bluuebunny/crossref_metadata_2025 huggingface dataset:
Investigation into the effect of tillage on solute movement to drains through a heavy clay soil
Authors: Brown C.D. , Marshall V.L. , Deas A. , Carter A.D. , Arnold D. , Jones R.L.
Published: August 2010

Abstract. A lysimeter experiment showed a decrease in maximum concentrations and total losses of the herbicide isoproturon leached from a heavy clay soil where the topsoil had a finer, deeper tilth than with a standard agricultural tilth. Volumes of leachate for the first flow event of the season were also smaller and leaching of bromide was slower. The isoproturon was radiolabelled so that its movement could be assessed using a novel radio‐scanning technique. Bypass flow began close to the surface as a scan at 8 cm depth showed that only 0.5% of the total soil area had an activity more than four times the nominal background level. At depths of 10–20 cm, isoproturon was preferentially retained within areas of very fine aggregates. No radioactivity was detected in the scans below 20 cm depth, suggesting little or no retention of isoproturon during transport through the subsoil to the bottom of the lysimeter. Rhodamine‐B dye injected to the base of the topsoil (approximately 20 cm depth) was also used to assess flow pathways through the subsoil. The dye spread laterally across the interface between topsoil and subsoil and then penetrated the subsoil through cracks and fissures. Even within cracks, transport of dye frequently occurred through only a very small proportion of the total crack area. The macropore flow model MACRO 4.0 was used to simulate results from the lysimeter experiment. The fourfold decrease in maximum concentrations of herbicide from the finer tilth lysimeter could be predicted by varying only a parameter describing aggregate sizes at depths of 6–24 cm, suggesting that transfer of herbicide between macropore and micropore regions was faster in the finer tilth. Differences in concentrations of bromide could be simulated only by adjusting the soil hydraulic parameters for the fine tilth to reflect a slight decrease in the predominance of bypass flow relative to matrix flow.
Effects of afforestation on ammonification and nitrification rates in former agricultural soils
Authors: Haque S.M.S. , Billett M.F. , Grayston S. , Ord B.G.
Published: August 2010

Abstract. The effects of afforestation on potential nitrification, nitrification and ammonification rates were studied at an experimental site in NE Scotland 4½ years after afforestation of former arable land. The site had been planted with three tree species (Sitka spruce, sycamore and hybrid larch) at three different planting densities, with half the plots treated with inorganic NPK fertilizer. Laboratory measurements of potential nitrification, nitrification and ammonification rates, measured using a perfusion system, were compared between the unforested control and combinations of the various treatments. Differences in soil pH and soil moisture content were also investigated.

Potential nitrification rates measured in plantation soils were significantly lower than in the unplanted control soil. Nitrification and ammonification rates were also consistently lower, although these differences were only significant in a few of the treatments. Soils planted with a normal tree density had a tendency to show higher nitrification rates compared to soils planted with a high tree density.

The results suggest that afforestation of former agricultural soils may cause changes in important parts of the soil N cycle soon after planting. At this early stage in the life of the plantation this appears to be unrelated to changes in soil pH or moisture content, even though soils beneath the trees are drier. The apparent change may be the result of differences in the soil microbial community associated with the type of organic matter substrate present in the unplanted and planted soils.
Effect of starter fertilizers on the yield and quality of lettuce grown on peaty soils
Authors: Stone D.A. , Tyler F.T. , Runham S.
Published: August 2010

Abstract. Increasing concerns for the financial and environmental impact of the use of broadcast fertilizer by the UK horticultural industry is leading to the development of alternative application techniques, which aim to reduce inputs through improved efficiency. One such technique, ‘starter’ fertilizer, was investigated with drilled and transplanted crisp lettuce (Lactuca sativa) on two fertile peaty soils. Starter fertilizers injected below the seed of the drilled crop, or as spot applications around the planting module, were tested alone and in various combinations with different rates of broadcast fertilizer. The work extended previous findings, based largely on mineral soils, and demonstrated that high yields of iceberg quality lettuce can be achieved with reduced inputs of broadcast fertilizer, and that there can be additional benefits of earlier maturity and improved quality. It is concluded that starter fertilizer can contribute to the development of environmentally beneficial farming practices whilst maintaining the productivity and competitiveness of the horticultural industry.
Relationships between land use, fertility and Andisol behaviour: examples from volcanic islands
Authors: Perret S. , Dorel M.
Published: August 2010

Abstract. Soils developed on volcanic parent materials have many intrinsic qualities favourable to cropping. However, fertility decreases dramatically when they are badly managed. A short review and case studies from Réunion and Guadeloupe highlight the special characteristics of these soils, and their response to management.

The interplay of cropping systems and physical characteristics of Andisols is first considered through the example of Pelargonium and food crop systems in Réunion. Progressive decrease in production and cropping potential shows in falling yields as well as in the overall decline of the system. The example of banana production in Guadeloupe highlights the increase in inputs needed to realise the land's potential and to maintain yields, in particular more tillage and pest treatment.

In both cases, these trends are connected to the co‐evolution of soil characteristics and cropping systems. They lead to an increase of risks with less security and less scope in the choice of cropping systems. Technical solutions in the form of erosion‐control measures, rotation and planting techniques have been developed and prove to be relevant and consistent in their benefit.
Evaluation of World Reference Base for Soil Resources and FAO Soil Map of the World using nationwide grid soil data from Denmark
Authors: Krogh L. , Greve M.H.
Published: August 2010

Abstract. Soil classification is a tool for stratifying and generalizing information on soil resources but most systems are tailored to handle only slightly disturbed soil. We tested the applicability of the legend of the FAO‐Unesco Soil Map of the World and the new World Reference Base for Soil Resources by classifying at the highest order 831 profiles from a nationwide 7 km grid survey in Denmark, where soils are developed in Quaternary glacial and marine sediments and intensively farmed. Comparison of the variability of pH and % clay +% silt of the master horizons (A, E, B, and C) within and between the major well‐drained soil groupings shows that liming, fertilizing and ploughing have produced significantly deeper A‐horizons with higher pH, lower % humus and C:N ratios on the two‐thirds of the country that is cultivated. ‘Anthropogenic’ mollic and umbric horizons are a common result but the liming causes a random final classification of these surface horizons and, hence, random allocation of the soils in both systems. It separates cultivated soils and their undisturbed equivalents, and results in considerable within‐group variation in soil texture. Grouping of cultivated and undisturbed soils, on the other hand, results in wide within‐horizon pH ranges for most groups, again compromising the advantage of making useful general statements on the basis of classification.

We propose that anthropogenic mollic and umbric horizons should be allowed in any soil group and that ‘anthric properties’ should be used to distinguish between profoundly changed cultivated soils and largely undisturbed soils, hereby constructing a two‐tier system within each highest‐order soil group. We classified the soils according to this proposal. The results show generally narrower ranges for both pH and % clay +% silt. We evaluated the within‐group homogeneity by multivariate analysis of variance of pH, % clay +% silt, % clay, % humus, C:N ratio, exchangeable cations, and CEC. The results (Wilks's Lamda) show a higher degree of group compactness compared to the original FAO and World Reference Base systems.
Changes in soil structure and hydraulic properties in regenerating rain forest
Authors: Deuchars S.A. , Townend J. , Aitkenhead M. J. , FitzPatrick E.A.
Published: August 2010

Abstract. The structure of soils in areas of rain forest cleared for pasture is often compacted due to trampling by animals. When pasture is abandoned, regeneration of forest cover may be achieved from natural seed sources nearby.However, the regeneration of soil structure is also important for local hydrology and successful establishment of some plant species. In this study we investigated changes in soil structure and hydraulic properties in a series of plots on volcanic soils in the San Luis Valley, Costa Rica. The plots were current pasture, 15‐ and 20‐year‐old regenerating forest, and primary rain forest.

Infiltration rate increased with increasing forest age and the water release characteristic reverted gradually from one with greater water retention at all matric potentials in the pasture plot towards that found in the primary forest. Compaction and low porosity were features of both the current pasture and 15‐year‐old regenerating forest in comparison to the primary forest.
Remediation of a long‐term copper‐contaminated soil using a polyacrylate polymer
Authors: de Varennes A. , Torres M.O.
Published: August 2010

Abstract. We investigated whether a polyacrylate polymer could be used to remediate a soil which had been contaminated with copper for many years. Perennial ryegrass was grown in a loamy sand containing 230 mg ammonium‐acetate‐EDTA extractable Cu kg−1 and amended with 0, 0.1 and 0.2% of polymer. Growth of perennial ryegrass was stimulated in the polymer‐amended soil, especially in the soil with 0.1% of polymer. After plant growth for 177 days, the amount of water extractable copper present in the unamended soil was 17 times that of the original soil. In the soil amended with 0.1% of polymer the level of copper after plant growth was only 0.11 times the amount present in the unamended soil. When the soil was incubated with polymer in the absence of plants, the level of water extractable copper was not reduced. The polymer seems to compete with plants for copper, and to prevent the increase of copper in soil solution brought about by root exudates.
Meeting the UK's climate change commitments: options for carbon mitigation on agricultural land
Authors: Smith P. , Powlson D.S. , Smith J.U. , Falloon P. , Coleman K.
Published: August 2010

Abstract. Under the Kyoto Protocol, the European Union is committed to an 8% reduction in CO2 emissions, compared to baseline (1990) levels, during the first commitment period (2008–2012). However, within the overall EU agreement, the UK is committed to a 12.5% reduction. In this paper, we estimate the carbon mitigation potential of various agricultural land‐management strategies (Kyoto Article 3.4) and examine the consequences of UK and European policy options on the potential for carbon mitigation.

We show that integrated agricultural land management strategies have considerable potential for carbon mitigation. Our figures suggest the following potentials (Tg yr−1) for each scenario: animal manure, 3.7; sewage sludge, 0.3; cereal straw incorporation, 1.9; no‐till farming, 3.5; agricultural extensification, 3.3; natural woodland regeneration, 3.2 and bioenergy crop production, 4.1. A realistic land‐use scenario combining a number of these individual management options has a mitigation potential of 10.4 Tg C yr−1 (equivalent to about 6.6% of 1990 UK CO2‐carbon emissions). An important resource for carbon mitigation in agriculture is the surplus arable land, but in order to fully exploit it, policies governing the use of surplus arable land would need to be changed. Of all options examined, bioenergy crops show the greatest potential. Bioenergy crop production also shows an indefinite mitigation potential compared to other options where the potential is infinite.

The UK will not attempt to meet its climate change commitments solely through changes in agricultural land‐use, but since all sources of carbon mitigation will be important in meeting these commitments, agricultural options should be taken very seriously.
The rice soils of Cambodia. I. Soil classification for agronomists using the Cambodian Agronomic Soil Classification system
Authors: White P. , Dobermann A. , Oberthür T. , Ros C.
Published: August 2010

Abstract. This paper describes a soil classification system developed for agronomists in Cambodia that has proved useful in improving soil fertility management. The classification system relies on soil characteristics that are easily identifiable in the field and have agronomic relevance. The system was used in the on‐farm trial programme of the Cambodia‐IRRI‐Australia Project (CIAP) in 1996 and 1997 to determine whether it could adequately discriminate between soil types and improve fertility management.  Using diagnostic criteria that could be identified in the field, 11 soil groups were defined and subdivided into a further 20 phases. Soil groups were defined as units of morphologically similar soils, which occurred at the same position in the landscape. Classification of soil phases within a soil group was primarily based on soil properties that had significance for crop production, this included information gained from local experience and expertise. A modified version of the Fertility Capability Classification (Sanchez et al., 1982) was added as a third level to allow a more quantitative classification in cases where soil analytical data was available, and to facilitate the transfer of agronomically important soil information from outside Cambodia.  The soil groups adequately predicted differences in grain yields of rice grown on the different soils in on‐farm trials and provided the basis for soil‐specific management recommendations. Local agronomists have welcomed the system and have incorporated it into their research and extension operations.
The rice soils of Cambodia. II. Statistical discrimination of soil properties by the Cambodian Agronomic Soil Classification system (CASC)
Authors: Oberthür T. , Dobermann A. , White P.
Published: August 2010

Abstract. A novel agronomic system of soil classification for managing rice soils in Cambodia (CASC) was developed recently. It integrates local knowledge about the soil with its conceptual and taxonomic understanding by soil scientists. Using quantitative soil survey data we evaluated the agronomic efficacy of the classification system. Although the CASC is based on simple field criteria it explained 25 to 44% of the variation in soil prop‐erties relevant for agronomic decision making. It failed, however, to differentiate soil types based on pH (6% of variances explained). Despite its simplicity it performed as well or better than the most widely used soil map in Cambodia (Crocker, 1962), and unlike this small‐scale soil map it allows classification on a field‐specific basis. The average values of soil properties were often significantly different between groups. Organic carbon, clay content and plant available magnesium and calcium contributed most to the discrimination of CASC soil groups. The predictive accuracy when allocating new samples on the basis of quantitative survey data to soil groups of the CASC was 50% to 100%, except for soil groups Kein Svay (0%) and Kampong Siem (20%). The CASC is valuable for managing Cambodian rice soils and may also be used for up‐scaling and mapping of soil information.
Increased predicted losses of phosphorus to surface waters from soils with high Olsen‐P concentrations
Authors: Jordan C. , McGuckin S.O. , Smith R.V.
Published: August 2010

Abstract. Diffuse soluble reactive P (SRP) & total P (TP) loads from over 50 major river catchments in Northern Ireland were predicted using an export coefficient modelling approach. Phosphorus export coefficients for each CORINE land cover class, derived from satellite imagery, allowed the prediction of P loads from a breakdown of the CORINE land cover classes by catchment using a GIS. This approach was validated using observed P loads calculated from flow and concentration data. Mean measured Olsen‐P concentrations in the soil A‐horizon were also determined on a catchment basis. Plots of P loads to the watercourse versus Olsen‐P concentrations in the soil showed a breakpoint around 22 mg Olsen‐ P l−1 for both SRP & TP data. Below Olsen‐P concentrations of 22 mg l−1, SRP & TP losses were essentially independent of Olsen‐P at 0.28 and 0.63 kg P ha−1 yr−1, respectively. Above Olsen‐P concentrations of 22 mg l−1, there was considerable spread in the P loss data. Nevertheless, significant upward trends in SRP and TP losses to watercourses were detected with increasing Olsen‐P at a rate of approximately 0.5 and 1.0 kg P ha−1 yr−1, for SRP and TP respectively, for each 10 mg l−1 increase in Olsen‐P.
Assessing potential production of maize using simulation models for land evaluation in Brazil
Authors: Alves H. M. R. , Nortcliff S.
Published: August 2010

Abstract. The paper highlights the advantages of modelling to simulate dynamic processes and to couple environmental data more closely with effects on crops. The CERES‐Maize crop model and the DSSAT software package were selected for the work and the region of the Triângulo Mineiro in the state of Minas Gerais was selected as the study area. The results showed that there are differences in the potential production of the Latosols of the Triângulo Mineiro and this should be taken into account when extrapolating or transferring technology for other regions within the same cerrado ecosystem of central‐west Brazil. It is essential to improve the number of points with weather data collection since, as demonstrated for Frutal, the climate of the Triângulo can determine differences in potential agricultural production as well as risk for production. The study showed that the use of crop models can improve land suitability evaluations, for land use planning, or establishing strategies for rural funding.
Modelling climatic erosivity as a factor for soil erosion in Denmark: changes and temporal trends
Authors: Leek R. , Olsen P.
Published: August 2010

Abstract. Daily measurements of precipitation and temperature at 82 locations in Denmark for periods of 10 to 43 years, were used for calculation of the impact energy and intensity of rain, climatic erosivity (hereafter called erosivity). The computed erosivity values were analysed for trends and variations in time and space. Analysis of 43 years of data from 6 locations showed a change in the annual distribution of intense (erosive) precipitation, with a tendency to bi‐modality, increasing erosivity in September, and decreasing erosivity in August. Amounts of precipitation in autumn have generally increased, but the erosive power of rain has increased even more. The geographic location of high erosivity varied considerably from year to year. Using a simple crop model, the interaction between crop cover and erosivity was investigated. This suggested that changes in climate in combination with changes in cropping and management practice have increased risk of serious erosion over the period 1954 to 1996. We recommend that present and future cropping and management practices be evaluated for risk of adverse interaction with high erosivity events.
Monitoring of water erosion on arable farms in England and Wales. 1990–94
Authors: Chambers B.J. , Garwood T.W.D.
Published: August 2010

Abstract. The incidence of soil water erosion was monitored in 12 erosion‐susceptible arable catchments (c. 80 fields) in England and Wales between 1990 and 1994. Factors associated with the initiation of erosion were recorded, and the extent of rills and gullies measured. Approximately 80% of the erosion events were on land cropped to winter cereals. In 30% of cases, the initiation of erosion was linked to valley floor features, which concentrated runoff. Poor crop cover, wheelings and tramlines were also assessed as contributory factors in 22%, 19% and 14% of cases, respectively. In c. 95% of cases rainfall events causing erosion were ≥10 mm day−1 and c. 80% were >15 mm day−1. Erosion was also associated with maximum rainfall intensities of >4 mm h−1 for c. 90% of cases and >10 mm h−1 for c. 20%. Mean net soil erosion rates were approximately 4 t ha−1 per annum (median value 0.41 t ha−1 per annum) and associated mean P losses 3.4 kg ha−1.
A laboratory investigation of the release of a conservative tracer and herbicide from topsoil aggregates under varying rainfall intensities
Authors: Heppell C.M. , Burt T.P. , Williams R.J. , Johnson A.C.
Published: August 2010

Abstract. This paper describes the results of laboratory‐based research which investigated the losses of the herbicide, isoproturon, and a non‐adsorbing solute, bromide, from topsoil aggregates under high (7 mm h−1 and low 2.7 mm h−1) intensity simulated rainfall. The structures of the micro‐ and macro‐aggregates from a clay soil of the Denchworth Series (from Wytham, Oxfordshire, UK) were observed using a scanning electron microscope, and the slaking of the topsoil aggregates was also investigated in order to provide a context for interpreting the experimental results. The topsoil at Wytham was found to have a bimodal structure with small microaggregates of 0.71 to 1 mm diameter clustered together to form larger macroaggregates of up to several centimetres diameter. Selected aggregates were air dried and then repacked in Buchner funnels to several centimetres depth in order to remove variability in the experimental results due to the effects of surface microrelief. Under saturated surface conditions high intensity simulated rainfall was less efficient at removing both non‐adsorbing and adsorbing solutes from the repacked topsoil aggregates than low intensity rainfall. The observed decrease in the concentration of isoproturon and bromide in the leachate with time could be explained by a transport non‐equilibrium effect.
Development and evaluation of a soil water evaporation model to assess the effects of soil texture, tillage and crop residue management under field conditions
Authors: Jalota S.K. , Arora V.K. , Singh O.
Published: August 2010

Abstract. A number of mathematical models to predict soil water evaporation are available in the literature which generally require complex input data. In the present study, a simple parametric model has been developed by coupling existing and newly developed equations to assess soil water evaporation and drainage under field conditions in relation to potential evaporation rate, soil texture, time and depth of tillage and crop residue management. The model has moderate input data requirements and predicts well the effects of tillage and crop residue management practices on soil water loss (evaporation+drainage) with multi‐drying and ‐wetting cycles prevailing under natural conditions. The root mean squares of deviations between observed and predicted cumulative water loss at different periods of study were 0.82, 2.04, 2.31 and 1.74 cm for untreated, residue‐mulch, tillage and residue‐incorporated treatments, respectively. Simulation analysis on cumulative evaporation and evaporation rate has shown that the evaporation reduction with different combinations of tillage and crop residue followed the order of residue‐undercut>residue‐mulch>residue‐incorporated>tillage. Thus, the magnitude of beneficial effects of crop residues and tillage on soil water evaporation reduction are associated with amount of residues, mode of residue management (mulched or incorporated in the soil) and time and depth of tillage.
Influence of municipal compost on temperature, water, nutrient status and the yield of maize in a temperate soil
Authors: Naeini S.A.R. Movahedi , Cook H.F.
Published: August 2010

Abstract. Composted domestic waste was applied either as a mulch or was incorporated into the topsoil. Mulching reduced the seasonal midday soil temperature ranges from between 14 °C and 27.5 °C to between 14 °C and 26 °C, averaging a 0.6 °C fall. However, at sub‐optimal temperatures for maize production under the temperate conditions of South East England, the difference may be critical. Compost mulch also improved soil‐water conservation in an average year, but not in a very dry year. Compost application increased soil‐available N, but increased K uptake was considered to be more important for crop yield than either N additions or the effect on retained soil water. Overall, compost applied as a surface mulch, or incorporated into medium‐textured soils in the south and east of England increased crop yield.
Strategies to encourage better use of nitrogen in animal manures
Authors: Chambers B.J. , Smith K.A. , Pain B.F.
Published: August 2010

Abstract. Research conducted in the MAFF Nitrate Programme has been used to formulate new and improved guidelines on the efficient use of manure nitrogen (N). In order to reduce nitrate leaching losses, manures containing large amounts of available N (i.e. slurries and poultry manures) should not be applied to free‐draining soils in the period from autumn to early winter. Also, for efficient nutrient utilization manure application rates should be consistent with agronomic requirements (up to 250 kg total N ha−1 yr−1). Existing farm machinery was shown to be capable of applying manures evenly to grassland and arable stubbles, but required an accurate estimate of application rate and the careful matching of spreading widths. To provide growers with detailed guidance on the fertilizer N replacement value of manures the computer‐based decision support system MANNER (MANure Nitrogen Evaluation Routine) has been developed. The much improved understanding of manure N losses and availability has been summarized in a series of ‘Managing Livestock Manures’ booklets, the MAFF Fertilizer Recommendation booklet and the Codes of Good Agricultural Practice.
MAGPIE: A modelling framework for evaluating nitrate losses at national and catchment scales
Authors: Lord E.I. , Anthony S.G.
Published: August 2010

Abstract. A national agri‐environmental database and nitrate modelling system has been developed to support the UK government's nitrate policy development. The framework, ‘MAGPIE’, consists of a database and models linked within a Geographical Information System and provides a user interface which allows detailed spatial and statistical investigation of the current state (data and model output) and the impact of changes in conditions or agricultural practice. Data on crops and livestock numbers taken from the annual agricultural census were modified in relation to land cover data derived from remote sensing, and other sources. These data and data on climate, soils and altitude were interpolated to a 1 km grid. The models of nitrate loss were adapted to work with this data set while retaining as far as possible the salient features of the more detailed models and data from which they were derived. The resulting Policy Decision Support System was found to give estimates of mean annual flow and nitrate load for agricultural catchments which matched measured data closely. The system has contributed to work on a number of policy issues both within the UK and in the UK's contribution to international policy development on pollution derived from agriculture.
Nutrient excretion by outdoor pigs: a case study of distribution, utilization and potential for environmental impact
Authors: Eriksen J. , Kristensen K.
Published: August 2010

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.
Estimating soil resilience to compaction by measuring changes in surface and subsurface levels
Authors: Tobias S. , Hennes M. , Meier E. , Schulin R.
Published: August 2010

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.
Aggregation of a soil with different cropping histories following the addition of organic materials
Authors: Watts C.W. , Whalley W.R. , Longstaff D.J. , White R.P. , Brook P.C. , Whitmore A.P.
Published: August 2010

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.
The influence of grass density on effectiveness of contour grass strips for control of soil erosion on low angle slopes
Authors: Melville N. , Morgan R.P.C.
Published: August 2010

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.
The use of soil data in natural heritage planning and management
Authors: Towers W. , Hester A. J. , Malcolm A. , Stone D. , Gray H.
Published: August 2010

Abstract. Native woodland restoration is a conservation priority within the UK and there is an increasing awareness that a long‐term strategy is required to guide this process. A GIS‐based modelling approach has been developed, which links site conditions as expressed in an integrated soil and land cover dataset with the site requirements for different woodland types. There are three important aspects to the model – the parameter weightings, the added value of the integrated dataset, and the woodland categories which are described and predicted. The initial quantitative and qualitative validation has been encouraging although more is required and planned. The results indicate that for broad strategic planning purposes, predictions of woodland potential are not improved significantly when climatic factors are incorporated. The concept that soil acts as an integrator of other environmental variables is discussed alongside the practical application of the model by a range of users.
The effect of soil texture and soil drainage on emissions of nitric oxide and nitrous oxide
Authors: Skiba U. , Ball B
Published: August 2010

Abstract. Agricultural soils are important sources of the tropospheric ozone precursor NO and the greenhouse gas N2O. Emissions are controlled primarily by parameters that vary the soil mineral N supply, temperature and soil aeration. In this field experiment, the importance of soil physical properties on emissions of NO and N2O are identified. Fluxes were measured from 13 soils which belonged to 11 different soil series, ranging from poorly drained silty clay loams to freely drained sandy loams. All soils were under the same soil management regime and crop type (winter barley) and in the same maritime climate zone. Despite this, emissions of NO and N2O ranged over two orders of magnitude on all three measurement occasions, in spring before and after fertilizer application, and in autumn after harvest. NO emissions ranged from 0.3 to 215 μg NO‐N m–2 h–1, with maximum emissions always from the most sandy, freely drained soil. Nitrous oxide emissions ranged from 0 to 193 μg N2O‐N m–2 h–1. Seasonal shifts in soil aeration caused maximum N2O emissions to switch from freely drained sandy soils in spring to imperfectly drained soils with high clay contents in autumn. Although effects of soil type on emissions were not consistent, N2O emission was best related to a combination of bulk density and clay content and the NO/N2O ratio decreased logarithmically with increasing water filled pore space.
A laboratory study of the effect of time and temperature on the decline in Olsen P following phosphate addition to calcareous soils
Authors: Javid S. , Rowell D.L.
Published: August 2010

Abstract. The effects of time and temperature on the changes in Olsen P after phosphate application were studied in 13 calcareous soils from Pakistan, an Oxisol from Colombia and an Inceptisol from England. The phosphate sorption reactions were monitored in two stages. The short‐term reaction (30 min shaking with added phosphate in the presence of the Olsen bicarbonate solution) showed that over this time the nature of the sorbing material and number of available sites for P adsorption were important but temperature was not. The extent of the short‐term sorption was not related to the amount of calcium carbonate. In the long‐term reaction (incubating the soils with phosphate at 10, 25 and 45 °C for one year) the amount of Olsen P decreased with time following a power relationship. Increased temperature increased the rate of reaction, following the Arrhenius principle i.e. Q10⊃ 3 (activation energy 83 kJ mol–1). The effects of time and temperature were well described by a modified power equation Y=a (1 +fTt)‐b, where Y is the amount of Olsen P extracted after time t, a is the Olsen P value after the short‐term reaction (the initial value), fT is the ratio of the rate constants at any two temperatures and b is a coefficient which represents the loss in extractability with time. On the basis of the initial Olsen P values and subsequent Olsen P values at different times and temperatures a unified decay curve Y/a= (1 +t)–0.20 was developed where the initial Olsen P values are normalized to 1. The parameters of this equation allow, with limitations, the prediction of changes in Olsen P in these soils if the initial Olsen P value of the soil is known.
Three‐dimensional visualization and quantification of soil macroporosity and water flow patterns using computed tomography
Authors: Mooney S.J.
Published: August 2010

Abstract. Efforts to assess the role of soil structure in soil and water processes have been limited by data based on two dimensional geometry or disturbed samples. Computed tomography (CT) is a non‐invasive technique that allows for the three dimensional, non‐destructive examination of heterogeneous materials. X‐ray CT scanning was used to acquire serial images of contrasting soil types that could be used to render, and hence, quantify important soil constituents in three dimensions. By repeating the scanning techniques after an infiltration period, it was also possible to examine the nature of water movement in real time. Macropore architecture between different soil types was highly variable and generally appeared as unconnected pore segments at the resolution examined. As expected, water flow characteristics were similar to macropore structure, with wetting patterns resembling both Darcian and preferential flow identified in different soils. From this, it was found that in the sandy clay soil c. 90% of macropore space was active following infiltration, compared with c. 50% for the sandy loam soil. In addition, it was possible to visualize the three dimensional distribution of stones and other mineral material. The results illustrated the benefits of computed tomography over more conventional analyses of soil structure, and its potential as a tool for examining dynamic soil processes. However, problems associated with accessibility, resolution and artefacts still provide limitations of the technique.
Phosphorus export from a paddy rice field during flood events
Authors: Zhang Zhijian , Zhu Yinmei , Cheng Jun , Bailey J.S.
Published: August 2010

Abstract. A field plot experiment was conducted to investigate P mobilization from fertilized rice fields during rainfall‐flooding events. The experiment tested the effects of inorganic fertilizer P, at two rates, and P fertilizer plus manure, at one rate, on the amounts of P lost in drainage water when the plots were subjected to four artificially simulated storm‐flooding/drainage events over an eight day period. During the first drainage event, two days after P application, the concentrations and loads of soluble reactive P (SRP) and particulate P (PP) in the drainage water were some three to five times lower than they had been just 24 hours earlier due to rapid sorption and sedimentation. At subsequent events, the concentrations and loads of SRP in drainage water were almost two orders of magnitude lower than at the first event, i.e. the equilibrium between P release from fertilizer and manure and P sorption/fixation by the soil mineral fraction had shifted strongly in favour of the latter processes. During the first drainage event, the concentrations and loads of SRP in drainage water from the low P fertilizer treatment were similar to those on the low P fertilizer plus manure treatment, whereas, 24 hours earlier they had been significantly greater. At subsequent events, though, the highest concentrations and loads of SRP occurred in drainage water from plots treated with equal amounts of P fertilizer and manure. It is suggested that extending the time period between P application and flooding events by applying fertilizer and manure outside the main rainy season should significantly reduce the risk of P loss from paddy rice fields.
The influence of tillage on NO and N2O fluxes under spring and winter barley
Authors: Skiba U. , Van Dijk S. , Ball B.C.
Published: August 2010

Abstract. There is a lack of information about the influence of tillage and time of sowing on N2O and NO emission in cereal production. Both factors influence crop growth and soil conditions and thereby can affect trace gas emissions from soils. We measured fluxes of NO and N2O in a tillage experiment where grassland on clay loam soil was converted to arable by either direct drilling or ploughing to 30 cm depth. We made measurements in spring for 20 days after fertilizer application to spring‐sown and to winter‐sown barley. Both were the second barley crop after grass. Direct drilling enhanced N2O emission primarily as a result of restricted gas diffusivity causing poor aeration after rainfall. Deep ploughing enhanced NO emission, because of the large air‐filled porosity in the topsoil. NO and N2O emissions were smaller from winter sown crops than from spring sown crops.  The three rates of N fertilizer application (40, 80 or 120 kg N ha–1) did not produce the expected linear response in either soil available N concentrations or in NO and N2O fluxes. We attributed this to the lack of rainfall in the ten‐day period after fertilizer application and therefore very slow incorporation and movement of fertilizer into and through the soil.
The use of a nitrification inhibitor, dicyandiamide (DCD), to decrease nitrate leaching and nitrous oxide emissions in a simulated grazed and irrigated grassland
Authors: Di H.J. , Cameron K.C.
Published: August 2010

Abstract. In grazed dairy pasture systems, a major source of NO3– leached and N2O emitted is the N returned in the urine from the grazing animal. The objective of this study was to use lysimeters to measure directly the effectiveness of a nitrification inhibitor, dicyandiamide (DCD), in decreasing NO3– leaching and N2O emissions from urine patches in a grazed dairy pasture under 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). The use of DCD decreased NO3–‐N leaching by 76% for the urine N applied in the autumn, and by 42% for urine N applied in the spring, giving an annual average reduction of 59%. This would reduce the NO3–‐N leaching loss in a grazed paddock from 118 to 46 kg N ha–1 yr–1. The NO3–‐N concentration in the drainage water would be reduced accordingly from 19.7 to 7.7 mg N L–1, with the latter being below the drinking water guideline of 11.3 mg N L–1. Total N2O emissions following two urine applications were reduced from 46 kg N2O‐N ha–1 without DCD to 8.5 kg N2O‐N with DCD, representing an 82% reduction. In addition to the environmental benefits, the use of DCD also increased herbage production by more than 30%, from 11 to 15 t ha–1 yr–1. The use of DCD therefore has the potential to make dairy farming more environmentally sustainable by reducing NO3– leaching and N2O emissions.
Ability of some Norwegian soils to supply grass with potassium (K) ‐ soil analyses as predictors of K supply from soil
Authors: Øgaard A.F. , Krogstad T. , Lunnan T.
Published: August 2010

Abstract.Uptake in grass crops of ammonium acetate lactate extractable K (KAL) and reserve K (interlayer K + structural K) in soil was studied in 16 field experiments at different locations on a range of mineral soil types in Norway. The K uptake from soil, both from KALand reserve K, was considerable, often even at the highest level of K fertilizer. During three years, only on the sandy soils with a low level of acid soluble K (KHNO3minus KAL) was there a yield response to K fertilization. The KALvalues declined rapidly and flattened off at a ‘minimum level’ which differed with soil type. This minimum level for KALis a useful parameter in fertilizer planning, because the grass usually took up the K in excess of the minimum level over two years. The minimum value of KALwas significantly correlated with the content of clay + silt in soil. The decrease in KALduring the growing season was closely correlated to the KALvalue in spring minus the minimum value and, therefore, the amount of K supplied to the grass from the KALfraction can be calculated. Furthermore, the KALvalue for the following spring may be estimated. The release from reserve K was partially related to acid soluble K.