ALBERT

Notes: Book reviewed in this article: The Identification of Soils for Forest Management. By Fiona Kennedy.

Notes: Abstract. A no-tillage (NT) system was developed in semiarid Morocco to improve the soil fertility and stabilize yield through conservation of water. Results in two long-term trials (4 and 11 years) were able to show the effects of a no-tillage system in increasing total soil organic matter and total nitrogen. Over time, the quality of the NT soil surface was improved compared with that under conventional tillage (CT) with disc harrows. This effect was the result of an increase in soil organic carbon (SOC) and a slight decline in pH. However, over time, nitrogen decreased in both tillage practices, especially in the 0–25 mm layer (from 0.59 to 0.57 t ha−1 and from 0.44 to 0.42 t ha−1 under NT and CT, respectively). After 4 years of NT an extra 5.62 t ha−1 of SOC was sequestered in the 0–25 mm layer, and after 11 years the SOC increased further to 7.21 t ha−1.

Notes: Book reviewed in this article: Agriculture, Hydrology and Water Quality. By P.M. Haygarth and S.C. Jarvis (Editors).

Notes: Abstract. For an efficient abatement of diffuse N pollution from arable land, it is important to have practical and reliable tools that can quantify the effect of different management practices on leaching, and also analyse the effect of alternative management scenarios aimed at reducing leaching. We present here an application of soilndb, a management-oriented model for quantifying nitrate leaching from arable land. Simulations with soilndb were compared with measurements of pipe-drain discharge of nitrate taken in a 14-year field experiment on a sandy loam soil in south-west Sweden. Following adjustment of parameters connected to litter and faeces decomposition and mineralization, the model gave satisfactory predictions of nitrate leaching for all 10 treatments. The temporal pattern was generally well captured by the model, as was confirmed by high model efficiency values (average = 0.59). This application also supports the model's ability to simulate the long-term influence of different crops and catch crops as well as different manure strategies on leaching. However, further studies should be done to evaluate the model under additional agro-environmental conditions (e.g. soils, climates, and crops).

Notes: Abstract. The Phosphorus Indicators Tool provides a catchment-scale estimation of diffuse phosphorus (P) loss from agricultural land to surface waters using the most appropriate indicators of P loss. The Tool provides a framework that may be applied across the UK to estimate P loss, which is sensitive not only to land use and management but also to environmental factors such as climate, soil type and topography. The model complexity incorporated in the P Indicators Tool has been adapted to the level of detail in the available data and the need to reflect the impact of changes in agriculture. Currently, the Tool runs on an annual timestep and at a 1 km2 grid scale.We demonstrate that the P Indicators Tool works in principle and that its modular structure provides a means of accounting for P loss from one layer to the next, and ultimately to receiving waters. Trial runs of the Tool suggest that modelled P delivery to water approximates measured water quality records. The transparency of the structure of the P Indicators Tool means that identification of poorly performing coefficients is possible, and further refinements of the Tool can be made to ensure it is better calibrated and subsequently validated against empirical data, as it becomes available.

Notes: Abstract. We present a semi-quantitative visual and tactile method for assessing soil physical fertility in terms of soil structure, root growth and soil surface condition. A block of topsoil is dug out with a spade. Horizontal layers (usually 2–4) are then identified as they appear. A brief one-page description of the soil is produced. Using a key, structural and rooting scores are assigned to each soil layer from the appearance of the soil and from its response to tactile assessment. These scores are then combined across depths, with weighting appropriate for the depth of each layer. A separate score was made of soil surface condition. Thus, overall soil physical fertility is assessed as three scores for topsoil structure, rooting and surface condition. The usefulness and sensitivity of the procedure were tested in two ley-arable organic rotation experiments on sandy loams in northeast Scotland.

Notes: Abstract. Eleven precipitated phosphates were evaluated as sources of phosphorus (P) for plant growth by comparing their effectiveness with that of monocalcium phosphate, a source of water soluble P that is generally considered to be fully plant available. The precipitated phosphates comprised struvites recovered from waste water discharges (mainly magnesium ammonium phosphate), laboratory synthesised struvites, a synthetic iron phosphate and a recovered calcium phosphate. Precipitating phosphates in these forms could be a way for removing P from waste water before it is discharged to rivers, so reducing the risk of eutrophication. Application to agricultural land would be one potential use for such phosphates. Evaluation was by pot experiments with a sandy loam soil and with a sandy clay loam soil using perennial ryegrass (Lolium perenne) as the test crop. The soils differed in pH (6.6 and 7.1) and in Olsen P (28 and 11 mg L−1). Measured variables were grass dry matter (DM) yield and grass P concentration which were used to calculate offtake of P in the harvested grass. DM yields of ryegrass and P offtakes given by the synthetic and recovered struvites were not significantly different statistically either between themselves or to MCP applied at the same rate. On this basis these struvites could be used to recycle P to similar soils and the effect of the P on crop yield should be similar to that of MCP

Notes: Abstract. The main inputs, outputs and transfers of potassium (K) in soils and swards under typical south west England conditions were determined during 1999/00 and 2000/01 to establish soil and field gate K budgets under different fertilizer nitrogen (N) (0 and 280 kg ha−1 yr−1) and drainage (undrained and drained) treatments. Plots receiving fertilizer N also received farmyard manure (FYM). Potassium soil budgets ranged, on average for the two years, from −5 (+N, drained) to +9 (no N and undrained) kg K ha−1 yr−1 and field gate budgets from +23 (+N, drained) to +89 (+N, undrained). The main inputs and outputs to the soil K budgets were fertilizer application (65%) and plant uptake (93%). Animals had a minor effect on K export but a major impact on K recycling. Nitrogen fertilizer application and drainage increased K uptake by the grass and, with it, the efficiency of K used. It also depleted easily available soil K, which could be associated with smaller K losses by leaching.

Notes: Abstract. Crops on sandy soils (〈5% clay) are exposed to K deficiency due to the small release and high leaching losses of K. Reliable tools are needed to improve the K management in cropping systems with limited K input, such as organic farming where import of nutrients are restricted according to the EC regulations. We investigated K balances and exchangeable K (Kexch) changes in an organic crop rotation experiment. Potassium leaching decreased from 42 kg ha−1 in 1998/99 to 21 kg ha−1 in 2000/01 as an average of a crop rotation (spring barley, grass-clover, winter wheat and pea/barley) with manure application and without catch crops. In the same period, spring Kexch decreased from 5.0 to 3.0 mg K 100 g soil−1 (0–20 cm). The retention of the straw K left in the field after harvest increased with decreasing levels of Kexch. The cereal crops did not respond to K application but in the pea/barley mixture the pea yield increased by 46%. The concordance between measured K balances and changes in Kexch was weak. Exchangeable K is suitable as a tool for K management on a rotational basis, and a Kexch above 3 mg 100 g soil−1 in the autumn should be avoided to minimize K leaching.

Notes: Abstract. Diagnosis of soil salinity and its spatial variability is required to establish control measures in irrigated agriculture. This article shows the usefulness of electromagnetic (EM) and soil sampling techniques to map salinity. We analysed the salinity of a 1-ha plot of surface-irrigated olive plantation in Aragon, NE Spain, by measuring the electrical conductivity of the saturation extract (ECe) of soil samples taken at 22 points, and by reading the Geonics EM38 sensor at 141 points in the horizontal (EMH) and vertical (EMV) dipole positions. EMH and EMV values had asymmetrical bimodal distributions, with most readings in the non-saline range and a sharp transition to relatively high readings. Most salinity profiles were uniform (i.e. EMH=EMV), except in areas with high salinity and concurrent shallow water tables, where the profiles were inverted as shown by EMH 〉 EMV, and by ECe being greater in shallow than in deeper layers. The regressions of ECe on EM readings predicted ECe with R2 〉 84% for the 0–100 to 0–150 cm soil depths. We then produced salinity contour maps from the 141 ECe values estimated from the electromagnetic readings and the 22 measured values of ECe. Owing to the high soil sampling density, the maps were similar (i.e. mean surface-weighted ECe values between 3.9 dS m−1 and 4.2 dS m−1), although the electromagnetically estimated ECe improved the mapping of details. Whereas soil sampling is preferred for analysing the vertical distribution of soil salinity, the electromagnetic sensor is ideal for mapping the lateral variability of soil salinity.

Notes: Abstract. The effects of soil management on soil losses from olive plantations in southern Spain were evaluated using the Revised Universal Soil Loss Equation (RUSLE), a review of published experiments, and preliminary results of an on-going field trial. Experimental data were used to parameterize the RUSLE for olive orchards under various soil management regimes. The predictions agreed qualitatively with the data available, and the model provided a simple way to assess the effects of soil management on erosion. Our results showed that no-tillage caused the greatest soil loss, while cover crops showed the least. Tillage and planting following contours proved only partially effective and did not reduce soil erosion as much as protective crops. One scenario studied suggests that, on slight to moderate slopes, land transformed from row crops to olive orchards may remain below the maximum tolerable soil erosion limit, if a cover crop is included between the trees. A scenario for marginal olive orchards located on steep slopes suggests that effective erosion control could only be achieved with a cover crop system that would have the side-effect of reducing the yield of rain-fed olives. Quantifying the effects of soil management on soil erosion in olive orchards is uncertain because very few experimental results are available. Further research that monitors soil loss in carefully selected long-term experiments at different scales and follows the changes in key soil parameters is urgently required to develop effective erosion control policies.

Notes: Abstract. Rainfall simulation experiments on a laboratory soil flume were conducted to test the hypothesis that the incorporation of slurry into the soil would reduce bacterial transport in overland flow. Presumptive faecal coliform (PFCs) concentrations were higher in the runoff from the surface applied treatment than from the incorporated treatments. The transport of PFCs and organic sediment were strongly correlated, with values of r ranging from 0.72 to 0.91.

Notes: Abstract. Land evaluation is the prediction of land performance over time under specific uses, to guide strategic land use decisions. Modern land evaluation has a 30 year history, yet the results have often been disappointing. Land users and planners have been reported to ignore land evaluations, perhaps reflecting poor quality, low relevance, or poor communication. To test the success of a large land evaluation exercise undertaken as part of micro-catchment project in Santa Catarina State, southern Brazil, we queried agricultural extensionists, considered as the primary land evaluation clients. We used a questionnaire with both structured and open questions, to determine their experiences with, and attitudes to, the current land evaluation method. The soil resource inventory and associated land evaluation had some usefulness, but were not in general used for their intended purpose, namely farm planning. This was mainly because they did not contain crucial information necessary to such planning in the actual context of the farmer taking decisions. The primary deficiencies were identified as:〈list xml:id="l1" style="custom"〉1no estimate of environmental degradation risk;2no financial analysis;3no social analysis of decision-makers' attitudes and preferences;4no risk assessment for weather, yields, profits and market; and5insufficiently-specific alternative land uses.These deficiencies could have been avoided with a demand-driven approach, evaluating and reporting according to the true needs and opportunities of the decision-makers.

Notes: Abstract. The residual value of mineral N fertilizer applied in the spring was investigated in a field experiment where four cereals (winter wheat, winter barley, spring barley and spring oats) had been grown at reduced (0.7N), normal (1N) or high (1.3N) N fertilizer rates for 20 to 28 years. The effect of previous N fertilizer dressing was tested in two succeeding years by replacing the original N rate with five test N rates ranging from 0 to 240 kg N ha−1 for winter cereals and 0 to 200 kg N ha−1 for spring cereals. In the first test year, winter wheat grown on plots previously supplied with the high rate of mineral fertilizer (202 kg N ha−1 yr−1) yielded more grain and straw and had a higher total N uptake than wheat on plots previously supplied with the normal (174 kg N ha−1 yr−1) or reduced (124 kg N ha−1 yr−1) rate. The grain yield response and N uptake was not significantly affected by the N supply in the test year. The winter wheat grown in the second test year was unaffected by the previous N supply. Grain and straw yield response and total N uptake for spring barley, winter barley and oats, were almost identical irrespective of the previous N rate.After 20 to 28 years there were no significant differences in soil C and N (0 to 20 cm) between soil receiving three rates of N fertilizer. Soil from differently fertilized oat plots showed no significant differences in N mineralizing capacity. Nitrate leaching losses from the soils at the three N rates were estimated and the N balances for the 20 to 28 years experimental period calculated. The data indicated a reduction in overall loss of 189 to 466 kg N ha−1 at the normal and high N rates compared with the reduced N rate. We conclude that the N supplying capacity and soil organic matter content of this fertile sandy loam soil under continuous cereal cropping with straw removal was not significantly affected by differences in N fertilizer residues.

Notes: Abstract. 15N labelled NH4NO3 (fertilizer N) was applied at a rate of 50 kg N ha–1 to an Ando-Humic Nitisol and two maize crops grown on it. About 20 months later, soil cores were taken to a depth of 2.5 m. Leached fertilizer N was found between 1.4 m and 1.8 m deep and was delayed relative to net drainage by between 4.2 and 4.9 pore volumes. Anion exchange capacity (AEC) increased ten-fold down the profile, up to 2.9 cmolckg–1. The delay to fertilizer N leaching was predicted to be between 4.1 and 5.3 pore volumes when calculated from the AEC and from an equation relating delay due to AEC in laboratory columns of repacked soil obtained by Wong et al. (1990b). It was concluded that the nitrate leaching delay equation was also valid in undisturbed field profiles. Two concentration maxima for mineral N were found, which did not usually coincide with the fertilizer N and were thought to result from mineralization of soil organic matter and plant residues at the end of each season. The delay equation overestimated their leaching delay but the results were considered close enough to support the hypothesis for their formation.

Notes: Abstract. Regions in the Po Valley, Northern Italy, are characterized by intensive crop-livestock farming systems. A simulation model has been chosen for an inter-regional project, which should help in defining groundwater vulnerability and pollution risk on a regional scale, in relation to agricultural land use, by allowing the prediction of nitrate leaching under different climate, soil, crop and management scenarios. The model derives from the coupling of a hydrological model, MACRO, simulating water flow and solute transport in structured soils, with a model simulating soil N dynamics, SOILN. The aim of this work was to test the model's ability to simulate nitrate leaching through soil after land spreading of pig slurries. A dataset obtained from lysimeter experiments which had been carried out in the period 1976–1981 was used for this purpose. Four soil types were compared (silty clay, sandy loam, loam and sand) in factorial combination with four rates of pig slurry (0, 142, 284, 426 g of N m–2, accumulated values from 1976 to 1979) for a seven crop sequence. The efficiency of the MACRO model ranged from 0.96, in the sandy-loam soil, to 0.81, in the sand. Percolation was usually under-estimated, the relative error ranging from 0.7 to 14.6, depending on the soil. The low efficiency of the SOILN model in simulating nitrate leaching is attributed to the lack of knowledge of the mechanisms regulating N transformation processes and especially the mineralization of pig slurry N. This lack of knowledge hampers the correct setting of the N transformation parameter values. A remarkable improvement of the model's performance was obtained by changing a few coefficients which control the mineralization-immobilization turnover of the faeces-organic N. The model efficiency, following this recalibration, ranged from –0.62 to 0.84, and the relative error ranged from –56 to 35, depending on soil and treatment. N leaching was under-estimated at the low pig slurry N application rates and over-estimated at the high ones.

Notes: Abstract. The effectiveness of contour grass strips in erosion control was investigated in a field experiment involving two grass treatments (Festuca ovina and Poa pratensis) and a bare soil control on an erodible sandy loam soil on a 5° slope using simulated rainstorms of 40 mm h–1 for 45 minutes duration. The grass strips resulted in significantly (P 〈 0.05) lower runoff and soil loss than the bare soil but there was no significant difference in the performance of the two grasses, despite their differences in density, height and leaf size. The effect of the lower density of the Poa pratensis was offset by its larger stem diameter so that the surface area facing the flow was similar for both grasses. Instead of acting as a filter with sedimentation occurring within the barrier, the grass strips operated by ponding water upslope of the barriers. Deposition then occurred in the ponded area above the barrier.

Notes: Abstract. Since the 1980s, land use in rural areas of China has changed greatly as the result of political initiatives. These changes have caused soil nutrient changes which are examined in this paper for Zunhua County, northern China from 1980 to 1999. The areas of farmland, grassland, and paddy decreased greatly and were replaced by increases in forest and residential land. The soils under forest in 1999 transformed from farmland in 1980 increased in organic matter by 21%, total nitrogen by 18%, available nitrogen by 65%, available phosphorus by 17% and available potassium by 17%. Similarly, in the area which was converted from farmland in 1980 to grassland in 1999, soil organic matter, total nitrogen, available nitrogen, available phosphorus, and available potassium increased by 38%, 37%, 71%, 2% and 28%, respectively. Changes from farmland to forest and grassland not only changed land cover but also improved soil fertility and probably reduced soil nutrient losses.

Notes: Abstract. Much of the low-lying farmland around the coastline of south-east England was once inter-tidal salt marsh, which was subsequently reclaimed from the sea and converted to farmland. It is becoming increasingly uneconomic to maintain the embankments which protect this land from the sea. ‘Managed retreat’ involves relocating the embankments further inland and recreating inter-tidal habitat in front of them. Salt marsh not only provides a protective buffer for these sea walls by dissipating wave energy, but is also important as a habitat for birds and as a source of organic matter for fish and inter-tidal fauna. When ‘managed retreat’ takes place, the creation of inter-tidal habitat occurs on soils that have undergone physical and chemical changes, some of which are irreversible. However, the indications are that rapid sedimentation creates conditions in which salt marsh plants germinate and become established; soil salinity rises quickly to a level which restricts competition from terrestrial plants, and deposited sediment is relatively rich in available phosphorus. The physical properties of the old agricultural soil influence the subsequent development of creeks.

Notes: Abstract. When the farmers of the Highlands of Tigray (northern Ethiopia) consider rock fragment cover in their fields to be excessive, they remove some of them. In addition, large amounts of rock fragments of all sizes are removed from fields for building stone bunds. Semi-structured interviews indicate that the farmers are often reluctant to take away the smaller rock fragments (i.e. 〈 5 cm across) from their fields, since they believe these benefit soil moisture conservation and protect topsoil from erosion. A field experiment was carried out on a Vertic Cambisol (average slope: 0.125 m m–1), 2 km east of Hagere Selam (subhumid climate). Rock fragments were totally, partially or not removed from the 12 runoff plots (5 m × 6 m) before the beginning of the 1999 cropping season, during which a local mixture of wheat varieties (Triticum spp.) was sown. After harvest, erosion rates were assessed by measuring deposited sediment volume in trenches at the lower side of each subplot, and grain and straw yields were assessed. We found a significant negative relationship between rock fragment cover and soil loss by water erosion. However, the resulting positive relationship between rock fragment cover and grain and straw yield was weak. This might be explained by the fact that the plot did not suffer from drought due to soil and climatic conditions. Detailed analysis showed that cover by medium and large rock fragments (〉 2 cm diameter) showed an optimum percentage cover above which crop yields decrease. A recommendation resulting from this study is to rely on the farmers’ experience: smaller rock fragments should never be removed from the surface of fields during soil and water conservation works; instead rock fragment rich soil can be used to top the stone bunds.

Notes: Abstract. The fertilizer nitrogen requirement of winter wheat was assessed in sixteen experiments on marine silt soils in Eastern England. Eight experimental sites followed potatoes (Solanum tuberosum), six vining peas (Pisum sativum) and two wheat (Triticum aestivum). The yield response to nitrogen fertilizer was much less following peas than potatoes or wheat, five sites following peas showed little response to more than 30 kg N ha–1. Previous crop explained some 79.7% of the variation in nitrogen optima. When autumn soil mineral nitrogen was also taken into account 81.9% of the variation in optimum nitrogen rate was explained (P〈0.001). The study revealed noticeably higher levels of autumn soil mineral nitrogen following vining peas on some sites than those found elsewhere in the UK and as assumed in the standard national fertilizer recommendation system.

Notes: Abstract. The aim of this study was to investigate the effects of water submergence depth on radial oxygen loss (ROL), soil solution chemistry and rice growth performance in acid sulphate soils in southern Vietnam. ROL was measured in a solution culture. In a separate pot experiment the impact of water submergence depth on rice growth and soil solution chemistry was studied. Three submergence depths were used in the two experiments (5, 10 and 15 cm). ROL declined with submergence depth and was significantly greater in young roots (with no root hairs) than in older roots. In the pot experiment rice growth and soil solution chemistry were clearly affected by the submergence depth. During the first crop at 5 cm submergence, there was a significantly higher yield and a higher oxidation state (pe+pH) compared to 10 or 15 cm submergence. The Fe concentration was significantly greater at the 5 cm depth compared to the 10 or 15 cm depth. SO42– reduction was delayed at the 5 cm depth. Rice yield was c. 25% less at the 15 cm than at the 5 cm depth. During a second crop, there was a substantial SO42- reduction and H2S formation and almost no significant effects of submergence depth on either soil solution chemistry or crop yield. In a field experiment with a dry-season rice crop, yield and Fe, Al and SO42– concentrations were higher at a shallow submergence depth than at greater depths in the same field, showing similar depth trends to those found during the first crop in the pot experiment. Farmers should be advised to use a shallow submergence depth and, if possible, avoid deep-rooted rice varieties. A conceptual model is suggested, which summarizes the relationships between ROL and soil solution chemistry.

Notes: Abstract. Tillage displaces large amounts of soil from upper slopes and deposits soil in lower landscape positions, greatly affecting productivity in these areas. The long-term effect of tillage on soil erosion was studied in four field sites growing mainly rainfed wheat. The soil loss from landscape positions with slopes, ranging from 3 to 28%, was estimated by: (a) comparing data of horizon thickness described at the same position at different times; and (b) using soil movement tracers added to the soil. Existing empirical relationships were used for estimating soil loss by tillage and runoff water, and loss in wheat biomass production. The experimental data showed soil losses of 0.4 to 1.4 cm yr–1 depending on slope gradient, plough depth, and tillage direction. In two of the sites, soil depth has been reduced by 24–30 cm in a period of 63 years. The mean soil displacement of the plough layer (30 cm thick), measured by soil movement tracers, ranged from 31 to 95 cm yr–1 depending mainly on slope gradient, corresponding to a rate of soil loss of 0.3 cm to 1.4 cm yr–1. Soil eroded from the upper slopes was deposited on the lower slopes increasing soil thickness by 0.4 cm to 1.4 cm yr–1. The application of empirical relationships, estimating soil loss by tillage and water runoff, showed that soil erosion at the field sites can be mainly attributed to tillage. The loss in wheat biomass production due to erosion was estimated at 26% on upper slopes for a period of 63 years, while a 14.5% increase in wheat production was estimated due to deposition of soil material in the lower landscape.

Notes: Abstract. The most common way of assessing soil organic matter content is by loss on ignition, which is both simple and inexpensive. This method tends to overestimate organic matter content because additional weight losses occur during ignition. An alternative, more expensive and time-consuming method for determining soil organic matter content is by an acid dichromate oxidation. This paper compares the results of applying these methods to soil on different parent materials in two arable fields. Summary statistics and correlation coefficients showed that there were consistent relationships between the two sets of values: the stronger was for the sandy soil and the weaker was for the clay loam. This relationship can be used to improve the accuracy with which soil organic matter content is known while using fewer of the expensive measurements and more of the inexpensive ones. Two approaches to prediction were compared: the geostatistical method of cokriging, and simple linear regression. These were used to predict organic matter determined by an acid dichromate oxidation from the loss on ignition. The estimates from cokriging were more accurate but the method requires the spatial correlation to be modelled reliably. The regression results showed it to be a valuable and practical approach. Using the information from nine carefully selected sampling sites a regression line could be fitted that was representative of the full data.

Notes: Abstract. In 1983, an annual Survey of Fertiliser Practice in England and Wales was extended to Scotland, to provide comprehensive information on inorganic fertilizer, lime and also organic manure use in mainland Britain. It was based on an annual sample of about 1500 farms, selected from the Agricultural Census and stratified by farm type and size. Results from the first fifteen years (1983–97) show that fertilizer nitrogen (N) rates on both tillage crops and grassland peaked at 157 and 132 kg ha–1, respectively, in the mid 1980s and subsequently decreased by c.10%. The majority of N was applied in straight form (without P or K) to tillage crops and in compound form (containing two or more nutrients e.g. NPK; NK) to grassland. Total N use on cereals showed little change but autumn-applied N decreased on both winter cereals and winter oilseed rape. Total N rates decreased on oilseed rape and, to a smaller extent, on maincrop potatoes and sugarbeet. Between 1983–87 and 1993–97, mean phosphate (P2O5) rates declined by almost 10% on both tillage crops (from 58 to 53 kg ha–1) and on grassland (from 25 to 23kg ha–1). The corresponding mean potash (K2O) rates decreased slightly on both tillage crops (from 64 to 62 kg ha–1), and on grassland (from 32 to 31 kg ha–1), although annual usage was more variable on grassland. Sulphur use increased appreciably on cereal and oilseed rape crops between 1993, when S data were first recorded in the survey, and 1997 when 13% and 30%, respectively, of these crop areas received S-fertilizer. However, on grassland, S use remained very low. Average lime use increased on both tillage crops and grassland between the mid 1980s and mid 1990s, from 10 to 12% and 4 to 7% of the total area, respectively. The proportion of land receiving organic manures remained at c. 16% for tillage cropping but increased slightly for grassland, from a mean of 40% in 1983–87 to 44% in 1993–97. Manures were applied throughout the year but about half the applications to tillage land, and a quarter of those to grassland, were made in autumn when the risk of subsequent nitrate leaching loss is greatest.

Notes: Abstract. A two year field experiment was carried out in a semiarid Mediterranean area in order to evaluate, the effect on soil erosion of adding different urban organic wastes: a stabilized municipal waste (compost), an unstabilized municipal waste, and an aerobic sewage sludge. All the treatments significantly reduced soil erosion, compared to the control soil. The soil amended with compost was the most effective treatment, reducing soil loss by 94% and runoff by 54%.

Notes: Abstract. Cashew soils of South Eastern Tanzania become acidified due to sulphur used for controlling powdery mildew disease (Oidium anacardii Noack). The buffering capacity of surface and subsurface horizons of 35 soil profiles of major cashew growing areas –- the Makonde plateau, its piedmont and inland plains –- was studied. The buffering capacity of surface and subsurface horizons was strongly correlated with clay content and weakly with organic carbon content. In addition, it was only weakly correlated with total exchangeable bases and available P of the surface horizon, but strongly with soil pH, base saturation and cation exchange capacity of the clay fraction of the subsurface horizon. Highly weathered sandy soils, dominant on the Makonde plateau and common on the Piedmont, had the lowest buffering capacity. Soils from the inland plains had better buffering capacities as they are generally more clayey or are less weathered. The risk of severe acidification and of a decline in productivity of cashew and of food crops is highest on the Makonde plateau. Further development and dissemination of methods which can reduce the use of sulphur are required.

Notes: Abstract. Biomass productivity and soil microbial responses to long-term CO2 enrichment have been investigated in a Mediterranean natural forest ecosystem. Several biochemical parameters have been measured on soil samples taken from six open top chambers (OTCs), enclosing clumps of natural Mediterranean woody vegetation including: Quercus ilex L., Phillyrea angustifolia L., Pistacia lentiscus L. and Myrtus communis L. The CO2 concentration of the air inside the OTCs was either ambient or ambient plus 350 μmol mol–1 (c. 710 ppm as mean daily value). Microbial C biomass, microbial respiration, dehydrogenase, β-glucosidase, acid phosphatase and protease activities, inorganic N and soluble P, were tested in order to evaluate soil microbial size and activity. Statistically correlated seasonal patterns have been identified in some biochemical parameters in response to climatic conditions, soil nutritional status and the physiology of the vegetative cover. In situ soil respiration and above- and below-ground productivity were also measured. Microbial responses to CO2 enrichment were observed only at the beginning of the study and a general progressive reduction of the CO2 effect was recorded as monitoring continued. These results are in agreement with data from literature regarding similar studies on natural complex communities.

Notes: Abstract. The Century model was used for estimating soil carbon levels under grassland at the regional scale in the Pampean Region of Argentina. Predicted values were compared with observed soil carbon contents obtained from soil surveys and the differences considered to be the results of cropping on soil organic matter. The Pampean Region was divided into five major sub-regions and carbon in the top 20 cm of each estimated by Century using aggregated soil and climatic data. In four of the sub-regions small differences between predicted and observed carbon contents were obtained which suggested little land use effect on soils. In the Rolling Pampa, a northern portion of the Pampean Region, observed carbon content was about half of Century prediction. In this sub-region, the main agricultural area of the country, cropping intensity, rainfall and temperature are higher than in the rest of the Pampas. A degradation index constructed by a multiplicative approach, taking into account percentage of surface cropped, rainfall and temperature was 2–5 times higher in the Rolling Pampa than in the other pampean sub-region. The difference between predicted C and observed C in the Rolling Pampa was attributed to carbon losses by cropping in a warm and wet climate.

Notes: Abstract. Recent developments in in situγ ray spectrometry offer a new approach to measuring the activity of radionuclides such as 137Cs and 40K in soils, and thus estimating erosion or deposition rates and field moist bulk density (ρm). Such estimates would be rapid and involve minimal site disturbance, especially important where archaeological remains are present. This paper presents the results of a pilot investigation of an eroded field in Scotland in which a portable hyper pure germanium (HPGe) detector was used to measure γ ray spectra in situ. The gamma (γ) photon flux observed at the soil surface is a function of the 137Cs inventory, its depth distribution characteristics and ρm. A coefficient, QCs, derived from the forward scattering of 137Cs γ ray photons within the soil profile relative to the 137Cs full energy peak (662 keV), was used to correct the in situ calibration for changes in the 137Cs vertical distribution in the ploughed field, a function of tillage, soil accumulation and ρm. Based on only 8 measurements, the agreement between in situγ ray spectrometry and soil sample measurements of 137Cs inventories improved from a non significant r2=0.05 to a significant r2=0.62 (P〈0.05). Erosion and deposition rates calculated from the corrected in situ137Cs measurements had a similarly good agreement with those calculated from soil cores. Mean soil bulk density was also calculated using a separate coefficient, QK, derived from the forward scattering γ photons from 40K within the soil relative to the 40K full energy peak (1460 keV). Again there was good agreement with soil core measurements (r2=0.64; P〈0.05). The precision of the in situ137Cs measurement was limited by the precision with which QCs can be estimated, a function of the low 137Cs deposition levels associated with the weapons testing fallout and relatively low detector efficiency (35%). In contrast, the precision of the in situ ρm determination was only limited by the spatial variability associated with soil sampling.

Notes: Books Reviewed in this Article: Fertiliser recommendations for agricultural and horticultural crops (RB209) Published with the permission of MAFF by HMSO, 7th edition 2000.

Notes: Abstract. A field experiment was undertaken to assess the effectiveness of a combined treatment, involving addition of Aspergillus niger-treated sugar beet (SB) residue in the presence of rock phosphate and mycorrhizal inoculation of seedlings with Pisolithus tinctorius. The aim was to improve the physical, chemical, biochemical and biological properties of a degraded semiarid Mediterranean soil. Short-term effects of such improvements on the establishment of Cistus albidus L. seedlings were evaluated. Eight months after planting, macronutrients (NPK), total carbohydrates, water-soluble C, water-soluble carbohydrates, microbial biomass C and enzyme activities (dehydrogenase, urease, protease, acid phosphatase and β-glucosidase) measured in the rhizosphere soil of C. albidus were increased greatly by addition of fermented SB residue. Soil structural stability improved only with the fermented SB addition (about 79% higher in the amended soils than in the non-amended soils). The mycorrhizal inoculation was the most effective treatment in improving the growth of C. albidus plants, but only slightly improved soil quality. Growth of inoculated plants was about 33% greater than plants grown in the amended soil and about 131% greater than control plants. The combined benefit of mycorrhizal inoculation of seedlings and addition of fermented SB residue to soil on plant growth was similar to that of the treatments applied individually.

Notes: Abstract. Organic agriculture (OA) aims to identify a production regime that causes less environmental problems than conventional agriculture (CA). We examined whether the two systems differ in their susceptibility to soil erosion by water. To account for the large heterogeneity within the rotations practised on different farms, we chose a statistical evaluation which modelled erosion using the USLE method from the cropping statistics for 2056 districts in Bavaria (70 547 km2; 29.8% arable). Physical conditions of erosion were determined in a rectangular grid yielding 13 125 grid-cells of c. 5 km2 each. For validation, erosion was measured in 10 sub-watersheds on two neighbouring OA and CA farms over 8 years (287 erosive events). On average, about 15% less erosion on arable land was predicted for OA than for CA due to the larger area of leys, although OA occupies areas that are susceptible to erosion more often than CA. The same conclusions could be drawn from the validation data. These data also demonstrated that erosion could be reduced considerably below 1 t ha−1 yr−1 with best management practices under both farming systems. In contrast, at the countrywide scale, cropping did not change adequately with site conditions favouring erosion. The need for erosion control seems not to influence crop rotation decisions on erosion-prone sites.

Notes: Abstract. The effects of various fallow management systems and cropping intensities on water infiltration were measured on an Alfisol at Ibadan in southwestern Nigeria. The objective was to determine the influence of the land use systems (a combination of crop–fallow sequences and intercropping types) on soil hydraulic properties obtained by disc permeameter and double-ring infiltration measurements. The experiment was established in 1989 as a split-plot design with four replications. The main plots were natural fallow, planted Pueraria phaseoloides and planted Leucaena leucocephala. The subplots were 1 year of maize/cassava intercrop followed by 3-year fallow (25% cropping intensity), or 2-year fallow (33% cropping intensity), or 1-year fallow (50% cropping intensity), or no fallow period (100% cropping intensity). Water infiltration rates and sorptivities were measured under saturated and unsaturated flow. Irrespective of land use, infiltration rates at the soil surface (121–324 cm h−1) were greater than those measured at 30 cm depth (55–144 cm h−1). This indicated that fewer large pores were present below 30 cm depth compared with 0–30 cm depth. Despite some temporal variation, sorptivities with the highest mean value of 93.5 cm h−½ increased as the cropping intensity decreased, suggesting a more continuous macropore system under less intensive land use systems. This was most likely due to continuous biopores created by perennial vegetation under long fallow systems. Intercropped maize and cassava yields also increased as cropping intensity decreased. The weak relationship between crop yields and hydraulic conductivity/infiltration rates suggests that the rates were not limiting.

Notes: Abstract. Hierarchical crop growth models can contribute significantly to land quality research because the yield gap between the estimated optimum and the actual crop production has been identified as a major land quality indicator. This study describes a three-level, hierarchical crop production model, simulating radiation-thermal, water-limited and natural production potentials of annual crops. Input requirements have been kept low to ensure its applicability to developing regions, which often have access only to limited data. The simplicity of this model also has disadvantages: inconsistencies have been reported when applying this model in semiarid regions, which are characterized by very irregular rainfall patterns. Revision of the water balance, which simulates the availability of water, was required. The modified model was validated using the experimental yields of maize and sunflower in Guquka, a semiarid region of South Africa. Yields were estimated very well, possible improvements to crop production were identified and implications for land-use planning highlighted. Yield gap analysis revealed that radiation, sunshine and temperature are favourable for crop production, but the heavy dependence on rainfall makes the region very vulnerable to drought, with devastating impact on yields. The generally low chemical soil fertility further reduces crop performance.

Notes: Abstract. A potential technique for reducing overwinter leaching from high N containing crop residues is to immobilize the N released during decomposition by co-incorporating materials of a wider C : N ratio. This article describes the use of laboratory incubation experiments to investigate the effects of a wide range of such amendment materials on the mineralization of N from sugar beet and brassica leaf residues in a sandy loam and a silt loam. These materials were of varying quality, with C : N ratio ranging from 15 : 1 to 520 : 1, and cellulose content from 0 to 34%. Amendments were added at a fixed rate of 3.5 mg C g−1 of dry soil, equivalent to around 10 t ha−1 C (to 20 cm depth). The soils were then incubated at 15°C, and net mineral N derived from the leaves was measured at regular intervals over 168 days. Net mineralization of residue N was greatest with molasses (C : N ratio of 18 : 1), whereas paper waste (C : N ratio of 520 : 1) reduced N mineralized by up to 90% compared with a soil-only control. As the concentration of cellulose and lignin in the amendment materials increased, so the amounts of N mineralized decreased, with 62 and 54% of variance in N mineralized explained by cellulose and lignin content, respectively. Reduced levels of mineral N were associated with higher levels of biomass-N. The levels of N2O-N lost from sugar beet residues on day 14 were significantly reduced from 66 to 5 g ha−1 where compactor (cardboard) waste had been mixed into sandy loam, but this effect was not observed in the silt loam. These techniques could lead to greater efficiency of N use in rotations through reduction in N losses, and provide alternative routes for disposal of wastes when the EC Landfill Directive is implemented.

Notes: Abstract. The Olsen method is an indicator of plant-available phosphorus (P). The effect of time and temperature on residual phosphate in soils was measured using the Olsen method in a pot experiment. Four soils were investigated: two from Pakistan and one each from England (calcareous) and Colombia (acidic). Two levels of residual phosphate were developed in each soil after addition of phosphate by incubation at either 10 °C or 45 °C. The amount of phosphate added was based on the P maximum of each soil, calculated using the Langmuir equation. Ryegrass was used as the test crop. The pooled data for the four soils incubated at 10 °C showed good correlation between Olsen P and dry matter yield or P uptake (r2= 0.85 and 0.77, respectively), whereas at 45 °C, each soil had its own relationship and pooled data did not show correlation of Olsen P with dry matter yield or P uptake. When the data at both temperatures were pooled, Olsen P was a good indicator of yield and uptake for the English soil. For the Pakistani soils, Olsen P after 45 °C treatment was an underestimate relative to the 10 °C data and for the Colombian soil it was an overestimate. The reasons for these differences need to be explored further before high temperature incubation can be used to simulate long-term changes in the field.

Notes: Abstract. Nitrous oxide (N2O) from animal excreta in grazed pasture systems makes up a significant component (c. 10%) of New Zealand's total greenhouse gas inventory. We report an effective method to decrease N2O emissions from animal urine patches by treating the soil with the nitrification inhibitor dicyandiamide (DCD), in a simulated grazed dairy pasture system under spray irrigation. The soil was a free-draining Lismore stony silt loam (Udic Haplustept loamy skeletal) and the pasture was a mixture of perennial ryegrass (Lolium perenne) and white clover (Trifolium repens). By treating the soil with DCD, N2O emissions were decreased by 76% following urine application in the autumn, from 26.7 kg N2O-N ha−1 without DCD to an average of 6.4 kg N2O-N ha−1 with DCD over the 6-month experimental period. N2O flux was decreased by 78% following urine application in the spring, from 18 kg N2O-N ha−1 without DCD to 3.9 kg N2O-N ha−1 with the application of DCD over the 3-month period. A single application of DCD immediately after urine was sufficient to effectively mitigate N2O emissions from the urine. The results showed that repeated applications of DCD after urine application, or mixing DCD with urine, offered no advantage over a single application of DCD immediately after urine deposition.

Notes: Abstract. Pig slurry was applied by open-slot injection to experimental plots on a sandy loam site at ADAS Gleadthorpe, Nottinghamshire. Volume and distribution of over-winter drainage were adjusted through the use of rainfall exclusion covers or irrigation. The resultant slurry N leaching over the range of drainage values tested (up to 300 mm) could be satisfactorily described by curve-fitting, using a quadratic or exponential function. Initial simulations of slurry N leaching using the manure nitrogen decision support system manner (v. 3.0) compared poorly with the experimental data, predicting both earlier and greater amounts of nitrate leaching. However, the lack of fit could be explained by consideration of the likely ammonia emissions following slurry injection, the actual volumetric soil moisture capacity at the experimental site and the likely time delay for the nitrification of slurry N following application. Good agreement between modelled and observed data was achieved when these factors were taken into account. The manner model was used to simulate nitrate leaching beyond the range of drainage treatments tested in the experiments and the anticipated sigmoidal relationship between nitrate leaching and drainage was observed. The model was then used to study the effects of manure application timing and the likely impact on nitrate leaching, across the range of rainfall conditions found in Great Britain. Simulations for a range of manure types were undertaken, with manures applied at rates up to the limit of permitted N loading on freely draining sandy loams. Rainfall inputs for these simulations were based on long-term average climatic data. Results are presented for two contrasting manure types, cattle slurry and poultry manure, both of which are subject to controls in Nitrate Vulnerable Zones (NVZs) in Great Britain.

Notes: Abstract. As measures to reduce point source inputs of phosphorus (P) to water have been introduced, the effect of diffuse P has become more evident. Land drains can act as an effective conduit for transfer of sediment and sediment P from agricultural land to surface waters. This article describes the development of a national risk map, identifying areas of agricultural land in England and Wales that are most likely to be prone to such losses. The map is based on data obtained from a variety of sources, including field studies, laboratory-based rainfall simulation experiments and secondary sources. From these studies, eight factors relating to soil HOST class, rainfall, soil moisture deficit, land use and the type and condition of land drains were identified as influential in the process of sediment and sediment P transfer. Each factor was weighted to provide an estimate of risk and the combined total was used to plot a national risk estimate at a resolution of 25 km2. The exercise suggests that large areas of England and Wales may be at risk of subsurface sediment and sediment P transfer from agricultural land to rivers. The scale of the map is insufficient for planning at the farm level, but further work incorporating similar data and principles could make it more applicable to potential end-users on the ground.

Notes: Abstract. Detailed morphological, physical, chemical, mineralogical and micromorphological studies were carried out to identify properties that influence the yield of deep-rooted crops in 29 Vertisols of semiarid central India, since existing land evaluation methods are not adequate to explain the yield of cotton obtained by farmers. The studies indicated that among the soil parameters, CaCO3 in the clay fraction, the exchangeable Ca/Mg ratio, exchangeable sodium percentage (ESP) and saturated hydraulic conductivity (HC) were the yield-influencing factors. The pedogenetic relationships between the semiarid climate, formation of pedogenic calcium carbonate, exchangeable Ca/Mg, ESP and HC have been established. In view of the pedogenetic processes that ultimately impair the drainage of soils, evaluation of Vertisols for deep-rooted crops on the basis of HC alone may help in planning and management of soils, not only in the Indian semiarid tropics, but also in similar climatic areas elsewhere.

Notes: Abstract. Water retention properties of 219 horizons were measured in Cambisols, Luvisols and Fluvisols, mainly from the Paris basin. We derived class pedotransfer functions (class PTFs) based on texture alone and in a second stage class PTFs based on classes combining texture and clod bulk density. The performance of these two types of PTFs were discussed at −330 and −15000 hPa water potential on an independent set of 221 horizons. Results showed that PTFs based on sets grouped by texture and clod bulk density provide estimates with an accuracy that is (i) greater than with class PTFs based on texture alone, and (ii) similar to the estimation accuracy recorded with continuous PTFs. As a consequence, the lack of interest in class PTFs should be reconsidered to bridge the gap between the available basic soil data and hydraulic properties which are generally missing, particularly when pertinent soil characteristics can be derived from the data available in soil databases. The two types of class PTFs providing gravimetric water contents at seven water potentials ranging from −10 to −15 000 hPa were converted to volumetric water content using the soil bulk density. Finally, the parameters of van Genuchten's water retention curve model were computed for every class PTF.

Notes: Abstract. Soils can be used as a biospheric sink for carbon under Article 3.4 of the Kyoto Protocol and parties are able to use agricultural soil carbon sinks to contribute towards carbon emission reduction targets. This should be done ‘taking into account uncertainties, transparency in reporting, and verifiability’. Models are often tested against data sets of long-term changes in soil organic carbon (SOC), but most data sets have only mean SOC values available at each sample date, with no estimates of error about the mean. We show that when using data sets that do not include estimates of error about the mean, it is not possible to reduce the error (root mean squared error) between modelled and measured values below 6.8–8.5%, even with site-specific model calibration. Equivalent errors for model runs using regional default input values are 12–34%. Using error as an indicator of the certainty that can be attached to model projections, we show that a significant reduction in uncertainty is needed for Kyoto accounting. Uncertainties for modelling during the first Kyoto Commitment Period could be reduced by better replication of soil measurements at benchmark sites. This would allow model error to be separated from measurement error, which would allow more comprehensive model testing and, ultimately, more certainty to be attached to model predictions.

Notes: Abstract. Artificial urine containing 20.2 g N per patch of 0.2 m2 was applied in May and September to permanent grassland swards of a long-term experiment in the western uplands of Germany (location Rengen/Eifel), which were fertilized with 0, 120, 240, 360 kg N ha−1 yr−1 given as calcium ammonium nitrate. The effect on N2O fluxes measured regularly during a 357-day period with the closed-chamber technique were as follows. (1) N2O emission varied widely among the fertilized control areas without urine, and when a threshold water-filled pore space 〉60% was exceeded, the greater the topsoil nitrate content the greater the flux from the individual urine patches on the fertilized swards. (2) After urine application in May, 1.4–4.2% of the applied urine-N was lost as N2O from the fertilized swards; and after urine application in September, 0.3–0.9% of the applied urine-N was lost. The primary influence on N2O flux from urine patches was the date of simulated grazing, N-fertilization rate being a secondary influence. (3) The large differences in N2O emissions between unfertilized and fertilized swards after May-applied urine contrasted with only small differences after urine applied in September, indicating an interaction between time of urine application and N-fertilizer rate. (4) The estimated annual N2O emissions were in the range 0.6–1.6 kg N2O-N per livestock unit, or 1.4, 3.6, 4.1 and 5.1 kg N2O-N ha−1 from the 0–360 kg ha−1 of fertilizer-N. The study demonstrated that date of grazing and N-fertilizer application could influence the N2O emission from urine patches to such an extent that both factors should be considered in detailed large-scale estimations of N2O fluxes from grazed grassland.

Notes: Abstract. We studied the effects of five diverse non-agricultural organic wastes on soil composition, grass yield and grass nitrogen use in a 3–year field experiment. The applied wastes were distillery pot ale, dairy salt whey, abattoir blood and gut contents, composted green waste (two annual applications each), and paper-mill sludge (one annual application). With the exception of N immobilization in the paper-mill sludge treatment, the wastes had no unfavourable effects on the soil. In the 2–year treatments, grass dry matter yields from the abattoir and distillery wastes (26.3 t ha−1) were larger than those from a NH4NO3 fertilizer treatment (24.3 t ha−1) and from the dairy waste (20.4 t ha−1) and composted waste (22.8 t ha−1). Yield and N recovery were impaired markedly after the single application of paper-mill sludge, both in the year of application and in the following year. The results demonstrated clear differences in the ability of the applied wastes to provide crop-available N. We conclude that in order to improve prediction of both the benefits and risks from waste recycling to land, more information should be gathered on soil/waste/crop interactions.

Notes: Abstract. A laboratory study was conducted to investigate the effects of adding an intermediary byproduct of olive oil extraction (alperujo or solid olive-mill waste, SOMW) on the sorption, degradation and leaching of the herbicide simazine in a sandy loam soil. The effect of SOMW addition on soil porosity was also assessed. The soil was amended in the laboratory with SOMW at two different rates (5% and 10% w/w). Simazine sorption isotherms showed a great increase in herbicide sorption after SOMW addition to soil; sorption increased with the amount of SOMW added. Incubation studies showed extended persistence by reduced biodegradation of simazine in the soil amended with SOMW compared with the unamended soil. Although the addition of SOMW to soil increased the total porosity, breakthrough curves of simazine in handpacked soil columns showed that SOMW addition retarded the vertical movement of the herbicide through the soil and reduced the total amount of herbicide leached. It appeared that the longer residence time of simazine in the amended soil columns (〉20 days) compared with that in the unamended soil column (〈20 days) allowed enhanced degradation and/or irreversible sorption under column leaching conditions. The results revealed important changes in herbicide behaviour upon SOMW addition, confirming the need to assess these changes in order to optimize the combined use of organic wastes and soil-applied pesticides.

Notes: Abstract. Jute geotextiles are widely used to stabilize steep banks and road cuttings. Jute protects bare surfaces until seeded grass becomes established, then after several years, the jute decays. To evaluate two types of jute geotextiles, eight erosion plots were established in July 1994 at the Hilton Experimental Site, Shropshire, UK. On 10 April 1995, the plots were treated as follows:〈list xml:id="l1" style="custom"〉1jute geotextile net;2jute mat;3perennial rye grass (Lolium perenne); and4bare soil, with duplicates of each treatment.Over one year, sediment yields from jute net and jute mat were 1.1% and 1.2%, respectively, of the yield from the bare control. Although both had similar soil protection qualities, runoff was very different. The runoff from the jute net was 35% and the jute mat 247% of the control. Results demonstrate the effectiveness of jute net for erosion and runoff control, while the jute mat may both conserve soil and ‘harvest’ rain or redirect runoff.

Notes: Abstract. A predictive model of metal concentrations in crops was developed to optimize soil liming and sludge application strategies at a dedicated sewage sludge disposal site. Predictions of metal concentrations in plant tissue were derived from measured values of soil metal concentration, humus content and soil pH. The plant and soil data used to parameterize the model were collected on site using quadrat sampling of mature crop and underlying topsoil. The uptake model was used to map predicted metal concentrations in wheat grain and forage maize based upon a database of soil characteristics (metal content, % humus and pH) measured as part of a routine geochemical survey of the site. The effect of a management strategy to modify uptake of Cd by wheat by changing soil pH was investigated. The effect of soil dust adhering to maize plants at harvest was also simulated to investigate the importance of this pathway for Cd transfer to animal feed such as silage.The model gave satisfactory predictions for uptake of Cd and Zn but less useful simulations for Pb, Cu and Ni. The results for Cd uptake showed a greater dependence on soil pH in the case of wheat in comparison to maize. It is suggested that, for the study site, liming to pH 7.0 will reduce Cd concentrations in wheat grain to within EC legal standards. However the Cd content of maize may still exceed these guidelines, with a relatively minor contribution from contamination with soil dust.

Notes: Abstract. The transfer of suspended sediment (SS) and phosphorus (P) in overland flow from 30 m2 field plots receiving either nil, surface-applied or incorporated manure (slurry) were monitored to determine the vulnerability of land cropped to continuous forage maize to diffuse pollutant transfer in winter runoff. In the absence of slurry, P export was dominated by particulate forms, with up to 1 t SS ha−1 and 0.75 kg total P ha−1 collected from an individual storm event. Background concentrations of P in soluble (〈0.45 μm) form were large (c. 0.5 mg L−1) by eutrophication standards due to the previous build-up of soil P, and largely independent of SS concentrations. Largest P exports (representing up to 23% of the slurry P applied) were measured when dairy slurry (3–13% dry solids) was surface-applied. The P mobilized from the slurry accounted for up to 60% of total plot P export, with the majority occurring in a soluble bioavailable form during the first storm event. Initial P concentrations in runoff were in proportion to the amount of slurry P applied and significantly lower where rainfall was delayed after application. In one year, splitting the slurry application (3 × 10 kg ha−1) reduced total P export by 25% compared to a single surface application (30 kg P ha−1). In two years, incorporation of slurry, either by ploughing, or by tine cultivation, reduced the amount of overland flow by 50%, and the amount of P export by up to 60%, compared to the surface-applied slurry treatments. Timeliness of slurry spreading to avoid periods of wet weather and simple cultivation of maize fields after harvest are practical and effective options to minimize SS and P transfer in land runoff from maize fields. The results also draw attention to the need to grow maize, and apply slurry to fields with a low P loss risk.

Notes: Abstract. To determine the effects of low-input agriculture on soil properties, we compared several forms of arable land management in a rotation experiment lasting 8 years on a Cambisol in Lithuania. Conventional arable cropping with applications of inorganic fertilizers increased the potassium (K) status of the soil, but resulted in losses of nitrogen (N) from the soil by mineralization and leaching. With ley–arable integrated cropping, a similar fertilizer regime based on farmyard manure (FYM) augmented with inorganic fertilizers increased the phosphorus (P), K, organic matter and N in the soil, as well as increasing N loss by leaching. These two high-input regimes were compared to three systems with less or no input. A reference treatment with no input, which produced small crop yields, maintained its nutrient status and organic matter. An organic regime receiving FYM and green manure lost only P, but maintained its K and N status, while a second organic regime in which the FYM was replaced by composted sewage maintained its fertility. The microbial activity varied somewhat from treatment to treatment, with the largest numbers of almost all groups of microorganisms in the reference treatment. All treatments led to decreases in fulvic acid, and the soil managed conventionally lost humic acid, too. The content of humic acid increased in the treatments where FYM was applied and in the reference soil, and the fraction bound to calcium increased in the integrated and the first organic treatments. The soil structures under the integrated cropping and second organic regime were the most stable. Of the low-input systems, the second organic regime seemed the most sustainable.

Notes: Abstract. Emissions of N2O were measured after application of NH4NO3 fertilizer and incorporation of winter wheat and rye green manures in two field experiments in southeast England. Incorporation of green manure alone resulted in temporary immobilization of soil N, small N2O emissions and also low availability of N for the following crop. Emissions were increased after application of inorganic fertilizer, and were further increased from integrated management treatments whereby green manure residues were incorporated after fertilizer application. The highest emission was from the incorporated winter wheat green manure plus fertilizer treatment, with 1.5 kg N2O-N ha−1 (0.6% of N applied) being emitted over the first 55 days after incorporation. This high emission was attributed to the supply of C in the residues providing the energy for denitrification in the presence of large amounts of mineral N and the creation of anaerobic microsites during microbial respiration.

Notes: Abstract. Soil compaction has long been considered to be a problem in arable land, primarily because it causes damage to soil structure, which can lead to serious reduction in crop yields. However, few studies have sought to investigate the effects of soil compaction on the water transport regime of modified soil pore systems. We attempted to quantify the effects of soil compaction on the initiation of preferential flow by using dye tracers and image analysis. A laboratory methodology involving rainfall simulation enabled us to quantitatively evaluate differences in the mechanisms of water flow between two soil types at several degrees of compaction. The results suggested significant differences in the types of water flow pathways between clay loams and sandy loams at different extents of compaction. In the sandy loam, it was concluded that a high degree of compaction led to an increased likelihood of preferential flow, whereas a more uniform movement of soil water occurred at less compaction. By contrast, preferential routing of soil water was recorded in the clay loam, except at the highest measured compaction. The results indicate that the visual techniques of dye tracing and image analysis could enable improved understanding of flow pathways of soil water associated with soil compaction.

Notes: Abstract. Annual methane fluxes from an organic soil in eastern Finland, originally drained and planted with birch (Betula pendula) and then later cultivated, were studied for two years using a chamber technique. The agricultural soils growing grass or barley or without vegetation, generally acted as sinks for CH4. Surprisingly, the agricultural soils emitted CH4 during a warm dry summer. The CH4 oxidation capacity and CH4 uptake rate of the forested site was three times that of agricultural soils. Also, the forest soil better retained its capacity to take up CH4 during a dry summer. Despite periods of CH4 emission, the agricultural soils were annual sinks for CH4, with uptake rate of CH4-C varying from 0.1 to 3.7 kg ha−1 yr−1. The forested soil had a methane uptake rate of 3.9 kg CH4-C ha−1 yr−1. All the soils acted as sinks for CH4 during winter, which contributed up to half of the annual CH4 uptake. The capacity of soils to transport gases did not explain the larger CH4 uptake rate in the forest soil. At the same gas filled porosity, the forest soil had a much larger CH4 uptake rate than the agricultural soil. Neither the soil acidity (pH 4.5 and 6.0) nor high ammonium content appeared to limit CH4 uptake. The results suggest that CH4 oxidation in agricultural organic soil is more sensitive to soil drying than CH4 oxidation in forested organic soil.

Notes: Abstract. A study was conducted to assess the impact of agricultural land use history on macro-aggregate (4.0–4.8 mm) stability in the 0–5 cm layers of Chromic and ‘Hydromorphic’ Vertisols in north Cameroon. Macroaggregate stability to water drop impact was determined and the ASI50 index calculated. Macroaggregates from fallow and zero-tilled cropped soils disaggregated in a stepwise manner. Macroaggregates from ploughed cropped soils collapsed in one step into semi-liquefied microaggregates and primary particles. On both soil types, the ASI50 index of samples from ploughed land was 10.0 mJ, compared to 16.4– 21.9 mJ from zero-tilled slash and burn land use. The stepwise disintegration of macroaggregates indicated the existence of a hierarchy of aggregation within the size range 2–5 mm. Slash and burn land use on zero-tilled Vertisols significantly increased sand-sized organic carbon content and the stability of macroaggregates to water impact.

Notes: Abstract. Field experiments were carried out to evaluate the relative efficacy of organic manures in improving the productivity and pest tolerance of rice growing in a lateritic soil. The effects of three commercial manures: processed city waste (PCW), vermicompost (VC) and oil cake pellets (OCP), were assessed in comparison to farmyard manure (FYM) and inorganic fertilizer all at the same total N applied. Of the organic manures tested, FYM produced the maximum straw and grain yields. Differences in yield among the organic manure treatments were mainly attributed to variation in the amounts of available N, P, K and micronutrients. Effect of manures on soil physical condition was not studied. The uptake of N, P and K by rice plants with FYM was significantly greater than all other commercial manures and inorganic fertilizer. The tolerance of rice plants to attack by pathogens and pests, measured in terms of grain yield was highest in the treatment with FYM. Among the commercial manures PCW showed the greatest promise and emerged as a potential alternative to FYM.

Notes: Abstract. Soil management studies show that intensive arable agriculture can lead to a decline in both organic matter levels and the stability of the soil structure. It is a priority to understand how soil structure responds when fresh organic materials are added to poor quality degraded arable soils. This is of particular interest because of its implication for carbon sequestration. We investigate whether the addition of organic materials can form stable aggregates in a degraded soil. Grass or peat residues were added to samples of soil obtained from the continuous grassland and arable plots of the long-term experiment at highfield, IACR-Rothamsted (UK) and incubated at 2° and 24°C, for upto 8 weeks at -5 kPa. At 1 day and at 2, 4 and 8 weeks the soil was slaked in de-ionised water and the aggregate size distributions were measured. The data was used to calculate mean weight diameters (MWD). The treatments with added grass showed increased aggregated relative to the control; the treatments with added peat did not. At 24°C the value of MWD increased with the incubation period, but at 2°C there was no further aggregation beyond week two. Respiration measurements were made and the samples that released the most CO2 were also those which re-aggregated the most. This suggests that the process of aggregation is microbiologically mediated. The results are discussed within the broader context of the implications of soil organic matter content on soil management.

Notes: Abstract. By comparing field measurements from 1989, 1997, and 1998, the differences between farmland (sloping farmland, sloping farmland with contour cultivation, terraced farmland) and orchard (terraced orchard, unterraced orchard), in the Three Gorges Reservoir Area, were significant for runoff (P〈0.01), erosion (P〈0.05) and nutrient loss (P〈0.05). Taking into account economic costs and environmental influences, reasonable and sustainable land use on slopes of 25° in the Three Gorges Reservoir Area should be unterraced orchard.

Notes: Abstract. Paper sludge composted or stored in static piles for six months was compared to raw and lime-stabilized sludge in a three-year pot experiment (loam) and a four-year field experiment (silt loam) at rates of up to 40 t DM ha-l. The original sludge contained equal amounts of fibre sludge and biological sludge, mixed with bark in 1:1 ratio to improve the structure. The N content in composted sludge (1.30%) was markedly lower than that of the uncomposted piles (1.98%), indicating significant loss during composting. The yield results were generally inversely proportionate to the C:N ratios of the sludges applied. Sludge from the uncomposted piles gave significant grain yield increases in the year following sludge application, while the other sludge types gave variable results. In the residual years there was, generally, a small but positive effect on yield from all the sludge types. The N and P content in grain generally increased with sludge application, but only the higher rates gave statistically significant increases. Sludge application also increased the Zn content in grain, while Mn, B and Cu was less affected. The increase in Cd content was very small. The 40 t ha-l sludge rate tended to increase the residual mineral N in soil at the field site and thus the risk of nitrate leaching.

Notes: Abstract. An increasing number of breeding sows is kept outdoors in Europe. Outdoor pig production has benefits in terms of animalwelfare but may have hidden costs through nutrient losses. We investigated the distribution of nutrients in sow paddocks and the consequence for losses and utilization in the succeeding crop. Significant correlation between soil inorganicNand the distance to feeding sites was observed after the paddocks had been used by lactating sows for 6 months (P〈0.01). Near to feeders inorganic N levels became extremely high whereas 30–40m from feeders some patches hadN levels in the topsoil corresponding to the levels in the reference area without sows. In the following spring only a minor part of inorganic N was still present in the top 0–40 cm. Similarly, extractable P and exchangeable K in topsoil were significantly affected by distance to feeders with the highest values close to the feeders (P〈0.001). In addition there were significant effects of the distance to huts with increasing nutrient content closer to huts. Although huge variations in dry matter production and nutrient content occurred in the succeeding potato crop, these were only weakly related to the distribution of nutrients (N, P and K) in the previous year, which explained 17%of the total variation in dry matter production. To increase nutrient efficiency in outdoor pig production a uniformdistribution of nutrients should be obtained by manipulating the excretory behaviour of the sows and stocking densities must be adjusted to locally acceptable nutrient surpluses.

Notes: Abstract. A survey of cattle manure management was undertaken in England and Wales, in 1997, by postal questionnaire sent out to a stratified sample (by unit size) of 1750 dairy and 1750 beef producers. The level of response obtained, with 471 dairy farmers (27%) and 515 beef farmers (29%) returning questionnaires, reflects well on the interest shown by the industry and on the survey design. The survey provided information on manure production and storage, when and how applied and nutrient value. Dairy farms are estimated to produce manures in the form of c. 65% slurry and 35% farmyard manures (FYM) and, beef units, 80%FYM and 20%slurry (based on survey response data, animal numbers and calculations of undiluted outputs of excreta). Slurry storage within both dairy and beef systems is typically up to 3–6 months capacity, although there is no storage for an estimated 16% of dairy and 25% of beef slurry. Autumn and winter spreading is common practice, with 40–50% of slurry and 50–60% of FYM applied at that time. Although some evidence suggests that farmers make little allowance for the nutrient content of manures in planning fertilizer inputs, the results of this survey suggest that many farmers do make some effort to utilize manure nutrients. However, they currently fail to be assured by the advice available to them or they lack confidence in manures as nutrient sources for a number of technical reasons. Information provided by the survey may be important to policy makers, researchers and consultants, as well as farmers.

Notes: Abstract. Demand for water from catchments dominated by upland peat as a source of drinking water supplies in the UK is likely to increase in the future as demand per capita continues to rise (Thomsen 1990) and/or summer droughts increase in frequency (Arnell 1992). Concern has been expressed in recent years over rising colour levels (related to dissolved organic carbon (DOC) and iron (Fe)) from such catchments (e.g. Kay et al. 1989) causing reduced drinking water quality. One of the major causes of increased DOC concentrations is rewetting following periods of relative drought (Mitchell & McDonald 1992). Experimental rewetting of a naturally drained wetland in Mid-Wales over four years was found to substantially increase the concentrations of DOC, and Fe in the pore-water, with peak values of 〉60 mg dm–3 (Fe) and 〉300 mg dm–3 (DOC) after rewetting, compared with typical values of 〈1 mgdm–3 (Fe) and 〈15 mg dm–3 (DOC) under the drained conditions. Seasonal peak concentrations of Fe and DOC have since remained at these higher levels. Rewetting produced a selective enrichment of the 〉5000 to 〈90 000 apparent molecular weight (AMW) material and this fraction was found to yield peak Fe concentrations. Two additional peaks of DOC were also found in the experimental wetland (not present in the control wetland), of 〉90 000 to 〈200 000 AMW and 〉200 000 AMW material. The AMW spectrum of DOC in the experimental wetland changed with season, and the 〉90 000 to 〈200 000 AMW fraction could only be seen in spring, representing a transient pool of carbon that is rapidly transformed in or transported from the wetland. These findings suggest that rewetting of peatland following drought (e.g. due to climate change) has the potential to reduce water quality. Moreover, recent interest in restoration (rewetting) of drained peatlands (Wheeler & Shaw 1995) could create an additional source of DOC rich water.

Notes: Abstract. The hierarchial concept of land use planning becomes less relevant in a society with continuous interactions between stakeholders, researchers, planners and politicians. In this context, land use negotiation rather than land use planning appears to be the most appropriate concept. In the negotiation process, good quality data about the land is important as land properties are, obviously, key elements to be considered. Case studies at farm and regional level have been analysed to explore answers to a number of questions. How can soil data be presented most effectively? What are the research needs? How can the large existing body of data be mobilized most effectively? Studies on regional land use in Costa Rica used methods in a logical sequence including projections, explorations and predictions of land use patterns. The work involved upscaling of data, obtained at farm level, to the regional level. Work at farm level focussed on prototyping procedures in which farming systems were ‘designed’ by close interaction between farmers and scientists, including applications of precision agriculture. Soil data demands were analysed, emphasizing the effects of using data with different degrees of detail together with the application of pedotransfer functions which effectively transform existing data into parameters that are difficult or expensive to measure directly. This not only facilitated interactions with stakeholders but also with colleague scientists in interdisciplinary teams. In addition, use of Geographical Information Systems allowed visual presentations of alternative geographical land use patterns that were associated with various scenarios, thereby facilitating the interaction processes. A plea is made to increase interaction of stakeholders and researchers by considering research programmes as vehicles for joint learning.

Notes: Abstract. Topsoil (0–15 cm) bulk density, aggregate stability, soil dispersibility, water retention and infiltration were measured between 1989 and 1996 on an Alfisol under rehabilitation in southwestern Nigeria. The planted leguminous species were Pueraria phaseoloides, Senna siamea, Leucaena leucocephala, Acacia leptocarpa and A. auriculiformis. Also, plots with natural fallow and maize/cassava intercropping were included. Level (minimum) and mound tillage with hoes was adopted for the cultivated areas under study after 4 and 6 year fallow periods. Under fallow, the soil bulk density decreased from1.56 to 1.11 t m73.The continuously cropped treatment (level tillage) had significantly higher bulk density than the fallowed subplots after 6 years. Mean soil penetrometer resistance ranged from 75 to 157 kPa for fallowed plots and from 192 to 295 kPa for the continuously cropped (level tillage) subplot. Surface soilwater contentswere similar for all the treatments during the soil strength measurements. Although soil aggregates were generally of low stability and not well formed, they were improved by fallowing.Soil structural improvement by planted fallows was similar to that by natural fallow, but the trees were more promising for long-term fallow (〉6 years) than the herbaceous P. phaseoloides. However, the improvement in soil structure after 4 or 6 year fallow could not be maintained in subsequent cropping. Furthermore, the significant improvement in soil bulk density caused by A. auriculiformis and natural fallow was more rapidly lost on the cultivated subplots compared with other fallow treatments. Thus, soil structure recovery under a fallow does not imply a sustained improvement when stress is applied to this soil. Post-fallow soil management options such as residue incorporation and tillage to ameliorate compaction or soil strength will be necessary to enhance the improvements by fallow species.

Notes: Abstract. Restoration of landfill sites to a vegetated after-use is severely compromised if soil-forming materials (SFMs) have to be used as substitute growing media for the restoration cap, owing partly to their poorly-developed structure. The effects of crushed brick material (brick), composted green-waste organic matter (OM) and potassium chloride salt (KCl) in a clay SFM were assessed at the Brogborough Landfill Site (Shank Group plc) in the county of Bedfordshire, UK. Soil structure was characterized three times in a two-year experimental period through measuring drainage water release and aggregate stability and size distribution. Crushed brick and composted OM at 100 t ha−1 improved the ability of the clay to release water by drainage. In addition, the composted OM was associated with an increase in the size of stable aggregates, whereas the brick amendment reduced the overall aggregate stability. The KCl amendment had no consistent effect. Some beneficial structural improvements were thus associated with the brick and OM amendments, although these were rarely significant at the 5% level and the effects declined over time in the absence of vegetation and re-application. Nevertheless, incorporation of crushed brick and organic amendments may offer a potential structure-improving option in clay SFMs prior to vegetation establishment.

Notes: Abstract. We examined the effect on soil nutrient status and sustainability of water percolation through an irrigated paddy field in Japan, to the depth of drainage (40 cm). The difference between amounts of nutrients leached by percolation and those supplied by irrigation indicated that 25–130 kg ha−1 Ca, 8–24 kg ha−1 Mg, from −1 to 9 kg ha−1 K, and 8–17 kg ha−1 Fe, respectively, were lost each year from the 0–40 cm soil layer during rice cultivation, when the supply from fertilization and rainfall and the loss in grain harvest were not accounted for. When the supply of K from rainfall and the loss in grain harvest were taken into account, a total K loss of about 10 kg ha−1 was estimated. The electrical neutrality of inorganic ions in the percolating water was always maintained. From these results we estimate that the amounts of exchangeable Ca and Mg in the soil to a depth of 40 cm would decrease by 50% within 50–260 and 30–100 years, respectively, if similar management were continued without fertilization. The total amount of carbon dioxide (ΣCO2) leached in percolating water during the period of rice cultivation was 120–325 kg C ha−1, which corresponded to 0.47–0.94% of the soil organic carbon to 40 cm depth.

Notes: Abstract. Use of high biomass crops such as the willow Salix viminalis to extract metals for soil remediation has been proposed as an alternative to the low biomass-producing hyperaccumulating plants. High yields compensate for the moderate heavy-metal concentrations in the shoots of such species. We report the first long-term trials using Salix viminalis to extract heavy metals from two contaminated soils, one calcareous (5 years) and one acidic (2 years). Total metals extracted by the plants were 170 g Cd ha−1 and 13.4 kg Zn ha−1 from the calcareous soil after 5 years, and 47 g Cd ha−1 and 14.5 kg Zn ha−1 from the acidic soil after 2 years; in the first year outputs were negligible. After 2 years, Salix had performed better on the acidic soil because of larger biomass production and higher metal concentrations in shoots. Addition of elemental sulphur to the soil did not yield any additional benefit in the long term, but application of an Fe chelate improved the biomass production. Cd and Zn concentrations were significantly higher in leaves than stems, highlighting the necessity to collect leaves as well as shoots. On both soils, concentration in shoots decreased with time, indicating a decrease in extraction efficiency.

Notes: Abstract. This study was undertaken to test the hypothesis that an improved system of catchment management in combination with appropriate cropping practices can sustain increased crop production and improve soil quality of Vertisols, compared with prevailing traditional farming practices. Initiated in 1976, the improved system consisted of integrated land management to conserve soil and water, with excess rainwater being removed in a controlled manner. This was combined with improved crop rotation (legume based) and integrated nutrient management. In the traditional system, sorghum or chickpea was grown in the post-rainy season with organic fertilizers, and in the rainy season the field was maintained as a cultivated fallow. The average grain yield of the improved system over 24 years was 4.7 t ha−1 yr−1, nearly a five-fold increase over the traditional system (about 1 t ha−1 yr−1). There was also evidence of increased organic C, total N and P, available N, P and K, microbial biomass C and N in the soil of the improved system. A positive relationship between soil available P and soil organic C suggested that application of P to Vertisols increased carbon sequestration by 7.4 t C ha−1 and, in turn, the productivity of the legume-based system, thus ultimately enhancing soil quality.

Notes: Abstract. Soil organic matter (SOM) is considered to be key to sustainability of agriculture in the tropics. In southern Brazil, no-tillage has been adopted widely to control soil erosion, but its impact on the dynamics of SOM is not well established. We measured soil carbon (C) and δ13C in two crop rotations, one of which contained C4 maize (Zea mays L.), after 21 years of contrasting tillage (conventional tillage versus no-tillage). Adjacent sites that reflected historic land-uses were also sampled. In the tillage experiment there was no effect of tillage on the total amount of C in the 0–40 cm profile (even when contrasting bulk density was accounted for), and the concentration of C differed only in the 0–5 cm and 5–10 cm layers. However, the occasional input of C4 material in the maize rotation resulted in a significant effect of rotation on δ13C (P 〈0.001). Using 13C as a tracer for the SOM formed since the start of the experiment, we estimated the abundance of ‘recent’ and ‘old’ C within each depth interval. We found the main effect of tillage was to increase the medium-term turnover of SOM, particularly in the subsoil (i.e. below 20 cm depth). Compared with no-tillage, there was almost five times more recent C in the subsoil, and 20% more recent C in the 0–40 cm profile as a whole.

Notes: Abstract. Changes in particulate organic carbon (POC) relative to total organic carbon (TOC) were measured in soils from five agronomic trial sites in New South Wales, Australia. These sites covered a wide range of different land use and management practices. POC made up 42–74% of TOC and tended to be greater under pasture and more conservative management than traditional cropping regimes. It was the form of organic carbon preferentially lost when soils under long-term pasture were brought under cultivation. It was also the dominant form of organic carbon accumulating under more conservative management practices (direct drilling, stubble retained and organic farming). Across all sites, changes in POC accounted for 81.2% (range 69–94%) of the changes in total organic carbon caused by differences in land use and management. Significant differences were found between pasture and cropped soils in the carbon content in the 〈53 μm fraction, particularly for hardsetting soils. However, even with these, POC was a more sensitive indicator of change caused by land use and management practices than TOC. The current method for measuring POC involves dispersion using sodium hexametaphosphate. The dispersing agent was found to extract 4–19 % of the TOC, leading to a significant under-estimation of POC.

Notes: Abstract. An estimate of organic carbon stored in French soils to a depth of 30 cm was made using data from geo-referenced databases. We produced statistics on carbon stocks in soils according to land use, different land uses and soil type. Then, using a combination of maps of soil and land use we were able to estimate regional and national carbon stocks. This soil carbon map of France allowed us to identify the main controlling factors of the carbon distribution: land use, soil type in some cases, clay content, and elevation. Carbon stocks in French soils were found to be about 3.1 Pg (1015g).

Notes: Abstract. The problem of soil erosion is particularly evident in New Zealand, given the combination of coarse-textured soils, steep relief, high rainfall, and intensification of agriculture. A study was undertaken to assess the effects of land use change on soil erosion and sediment transport for the Ngongotaha catchment in New Zealand's North Island, using a GIS based decision support and modelling system. Model simulations considered the effect of increased catchment area under deer farming and forestry on the amount of sediment delivered to the catchment outlet, averaged over a period of six years. The simulations predicted that sediment loss from land under deer farming was considerably greater than from land under other livestock or forestry. Further model simulations testing best management practices demonstrated that sediment yield could be halved if deer farming was restricted to slopes under 20%.

Notes: Abstract. Measures to reduce ammonia (NH3) emissions by incorporating livestock manures into the soil may increase the potential for nitrate (NO3-) leaching. The Manure Evaluation Routine (MANNER) model estimates the amount of N available to crops following livestock manure applications after calculating losses due to NH3 volatilization and NO3- leaching. The main objective of this study was to use the MANNER model to quantify the impact on NO3- leaching of introducing measures to reduce NH3 emissions, following application of livestock manures. The data produced were also used to make preliminary estimates of the likely effect of selected NH3 abatement techniques on the potential for nitrous oxide (N2O) emissions. At typical UK rates of application, the potential for increased NO3- leaching following either injection of slurry or rapid incorporation of solid manures was greatest for broiler/turkey manure (22–58 kg N ha–1) and least for straw-based cattle manure (6–10 kg N ha–1). The results suggest that in order to avoid substantially increasing the potential for NO3- leaching as a consequence of NH3 abatement, livestock manures should not be applied by low NH3 emission techniques prior to autumn-sown crops in the UK. Instead, low-emission applications should be made from October onwards to grassland and where possible, late autumn-sown combinable crops or to arable land which will be planted in the spring. However, in several areas of England and Wales there is currently insufficient land planted to spring crops on which to incorporate the livestock manures produced in those areas.

Notes: Abstract. A survey of manure management practice was undertaken in 1996, by postal questionnaire submitted to a stratified sample of egg and broiler producers in England and Wales. Out of a target of 500 laying hen and 500 broiler (chickens produced for meat) production units in the survey sample, 356 (36%) returned questionnaires. The survey provided information on amount and type of manure production, manure storage and land application strategies (timing, techniques and awareness of nutrient content). Within the survey, no attempt was made to differentiate between organic and conventional production systems. About 45% of manure production was estimated to come from layer holdings, 55% from broiler litter. It was estimated that 70% of the national manure production is litter-based and about 30% are droppings collected without litter. Sawdust/shavings are the most popular bedding material, with an average final depth of 100 mm for broilers and 140 mm on litter-based layer units. Commonly, storage is available within housing for at least the length of the cropping cycle (6 weeks in broiler production, or 12 months in deep pit laying houses), around 60% of poultry manure is stored for a period following removal from the house, most commonly for 3-6 months. Overall, autumn was the peak period for manure spreading, with over 40% of laying hen manure and 50% of broiler manure applied at that time. On grassland, spreading was reasonably evenly distributed throughout the year but autumn application was favoured for arable crops, especially before the establishment of cereals and root crops, overall, almost 50% of layer and broiler manure was applied in the autumn. In the survey, up to 10% of manures were claimed to be incorporated within a day of application and about 60% within a week of application, presumably because of concern about odour nuisance. Around 25% of poultry manure was applied by contractors. A high proportion of farmers (c. 40% with layers, c. 60% with broilers) exported manures from their holdings, the proportion removed amounting to almost 90% on these farms. Although evidence elsewhere indicates that farmers make little allowance for manures in planning crop fertilizer inputs, the survey responses suggested that farmers do make an effort to allow for manures but that their confidence in the advice available to them is lacking, or they may have other technical reasons for not taking advantage of the manurial value. Information provided by the survey is of significant importance to policy makers (e.g. for the construction of environmental emissions inventories), researchers, consultants and farmers.

Notes: Abstract. The phosphorus (P) sorption and desorption dynamics of eleven major agricultural grassland soil types in Ireland were examined using laboratory techniques, so that soils vulnerable to P loss might be identified. Desorption of P from soil using the iron-oxide paper strip test (Pfeo), water extractable P (Pw) and calcium chloride extractable P (Pcacl2) depended on soil P status in all soils. However, soil types with high organic matter levels (OM), namely peat soils (%OM 〉30), had lower Pfeo and Pw but higher Pcacl2 values compared to mineral soils at similar soil test P levels. Phosphorus sorption capacity remaining (PSCr) was measured using a single addition of P to soils and used to calculate total P sorption capacities (PSCt) and degree of P saturation (DPS). Phosphorus sorption capacities correlated negatively with % OM in soils indicating that OM may inhibit P sorption from solution to soil. High organic matter soils exhibited low P sorption capacities and poor P reserves (total P, oxalate extractable P) compared to mineral soils. Low P sorption capacities (PSCt) in peat soils were attributed to OM, which blocked or eliminated sorption sites with organic acids, therefore, P remained in the soil solution phase (Pcacl2). In this work, peat and high organic matter soils exhibited P sorption and desorption characteristics which suggest that these soils may not be suitable for heavy applications of manure or fertilizer P owing to their low capacities for P sorption and storage.

Notes: Abstract. Leaching of faecal coliforms to rivers, lakes and groundwater following the spreading of animal slurry on land is of environmental and public health concern. A two-stage approach was adopted to modelling the transport processes by which Escherichia coli passes through the soil to receiving waters via field drains. First, parameter values were selected for the dual-porosity contaminant transport model macro to simulate through-soil flows, sorption and die-off of E. coli. These simulations reproduced experimental measurements showing rapid flows of the microorganisms to field drains after slurry spreading, which could be explained in terms of macropore flow in which trapping of colloids such as E. coli does not take place. Second, a series of predictive simulations was carried out to test the influence of soil and weather conditions on E. coli losses. These showed that losses are strongly influenced by soil wetness conditions at the time of spreading, and to a lesser degree by rainfall occurring soon after spreading. Selection of spreading ‘workdays’ with particular weather and soil wetness conditions is beneficial, which indicates opportunities for substantial reductions in the environmental risks of water pollution by E. coli and other faecal microorganisms.

Notes: Abstract. The purpose of the study was to determine the soil organic carbon (SOC) stock for Flanders, Belgium and to evaluate various methods for assessing SOC stock. The assessment methods first determined the SOC density (C mass per unit area) for pedons in a database of soil properties, and then spatially distributed the SOC density to soil and soil/land use categories on a map. The results showed that the pedon SOC density is influenced by drainage class, texture and land use/land cover. The SOC density estimation method significantly influences results and leads to differences of up to 6% in total estimated SOC stock for Flanders. Use of various spatial distributing methods creates differences of up to 2% in total estimated SOC stock. The largest difference in SOC stock estimate between any combination of assessment methods was 7% (125.6 Tg vs 134.9 Tg). These findings emphasize the importance of complete spatial soil databases of high quality that reduce uncertainty of estimates for use in research examining the role of soils in the C cycle. The results indicate that the need for these databases is greater than the need to standardize methods to determine the spatial distribution of SOC. A map of the distribution of SOC density shows that in Flanders a large proportion of SOC is stored in sandy soils in the north of the territory.

Notes: Abstract. The Bocage in the western part of Europe is an ancient rural landscape characterized by a network of hedgerows. The system studied here consists of hedges growing on earth and stone banks, which are found in the Armorican Massif (western France). Seven sites were analysed, which represented a large, but not complete, set of situations. We investigated the influence of hedges parallel to contour lines on soil characteristics, soil profile morphology and carbon storage at the hillslope scale. The analysis is based on a morphological description of the soil catena from the top of the hill to downslope of the hedge, and on measurements of bulk density and organic carbon in different soil profiles on the slopes. The results show that thickness of the organic horizon increases slowly from the top of the hill as far as the hedge, whereas under the hedge the bulk density is low and the soil organic carbon (SOC) storage large. Two effects of the hedges on SOC storage are apparent, namely, a local effect under the hedge, due to tree activity, and an anti-erosive effect at the hillslope scale. A rough approximation based on these data assessed the fraction of SOC storage attributed to the hedge network of between 13 and 38% of the total carbon stock.

Notes: Abstract. Muddy floods due to runoff are a widespread problem on the South Downs of southern England and are associated with increased growing of autumn-sown cereals over the last two decades. The 10.6 km2 Sompting catchment has been monitored over the 12-year period 1990/91–2001/02. A housing estate at the lower end of the catchment that was frequently inundated by muddy floods in the late 1980s and early 1990s has not been flooded since the winter of 1993/94, even during the heavy rainfall events of October and November 2000. This is a result of the ameliorative measures put in place in the early 1990s, primarily the reversion of some winter cereal fields to permanent grassland (set-aside). Other land management changes helped, for example, some parts of the catchment were put down to short-term grass leys and small dams were constructed to impound runoff. Flooding of the housing estate occurred when more than 30% of the catchment was covered by eroded fields, which contributed runoff to the valley floors leading down to the housing estate. The length of continuous down-valley flow was greater in the early 1990s compared with later years. The introduction of grassland reduced the risk of flooding not only by reducing the area contributing to runoff, but also by stopping valley floor flows linking up. Such measures to alleviate runoff, erosion and flooding fit well with policies proposed in the recent report by the UK Policy Commission on the Future of Farming and Food.

Notes: Abstract. Weakly weathered clay bedrock and samples of A horizon of a developed Biancana soil were incubated with compost or green manure in the presence of two physical forms of gypsum: one mined and ground and the other from flue-gas desulphurization (FGDG). The gypsum efficiency was evaluated in combination with two organic polymers: polyvinyl alcohol (PVA) and polyacrylamide. Compost and green manure increased permeability only in the presence of gypsum. The FGDG was more effective than the mined gypsum, alone or in combination with PVA.

Notes: Abstract. In the semiarid regions of sub-Saharan Africa, fertilizer recovery and nutrient release from organic sources are often moisture limited. Moreover, in these regions runoff brings about large nutrient losses from fertilizer or organic inputs. This study was conducted in the north sudanian climate zone of Burkina Faso (annual rainfall 800 mm, PET 2000 mm yr−1). We assessed the combined and interactive effects of two types of permeable barriers (stone rows and grass strips of Andropogon gayanus Kunth cv. Bisquamulatus (Hochst.) Hack.) and organic or mineral sources of nitrogen on erosion control and sorghum yield. The field experiment (Ferric Lixisol, 1.5% slope) was carried out during three rainy seasons and consisted of 2 replications of 9 treatments, in which the barriers were put along contours and combined with compost, manure and fertilizer nitrogen (N). Compared with the control plots, the average reduction in runoff was 59% in plots with barriers alone, but reached 67% in plots with barriers + mineral N and 84% in plots with barriers + organic N. On average, stone rows reduced soil erosion more than grass strips (66% versus 51%). Stone rows or grass strips without N input did not induce a significant increase of sorghum production. Supplying compost or manure in combination with stone rows or grass strips increased sorghum grain yield by about 142%, compared with a 65% increase due to mineral fertilizers. The sorghum grain yields at 1 m upslope from the grass strips were less than those 17 m from the grass strips. As stones do not compete with plants, the opposite trend was observed with stone rows. We conclude that for these nutrient depleted soils, permeable barriers improve nutrient use efficiency and therefore crop production. However, grass strips must be managed to alleviate shade and other negative effects of the bunds on adjacent crops.

Notes: Abstract. Nitrogen (N), phosphorus (P) and potassium (K) budgets were calculated for nine organic farms in the UK. The farms were situated on sandy loams, silty clay loams and silty loams over chalk with stockless farming systems and cattle, pig and poultry enterprises with a significant proportion of arable cropping. A soil surface nutrient budget was calculated for the target rotation on each farm using information about field management and measurements of the soil, crops and manure. Losses of N through leaching and volatilization were calculated independently using the nitcat and manner models. Nutrient budgets for seven of the farm rotations showed an N surplus, six a P surplus and three a K surplus. The ratio of N inputs supplied in the form of biological fixation : manure : atmospheric deposition was approximately 2 : 2 : 1 for stocked systems and 2 : 0 : 1 for stockless systems. Phosphorus surpluses resulted from supplementary P fertilizer (rock phosphate) and additional feed for non-ruminant livestock. The stockless system without P fertilizer resulted in a large P deficit and stocked systems, which relied on recycling manure alone, a small P deficit. Only rotations with large returns of manure or imported feed showed a K surplus or a balanced K budget.

Notes: Abstract. Phytoextraction is the remediation of heavy metal contaminated soils using plants that take up metals. Hyperaccumulating plants such as Thlaspi caerulescens are often studied for their possible use for decontamination of Cd and Zn rich soils, but few field trials have been reported, although they are necessary to validate the results of hydroponic and pot studies. This article reports field data for T. caerulescens grown on a calcareous and an acidic soil, both contaminated 20 years ago by either atmospheric depositions or septic-tank wastes. Accelerated cropping using transplants grown three times in eight months was compared to Thlaspi sown twice during the same period. Both were followed by one crop of sown Thlaspi. High Cd and Zn concentrations in the plant shoots compensated for the low biomass production. Annual metal exports with transplanted Thlaspi were 130 g Cd ha−1 and 3.7 kg Zn ha−1 on the calcareous soil and 540 g Cd ha−1 and 20 kg Zn ha−1 on the acidic soil. We concluded that within the framework of the Swiss legislation, remediation of Cd-contaminated soils could be achieved within less than 10 years with one crop of Thlaspi per year, but differences in soil properties could affect the rate of phytoextraction significantly. Total Zn content in both soils was too high to be remediated by T. caerulescens in a realistic time span. Thlaspi did not decrease the NaNO3-extractable fraction of Cd or Zn in either of the soils.

Notes: Abstract. We compared the effects of conventional and organic arable farming on soil organic matter (SOM) content, soil structure, aggregate stability and C and N mineralization, which are considered important factors in defining sustainable land management. Within one soil series, three different farming systems were selected, including a conventional and an organic arable system and permanent pasture without tillage. The old pasture represents optimal conditions in terms of soil structure and organic matter inputs and is characterized by high earthworm activity. More than 70 years of different management has caused significant differences in soil properties. SOM content, mineralization, earthworm activity and water-stable aggregation decreased as a result of tillage and arable cropping when compared with pasture, but were significantly greater under organic farming than under conventional farming. Total SOM contents between 0 and 20 cm depth amounted to 15, 24 and 46 g kg−1 for the conventional arable, organic arable and permanent pasture fields, respectively. Although less sensitive to slaking than the conventionally managed field, the soil under organic farming was susceptible to compaction when high pressures were exerted on the soil under wet conditions. The beneficial effects of organic farming are generally associated with soil biochemical properties, but soil physical aspects should also be considered. Depending on soil type and climate, organic farmers need to be careful not to destroy the soil structure, so that they can enjoy maximum advantage from their organic farming systems.

Notes: Abstract. Article 3.4 of the Kyoto Protocol allows carbon emissions to be offset by demonstrable removal of carbon from the atmosphere by improved management of agricultural soils. To make use of this possibility, a good estimate of soil organic carbon (SOC) stocks and baseline emissions (in 1990) are crucial factors. Over 210 000 topsoil (0–24 cm) measurements have been made in Belgian cropland in the period 1989–1999, which are available for seven different agro-pedological regions and for three periods (1989–91, 1992–95, 1996–99). We used this extensive SOC data set to estimate SOC stocks and fluxes in Belgian cropland. The measurements of SOC were extrapolated to 1 m depth using an exponential SOC depth distribution model, based on another large data set of over 5184 fully described soil profiles on Belgian cropland made during the National Soil Survey. The SOC data were combined with cropland area figures to calculate SOC stocks to 1 m depth. The 1990 baseline SOC flux of Belgian cropland was then obtained using two different calculation methods, which each yielded similar results and showed that SOC stocks were decreasing in the 1990s at a mean rate of 608 kton OC yr−1. Consequently, a large part of the Belgian cropland acted as a net source of CO2 emissions during the period 1989–1999.

Notes: Abstract. Less Intensive Farming and Environment (LIFE) management is a form of integrated farming which aims to meet farming's economic and environmental requirements. We used a farm-scale LIFE demonstration to measure nitrogen (N) leaching losses over a 6 year period (1995–2001) using ceramic suction cups and a meteorological model to give estimates of drainage volumes. Losses from the system averaged 49 kg N ha−1, with an average drainage nitrate concentration of 15.5 mg N L−1. Rainfall and its distribution strongly influenced the loss, and drainage N concentration only fell below the nominal target of 11.3 mg N L−1 (the EU limit for potable water) in the two wettest seasons. Crop type did not have a significant effect on either postharvest mineral N (PHMN) in soil or the leaching loss in the subsequent winter. However PHMN and overwinter N leaching declined with increasing crop yield. Overwinter crop N uptake increased with early sowing: leaching loss was only 5 kg N ha−1 under grass sown in early September. Measurements of PHMN, crop sowing date and drainage data were used to construct simple equations to predict average drainage N concentration under various scenarios. The large N loss from our site is partially attributable to soil type (shallow over limestone), indeed on similar soil the loss from a conventional farm nearby was greater. The LIFE practices of postharvest harrowing and late cereal sowing will minimize the need for agrochemical use but they stimulate mineralization and reduce plant N uptake in autumn, leaving more N at risk to leaching. Some assessment of all environmental impacts is needed if the benefits of integrated practices such as those used in LIFE are to be quantified.

Notes: Abstract. The concept and the effects of a multi-purpose grassed waterway (GWW) were investigated over an eight year period. A GWW, half of it seeded, the remainder left to natural succession, and an intensive soil consevation system in the fields nearby were established in an agricultural watershed (13.7 ha). This combination minimized the maintenance in the GWW without sward damaging sedimentation. In consequence the GWW, as well as providing safe drainage for surface runoff, also served additional ecological roles. During the experiment it reduced runoff and sediment delivery from the watershed by 39% and 82%, respectively. Moreover it improved biodiversity on the research farm and acted as a refuge for beneficial organisms. Soil mineral nitrogen content decreased by 84% after the installation of the GWW, indicating that although infiltration into the GWW was rapid, the risk of groundwater contamination from leached nitrate was diminished. The agricultural assets and drawbacks of establishing GWWs were also studied. We showed that the economic returns were more likely to be improved than reduced. Creating the GWW by natural succession had some advantages compared to seeding with grass.

Notes: Abstract. The accuracy of a ThetaProbe (Delta-T Devices Ltd, UK) to obtain repeated measures of soil water content in pot plants was tested. This alternative to balance determinations led to a large underestimation of water content, varying from 12.2 to 21.8% of the total water content, depending on soil type.

Notes: Abstract. Field peas (Pisum sativum L.) were grown in sequence with winter wheat (Triticum aestivum L.) or spring barley (Hordeum vulgare L.) in large outdoor lysimeters. The pea crop was harvested either in a green immature state or at physiological maturity and residues returned to the lysimeters after pea harvest. After harvest of the pea crop in 1993, pea crop residues (pods and straw) were replaced with corresponding amounts of 15N-labelled pea residues grown in an adjacent field plot. Reference lysimeters grew sequences of cereals (spring barley/spring barley and spring barley/winter wheat) with the straw removed. Leaching and crop offtake of 15N and total N were measured for the following two years. These treatments were tested on two soils: a coarse sand and a sandy loam. Nitrate concentrations were greatest in percolate from lysimeters with immature peas. Peas harvested at maturity also raised the nitrate concentrations above those recorded for continuous cereal growing. The cumulative nitrate loss was 9–12 g NO3-N m–2 after immature peas and 5–7 g NO3-N m–2 after mature peas. Autumn sown winter wheat did not significantly reduce leaching losses after field peas compared with spring sown barley. 15N derived from above-ground pea residues accounted for 18–25% of the total nitrate leaching losses after immature peas and 12–17% after mature peas. When compared with leaching losses from the cereals, the extra leaching loss of N from roots and rhizodeposits of mature peas were estimated to be similar to losses of 15N from the above-ground pea residues. Only winter wheat yield on the coarse sand was increased by a previous crop of peas compared to wheat following barley. Differences between barley grown after peas and after barley were not statistically significant. 15N lost by leaching in the first winter after incorporation accounted for 11–19% of 15N applied in immature pea residues and 10–15% of 15N in mature residues. Another 2–5% were lost in the second winter. The 15N recovery in the two crops succeeding the peas was 3–6% in the first crop and 1–3% in the second crop. The winter wheat did not significantly improve the utilization of 15N from the pea residues compared with spring barley.

Notes: Abstract. In view of the increasing wheel loads of agricultural vehicles, the question arises as to whether soil can recover from the mechanical impact of traffic. The damage to soil quality depends also on the soils resilience. This paper presents a new approach to monitoring vertical soil movement in situ. We assessed the effects of trafficking the soil with excavators and sugarbeet harvesters by monitoring surface and subsurface levels. The caterpillar loads of the crawlers varied from 13 to 19 t, the wheel loads of the sugarbeet harvesters from 6 to 11 t. Classical geodetic levelling was used to record soil surface movement and a hydrostatic settlement meter measured deformation at three depths within the soil profile. The results of three field tests prove the importance of wheel load and soil moisture for soil compaction. Trafficking very dry soil with an excavator did not cause significant plastic deformation in 30 cm depth. Conversely, trafficking wet soil with a sugarbeet harvester led to soil sinkage of 1 to 2 cm even at 60 cm depth. Increased wheel load in subsequent passes led to greater subsidence than during the first pass. Settlement decreased from the soil surface to deeper layers, but it remained throughout the monitoring period of up to 12 days. No soil recovery from plastic deformation was recorded within this time. The measuring system has the potential for long-term monitoring of the mechanical recovery of the soil. Additionally, it can contribute to the validation of mechanical impact models, which are based on soil stresses.

Notes: Abstract. Two case studies on Danish sandy loams investigated the long-term effects of fertilization and crop rotation. Case Study 1 compared a diversely cropped organically farmed soil (DFG(1)) with a conventionally farmed soil predominantly growing annual crops (DFA), both receiving animal manure. In Case Study 2, a diversely cropped organically managed soil (DFG(2)) receiving animal manure was compared with an almost exclusively cereal cropped conventionally farmed soil receiving no animal manure (CCC). A multi-level experimental strategy was followed to compare integrating field methods with specialized laboratory methods. Ease of tillage was described in the field and characterized using a drop shatter field test and by measuring aggregate tensile strength. Fitness as a seedbed was characterised visually in the field and from the drop shatter test. Impedance to seedling emergence and root penetration was evaluated by measuring bulk soil shear strength. For Case Study 1, soil tilth was better for the DFA soil than for the DFG(1) soil (i.e. lower soil strength and higher ease of fragmentation and friability index for DFA). However, a crumbly structure and a moderate bulk density suggested that the DFG(1) soil was also a favourable medium for plant growth. For Case Study 2, the CCC soil had a lower organic matter content, higher bulk density, higher soil strength, and lower ease of fragmentation in comparison with the DFG(2) soil.

Notes: Abstract. A two year field study was conducted to evaluate the effects of straw management and tillage on the soil profile (1.5m) water storage, nature of the moisture profile, infiltration and sorptivity as influenced by rainfall, evaporativity (E0) and soil texture. The straw mulch treatment stored more moisture under low E0 rainy conditions in three coarse to medium textured soils. Straw incorporation treatment was better under low E0 rain free conditions, as well as under high E0 rainy conditions in the two coarser textured soils. In the coarsest textured soil, tillage and straw mulching were not effective in maintaining greater soil water storage under high E0 because of the very open nature of the soil. The soil moisture profiles showed a sharper increase in water content below the tilled layer in the tillage and straw- incorporation treatments than the untreated and straw mulch treatments. Tillage and straw incorporation treatments increased the sorptivity of the soil compared with untreated and straw mulch treatments respectively. The results of this study suggest that when selecting a suitable soil water conservation practice to increase water storage in the soil profile, information on soil texture and weather (rain and evaporativity) must be considered.

Notes: Abstract. Phosphorus (P) use in UK agriculture is reviewed and a P balance sheet presented. The productive grassland and arable area has accumulated an average P surplus of c. 1000 kg ha–1 over the last 65 years. Over the period 1935–1970, the annual P surplus more than doubled due to an increase in animal numbers and associated requirements for inorganic fertilizers and livestock feeds. Since 1970, surplus P has declined by c. 40% as crop yields and P offtake have continued to increase while fertilizer and manure P inputs have remained relatively constant. In 1993, P use efficiency (P imports/P exports) in UK agriculture was estimated at 25% leading to an average annual surplus of 15 kg P ha–1 yr–1, although the latter has since decreased slightly due to reduced fertilizer use. Intensification and specialization of agriculture has also increased the range in P surpluses that are likely between livestock and arable dominated systems. The largest P surpluses occur in the relatively limited areas of arable soils which receive manure from intensive pig and poultry units, whilst farms without manure inputs generate only small surpluses, or are in balance. The cumulative P surplus has led to a build-up of soil total and easily-exchangeable P, especially in areas receiving both fertilizers and manures. Fundamental differences in P use efficiency, surplus P accumulation and the potential for P loss to water, exist between arable and grassland farms and it is important to separate these, due to the marked regionalization of UK agriculture. More judicial use of feeds and fertilizers is required to further reduce the P surplus and minimize the long-term risk of water eutrophication.

Notes: Abstract. The ability of two nitrogen cycle models, of contrasting complexity, to predict N mineralization from a range of grassland soils in the UK, was evaluated. These were NCYCLE, a simple mass balance model of the N cycle in UK grasslands, and CENTURY, a more complex model simulating long-term C, N, P & S dynamics in grassland ecosystems. The models were tested using field measurements of net N mineralization from a range of grassland soils (differing in soil type, history & management practice), obtained over a 2 year period using a soil core incubation technique. This method was considered to measure the total net release of mineral N from the soil organic matter over a specified time, including N which may have been recycled several times. NCYCLE consistently under-estimated mineralization rates at all sites. By contrast, there was some correlation between CENTURY predictions of net N mineralization and field measurements. This may have reflected the different abilities of the two models to simulate N recycling. Neither model, however, was able to predict adequately the effect of cultivation and reseeding on net N mineralization.

Notes: Abstract. Nitrate leaching and soil mineral N status under grassland were measured on three contrasting soils, spanning winters 1995/96, 1996/97 and 1997/98, in Western England. The soils investigated were a freely draining silty clay loam (Rosemaund), a well drained loam (IGER 1) and a poorly drained clay loam (IGER 2). The effects of reseeding (ploughing and resowing grass) at IGER 1 and IGER 2 in autumn 1995 or 1996 were compared with undisturbed pasture. Reseeding at Rosemaund, in autumns 1995 or 1996, or spring 1996 was compared with undisturbed pasture of 3 sward ages (2, 5, 〉50 years).Nitrate-N leaching losses during the winter immediately following autumn reseeding ranged between 60 and 350 kg N ha–1 in 1995/96, depending on soil type, sward management history and rainfall. Losses were much less in the following winter when treatments were repeated (10–107 kg N ha–1).Reseeding in spring had little effect on soil mineral N content or leaching losses in the following autumn, compared with undisturbed pasture. Similarly, leaching losses from autumn reseeds in the second winter after cultivation were the same as undisturbed pasture (1-19 kg N ha–1). The effect of ploughing grassland for reseeding was relatively short-term, in contrast to the effect of repeated annual cultivation associated with arable rotations.

Notes: Abstract. Intensively managed grasslands are potentially a large source of N2O in the North Coast of Spain because of the large N input, the wet soil conditions and mild temperatures. To quantify the effect of fertilizer type and management practices carried out by farmers in this area, field N2O losses were measured over a year using the closed chamber technique. Plots received two types of fertilizer: cattle slurry (536 kg N ha–1) and calcium ammonium nitrate (140 kg N ha–1). N2O losses were less in the slurry treatment than after mineral fertilizer. This was probably due to high, short-lived peaks of N2O encountered immediately following mineral N addition. In contrast, the seasonal distribution of N2O losses from the slurry amended plot was more uniform over the year. The greater N2O losses in the mineral treatment might have been enhanced by the combined effect of mineral fertilizer and past organic residues present from previous organic amendments. Weak relationships were found between N2O emission rates and soil nitrate, soil ammonium, soil water content and temperature. Better relationships were obtained in the mineral treatment than in the slurry plots, because of the wider range in soil mineral N. Water filled pore space (WFPS) was a key factor controlling N2O emissions. In the 〉 90% WFPS range no relationships were found. The best regressions were found for the mineral treatment in the 40–65% WFPS range, 49% of the variance being explained by soil nitrate and ammonium content. In the 65–90% WFPS range, 43% of the variance was explained by nitrate only, but the inclusion of soil ammonium did not improve the model as it did in the 40–65% WFPS range. This fact indicates that nitrification is likely to be an important process involved in N2O emissions at the 40–65% WFPS.

Notes: Abstract. Boreholes have been constructed at eight sites on the Permo-Triassic Sandstone and Chalk aquifers to assess the extent of chemical and microbiological contamination emanating from unlined farm manure stores. Slurry along fracture faces in the Chalk was found on cores taken from beneath two stores. Porewaters from the Chalk sites and one of the Sandstone sites were discoloured and showed high concentrations of nitrate, ammonium and organic carbon to depths in excess of 10 m. Although Cryptosporidia and Escherichia coli O157 were found in many of the cattle slurry lagoons, neither were found in the aquifer material beneath. The self-sealing of unlined slurry stores is seen as a crucial step in minimizing leakage. A simple mass balance shows farm boreholes near to contaminant sources are at greater risk than public supply wells. Contaminant modelling shows discontinuing use of an unlined farm manure store will lead to little difference in solute concentrations over the short to medium term. Groundwater is most at risk where the water table is shallow since direct hydraulic connection between the lagoon base and the water table considerably increases the rate of vertical migration. This is of greatest significance for pathogens that are thought to be relatively short lived in the subsurface. Under the majority of situations minimal threat is posed to potable groundwater drinking supplies.

Notes: Errors in acoustic logs have a significant influence on the assessment of formations, the description of oil deposits and modelling using synthetic seismograms. The elimination of these errors is a problem that many researchers have been trying to solve for many years. We derive theoretical formulae for calculating the radial depth of investigation of acoustic logging, and analyse the relationship between the error in acoustic interval transit time and the altered zone thickness. We explain in detail how mud affects the acoustic interval transit time. We also describe the variation of altered zone thickness with time and a method for calculating the altered zone thickness. Finally, we present a set of new methods that can be directly applied to correct the disturbing influence on acoustic curves. Our results are obtained based on the fact that acoustic velocities in the altered zone show a small lateral variation. Examples are given of analysing the acoustic log data, which are collected from a BS well at three different times. This paper is significant both for selection of the acoustic logging device with proper transmitter-to-receiver distance (spacing) and improvement of the device.

Notes: We characterize the seismic response of Lake Vostok, an Antarctic subglacial lake located at nearly 4 km depth below the ice sheet. This study is relevant for the determination of the location and morphology of subglacial lakes. The characterization requires the design of a methodology based on rock physics and numerical modelling of wave propagation. The methodology involves rock-physics models of the shallow layer (firn), the ice sheet and the lake sediments, numerical simulation of synthetic seismograms, ray tracing, τ–p transforms, and AVA analysis, based on the theoretical reflection coefficients. The modelled reflection seismograms show a set of straight events (refractions through the firn and top-ice layer) and the two reflection events associated with the top and bottom of the lake. Theoretical AVA analysis of these reflections indicates that, at near offsets, the PP-wave anomaly is negative for the ice/water interface and constant for the water/sediment interface. This behaviour is shown by AVA analysis of the synthetic data set. This study shows that subglacial lakes can be identified by using seismic methods. Moreover, the methodology provides a tool for designing suitable seismic surveys.