the lysimeters. Second, increased concentrations of isoproturon in macropore and throughflow under the sealed treatments were attributed to the physical and chemical characteristics of the surface seal. Localized reductions in infiltration capacity, changes in soil composition, and decrease in diffusion depth of herbicide within the surface seal are presented as possible mechanisms by which herbicide losses from the sealed soil lysimeters were enhanced.

Notes: Abstract. Three different management systems were compared in an olive grove on a Vertic soil, near the city of Cordoba, Spain. Rainfall, runoff and soil loss were recorded from experimental plots of 6×12 m for three years. Results indicated that the no-tillage system, which was kept weed-free with herbicides, gave the largest soil loss (8.5 t ha−1 yr−1) and average annual runoff coefficient (21.5%), due to increased soil compaction, particularly outside the canopy projection area. A system that used a grass cover gave the lowest soil losses (1.2 t ha−1 yr−1) and average annual runoff coefficient (2.5%) due to the protective effects of the cover and increased soil aggregate stability. The third system, conventional tillage, gave intermediate results, with a soil loss of 4.0 t ha−1 yr−1 and an average runoff coefficient of 7.4%. The search for alternative soil management to conventional tillage should consider occasional light tillage to establish a grass cover that would keep both soil erosion and runoff losses to a minimum.

Notes: Abstract. Remediation techniques for soil pollution have been studied in the aftermath of a tailing spill from a pyrite-mine holding pond in Aznalcóllar (southwest Spain). Given the extent of the accident and the characteristics of the affected area, we conclude that, after the removal of the tailings, the only feasible remediation measure involves chemical immobilization of the pollutants. The best treatment tested proved to be liming in combination with amendment materials such as soils rich in iron oxides and clay. Monitoring for 3 years has demonstrated that the system is effective for reducing the solubility of the most mobile forms of the main pollutant elements, although further monitoring is recommended.

Notes: Book reviewed in this article: Uncertain science… uncertain world. By H.N. Pollack.

Notes: The total mean-square error (MSE) of the estimated model, defined as the sum of the standard model variance and the bias variance, is used to define the truncation level of the singular-value decomposition to give a reasonable balance between model resolution and model variance. This balance is determined largely by the data and no further assumptions are necessary except that the bias terms are estimated sufficiently well. This principle has been tested on the 1D magnetotelluric inverse problem with special emphasis on high-frequency radio magnetotelluric (RMT) data. Simulations clearly demonstrate that the method provides a good balance between resolution and variance. Starting from a homogeneous half-space, the best solution is sought for a fixed set of singular values. The model variance is estimated from the sum of the inverse eigenvalues squared, up to a certain threshold, and the bias variance is estimated from the model projections on the remaining eigenvectors. By varying the threshold, the minimum of the MSE is found for an increasing number of fixed singular values until the number of active singular values becomes greater than or equal to the estimated number. As a side-effect, the depth of penetration of a given set of measurements can be estimated very efficiently by simply noting at which depth the final model deviates little from the starting homogeneous half-space model. A suite of synthetic data is inverted and an example of inversion of one site is shown to illustrate how the truncation is carried out as the non-linear inversion process proceeds. A field example with a profile across a plume of contaminated groundwater in the Netherlands shows good agreement with the electrical resistivity obtained in a nearby borehole.

Notes: Faithful recording of the elastic wavefield at the sea-bed is required for quantitative applications of 4C seismic. The accuracy of the recorded vectorial wavefield depends on factors that vary from deployment to deployment. This paper focuses on one such factor: the interaction of the acquisition system with the sea-bed, which is referred to here as coupling. We show, using multi-azimuth data recorded with a cable-based sea-bed acquisition system, whose sensor housing is cylindrically shaped and with the in-line geophone fixed to the cable, that coupling depends on the propagation direction and wave type (P- or S-waves) of the incident wavefield. We show that coupling is more critical for S-waves than for P-waves. Detection of inconsistent coupling using both P- and S-waves is therefore mandatory. A data-driven processing method to compensate for the frequency-dependent coupling response of the cross-line geophone is derived. Its application to field data verifies the effectiveness of the method.

Notes: The combined use of time-lapse PP and PS seismic data is analysed for optimal discrimination between pressure and saturation changes. The theory is based on a combination of the well-known Gassmann model and the geomechanical grain model derived by Hertz and Mindlin. A key parameter in the discrimination process is the opening angle between curves representing constant changes in PP and PS reflectivity plotted against pressure and saturation changes. The optimal discrimination angle in the pressure–saturation space is 90° and this is used to determine optimal offset ranges for both PP and PS data. For typical production scenarios, we find an optimal offset range corresponding to an angle of incidence of 25–30°, for both PP and PS data. For gas we find slightly different results. This means that conventional survey parameters used in marine multicomponent acquisition should be sufficient for the purpose of estimating pressure and fluid saturation changes during production.

Notes: Cross-hole anisotropic electrical and seismic tomograms of fractured metamorphic rock have been obtained at a test site where extensive hydrological data were available. A strong correlation between electrical resistivity anisotropy and seismic compressional-wave velocity anisotropy has been observed. Analysis of core samples from the site reveal that the shale-rich rocks have fabric-related average velocity anisotropy of between 10% and 30%. The cross-hole seismic data are consistent with these values, indicating that observed anisotropy might be principally due to the inherent rock fabric rather than to the aligned sets of open fractures. One region with velocity anisotropy greater than 30% has been modelled as aligned open fractures within an anisotropic rock matrix and this model is consistent with available fracture density and hydraulic transmissivity data from the boreholes and the cross-hole resistivity tomography data. However, in general the study highlights the uncertainties that can arise, due to the relative influence of rock fabric and fluid-filled fractures, when using geophysical techniques for hydrological investigations.

Notes: Shear-wave polarization and time delay are attributes commonly used for fracture detection and characterization. In time-lapse analysis these parameters can be used as indicators of changes in the fracture orientation and density. Indeed, changes in fracture characteristics provide key information for increased reservoir characterization and exploitation. However, relative to the data uncertainty, is the comparison of these parameters over time statistically meaningful? We present the uncertainty in shear-wave polarization and time delay as a function of acquisition uncertainties, such as receiver and source misorientation, miscoupling and band-limited random noise. This study is applied to a time-lapse borehole seismic survey, recorded in Vacuum Field, New Mexico. From the estimated uncertainties for each survey, the uncertainty in the difference between the two surveys is 31° for the shear-wave polarization angle and 4 ms for the shear-wave time delay. Any changes in these parameters greater than these error estimates can be interpreted with confidence. This analysis can be applied to any time-lapse measurement to provide an interval of confidence in the interpretation of shear-wave polarization angles and time splitting.

Notes: A series of downhole magnetometric resistivity (DHMMR) and downhole electromagnetic (DHEM) surveys were conducted near Broken Hill, New South Wales, Australia, and at Zinkgruvan, Sweden, to determine how probe and receiver equipment choices affect the amount of noise visible in borehole MMR and EM data. Noise analyses performed on the data, using the standard deviation to gauge the relative noise levels between different probes and receiver systems, indicate that high noise levels in MMR data result primarily from the use of a three-component EM probe, which has a reduced effective area and hence a higher noise floor compared with a single-component EM probe. High noise, attributable to cultural sources such as nearby power lines, in either MMR or EM data can be reduced through the use of full-waveform, multipurpose receiver systems. These systems allow for the use of tapered stacking, which is a more effective method of eliminating coherent noise associated with power-line transients than the boxcar-stacking method used by traditional receiver systems.

Notes: Interlayer slipping breccia-type gold deposit – a new type of gold deposit, defined recently in the northern margin of the Jiaolai Basin, Shandong Province, China – occurs in interlayer slip faults distributed along the basin margin. It has the features of large orebody thickness (ranging from 14 m to 46 m, with an average thickness of 30 m), shallow embedding (0–50 m thickness of cover), low tenor of gold ore (ranging from 3 g/t to 5 g/t), easy mining and ore dressing. This type of gold deposit has promising metallogenic forecasting and potential for economic exploitation.A ground gamma-ray survey in the Pengjiakuang gold-ore district indicates that the potassium/thorium ratio is closely related to the mineralization intensity, i.e. the larger the potassium/thorium ratio, the higher the mineralization. The gold mineralized alteration zone was defined by a potassium/thorium ratio of 0.35. A seismic survey confirms the location of the top and bottom boundaries and images various features within the Pengjiakuang gold mineralization belt. The gold-bearing shovel slipped belt dips to the south at an angle of 50–55° at the surface and 15–20° at depth. The seismic profile is interpreted in terms of a structural band on the seismic section characterized by a three-layered model. The upper layer is represented by weakly discontinuous reflections that represent the overlying conglomerates. A zone of stronger reflections representing the interlayer slip fault (gold-bearing mineralized zone) is imaged within the middle of the section, while the strongest reflections are in the lower part of the section and represent metamorphic rocks at depth. At the same time, the seismic reflection survey confirms the existence of a granite body at depth, indicating that ore-forming fluids may be related to the granite. A CSAMT survey showed that the gold-bearing mineralized zone is a conductive layer and contains a low-resistivity anomaly ranging from 2 Ωm to 200 Ωm.

Notes: The elastic properties and anisotropy of shales are strongly influenced by the degree of alignment of the grain scale texture. In general, an orientation distribution function (ODF) can be used to describe this alignment, which, in practice, can be characterized by two Legendre coefficients. We discuss various statistical ODFs that define the alignment by spreading from a mean value; in particular, the Gaussian, Fisher and Bingham distributions. We compare the statistical models with an ODF resulting from pure vertical compaction (no shear strain) of a sediment. The compaction ODF may be used to estimate how the elastic properties and anisotropy evolve due to burial of clayey sediments.Our study shows that the three statistical ODFs produce almost identical correspondence between the two Legendre coefficients as a function of the spreading parameter, so that the spreading parameter of one ODF can be converted to the spreading parameter of another ODF. In most cases it is then sufficient to apply the spreading parameter for the ODF instead of the two Legendre coefficients. The effect of compaction on the ODF gives a slightly different correspondence between the two Legendre coefficients from that for the other models. In principle, this opens up the possibility of distinguishing anisotropy effects due to compaction from those due to other processes.We also study reflection amplitudes versus angle of incidence (AVA) for all wave modes, where shales having various ODFs overlie an isotropic medium. The AVA responses are modelled using both exact and approximation formulae, and their intercepts and gradients are compared. The modelling shows that the S-wave velocity is sensitive to any perturbation in the spreading parameter, while the P-wave velocity becomes increasingly sensitive to a perturbation of a less ordered system. Similar observations are found for the AVA of the P-P and P-SV waves. Modelling indicates that a combined use of the amplitude versus offset of P-P and P-SV reflected waves may reveal certain grain scale alignment properties of shale-like rocks.

Notes: Although it is believed that natural fracture sets predominantly have near-vertical orientation, oblique stresses and some other mechanisms may tilt fractures away from the vertical. Here, we examine an effective medium produced by a single system of obliquely dipping rotationally invariant fractures embedded in a transversely isotropic with a vertical symmetry axis (VTI) background rock. This model is monoclinic with a vertical symmetry plane that coincides with the dip plane of the fractures.Multicomponent seismic data acquired over such a medium possess several distinct features that make it possible to estimate the fracture orientation. For example, the vertically propagating fast shear wave (and the fast converted PS-wave) is typically polarized in the direction of the fracture strike. The normal-moveout (NMO) ellipses of horizontal reflection events are co-orientated with the dip and strike directions of the fractures, which provides an independent estimate of the fracture azimuth. However, the polarization vector of the slow shear wave at vertical incidence does not lie in the horizontal plane – an unusual phenomenon that can be used to evaluate fracture dip. Also, for oblique fractures the shear-wave splitting coefficient at vertical incidence becomes dependent on fracture infill (saturation).A complete medium-characterization procedure includes estimating the fracture compliances and orientation (dip and azimuth), as well as the Thomsen parameters of the VTI background. We demonstrate that both the fracture and background parameters can be obtained from multicomponent wide-azimuth data using the vertical velocities and NMO ellipses of PP-waves and two split SS-waves (or the traveltimes of PS-waves) reflected from horizontal interfaces. Numerical tests corroborate the accuracy and stability of the inversion algorithm based on the exact expressions for the vertical and NMO velocities.

Notes: The azimuth moveout (AMO) operator in homogeneous transversely isotropic media with a vertical symmetry axis (VTI), as in isotropic media, has an overall skewed saddle shape. However, the AMO operator in anisotropic media is complicated; it includes, among other things, triplications at low angles. Even in weaker anisotropies, with the anisotropy parameter η= 0.1 (10% anisotropy), the AMO operator is considerably different from the isotropic operator, although free of triplications. The structure of the operator in VTI media (positive η) is stretched (has a wider aperture) compared with operators in isotropic media, with the amount of stretch being dependent on the strength of anisotropy. If the medium is both vertically inhomogeneous, i.e. the vertical velocity is a function of depth (v(z)), and anisotropic, which is a common combination in practical problems, the shape of the operator again differs from that for isotropic media. However, the difference in the AMO operator between the homogeneous and the v(z) cases, even for anisotropic media, is small. Stated simply, anisotropy influences the shape and aperture of the AMO operator far more than vertical inhomogeneity does.

Notes: The attenuation of ground-penetrating radar (GPR) energy in the subsurface decreases and shifts the amplitude spectrum of the radar pulse to lower frequencies (absorption) with increasing traveltime and causes also a distortion of wavelet phase (dispersion). The attenuation is often expressed by the quality factor Q. For GPR studies, Q can be estimated from the ratio of the real part to the imaginary part of the dielectric permittivity.We consider a complex power function of frequency for the dielectric permittivity, and show that this dielectric response corresponds to a frequency-independent-Q or simply a constant-Q model. The phase velocity (dispersion relationship) and the absorption coefficient of electromagnetic waves also obey a frequency power law. This approach is easy to use in the frequency domain and the wave propagation can be described by two parameters only, for example Q and the phase velocity at an arbitrary reference frequency. This simplicity makes it practical for any inversion technique. Furthermore, by using the Hilbert transform relating the velocity and the absorption coefficient (which obeys a frequency power law), we find the same dispersion relationship for the phase velocity. Both approaches are valid for a constant value of Q over a restricted frequency-bandwidth, and are applicable in a material that is assumed to have no instantaneous dielectric response.Many GPR profiles acquired in a dry aeolian environment have shown a strong reflectivity inside dunes. Changes in water content are believed to be the origin of this reflectivity. We model the radar reflections from the bottom of a dry aeolian dune using the 1D wavelet modelling method. We discuss the choice of the reference wavelet in this modelling approach. A trial-and-error match of modelled and observed data was performed to estimate the optimum set of parameters characterizing the materials composing the site. Additionally, by combining the complex refractive index method (CRIM) and/or Topp equations for the bulk permittivity (dielectric constant) of moist sandy soils with a frequency power law for the dielectric response, we introduce them into the expression for the reflection coefficient. Using this method, we can estimate the water content and explain its effect on the reflection coefficient and on wavelet modelling.

Notes: The forward computation of the gravitational and magnetic fields due to a 3D body with an arbitrary boundary and continually varying density or magnetization is an important problem in gravitational and magnetic prospecting. In order to solve the inverse problem for the arbitrary components of the gravitational and magnetic anomalies due to an arbitrary 3D body under complex conditions, including an uneven observation surface, the existence of background anomalies and very little or no a priori information, we used a spherical coordinate system to systematically investigate forward methods for such anomalies and developed a series of universal spherical harmonic expansions of gravitational and magnetic fields. For the case of a 3D body with an arbitrary boundary and continually varying magnetization, we have also given the surface integral expressions for the common spherical harmonic coefficients in the expansion of the magnetic field due to the body, and a very precise numerical integral algorithm to calculate them. Thus a simple and effective method of solving the forward problem for magnetic fields due to 3D bodies of this kind has been found, and in this way a foundation is laid for solving the inverse problem of these magnetic fields. In addition, by replacing the parameters and unit vectors in the spherical harmonic expansion of a magnetic field by gravitational parameters and a downward unit vector, we have also derived a forward method for the gravitational field (similar to that for the magnetic case) of a 3D body with an arbitrary boundary and continually varying density.

Notes: 2.5D modelling approximates 3D wave propagation in the dip-direction of a 2D geological model. Attention is restricted to raypaths for waves propagating in a plane. In this way, fast inversion or migration can be performed. For velocity analysis, this reduction of the problem is particularly useful.We review 2.5D modelling for Born volume scattering and Born–Helmholtz surface scattering. The amplitudes are corrected for 3D wave propagation, taking into account both in-plane and out-of-plane geometrical spreading. We also derive some new inversion/migration results. An AVA-compensated migration routine is presented that is simplified compared with earlier results. This formula can be used to create common-image gathers for use in velocity analysis by studying the residual moveout. We also give a migration formula for the energy-flux-normalized plane-wave reflection coefficient that models large contrast in the medium parameters not treated by the Born and the Born–Helmholtz equation results. All results are derived using the generalized Radon transform (GRT) directly in the natural coordinate system characterized by scattering angle and migration dip. Consequently, no Jacobians are needed in their calculation.Inversion and migration in an orthorhombic medium or a transversely isotropic (TI) medium with tilted symmetry axis are the lowest symmetries for practical purposes (symmetry axis is in the plane). We give an analysis, using derived methods, of the parameters for these two types of media used in velocity analysis, inversion and migration. The kinematics of the two media involve the same parameters, hence there is no distinction when carrying out velocity analysis. The in-plane scattering coefficient, used in the inversion and migration, also depends on the same parameters for both media. The out-of-plane geometrical spreading, necessary for amplitude-preserving computations, for the TI medium is dependent on the same parameters that govern in-plane kinematics. For orthorhombic media, information on additional parameters is required that is not needed for in-plane kinematics and the scattering coefficients.Resolution analysis of the scattering coefficient suggests that direct inversion by GRT yields unreliable parameter estimates. A more practical approach to inversion is amplitude-preserving migration followed by AVA analysis.SYMBOLS AND NOTATIONA list of symbols and notation is given in Appendix D.