ALBERT

Notizen: Abstract. The effect of land use on the water retention capacity of Umbric Andosols in south Ecuador was studied. The objective was to acquire a better insight into the hydrological processes of the ecosystem and the role of the soil, in order to assess the impact of changing soil properties due to land use change on the hydrology of the high Andes region. Field data on the water retention capacity at wilting point of Umbric Andosols were collected for both cultivated field conditions and original bush vegetation. The pH in water and in NaF, texture, organic matter content and dry bulk density were measured to show which physicochemical soil characteristics are responsible for the water retention of the Umbric Andosols and for the irreversible loss in water retention due to air drying. Organic matter content appears to be very important and certainly more important than allophane clay content. Water retention of the organic litter layer was calculated to be 16 mm, this would be lost when vegetation was cleared and the land cultivated.

Notizen: Abstract. The effects of time and temperature on the changes in Olsen P after phosphate application were studied in 13 calcareous soils from Pakistan, an Oxisol from Colombia and an Inceptisol from England. The phosphate sorption reactions were monitored in two stages. The short-term reaction (30 min shaking with added phosphate in the presence of the Olsen bicarbonate solution) showed that over this time the nature of the sorbing material and number of available sites for P adsorption were important but temperature was not. The extent of the short-term sorption was not related to the amount of calcium carbonate. In the long-term reaction (incubating the soils with phosphate at 10, 25 and 45 °C for one year) the amount of Olsen P decreased with time following a power relationship. Increased temperature increased the rate of reaction, following the Arrhenius principle i.e. Q10⊃ 3 (activation energy 83 kJ mol–1). The effects of time and temperature were well described by a modified power equation Y=a (1 +fTt)-b, where Y is the amount of Olsen P extracted after time t, a is the Olsen P value after the short-term reaction (the initial value), fT is the ratio of the rate constants at any two temperatures and b is a coefficient which represents the loss in extractability with time. On the basis of the initial Olsen P values and subsequent Olsen P values at different times and temperatures a unified decay curve Y/a= (1 +t)–0.20 was developed where the initial Olsen P values are normalized to 1. The parameters of this equation allow, with limitations, the prediction of changes in Olsen P in these soils if the initial Olsen P value of the soil is known.

Notizen: Abstract. This study investigated the effect of the same volume of leaching water applied consecutively in either equal amounts or increasing amounts or decreasing amounts on the hydraulic conductivity of a saline sodic soil in 30 cm plastic columns in the laboratory. Gypsum was mixed with the surface 2–3 cm of soil. After leaching, the hydraulic conductivity was measured in each 10 cm depth of soil. Hydraulic conductivity decreased strongly (P〈0.05) with depth and the most effective method of applying the water was in gradually increasing amounts.

Notizen: Abstract. The field experiment tested the effects of three management systems on nitrate leaching losses from a five crop rotation on the Lincolnshire Limestone in Eastern England. The Standard system was similar to farming practice in the area. The Protective system integrated individual practices which were expected to decrease nitrate losses (e.g. cover crops, cultivation delay in autumn and reduced intensity, manipulation of drilling dates and, during the first few years of the first rotation, straw incorporation). The Intermediate system was a compromise between the two extremes. All crops were grown at full and half recommended nitrogen rates. This paper reports data from the second full rotation (years 6–10), thus enabling the medium-term effects of continued management practices to be investigated. Average annual nitrogen leaching losses at 49, 35 and 25 kg N ha–1 for Standard, Intermediate and Protective systems, respectively, were significantly different. The respective flow-weighted average NO3 concentrations were 167, 131 and 96 mg l–1. Thus, adopting nitrate retentive practices through the rotation was able to substantially decrease losses. The Protective system was as effective as in the first full rotation, demonstrating that 10 years of such practices had not failed in the medium-term. However, continued minimal cultivation caused serious problems of weed build-up. The cost of weed control and yield loss caused by grass weeds made cereal production uneconomic in some years. Thus, rules for nitrate leaching control need to be tempered with practical and agronomic considerations. Also, few (if any) management techniques tested guaranteed that nitrate losses would be small in all years, as the interaction with winter weather, particularly rainfall, was of vital importance.

Notizen: Abstract. The Pilot Nitrate Sensitive Areas Scheme was set up in England in 1990 to test measures aimed at reducing nitrate losses from agricultural land. Ten groundwater catchments were chosen to typify the geology and farming of areas where nitrate concentrations in abstracted water were high. Voluntary and compensated controls on farming, based on recent research, were introduced. Scheme membership was for 5 years from 1990 or 1991, and 86% of the agricultural land entered the Scheme. On all farms entering the Scheme, manure and fertilizer use were restricted and green cover crops were required over winter (Basic Scheme). Additional payments were available for conversion of arable land to zero or low-input grassland (Premium Scheme). Intensive pig and poultry farmers were assisted with the costs of transporting manure for spreading over a wider area. The most effective changes were improved management of livestock manures, especially of the very large local quantities from housed pig or poultry units; conversion of arable land to low-input grassland; and use of cover crops. There were no indications of reduced crop yields but some requirements increased costs and management complexities. Estimates based on both model calculations and measurements indicated that nitrate losses from agricultural land decreased by about 30%, with considerable variation between areas.

Notizen: Abstract. The structure of soils in areas of rain forest cleared for pasture is often compacted due to trampling by animals. When pasture is abandoned, regeneration of forest cover may be achieved from natural seed sources nearby.However, the regeneration of soil structure is also important for local hydrology and successful establishment of some plant species. In this study we investigated changes in soil structure and hydraulic properties in a series of plots on volcanic soils in the San Luis Valley, Costa Rica. The plots were current pasture, 15- and 20-year-old regenerating forest, and primary rain forest.Infiltration rate increased with increasing forest age and the water release characteristic reverted gradually from one with greater water retention at all matric potentials in the pasture plot towards that found in the primary forest. Compaction and low porosity were features of both the current pasture and 15-year-old regenerating forest in comparison to the primary forest.

Notizen: Abstract. Over 170 countries have ratified the UN Framework Convention on Climate Change (UNFCCC) which aims at ‘the stabilisation of greenhouse gases in the atmosphere at a level that will prevent dangerous anthropogenic interference with the climate system’. The Kyoto Protocol, signed in 1997, commits the developed (‘Annex 1′) countries to a reduction in gaseous emissions. The global increase in atmospheric CO2, the main greenhouse gas, comes mainly from fossil fuels (6.5 Gt C yr−1), together with about 1.6 Gt C yr−1 from deforestation. The atmospheric increase is only 3.4 Gt C yr−1, however, due to a net sink in terrestrial ecosystems of about 2 Gt C yr−1, and another in the oceans. Increasing net carbon sequestration by afforestation of previously non-forested land is one way of reducing net national emissions of CO2 that is permitted under the Kyoto Protocol. Future modifications may also allow the inclusion of carbon sequestration brought about by other forestry and agricultural land management practices. However, associated changes in net fluxes of two other greenhouse gases identified in the Protocol — nitrous oxide (N2O) and methane (CH4) — will have to be taken into account. Growth of biomass crops can increase N2O emissions, and drainage of wetlands for forestry or agriculture also increases them, as well as emissions of CO2, while decreasing those of CH4. The problems of how to quantify these soil sources and sinks, to maximize soil C sequestration, and to minimize soil emissions of CH4 and N2O, will present a major scientific challenge over the next few years — one in which the soil science community will have a significant part to play.

Notizen: Abstract. The effectiveness of Festuca ovina and Poa pratensis as contour grass strips for erosion control was examined in a laboratory experiment for an crodible sandy loam soil on 21, 25 and 29% slopes. No significant differences P〈0.05 were observed in runoff between the plots with grass strips and bare soil but significant differences in soil loss were recorded. Both grasses reduced crosion in the early part of the simulated storms by ponding water behind the barrier, filtering sediment and causing deposition within the ponded area. The P. pratensis barrier was less rigid and became flattened under submergence in the later part of the storms. Runoff flowed over the grass strip forming rills on the slope below, which then cut back and undermined the barrier. These barriers resulted in as much soil loss as bare soil towards the end of the storms on all three slopes. The F. ovina was effective in controlling erosion on the 21% and 25% slopes but not on the 29% slope.

Notizen: Abstract. The recommended method of reducing the emission of NH3 while spreading manure is to plough or harrow the manure into the soil. This in turn increases the possibility of N2O emission. At two sites in southern Sweden emissions of NH3 and N2O were measured after spreading pig slurry by broadcasting and band spreading. The band spreading technique can be used in growing crops i.e. when nitrogen is most needed, and it is thought that the NH3 emission is smaller with this technique compared to broadcasting. The average NH3 loss was 50% of applied NH4+ during warm/dry conditions and 10% during cold/wet conditions. The N2O emission was always less than 1% of applied NH4+. When the NH3 emission decreased, the direct N2O emission increased. However, when taking into account the indirect N2O emission due to deposition of NH3 outside the field, the spreading techniques all produced similar total N2O emissions. The ammonia emission was not much lower for the band spreading technique compared to broadcasting, when compared on seven occasions.

Notizen: Book reviewed in this article: Soil Erosion at Multiple Scales: Principles and Methods for Assessing Causes and Impacts Edited by F. W. T. Penning de Yries, F. Agus & J. Kerr

Notizen: 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.

Notizen: 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.

Notizen: 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.

Notizen: 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.

Notizen: 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.

Notizen: 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.

Notizen: 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.

Notizen: 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.

Notizen: 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.

Notizen: 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.

Notizen: 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.

Notizen: 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.

Notizen: 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.

Notizen: 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.

Notizen: 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.

Notizen: 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.

Notizen: 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.

Notizen: 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.

Notizen: 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.

Notizen: 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.

Notizen: 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).

Notizen: 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.

Notizen: 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.

Notizen: 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.

Notizen: Abstract. A field plot experiment was conducted to investigate P mobilization from fertilized rice fields during rainfall-flooding events. The experiment tested the effects of inorganic fertilizer P, at two rates, and P fertilizer plus manure, at one rate, on the amounts of P lost in drainage water when the plots were subjected to four artificially simulated storm-flooding/drainage events over an eight day period. During the first drainage event, two days after P application, the concentrations and loads of soluble reactive P (SRP) and particulate P (PP) in the drainage water were some three to five times lower than they had been just 24 hours earlier due to rapid sorption and sedimentation. At subsequent events, the concentrations and loads of SRP in drainage water were almost two orders of magnitude lower than at the first event, i.e. the equilibrium between P release from fertilizer and manure and P sorption/fixation by the soil mineral fraction had shifted strongly in favour of the latter processes. During the first drainage event, the concentrations and loads of SRP in drainage water from the low P fertilizer treatment were similar to those on the low P fertilizer plus manure treatment, whereas, 24 hours earlier they had been significantly greater. At subsequent events, though, the highest concentrations and loads of SRP occurred in drainage water from plots treated with equal amounts of P fertilizer and manure. It is suggested that extending the time period between P application and flooding events by applying fertilizer and manure outside the main rainy season should significantly reduce the risk of P loss from paddy rice fields.

Notizen: Abstract. Natural secondary succession, forest planting and agricultural practices after deforestation affect soil properties in many ways. During the last 50 years, land uses have greatly changed in the mountainous areas in southwestern China as the result of deforestation and cultivation. A study was initiated in Wolong Nature Reserve, Sichuan province to elucidate the complex relationships in a humid mountainous region. Soil properties under six typical land use types (natural forest, grassland, shrub, secondary forest, cultivated land and reforested land) were compared. Significant differences between land uses were found for soil bulk density (BD), total nitrogen (TN), soil organic carbon (SOC), available phosphorus (AP) and available potassium (AK). Cultivated land had the lowest levels for most soil properties compared to other land uses and shrubland had a higher SOC, TN and available nitrogen (AN) than other land uses. Soils under grassland and shrub contained the greatest carbon mass (TC). Further studies on reforested land indicated that soil properties could be changed by length of reforestation. The SOC and TN in particular showed a linear relationship with years since reforestation. The results suggested that in an area of China where the climate favours secondary succession, ‘leave nature as it is’ is a better choice than the policy ‘change farmland to forest land ‘, especially for the mountainous regions where there is lack of labour and financial support.

Notizen: Abstract. Soil erosion and sediment delivery cause many environmental problems posing a substantial financial burden upon society. Policy makers therefore look for a strategy to minimize their impact. The spatial nature of soil erosion and sediment delivery, as well as the variety of possible soil conservation and sediment control measures, requires an integrated approach to catchment management. To evaluate such management, a spatially distributed soil erosion and sediment delivery model is necessary. Such a model (WaTEM/SEDEM) was applied to three agricultural catchments in Flanders (Belgium). The model was first used to identify where the measures to control soil loss should be taken. Secondly, a scenario analysis was used to select the most effective set of techniques. The findings showed that soil conservation measures taken in fields are not only effective in reducing on-site soil loss, but also in drastically reducing sediment yield. Off-site sediment control measures appear to be much less effective in reducing sediment yield than previously thought. The results also suggest that data from field experiments cannot be extrapolated to a catchment scale.

Notizen: Abstract. When over exploited and coupled with climatic conditions, tropical soils are subject to increased erosion and a loss of soil organic matter. Countermeasures include the incorporation of organic materials such as crop and animal residues. We studied the effect of adding crop residues and manure to soil, at five sites in Ethiopia, on carbohydrate properties, aggregate stability and the C and N distribution within water-stable aggregates. The effects of organic amendments varied between sites. The largest content of carbohydrates was obtained in the control treatment at Holeta, Ginchi (90 kg ha–1 mustard meal), Jimma (5 t ha–1 cow dung + 9 t ha–1 coffee husk), Awassa (forested soil), and Sirinka (soil alley-cropped with Leuceanae). The aggregate stability of these soils was highly correlated with the OM content but not with carbohydrates. The smaller aggregates (〈1.00 mm) accumulated more carbohydrates than the larger (〉1.00 mm), thereby suggesting a protecting effect within the finer soil fractions. A protecting role played by humified OM components was also indicated by the C and N distribution as well as the C:N ratios which showed preferential accumulation in small rather than in large aggregates. The isotopic 13C-OC values of carbohydrate extracts were generally low, suggesting that OM was from plants with C3 photosynthetic pathways. Soil treatments with maize alone or combined with coffee husks at Jimma decreased the δ13C‰ values slightly, revealing that maize contributed a share of the labile OM. Despite the improvement in the soil OM content, neither the carbohydrate content nor the aggregate stability were increased to the level of the forested sites, suggesting that the additions of crop residues and manure were not alone sufficient to restore the soil physical quality.

Notizen: Abstract. This paper reviews information from the literature and case studies to investigate whether productivity in organic systems is restricted by the supply of available N during the major phases of crop growth. Organic systems have the potential to supply adequate amounts of available N to meet crop demand through the incorporation of leys, N rich cash crop residues and uncomposted manures. However, this is seldom achieved because leys are only incorporated once every few years and organically produced crop residues and manures tend to have low N contents and slow mineralization rates. N availability could be improved by delaying ley incorporation until spring, applying uncomposted manures at the start of spring growth, transferring some manure applications from the ley phase to arable crops, preventing cover crops from reaching a wide C:N ratio and better matching crop type with the dynamics of N availability.

Notizen: Abstract. Previous studies of the microbial status of soils managed under ‘organic’ and ‘conventional’ regimes have produced conflicting evidence of whether there are distinct differences in the size, composition and activity of the soil microbial biomass which may be attributed to management practice. In the present study, we have compared the microbiology of organically- and conventionally-managed soils at (primarily) two farms in England, over a two year period. Differences in microbial communities in soils under different management practice were subtle rather than dramatic. Many of the parameters measured, including total C and microbial biomass C, often showed no consistently significant differences in soils under different management. In soils from one farm, concentrations of ATP in Ringers solution soil extracts were mostly found to be significantly greater in organically-managed than in comparable conventionally-managed soils. While indirect (plate) counts showed that there were similar numbers of cultivable microorganisms present in these soils, total counts of bacteria (via DAPI-staining) were found to parallel the trends found for readily-extractable ATP. Numbers of metabolically-active bacteria, determined by FISH analysis using a EUB338 probe to detect ribosome-rich cells, indicated that the percentage of metabolically-active bacteria present was not determined by management practice. Total and active fungi were also found to be more abundant in organically-managed soils. It was concluded that changes in soil microbiology may occur as a consequence of switching to organic land management, but these may not be detectable by methods used frequently to assess soil biomass. In particular, increased numbers of viable but non-culturable bacteria and fungi in organically-managed soils points to a greater physiological diversity of microorganisms in such situations.

Notizen: Abstract. Under a UK Government consultation procedure announced in 2001, it was proposed that measures agreed within already designated Nitrate Vulnerable Zones (NVZ ‘s) would be extended to include a considerably increased area of England, Wales and Scotland. Since existing NVZ ‘s in the UK have included relatively little grassland, it is important to examine how nitrate losses from grassland areas, especially from animal manures, one of the major potential sources of nitrate loss, can be minimized. Experiments were carried out on freely draining grassland soils at four sites (Devon, Hampshire, Shropshire and N Yorkshire) representative of a wide range of climatic and farming conditions across lowland England, over a four year period, 1990/91 to 1993/94. Slurry was applied to experimental plots over a range of times (including June and then monthly, from September to January) at a target rate of 200 kg N ha–1. Nitrogen leaching over the four years ranged from 0 to 〉50% of applied slurry N, with the largest losses occurring following applications in the September to November period. The use of a nitrification inhibitor with slurry applied in November failed to provide consistent reduction in nitrate leaching.A strategy to reduce the risk of N leaching from manures applied to freely draining grassland soils must take account of the characteristics of the manure, in particular its N content, the application rate and the amount of excess rainfall following application. The experimental results suggest that slurry applications to freely draining grassland, in September, October and November should generally be avoided, the rationale for this being dependent on the amount of excess rainfall subsequent to application. Farmyard manure represents a lower risk and does not justify the restrictions on application timing that appear to be necessary with slurry.

Notizen: Abstract. A numerical model that incorporates the spatial variability of infiltration, surface storage and resistance to overland flow was developed, calibrated and validated for olive orchards. The model reproduced accurately amounts of runoff used in validation, and predicted runoff in olive orchards managed in different ways, in line with published results. The model was used to analyse the runoff generation in a virtual, 180 m length, 5% steep, olive grove, using 54 different scenarios which combined three different soil types, two tree canopy sizes and nine soil management techniques (four tillage scenarios: freshly or degraded tillage with and without a compacted plough layer; no-till, and four cover crops in strips differing in width and plant density). The results of the numerical experiment showed that no-till had the highest runoff coefficient, while a dense cover crop had the lowest. Recently tilled soils also exhibited some of the lowest runoff coefficients. The effects of increasing soil cover due to a greater tree canopy on runoff were significant and caused by the greater area of high infiltration beneath the canopy. Effects of tree canopy size were less important than the impact of soil management practices on runoff.

Notizen: Abstract. In the Sahel, promising technologies for agricultural intensification include millet stover mulching and ridging. A four year on-farm experiment was set-up in order to assess the effect of various combinations of these two technologies on soil chemical and physical quality in a millet (Pennisetum glaucum (L.) R. Br.) –- cowpea (Vigna unguiculata (L.) Walp.) relay intercropping system. Treatments included bare surface, ridging, a surface applied banded millet stover mulch (2 t ha–1) and a banded millet stover mulch (2 t ha–1) buried in ridges. The latter three treatments were implemented exclusively in the cowpea rows, with an annual rotation between the millet and cowpea rows. Both the bare and ridge plots experienced a rapid loss of organic carbon, acidification and the development of extensive surface crusts but no increase in bulk density or penetration resistance. In the year of application, mulching improved soil quality in the cowpea row with respect to pH, organic carbon and exchangeable K+ and Mg++ content, penetration resistance and bulk density, and it reduced the decline in exchangeable Ca++ and total N content. In the year following mulch application, a general decline in soil chemical quality was observed in the millet row, except for organic carbon content, and a positive residual effect was observed on penetration resistance and bulk density. As a rule, the effects of mulching in the year of application tended to be stronger in the ridged treatment with buried residue than in the banded surface mulch. In the year following application, this tendency was reversed. For the purpose of reducing soil degradation by nutrient mining and wind erosion, a banded surface mulch therefore appeared more effective than buried mulch.

Notizen: Abstract. Slurry from farm animals may contaminate water supplies, rivers and bathing waters with faecal coliforms, such as Escherichia coli. Where animals harbour the O157 strain the hazard to human health is particularly high, but both the hazard level, and the low incidence and sporadic nature of the excretion of E. coli O157 make it difficult to study this strain under field conditions. The survival of total E. coli and of E. coli O157 were compared in the laboratory for two soils under controlled temperature and moisture. E. coli O157 die-off rate was the same as or quicker than for total E. coli. This result meant that field experiments studying the fate of total E. coli should give a satisfactory evaluation of the risk of water contamination by the O157 strain. In four field experiments at three sites, slurry containing total E. coli numbers of 2.2 × 104 to 5.7 × 105 colony forming units per mL (c.f.u. mL–1) was applied to drained field plots. Field die-off was faster than expected from laboratory experiments, especially in one experiment where two weeks dry weather followed application. In all but this experiment, the first drain flow events after slurry application led to very high E. coli concentrations in the drains (103 to 104 c.f.u. mL–1). E. coli O157 was present in the slurry used for two of the experiments (33 c.f.u. per 100 mL in each case). However the proportion of E.coli O157 was very low (about 1 in 105) and it was not detected in the drainage water. After the first week E. coli drainage water numbers decreased rapidly but they were 1–10 c.f.u. mL–1 for much of the sampling period after slurry application (1–3 months).

Notizen: Abstract. Predictive, regional use of soil organic matter (SOM) models requires evaluation of the performance of models with datasets from long-term experiments relevant to the scenarios of interest to the regional scale study, and relevant to the climate of the study region. Datasets from six long-term experiments were used to evaluate the performance of RothC and CENTURY, two of the most widely used and tested SOM models. Three types of model run were completed for each site: (1) CENTURY model alone; (2) RothC model run to fit measured SOC values, by iteratively adjusting C inputs to soil; and (3) RothC model run using C inputs derived from CENTURY runs. In general, the performance of both models was good across all datasets. The runs using RothC (iteratively changing C inputs to fit measured SOC values) tended to have the best fit to model data, since this method involved direct fitting to observed data. Carbon inputs estimated by RothC were, in general, lower than those estimated by CENTURY, since SOC in CENTURY tends to turn over faster than SOC in RothC. The runs using RothC with CENTURY C inputs tended to have the poorest fit of all, since CENTURY predicted greater C inputs than were required by RothC to maintain the same SOC content. A plausible model fit to measured SOC data may be obtained with widely differing C input values, due to differences in predicted decomposition rates between models. It remains unclear which, if either, modelling approach most closely represents reality since both C inputs to soil and decomposition rates for bulk SOM are difficult to determine experimentally. Further progress in SOM modelling can only be the result of research leading to better process understanding, both of net C inputs to soil and of SOM decomposition rates.  The use of default methods for estimating initial SOC pools in RothC and CENTURY may not always be appropriate and may require adjustment for specific sites. The simulations presented here also suggest details of SOC dynamics not shown by available measured data, especially trends between sampling intervals, and this emphasizes the importance of archived soil samples in long-term experiments.

Notizen: Abstract. Efforts to assess the role of soil structure in soil and water processes have been limited by data based on two dimensional geometry or disturbed samples. Computed tomography (CT) is a non-invasive technique that allows for the three dimensional, non-destructive examination of heterogeneous materials. X-ray CT scanning was used to acquire serial images of contrasting soil types that could be used to render, and hence, quantify important soil constituents in three dimensions. By repeating the scanning techniques after an infiltration period, it was also possible to examine the nature of water movement in real time. Macropore architecture between different soil types was highly variable and generally appeared as unconnected pore segments at the resolution examined. As expected, water flow characteristics were similar to macropore structure, with wetting patterns resembling both Darcian and preferential flow identified in different soils. From this, it was found that in the sandy clay soil c. 90% of macropore space was active following infiltration, compared with c. 50% for the sandy loam soil. In addition, it was possible to visualize the three dimensional distribution of stones and other mineral material. The results illustrated the benefits of computed tomography over more conventional analyses of soil structure, and its potential as a tool for examining dynamic soil processes. However, problems associated with accessibility, resolution and artefacts still provide limitations of the technique.

Notizen: Abstract. Continuous cultivation of soils of the semiarid tropics has led to significant land degradation. Soil erosion and nutrient loss caused by high runoff volumes have reduced crop yields and contributed to offsite damage. We compared a number of soil management practices (tillage, mulch and perennial/annual rotational based systems) for their potential to improve crop production and land resource protection in an Alfisol of the semiarid tropics of India. Runoff and soil erosion were monitored and surface soil and sediment were analysed for nitrogen and carbon to determine enrichment ratios. Amelioration of soils with organic additions (farmyard manure, rice straw) or rotating perennial pasture with annual crops increased soil carbon and nitrogen contents and reduced runoff, soil erosion and nutrient loss. Soil erosion totalled less than 7 t ha–1, but enrichment ratios were often greater than 2 resulting in up to 27 kg N ha–1 and 178 kg C ha–1 being lost in sediment. Up to an extra 250 mm of water per year infiltrated the soil with organic additions and was available for crop water use or percolation to groundwater. The results show that there are good opportunities for reducing degradation and increasing productivity on farms.

Notizen: Abstract. Native woodland restoration is a conservation priority within the UK and there is an increasing awareness that a long-term strategy is required to guide this process. A GIS-based modelling approach has been developed, which links site conditions as expressed in an integrated soil and land cover dataset with the site requirements for different woodland types. There are three important aspects to the model – the parameter weightings, the added value of the integrated dataset, and the woodland categories which are described and predicted. The initial quantitative and qualitative validation has been encouraging although more is required and planned. The results indicate that for broad strategic planning purposes, predictions of woodland potential are not improved significantly when climatic factors are incorporated. The concept that soil acts as an integrator of other environmental variables is discussed alongside the practical application of the model by a range of users.

Notizen: Abstract. Spate irrigation is a system used for wetting land prior to planting. Use is made of seasonal rivers (wadis) producing flash floods in the uplands, which are directed by structures to irrigate fields in the lowlands. A land suitability system for spate irrigation schemes in Eritrea was studied in the Sheeb area of Eritrea with and without land improvements. The availability of floods and soil moisture were the major land use requirements for spate-irrigated sorghum and maize, while salinity hazard has only a minor effect in spate irrigation systems. The suitable land for spate irrigation in the Sheeb area is distributed as follows: 16% is highly to moderately suitable, 24% is moderately suitable and 17% is marginally suitable. About 40% of the study area was found to be currently unsuitable for spate irrigation mainly due to a lack of floodwater and poor soils. With improvements to the spate irrigation system, such as construction of permanent flood diversion structures, the area of land suitable for spate irrigation will expand. The land suitability system presented in this study could be applied in other spate irrigation schemes of Eritrea and perhaps in other countries also.

Notizen: Abstract. Forest soil sustainability and future crop productivity is at risk if mechanised harvesting operations cause soil damage. In UK upland forestry, soil protection is usually provided by placing harvesting residues (brash) over areas where machinery traffic is required. In this study, various thicknesses of brash mat were tested for their ability to reduce compaction of a surface water gley soil at Kielder Forest, Northumberland. Changes in penetration resistance and dry soil bulk density were studied after passes by forest harvesting and timber extraction machinery running on the brash. The study shows that normal harvesting operations caused some soil compaction. However, the brash mat system was shown as important in protecting the soil. Soil under brash mats experienced some compaction to at least 45 cm depth. The thickest brash mat, composed of residues from 10 rows of trees, was unable to prevent compaction completely. Nevertheless, the protective role of the brash mat system was clearly confirmed when compared to timber extraction over bare soil. The point at which compaction has a detrimental effect on the establishment and stability of future tree rotations remains uncertain.

Notizen: Abstract. Agricultural soils are important sources of the tropospheric ozone precursor NO and the greenhouse gas N2O. Emissions are controlled primarily by parameters that vary the soil mineral N supply, temperature and soil aeration. In this field experiment, the importance of soil physical properties on emissions of NO and N2O are identified. Fluxes were measured from 13 soils which belonged to 11 different soil series, ranging from poorly drained silty clay loams to freely drained sandy loams. All soils were under the same soil management regime and crop type (winter barley) and in the same maritime climate zone. Despite this, emissions of NO and N2O ranged over two orders of magnitude on all three measurement occasions, in spring before and after fertilizer application, and in autumn after harvest. NO emissions ranged from 0.3 to 215 μg NO-N m–2 h–1, with maximum emissions always from the most sandy, freely drained soil. Nitrous oxide emissions ranged from 0 to 193 μg N2O-N m–2 h–1. Seasonal shifts in soil aeration caused maximum N2O emissions to switch from freely drained sandy soils in spring to imperfectly drained soils with high clay contents in autumn. Although effects of soil type on emissions were not consistent, N2O emission was best related to a combination of bulk density and clay content and the NO/N2O ratio decreased logarithmically with increasing water filled pore space.

Notizen: Abstract. Solutions collected from lysimeters of acid soils can show pH values close to or even above neutral. Laboratory experiments on an acid soil from Burundi were planned to test if denitrification or CO2 degassing might explain such a paradox. In the first experiment, soil profiles were reconstituted in columns and leached with 55 μm Ca(NO3)2 solutions at 30 °C and 4 °C. Two drainage regimes were applied: intermittent suction or no suction at the bottom of the columns. In the second experiment, pH values were measured in solutions drained from different horizons at 30 °C, before and after equilibration with ambient air. Sterilized soil was also tested in the same way. Results from experiment 1 showed that despite the accumulation of water in the bottom of soil profiles when no suction was applied, aeration still existed so that reduction reactions, namely denitrification, are not expected to affect greatly the percolate composition. Indeed nitrate concentration was similar in both drainage regimes and was close to the input value. The pH values in percolates were close to 7 at 30 °C and they dropped to about 5.5 when the columns were at 4 °C. In experiment 2, equilibration of percolates with ambient air resulted in pH increase which was greater for the top horizon (C-rich) but negligible when the soil was first sterilized. These convergent results illustrate the very important effect of CO2 degassing on pH of drained solutions when microbial activity is stimulated at high temperatures, in C-rich soil. This is of prime importance when interpreting results from lysimeter experiments. By chance, this study also showed that large quantities of nitrate can be produced in soil at low temperatures.

Notizen: Abstract. As leaching of nutrients and agrochemicals can occur readily in cracking clay soils, which are important to UK agriculture, it is essential to identify management systems for them that can minimize the risk of contaminants reaching surface waters. The long-term Brimstone Farm study has provided considerable evidence on the movement of water and solutes through such soils and offers a unique opportunity to determine the factors influencing these processes. Management procedures, such as subsurface drainage and tillage, which are widely used for the production of cereals in these soil types, greatly influence the risk of contamination. At Brimstone Farm, tillage has been shown to change the hydrology in terms of both water table control and the route of water movement, and to increase the mineralization of nitrogen and the consequent risk of nitrate leaching. Drainage, essential in these soils, also creates a risk of solute losses, especially pesticides. Ways to retain effective drainage yet decrease losses to surface waters are discussed.

Notizen: Abstract. Sustaining soil fertility under agricultural intensification and expansion onto marginal lands is a significant challenge in the Nepalese Middle Mountains. In a detailed watershed study it was shown that the overall soil fertility is poor, forest soils display the poorest conditions as a result of biomass removal, and sustaining agriculture is questionable due to the transformation from traditional to multiple cropping systems. Parent material is a significant factor influencing low phosphorus status while insufficient inputs create deficiencies in total carbon, nitrogen and bases. A nutrient budget model was developed to assess inputs, redistribution and losses relative to soil fertility. Yield, input and management data obtained from farm interviews, and soil analysis data were used in the calculation of nutrient budgets. Results from modelling indicate declining soil fertility under rainfed agriculture, forest and rangelands, and marginal conditions under irrigated agriculture subject to intensive cultivation. Nutrient deficits were relatively low for irrigated rice-wheat systems, which benefit from nutrient inputs via sediments and irrigation waters, but the introduction of triple cropping showed greater deficits. Nutrient balances were most critical under rainfed maize production where 94% of the farms were in deficit. Current shortages of organic matter make elimination of nutrient deficits problematic but improvement of composting, biological N-fixation and fertilizer efficiency and reducing erosion were found to be potential options.

Notizen: Abstract. During three consecutive years (1993–1995) a split-plot design with three replications was used to study the biological and physical role of mulch in the improvement of crusted soil water balance and its productivity in the north of Burkina Faso. The main treatment was the use of an insecticide, to obtain plots with and without soil fauna (SF and NSF). The subsidiary treatment consisted of four mulch types randomly applied on subplots. These were straw of Pennisetum pedicellatum applied at 3 t ha−1, woody material of Pterocarpus lucens applied at 6 t ha−1 and composite (woody material and straw) treatments applied at 4 t ha−1. In addition there was a control, with no mulch (bare plot). Data on soil faunal activity, runoff, sediment accumulation from wind blown soil, vegetation cover and vegetation dry matter yield were collected on all plots.The biological activity (mainly termites) in mulched plots was the key element in the efficacy of mulching to rehabilitate crusted soil. Water infiltration and dry matter yield were statistically lower on NSF plots than on SF plots and runoff and dry matter yield were not different from the values obtained on bare plots. A significant correlation was found between runoff, all vegetation data and termite-voids. Sediment accumulation due to the physical barrier of the mulch was not found to be a significant factor in the improvement of vegetation performance and the reduction of runoff.

Notizen: Abstract. Ammonia volatilization with and without gypsum incorporation was measured in Gujranwala soil (Udic Haplustalf) in an incubation study using different nitrogen fertilizers e.g. urea, ammonium sulphate (AS), calcium ammonium nitrate (CAN), and urea nitrophos (UNP). Nitrogen from different fertilizers was applied at the rate of 200 mg N kg−1 to two sets of soils in plastic bags (1.0 kg soil) and plastic jars (0.5 kg soil). Soil moisture was maintained at field capacity. Application of urea increased soil pH to 9, three hours after its addition. Ammonium sulphate and calcium ammonium nitrate had little effect on soil pH. Ammonium volatilization losses from fertilizers were related to the increase in soil pH caused by the fertilizers. Consequently maximum losses were recorded due to application of urea. Losses through ammonia volatilization were significantly lower with AS, CAN and UNP in descending order. Gypsum incorporation significantly reduced the losses. Therefore, application of gypsum to soil before urea may substantially improve N use efficiency for crop production by reducing N losses.

Notizen: Abstract. Precision farming is the process of adjusting husbandry practices within a field according to measured spatial variability. In this review, we explore the prospects for precision farming using the principles that underly conventional soil management and agronomy.The cost-effectiveness of precision farming is determined by the cost of defining zones within fields, the stability of zones through time, the difference in treatment between zones in terms of cost, and the responsiveness of the crop in terms of yield and quality to changes in treatment. Cost-effective precision farming is most likely where prior knowledge indicates large heterogeneity and where treatment zones can be predicted, for example from soil type or field history.Soil related factors are likely to provide the main basis for precision farming because they tend to be stable through time and influence crop performance. In particular, soil mapping may usefully indicate the moisture available for crop growth, organic matter maps may be utilized for precision application of fertilizers and soil acting herbicides, and variation in soil pH can be mapped and used as a basis for variable lime application. However, comprehensive nutrient mapping is less likely to be economic with existing techniques of chemical analysis. The value of yield mapping lies in identifying zones which are sufficiently stable to be of use in determining future practices. Maps of grain quality and nutrient content would significantly augment the value of yield maps in guiding marketing decisions and future agronomy. Interactions between soil differences and seasonal weather are large, so yield maps show considerable differences from season to season. Interpretation of such maps needs to follow a careful, informed, analytical process.Extensive and thorough field experimentation by crop scientists over many years has shown that yield variation arises as a result of a large and complex range of factors. It is highly improbable that simple explanations will be appropriate for much in-field yield variation. However, the capacity to sense yield variability within fields as opposed to between fields, where there are many confounding differences, provides an opportunity for the industry to improve its understanding of soil-based effects on crop performance. This should support its decision taking, whether through precision farming or through field-by-field agronomy.The main obstacle to the adoption of precision farming is the lack of appropriate sensors. Optimal sensor configurations that will measure the specific needs identified by end-users need to be developed.The conclusions reached in this paper probably apply to farming throughout northern Europe.

Notizen: Abstract. A lysimeter experiment showed a decrease in maximum concentrations and total losses of the herbicide isoproturon leached from a heavy clay soil where the topsoil had a finer, deeper tilth than with a standard agricultural tilth. Volumes of leachate for the first flow event of the season were also smaller and leaching of bromide was slower. The isoproturon was radiolabelled so that its movement could be assessed using a novel radio-scanning technique. Bypass flow began close to the surface as a scan at 8 cm depth showed that only 0.5% of the total soil area had an activity more than four times the nominal background level. At depths of 10–20 cm, isoproturon was preferentially retained within areas of very fine aggregates. No radioactivity was detected in the scans below 20 cm depth, suggesting little or no retention of isoproturon during transport through the subsoil to the bottom of the lysimeter. Rhodamine-B dye injected to the base of the topsoil (approximately 20 cm depth) was also used to assess flow pathways through the subsoil. The dye spread laterally across the interface between topsoil and subsoil and then penetrated the subsoil through cracks and fissures. Even within cracks, transport of dye frequently occurred through only a very small proportion of the total crack area. The macropore flow model MACRO 4.0 was used to simulate results from the lysimeter experiment. The fourfold decrease in maximum concentrations of herbicide from the finer tilth lysimeter could be predicted by varying only a parameter describing aggregate sizes at depths of 6–24 cm, suggesting that transfer of herbicide between macropore and micropore regions was faster in the finer tilth. Differences in concentrations of bromide could be simulated only by adjusting the soil hydraulic parameters for the fine tilth to reflect a slight decrease in the predominance of bypass flow relative to matrix flow.

Notizen: Abstract. Degradation of isoproturon in a heavy clay soil followed first-order reaction kinetics with half-lives at 15 °C of 27 and 208 days in the topsoil and subsoil, respectively. Adsorption when shaken with 3 mm sieved samples of the soil fitted the empirical Freundlich relationship with k values of 3.25 in the topsoil and 1.06 in the subsoil. Adsorption in a static system with different sized aggregates of soil did not reach equilibrium, even after 24 hours contact, and the rate of adsorption was slower with larger aggregates. Following an adsorption period of 24 hours, desorption equilibrium was reached more rapidly with larger (6–10 mm) than with smaller (〈3 mm) aggregates. Adsorption isotherms measured in a static system with a soil:water ratio typical of field conditions in winter also indicated less adsorption than that measured in shaken, laboratory systems with low soil:water ratios. The rate of change in water extractable residues of the herbicide was more rapid than that of total extract-able residues following application of isoproturon to the heavy clay soil in the field. The implications of the results for isoproturon leaching under field conditions are discussed.

Notizen: Book reviewed in this article: Land Resources: Now and for the future By A. Young.

Notizen: Abstract. In order to optimize the management of the N-fertilizer inputs with drip fertigation on sandy-silt soil under apple tree orchard cultivation, we observed in situ: (i) the N and water soil transfers, (ii) the N levels in all leaves, fruits and annual shoots, and (iii) the root distribution. Then we used a mechanistic one-dimensional model (WAVE, Vanclooster et al., 1994) to quantify the annual parameters of the water and nitrogen balance on a daily basis. The horizontal heterogeneity along the row of the tree-soil-dripper system has been treated with two adjacent compartments: one under the dripper and receiving fertigation and the other outside this zone. N transfers in the tree make it impossible to estimate directly N uptake by roots over time.The simulated N losses were due to equal amounts of N leaching below 0.9 m deep (9 g N tree−1year−1 and denitrification (7 g N tree−1year−1. The simulated losses of gaseous N were localized predominantly in the compartment under the dripper and showed a higher rate of leaching during the period of N input when the wet conditions and the high NO3− concentrations were favourable to denitrification. The N-leaching at 0.9 m depth was greatest outside the growing season and was caused by the extension of the N-inputs after the harvest date. This practice, based on the objective to store nitrogen before the period of dormancy does not seem to be justified.

Notizen: Abstract. People in the Southern Highlands of Papua New Guinea cultivate some land semi-continuously within a regime of shifting cultivation; the staple crop is sweet potato (Ipomoea batatas). The fertility of Tropepts, variably affected by falls of volcanic ash, was investigated to give further understanding of how subsistence farmers avoid the soil constraints that commonly prompt abandonment. While organic matter, N and K all decrease significantly with time under cultivation, they do not reach critical levels. Phosphorus also decreases significantly over time, although contents are small throughout. Other nutrients show no significant variation with period of use or abandonment. These findings comply with the diversity of crops cultivated early in the life of ‘gardens’, followed by sweet potato, cultivated as a virtual monocrop in long established ‘gardens’. It continues yielding adequately regardless of decrease in nutrient availabilities, notably because nutrient ratios remain favourable for tuberisation and because of sweet potato's tolerance of small phosphorus concentrations. It appears that burning of vegetation significantly increases available minerals and helps maintain a supply which is adequate for longterm sweet potato monoculture. Similar situations are postulated for other areas of less-weathered soils within the tropics.

Notizen: 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.

Notizen: 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.

Notizen: 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.

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

Notizen: Abstract. Complex relationships exist between different components of the organic farm and the quantity and quality of the end products depend on the functioning of the whole system. As such, it is very difficult to isolate soil fertility from production and environmental aspects of the system. Crop rotation is the central tool that integrates the maintenance and development of soil fertility with different aspects of crop and livestock production in organic systems. Nutrient supply to crops depends on the use of legumes to add nitrogen to the system and limited inputs of supplementary nutrients, added in acceptable forms. Manures and crop residues are carefully managed to recycle nutrients around the farm. Management of soil organic matter, primarily through the use of short-term leys, helps ensure good soil structure and biological activity, important for nutrient supply, health and productivity of both crops and livestock. Carefully planned diverse rotations help reduce the incidence of pests and diseases and allow for cultural methods of weed control. As a result of the complex interactions between different system components, fertility management in organic farming relies on a long-term integrated approach rather than the more short-term very targeted solutions common in conventional agriculture.

Notizen: Abstract. On organic farms, where the importation of materials to build/maintain soil fertility is restricted, it is important that a balance between inputs and outputs of nutrients is achieved to ensure both short-term productivity and long-term sustainability. This paper considers different approaches to nutrient budgeting on organic farms and evaluates the sources of bias in the measurements and/or estimates of the nutrient inputs and outputs. The paper collates 88 nutrient budgets compiled at the farm scale in nine temperate countries. All the nitrogen (N) budgets showed an N surplus (average 83.2 kg N ha–1 yr–1). The efficiency of N use, defined as outputs/inputs, was highest (0.9) and lowest (0.2) in arable and beef systems respectively. The phosphorus (P) and potassium (K) budgets showed both surpluses and deficits (average 3.6 kg P ha–1 yr–1, 14.2 kg K ha–1 yr–1) with horticultural systems showing large surpluses resulting from purchased manure. The estimation of N fixation and quantities of nutrients in purchased manures may introduce significant errors in nutrient budgets. Overall, the data illustrate the diversity of management systems in place on organic farms, and suggest that used together with soil analysis, nutrient budgets are a useful tool for improving the long-term sustainability of organic systems.

Notizen: Abstract. Earthworms influence a wide range of soil properties. They are affected by practices that perturb the soil or change organic inputs. This study compared populations in UK organic and conventional rotations differing in such practices. Three farm pairs, ranging from stockless to arable-grassland systems, were sampled on three occasions in each of two crop years. Additional farm pairs were sampled on a single occasion. Nine common earthworm species were grouped into three classes based on the depth ranges from which they were recovered. Cast and soil samples were taken from leys to compare aggregate stability, organic and nutrient content, and microbial biomass.  For similar rotation stages, populations of surface and shallow species classes were often larger in organic systems. In some comparisons the reverse was the case, particularly as the proportion of ley within each pair increased. System differences in biomass, but not abundance, could be attributed to the proportion of leys in rotations; individual earthworm weights were larger in conventional systems. Casts from both systems had markedly higher organic contents, stability, available P and K concentrations, and microbial biomass than underlying soil. This trend was more pronounced in conventional sites for nutrients and microbial biomass. Differences in populations and cast properties may have implications for soil fertility and wider ecosystem function.

Notizen: Abstract. Generally, traditional soil surveys do not adequately account for the spatial variability of soil properties. Maps that are derived using these cursory soil data are likely to contain errors and thus make interpretation and soil management difficult. On the other hand quantitative methods of soil inventory at the field scale involve the design and adoption of sampling regimes and laboratory analysis that are time consuming and costly. In the latter case new technologies are required to efficiently sample and observe the soil in the field. This is particularly the case where soil salinization is prevalent, and detailed quantitative information for determining its cause is required. In this paper, a Mobile Electromagnetic Sensing System (MESS) is described and its application in an irrigated-cotton field, located in the lower Namoi valley in New South Wales, Australia. Results from the EM38 instrument were found to be correlated with the effective cation exchange capacity (r2= 0.81). This was related to variability in soil mineralogy across the field. In addition, differences in soil chemical and textural variables, measured along a transect and adjacent to water storage, were used to identify seepage areas near a water reservoir where soil salinization was evident.

Notizen: Abstract. Precision Agriculture seeks to match resource application and agronomic practice with soil and crop requirements as they vary in both space and time. Therefore, an understanding of both the temporal and the spatial components of variability is essential before decisions can be made about the feasibility of site-specific management. In the present study, the spatial and the temporal components of variability in certain key soil properties of a grassland field were evaluated to assess the likely feasibility of adopting a site-specific approach to grassland management. A 7.9 ha grassland field was selected for the study and soil samples were taken three times at regular 25 m intervals across the field over a two year period, and chemically analysed. Classical and geostatistical procedures were used to evaluate the spatial variability and the temporal stability of soil property distributions. Soil extractable P and K had the greatest within-field variability and soil pH the least. Soil K distributions were also highly unstable over time and it was concluded that the optimal risk aversion strategy would be to apply uniform dressings of this nutrient to the entire field. In contrast, soil pH, P, Mg and sulphate distributions were not only temporally stable, but were also spatially correlated over reasonably large ranges. It was concluded that these properties might be managed in a site-specific way based on the results of periodic soil testing in three clearly defined management sub-units within the field. Over the two year period, C and N accumulated in the soil at surprisingly high rates on certain parts of the field but not in others.

Notizen: Abstract. The worldwide occurrence of saline sodic and sodic soils on more than half a billion hectares warrants attention for their efficient, inexpensive and environmentally acceptable management. These soils can be ameliorated by providing a source of calcium (Ca2+) to replace excess sodium (Na+) from the cation exchange sites. Although chemical amendments have long been used to ameliorate such soils, the chemical process has become costly during the last two decades in several developing countries. As a low-cost and environmentally acceptable strategy, the cultivation of certain salt tolerant forage species on calcareous sodic and saline sodic soils, i.e. phytoremediation, has gained interest among scientists and farmers in recent years. In a field study conducted at three calcareous saline sodic sites (pHs=8.1–8.8, ECe=7.8–12.5 dS m–1, SAR=30.6–76.1) in the Indus Plains of Pakistan, we compared chemical and phytoremediation methods. There were four treatments; two involved plants: Kallar grass (Leptochloa fusca (L.) Kunth), and sesbania (Sesbania bispinosa (Jacq.) W. Wight). The other two treatments were uncropped: soil application of gypsum and an untreated control. All treatments were irrigated with canal water (EC=0.22–0.28 dS m–1). The plant species were grown for one season (5–6 months). Sesbania produced more forage yield (34 t ha–1) than Kallar grass (23 t ha–1). Phytoremediation and chemical treatments resulted in similar decreases in soil salinity and sodicity, indicating that phytoremediation may replace or supplement the more costly chemical approach. The soil amelioration potential of sesbania was similar to that of the Kallar grass, which suggests that moderately saline sodic calcareous soils can be improved by growing a forage legume with market value.

Notizen: Abstract. Nitrate leaching was measured for four years at the Royal Agricultural College ‘s Coates Farm in the Cotswolds, England. Coates is a typical Cotswold mixed farm with thin, well-drained calcareous soils especially prone to leaching. Over the duration of this study there were dairy, sheep and arable enterprises on the farm. A ‘Farm Gate’ nitrogen (N) budget was constructed. Small 120 m × 20 m ‘farmlets’ were sited in ten fields across the farm, covering all parts of the rotation, as the sites for detailed measurements. Each farmlet received the same management as the rest of the field in which they were situated. Using ceramic probes inserted to 60 cm, soil water was sampled every two weeks throughout the winter drainage season. The annual drainage varied from 135 mm under grassland in 1996/7 to 600 mm under cereals in 1998/9. Average N losses by leaching were determined mostly by rainfall and were 65 kg N ha–1 yr–1, accounting for 25% of the N inputs. Especially leaky parts of the rotation were the ploughing out of a lucerne ley and the grazing of stubble turnips with sheep, both typical Cotswold farm practices. The research highlights some of the difficulties in developing practicable, profitable management practices to decrease nitrate losses.

Notizen: Abstract. Differences in land-use history within soil series, although not influencing soil classification, lead to variability of non-diagnostic soil properties in soil databases. Regional studies that use soil databases are confronted with this considerable variability. This has, for example, been reported in regional studies focused on nitrate leaching from agricultural land. Such findings have a direct impact on regional assessments of nitrate leaching from dairy farms on sandy soils, a major environmental issue in the Netherlands. There is thus a need to deal with this variability in soil properties.We were able to relate soil organic nitrogen, soil organic carbon and its dynamics to land use history for a Dutch sandy soil series. Within one soil series, three different land use histories were identified: old grassland, reseeded grassland and grassland converted from continuous cropping with silage maize. The addition of landscape characteristics significantly improved the regression models based on land-use only. Once established for any given soil series, such relationships can significantly improve soil survey input into dynamic models of soil behaviour such as regional nitrate leaching studies.

Notizen: Abstract. Many former estimates of regional scale C sequestration potential have made use of linear regressions based on long-term experimental data, whilst some have used dynamic soil organic matter (SOM) models linked to spatial databases. Few studies have compared the two methods. We present a case study in which the potential of different land management practices to sequester carbon in soil in arable land is estimated by different methods. Two dynamic SOM models were chosen for this study, RothC (a soil process model) and CENTURY (a whole ecosystem model with a SOM module). RothC and CENTURY are the two most widely used and validated SOM models worldwide. A Geographic Information System (GIS) containing soil, land use and climate layers, was assembled for a case study in central Hungary. GIS interfaces were developed for the RothC and CENTURY models, thus linking them to the spatial datasets at the regional level. This allowed a comparison of estimates of the C sequestration potential of different land management practices obtained using the two models and using regression based approaches. Although estimates obtained by the different approaches were of the same order of magnitude, differences were observed. Some of the land management scenarios studied here showed sufficient C mitigation potential to meet Hungarian CO2 reduction commitments. For example, afforestation of 12% current arable land could sequester 0.042–0.092 Tg yr–1 in the soil alone, or 0.285–0.588 Tg C yr–1 in both soil and biomass; 1990 level CO2 emissions for the study area were 4.7 Tg C with a corresponding reduction commitment of 0.282 Tg C. It is not, however, suggested that this is the only, or the most favourable way, in which to meet the commitments.

Notizen: Abstract. A revised set of physical and chemical parameter estimates is presented for the soil units of the world, as described by the two FAO soil legends (version 1974 and 1988). The study is based on 9607 soil profiles, which include profiles held in version 1.0 of the WISE database. Upon a screening of data integrity and comparability of analytical methods, derived statistics were generated for 28 soil chemical and physical attributes identified as being useful for assessment of land suitability, crop growth simulation datasets, and analyses of global environmental change.

Notizen: Abstract. Drainage of peat soils for agriculture can lead to large carbon losses due to oxidation of peat. We estimated peat subsidence rates and total carbon losses, due to 40 years of dairy farming on a former peat bog, by measuring the thickness of peat and total carbon of farmland and of an adjacent unmodified peat bog above a marker tephra layer that was deposited about 200 AD. Subsidence rates averaged 3.4 cm yr–1 (95% confidence interval of 3.2 to 3.5 cm yr–1) and carbon loss averaged 3.7 t ha–1 yr–1 (95% confidence interval of 2.5 to 5.0 t ha–1 yr–1). On average, 63% of the subsidence was due to consolidation, with the remainder (37%) attributed to losses of organic matter due to peat mineralization.

Notizen: Abstract. In organic agriculture, where K may be a limited resource, reliable tools are important in the assessment of K availability in the soil in order to avoid K deficiency. We investigated the effect of four organic farming systems on the exchangeable K in the plough layer of a six-course crop rotation from 1994 to 1997. The accumulated K balances over the four years varied between −49 and +120 kg K ha–1and the corresponding exchangeable K (0–20 cm) in autumn 1997 was 7.1 and 9.6 mg K 100 g soil–1, respectively, as an average of the crop rotation. The exchangeable K fraction responded to the K application in manure and to the crop in the rotation. In an additional experiment, no yield response to K was found, despite a low level of exchangeable K. The exchangeable K was a useful indicator of changes in the K status in the farming system with the largest positive K balance, but this K fraction was insufficient as an indicator in the other three farming systems. The considerable variation of exchangeable K through the crop rotation makes the soil test method most suitable at the crop rotation level where fluctuations caused by crop and management are smoothed out.

Notizen: Abstract. Phosphorus (P) in overland flow is mediated by soil P, added P, erosion, and hydrological processes and their interaction as affected by landscape position and length of flow. We investigated the effect of flow path length (1 to 10 m long plots) on P transport in overland flow with and without a localized dairy manure application (75 kg P ha–1 added to the upslope end [0.5 m] of each plot) and simulated rainfall (7 cm h–1), at two sites within an agricultural watershed in Pennsylvania, USA. Particulate loss in overland flow was c. 20% greater from manured than unmanured plots due to the less dense nature of manure than soil. Increased soil moisture at Site 2 contributed to a greater loss of P compared to Site 1, both with and without manure; with most occurring as particulate P (60 to 90% of total P). Further, the selective erosion of fine particulates (24 to 34% clay) and P loss increased with plot length. From a management perspective our results demonstrate that the forms and amounts of P loss are greatly influenced by flow path length and interactions among antecedent moisture, soil P, and texture.

Notizen: Abstract. Nitrous oxide (N2O) is involved in both ozone destruction and global warming. In agricultural soils it is produced by nitrification and denitrification mainly after fertilization. Nitrification inhibitors have been proposed as one of the management tools for the reduction of the potential hazards of fertilizer-derived N2O. Addition of nitrification inhibitors to fertilizers maintains soil N in ammonium form, thereby gaseous N losses by nitrification and denitrification are less likely to occur and there is increased N utilization by the sward. We present a study aimed to evaluate the effectiveness of the nitrification inhibitor dicyandiamide (DCD) and of the slurry additive Actilith F2 on N2O emissions following application of calcium ammonium nitrate or cattle slurry to a mixed clover/ryegrass sward in the Basque Country. The results indicate that large differences in N2O emission occur depending on fertilizer type and the presence or absence of a nitrification inhibitor. There is considerable scope for immediate reduction of emissions by applying DCD with calcium ammonium nitrate or cattle slurry. DCD, applied at 25 kg ha–1, reduced the amount of N lost as N2O by 60% and 42% when applied with cattle slurry and calcium ammonium nitrate, respectively. Actilith F2 did not reduce N2O emissions and it produced a long lasting mineralization of previously immobilized added N.

Notizen: Abstract. We evaluated the effectiveness of capillary-wick samplers (PCAPS) for continuous monitoring of resident nitrate concentration in three ‘soil-crop-climate’ systems differing in soil type, land use and climate. These systems involved: (i) acid silty soils under a beech-oak forest affected by heavy N-NH4+ deposition in Belgium; (ii) silty soils under wheat cropping and a short rotation willow coppice plantation (SRC) in Belgium; and (iii) volcanic ash soils under plantain cultivation with and without urea fertilization in Colombia. The PCAPS continuously applied a suction of 0 to 5.4 kPa to the soil water below the effective rooting zone without the need for an auxiliary vacuum source. The nitrate concentrations showed large variations over time and ranged between 6–192 mg l–1 under forest, 19–143 mg l–1 under wheat, 11–47 mg l–1 under SRC and 3–138 mg l–1 under fertilized plantain. The analysis of the soil leachates collected with PCAPS confirms previous results dealing with leaching of nitrate and alkaline and alkaline-earth cations in similar ‘soil-crop-climate’ systems. It was concluded that PCAPS was a suitable tool to collect soil solutions and that it could help to assess nitrate leaching losses in various ecological or cropping conditions.

Notizen: Abstract. The páramo is a high-altitude ecosystem of the northern Andes. The vegetation is continuous, with grasses as the dominant groundcover. Because of their high water retention, páramos play a fundamental role in water availability for all the population of the inter-Andean valleys. There are many studies of this specific ecosystem, but very few are focussed on overgrazing and its effect on vegetation and soil properties. Intensive grazing started less than 20 years ago and was studied in a representative area in the western Cordillera of central Ecuador covered by recent volcanic ash deposits. Intensive sheep grazing has led to a strong decline in the number of plant species, the replacement of the tussock grass vegetation by a short carpet grass vegetation, and an increase of bare land. In that area, the upper 50 cm of Andisols are deeply affected by a convergent decrease of Al and Fe oxalate and pyrophosphate in soil extracts, carbon contents decrease from 100 g kg–1 to less than 50 g kg–1 in the humid zone, from 70 to 40 g kg–1 in the dry zone and a reduction of water-retention capacity at −33 kPa matrix potential from 800 g kg–1 to 200 g kg–1 in humid zones, from 350 to less than 100 g kg–1 in drier areas. They showed also a decrease in the macrostructure and the development of a highly water repellent microstructure. All these important transformations favour the development of aeolian erosion in dry areas, runoff on bare surfaces, and gully erosion on slopes. The role of the páramo in water-regulation of this ecosystem seems to have been adversely affected for the future.

Notizen: Abstract. The mean extractable sulphur (S) concentration in 315 upland topsoil samples collected in 1988/89 from beneath pasture in NE Scotland was 13 μg S g−1 (range 2–77 μg S g−1). More than two thirds of the samples had S concentrations less than that acceptable for productive soils. Continued decreases in atmospheric S inputs may have increased this proportion subsequently. The analysis of herbage S also indicated that two-thirds of the samples were below 0.2% S. A ‘respirometric index’, namely CO2 produced during cellulose decomposition without added S as a percentage of that produced with added S, was significantly less than 100% in a quarter of the soils. Results of three different extraction procedures suggested that sulphate in the soils was present mainly as free plus adsorbed rather than precipitated forms. Soil extraction identified a significant non-sulphate S fraction, presumably organic S. The variability in extractable S stemmed from a combination of geographical, depositional and local site and soil factors. Extractable S was significantly correlated with soil organic matter content and inversely with soil pH and together these factors explained 37% of the variability. While significant differences in mean concentrations between geographical area, soil association and drainage status were evident, no trends could be observed between the major soil subgroups or with altitude.

Notizen: Abstract. We investigated whether a polyacrylate polymer could be used to remediate a soil which had been contaminated with copper for many years. Perennial ryegrass was grown in a loamy sand containing 230 mg ammonium-acetate-EDTA extractable Cu kg−1 and amended with 0, 0.1 and 0.2% of polymer. Growth of perennial ryegrass was stimulated in the polymer-amended soil, especially in the soil with 0.1% of polymer. After plant growth for 177 days, the amount of water extractable copper present in the unamended soil was 17 times that of the original soil. In the soil amended with 0.1% of polymer the level of copper after plant growth was only 0.11 times the amount present in the unamended soil. When the soil was incubated with polymer in the absence of plants, the level of water extractable copper was not reduced. The polymer seems to compete with plants for copper, and to prevent the increase of copper in soil solution brought about by root exudates.

Notizen: Abstract. Soils developed on volcanic parent materials have many intrinsic qualities favourable to cropping. However, fertility decreases dramatically when they are badly managed. A short review and case studies from Réunion and Guadeloupe highlight the special characteristics of these soils, and their response to management.The interplay of cropping systems and physical characteristics of Andisols is first considered through the example of Pelargonium and food crop systems in Réunion. Progressive decrease in production and cropping potential shows in falling yields as well as in the overall decline of the system. The example of banana production in Guadeloupe highlights the increase in inputs needed to realise the land's potential and to maintain yields, in particular more tillage and pest treatment.In both cases, these trends are connected to the co-evolution of soil characteristics and cropping systems. They lead to an increase of risks with less security and less scope in the choice of cropping systems. Technical solutions in the form of erosion-control measures, rotation and planting techniques have been developed and prove to be relevant and consistent in their benefit.

Notizen: Abstract. Soil classification is a tool for stratifying and generalizing information on soil resources but most systems are tailored to handle only slightly disturbed soil. We tested the applicability of the legend of the FAO-Unesco Soil Map of the World and the new World Reference Base for Soil Resources by classifying at the highest order 831 profiles from a nationwide 7 km grid survey in Denmark, where soils are developed in Quaternary glacial and marine sediments and intensively farmed. Comparison of the variability of pH and % clay +% silt of the master horizons (A, E, B, and C) within and between the major well-drained soil groupings shows that liming, fertilizing and ploughing have produced significantly deeper A-horizons with higher pH, lower % humus and C:N ratios on the two-thirds of the country that is cultivated. ‘Anthropogenic’ mollic and umbric horizons are a common result but the liming causes a random final classification of these surface horizons and, hence, random allocation of the soils in both systems. It separates cultivated soils and their undisturbed equivalents, and results in considerable within-group variation in soil texture. Grouping of cultivated and undisturbed soils, on the other hand, results in wide within-horizon pH ranges for most groups, again compromising the advantage of making useful general statements on the basis of classification.We propose that anthropogenic mollic and umbric horizons should be allowed in any soil group and that ‘anthric properties’ should be used to distinguish between profoundly changed cultivated soils and largely undisturbed soils, hereby constructing a two-tier system within each highest-order soil group. We classified the soils according to this proposal. The results show generally narrower ranges for both pH and % clay +% silt. We evaluated the within-group homogeneity by multivariate analysis of variance of pH, % clay +% silt, % clay, % humus, C:N ratio, exchangeable cations, and CEC. The results (Wilks's Lamda) show a higher degree of group compactness compared to the original FAO and World Reference Base systems.

Notizen: Abstract. In dairy farming systems the risk of nitrate leaching is increased by mixed rotations (pasture/arable) and the use of organic manure. We investigated the effect of four organic farming systems with different livestock densities and different types of organic manure on crop yields, nitrate leaching and N balance in an organic dairy/crop rotation (barley–grass-clover–grass-clover–barley/pea–winter wheat–fodder beet) from 1994 to 1998. Nitrate concentrations in soil water extracted by ceramic suction cups ranged from below 1 mg NO3-N l−1 in 1st year grass-clover to 20–50 mg NO3-N l−1 in the winter following barley/pea and winter wheat. Peaks of high nitrate concentrations were observed in 2nd year grass-clover, probably due to urination by grazing cattle. Nitrate leaching was affected by climatic conditions (drainage volume), livestock density and time since ploughing in of grass-clover. No difference in nitrate leaching was observed between the use of slurry alone and farmyard manure from deep litter housing in combination with slurry. Increasing the total-N input to the rotation by 40 kg N ha−1 year−1 (from 0.9 to 1.4 livestock units ha−1) only increased leaching by 6 kg NO3-N ha−1. Nitrate leaching was highest in the second winter (after winter wheat) following ploughing in of the grass-clover (61 kg NO3-N ha−1). Leaching losses were lowest in 1st year grass-clover (20 kg NO3-N ha−1). Averaged over the four years, nitrate concentration in drainage water was 57 mg l−1. Minimizing leaching losses requires improved utilization of organic N accumulated in grazed grass-clover pastures. The N balance for the crop rotation as a whole indicated that accumulation of N in soil organic matter in the fields of these systems was small.

Notizen: Abstract. Eight lysimeters, each with a surface area of 0.5 m2 and a length of 60 cm, were taken over mole drains from a Denchworth soil and divided into two groups with either a standard agricultural tilth or a finer, deeper topsoil tilth. They were variously instrumented to measure soil moisture content at three depths and losses of nitrate, a bromide tracer and radiolabelled isoproturon, all of which were followed over a year. Leaching of isoproturon was initiated by artificial irrigation either 1 or 39 days after application. The finer tilth seemed to increase the water-holding capacity of the topsoil, and this resulted in slower wetting of the subsoil, decreased flow volumes from the first events of the season and a delay of approximately four weeks in the time to the maximum concentration of the bromide tracer in leachate. The finer topsoil tilth also decreased maximum concentrations of isoproturon from 29 to 15 μg l−1 following irrigation 1 day after treatment and from 43 to 9 μg l−1 following irrigation 39 days after treatment. Total losses of isoproturon were three times larger with the standard agricultural tilth. Differences were attributed to a decrease in bypass flow through the topsoil with the finer tilth, particularly during events early in the season. There was a small decrease in total losses of nitrate in leachate from the finer tilth compared to that from the standard tilth.

Notizen: Abstract. The effects of afforestation on potential nitrification, nitrification and ammonification rates were studied at an experimental site in NE Scotland 4½ years after afforestation of former arable land. The site had been planted with three tree species (Sitka spruce, sycamore and hybrid larch) at three different planting densities, with half the plots treated with inorganic NPK fertilizer. Laboratory measurements of potential nitrification, nitrification and ammonification rates, measured using a perfusion system, were compared between the unforested control and combinations of the various treatments. Differences in soil pH and soil moisture content were also investigated.Potential nitrification rates measured in plantation soils were significantly lower than in the unplanted control soil. Nitrification and ammonification rates were also consistently lower, although these differences were only significant in a few of the treatments. Soils planted with a normal tree density had a tendency to show higher nitrification rates compared to soils planted with a high tree density.The results suggest that afforestation of former agricultural soils may cause changes in important parts of the soil N cycle soon after planting. At this early stage in the life of the plantation this appears to be unrelated to changes in soil pH or moisture content, even though soils beneath the trees are drier. The apparent change may be the result of differences in the soil microbial community associated with the type of organic matter substrate present in the unplanted and planted soils.

Notizen: Abstract. Increasing concerns for the financial and environmental impact of the use of broadcast fertilizer by the UK horticultural industry is leading to the development of alternative application techniques, which aim to reduce inputs through improved efficiency. One such technique, ‘starter’ fertilizer, was investigated with drilled and transplanted crisp lettuce (Lactuca sativa) on two fertile peaty soils. Starter fertilizers injected below the seed of the drilled crop, or as spot applications around the planting module, were tested alone and in various combinations with different rates of broadcast fertilizer. The work extended previous findings, based largely on mineral soils, and demonstrated that high yields of iceberg quality lettuce can be achieved with reduced inputs of broadcast fertilizer, and that there can be additional benefits of earlier maturity and improved quality. It is concluded that starter fertilizer can contribute to the development of environmentally beneficial farming practices whilst maintaining the productivity and competitiveness of the horticultural industry.

Notizen: Abstract. Ancient forests which have never been under agriculture often have larger ecological and pedological value than later established forests. We made a reconstruction of the land use history of the Meerdaal forest complex in central Belgium since 1759. Soil profiles of 33 recent forest sites and of contiguous forest parcels were examined morphologically by augering to 120 cm depth. pHKC1 was determined on samples from every horizon. The data were analysed by Principal Component Analysis, and the axes were used as a basis for derivation of horizon parameters. Former agricultural land use since 1759 can still be recognized in three soil morphological characteristics: colour of the eluviation horizon, intactness of the horizon containing illuviated clay and thickness of the organic layer. These parameters were combined into a ‘naturalness index’, which differs significantly between ancient and recent forest and can be easily and cost-effectively obtained to assess the degree of man-made disturbance of forests on loess-derived soils.

Notizen: Abstract. A long-term lysimeter experiment with undisturbed monoliths studied leaching behaviour and balances of phosphorus (P), potassium (K) and nitrogen (N) during a seven year crop rotation on four types of soil receiving inorganic fertilizers, manure and grass compost respectively. It was shown that application of manure did not lead to any direct change in nutrient leaching, unlike the application of fertilizers to soils of normal fertility. However, soil type considerably affected the nutrient concentrations in the drainage water.Manure applied in amounts equal to the maximum animal density allowed by Swedish legislation slightly oversupplied P and N (0.5–3.5 and 18–38 kg ha−1 y−1 respectively) compared to the crop requirement and leaching losses for most of the soils. The relationship between lactate-soluble P in the topsoil and the concentrations of dissolved P in the drainage water was very strong. However the strength of this relationship was dependent on just one or two soils. P losses from a fertile sandy soil were large (1–11 kg ha−1 y−1) throughout the crop rotation and average crop removal (13 kg ha−1 y−1) plus the leaching losses were not balanced (average deficit 3–6 kg ha−1 y−1) by the addition of fertilizer, manure or grass compost. No decreasing trend was found in the P losses during seven years. However, the K deficit (average 26 kg ha−1 y−1) led to a significant reduction in the leaching trend from this soil. The other soils that had a smaller K deficit showed no significant reduction in the leaching of K.

Notizen: Abstract. Guizhou province has one of the most severe soil erosion problems in China, with 44% of its total area affected. Within the province, Bijie prefecture is the most severely eroded with 63% of the total area affected. In recent decades this erosion is mainly caused by man's agricultural and industrial development. Not only is erosion restricting crop production, it is the cause of disastrous floods which recur with a frequency far greater than in the past. Reduced infiltration of rain has led to a third of the wells and a fifth of the streams running dry, depriving people and livestock of drinking water.This unsustainable use of land can only be corrected by a combination of population control, prevention of slash and burn cultivation and return of steeply sloping land to forest and grassland. Greater appreciation of the need for soil and water conservation is an essential part of this process.

Notizen: 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.

Notizen: 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.

Notizen: 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.

Notizen: 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.

Notizen: 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.

Notizen: 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.