bluuebunny/crossref_metadata_2025 huggingface dataset:
Preferential neural processing of attended stimuli in attention‐deficit hyperactivity disorder and normal boys
Authors: SATTERFIELD JAMES H. , SCHELL ANNE M. , NICHOLAS THOMAS
Published: February 2007

Event‐related auditory and visual potentials were recorded from 36 attention‐deficit hyperactivity disorder (ADHD) and 35 normal 6‐year‐old subjects engaged in a two‐choice discrimination task. When normal subjects attended to stimuli in a given modality, enhanced negative (N2) and positive (P3b) responses (as compared with responses to nonattended stimuli) were found for auditory and visual target stimuli. In contrast, when ADHD subjects attended, little or no enhanced negative responses were found in either modality, and enhanced positive P3b responses were found only in response to visual target stimuli. Auditory N1, N2, and P3b and visual N2 amplitudes to attended target stimuli were significantly reduced in ADHD subjects as compared with normal subjects. No between‐group differences were found for responses to nonattended stimuli. Both amplitude and latency abnormalities indicate that ADHD boys suffer from deficient preferential processing of attended stimuli. P3b and N2 abnormalities found here suggest deficiencies in two independent cognitive processes thought to be crucial to what we perceive, learn, and remember.
The relationship of sweat gland count to electrodermal activity
Authors: FREEDMAN LAUREN W. , SCERBO ANGELA SCARPA , DAWSON MICHAEL E. , RAINE ADRIAN , McCLURE WILLIAM O. , VENABLES PETER H.
Published: February 2007

This study assessed whether greater skin conductance activity at the distal versus medial site (Scerbo, Freedman, Raine, Dawson, & Venables, 1992) is attributable to a greater number of active (open) sweat glands at the distal site. The number of sweat glands was measured using the Palmar Sweat Index (PSI). Twenty‐four subjects were exposed to 10 auditory stimuli. Electrodes were placed on the fore and middle fingers of each hand, using distal sites on one hand and medial sites on the other. The PSI was measured at the medial and distal phalanges adjacent to the electrode placement sites. The distal site contained more open and total sweat glands. Open gland count had the strongest correlations with skin conductance. Multivariate analyses of covariance revealed that site effects for nonspecific and orienting response frequency and trials to habituation were associated with site differences in open glands. Skin conductance measures and the PSI reveal greater electrodermal activity at the distal site. In addition, the number of open glands may be a useful measure related to electrodermal response frequency when polygraph measurement is unavailable.
ERP and behavioral changes during the wake/sleep transition
Authors: HARSH JOHN , VOSS URSULA , HULL JOHN , SCHREPFER STEFFI , BADIA PIETRO
Published: February 2007

Event‐related potentials (ERPs) following infrequent and frequent stimuli were studied as subjects moved from wakefulness to sleep. Subjects were instructed to respond to the infrequent “target” stimuli (attend condition) or to ignore the stimuli (ignore condition). Parietal P300, prominent following target ERPs in wakefulness under the attend condition, disappeared in association with reduced behavioral responsiveness and emergence of a central negativity (N350). The N350 and preceding and following positivities (P220 and P450) became the dominant feature of both target and nontarget ERPs under both attend and ignore conditions. The P220‐N350‐P450 complex was larger and peak latencies were shorter under the attend condition. Peak amplitudes tended to be larger following targets, especially under the attend condition. The findings suggest that, although the processes under‐lying P300 are less likely to be engaged, processing of stimulus deviance and task relevance continues in sleepiness and sleep, and is reflected by variance in N350 and related activity.
Influence of caffeine on selective attention in well‐rested and fatigued subjects
Authors: LORIST MONICQUE M. , SNEL JAN , KOK ALBERT , MULDER GIJSBERTUS
Published: February 2007

Effects of caffeine were studied in a visual focused selective search task in well‐rested and fatigued subjects. A dose of 200 + 50 mg caffeine or placebo, dissolved in decaffeinated coffee, was administered in a double‐blind and deceptive fashion. The task was to detect a target letter on one diagonal of a visual display designated as relevant and ignore stimuli presented on the irrelevant diagonal. Behavioral measures were supplemented by event‐related potential (ERP) measures. Subjects reacted faster in the caffeine condition. Caffeine enhanced the N1 and the N2b components. Selection of relevant information apparently was more adequate in this condition. Search negativity was not affected by caffeine. Caffeine effects on the P3 elicited by target letters were more pronounced in the fatigued than in the well‐rested subjects, indicating that the effects of caffeine are dependent on the state of the subject. The results suggest that caffeine has specific rather than general effects on information processing.
Changes in brain activity patterns in aging: The novelty oddball
Authors: FABIANI MONICA , FRIEDMAN DAVID
Published: February 2007

A decrease in the frontal lobes' efficiency is supposed to play a role in age‐related changes in cognitive function. If frontal lobes are involved in the maintenance of working memory, the elderly may require increased frontal activity because of more rapid memory decay. This is consistent with the fact that the P3 component of the eventrelated potential (ERP) has a more frontal orientation with increasing age. However, frontally distributed P3s are also observed in young people when novel stimuli are unexpectedly presented in an oddball paradigm. Young and old subjects were run in an auditory novelty oddball in which ERPs were recorded from 30 scalp sites. The young adults' P3s showed either a posterior (targets) or more frontally oriented (novels) scalp focus. The elderly were less accurate in their memory for the novel stimuli, and their P3s showed anterior and posterior foci to both targets and novels. The young adults' target P3s changed over time from a frontal to a posterior focus, whereas the old adults' did not. These results are consistent with decreased ability of the elderly to maintain the templates needed for stimulus categorization.
Cardiac function and behavioral reactivity during infancy
Authors: SNIDMAN NANCY , KAGAN JEROME , RIORDAN LINDA , SHANNON DANIEL C.
Published: February 2007

Longitudinal cardiac data from the end of the fetal period to 21 months of age were examined for change and stability over age and relations to the temperamental characteristics of high and low reactivity at 4 months of age and fear to the unfamiliar in the second year. Heart period and power in the cardiac spectra changed dramatically over the first 2 years, and individual differences were not preserved until 9‐14 months of age. Sleep heart period at 2 weeks of age and low frequency power at 2 months of age were better predictors of the temperamental categories than later measures of the same variables, suggesting that cardiac function early in life may be an especially sensitive index of temperamental qualities.
P300 topography in Alzheimer's disease
Authors: HOLT LORI E. , RAINE ADRIAN , PA GRACE , SCHNEIDER LON S. , HENDERSON VICTOR W. , POLLOCK VICKI E.
Published: February 2007

This study assessed whether P300 scalp topography distinguishes subjects with Alzheimer's disease (AD) from controls. Specifically, it was predicted that the AD group would show maximum P300 amplitude over frontal areas and t he largest P300 reduction over parietal and left hemisphere areas. These hypotheses were tested using a standard auditory oddball paradigm to compare 26 AD subjects and 26 controls matched on age, sex, handedness, and education. P300 was measured at frontal, central, parietal, and occipital sites over left and right hemispheres and along the midline. Results revealed that the distribution of P300 was different for the two groups such that the controls manifested a maximum over parietal areas, whereas the AD subjects showed a maximum at frontal sites with the largest reductions in P300 over parietal areas. No hemispheric differences in P300 were found. These results are consistent with the hypothesis that P300 represents the activity of multiple neural generators that are differentially disrupted by the disease process.
Attentional modulation of startle in psychosis‐prone college students
Authors: SCHELL ANNE M. , DAWSON MICHAEL E. , HAZLETT ERIN A. , FILION DIANE L.
Published: February 2007

Attentional modulation of startle eyeblink was studied in college students putatively at risk for psychosis and in normal controls. At‐risk subjects had extreme scores on scales for either anhedonia or perceptual aberration‐magical thinking (per‐mags). Subjects were presented with to‐be‐attended and to‐be‐ignored tones; white noise startle probes were presented at lead intervals of 60, 120, 240, or 2,000 ms following the onset of attended and ignored tones and during intertone intervals. Controls showed greater inhibition of startle blink at 120 ms and greater facilitation at 2,000 ms during to‐be‐attended than to‐be‐ignored tone, demonstrating attentional modulation of prepulse inhibition and facilitation. Both at‐risk groups showed normal overall levels of early inhibition and late facilitation. However, per‐mags failed to show attentional modulation of either inhibition at 120 ms or facilitation at 2,000 ms; anhedonics showed no modulation of inhibition and modulation of facilitation was delayed in development. The results for the per‐mags are strikingly similar to those observed in schizophrenic patients and suggest that these deficits index a trait‐linked vulnerability to disorders in the schizophrenic spectrum.
Hebb's concept of cell assemblies an the psychophysiology of word processing
Authors: PULVERMÜLLER FRIEDEMANN
Published: February 2007

Hebb's brain‐theoretical approach suggests that tightly connected networks of neurons, Hebbian cell assemblies, are the building blocks of cognitive functions. These assemblies are not necessarily restricted to a small cortical locus but may be dispersed over distant cortical areas. Assemblies with different topographies can be postulated for different kinds of words, such as meaningful content versus grammatical function words or words eliciting motor versus visual associations. Evidence from evoked potentials and gamma‐band electrocortical responses elicited by lexical material supports a cell assembly model of language and other higher cognitive functions.
On the validity of estimating EEG correlation dimension from a spatial embedding
Authors: PRITCHARD WALTER S. , KRIEBLE KELLY K. , DUKE DENNIS W.
Published: February 2007

We demonstrate by using simulations that spatial embedding of single‐variable time series data does not reliably reconstruct state‐space dynamics. Instead, correlation dimension estimated from spatially embedded data is largely a measure of linear cross‐correlation in the data set. For actual electroencephalographic (EEG) data, we demonstrate a high negative correlation between spatial correlation dimension and the average amount of lag‐zero cross‐correlation between “nearest‐neighbor” embedding channels (the greater the cross‐correlation, the lower the dimension). We also show that the essential results obtained from spatially embedding EEG data are also obtained when one spatially embeds across a set of highly cross‐correlated stochastic (second‐order autoregressive) processes. Although, with appropriate surrogate data, correlation dimension estimated from spatially embedded data detects nonlinearity, its use is not recommended because correlation dimension estimated from temporally embedded data both reconstructs state‐space dynamics and, with appropriate surrogate data, detects nonlinearity as well.
Predicting sleep latency from the three‐process model of alertness regulation
Authors: ÄKERSTEDT TORBJÖRN , FOLKARD SIMON
Published: February 2007

This paper presents a modification of the quantitative “three‐process model of alertness regulation” to predict sleep latency in connection with irregular sleep/wake patterns. This model uses a circadian and a homeostatic component(sleep loss) that are summed to yield predicted alertness (on a scale of 1 to 20) across a specified time span. The timing of sleep from two studies of irregular sleep were used as input to the model. The predicted alertness at bedtime was regressed on empirical sleep latency from two studies. The maximum R2 (0.88) was reached for an exponential function, with the model acrophase set to 2048. The predictions were cross validated on another set of sleep latency data from an irregular sleep study and a maximum R2 of 0.65 was obtained. In both studies, the prediction from the model explained more variance that did self‐rated alertness at bedtime. Cross validation was also carried out sucessfully with published data from two studies of shift work. It was concluded that sleep latency on irregular schedules may be predicted with accuracy from knowledge of the prior sleep/wake pattern. This may have practical consequences for rest/actvity management.
Effects of interstimulus interval on scalp topographies evoked by noxious sural nerve stimulation
Authors: DOWMAN ROBERT
Published: February 2007

The amplitude of the late pain‐related negative‐positive peak complex, which we have labeled SP3 (134–150 ms) and SP6 (277–331 ms), respectively, increased with increasing interstimulus interval (ISI). This contrasts with the nociceptive spinal withdrawal reflex and subjective pain rating data, which implied that nociceptive somatosensory processes were unaffected by ISI at stimulus levels that were well within the pain range. A scalp topographic analysis strongly suggested that none of the brain areas responsible for SP3 or SP6 are involved exclusively in nociception. We also observed a pain‐related positive potential apporximately 161–177 ms following sural nerve stimulation that has not been reported by others. A dipole source localization analysis and the effects of ISI and stimulus intensity on this potential suggest that it is generated by the response of primary somatosensory cortex neurons to inputs arising from the innocuous peripheral afferents and that this response is inhibited by noxious inputs.
Probing picture perception: Activation and emotion
Authors: Cuthbert Bruce N. , Bradleym Margaret M. , Lang Peter J.
Published: February 2007

When acoustic startle probes are presented during picture viewing, the blink reflex is augmented for unpleasant foreground stimuli and reduced during pleasant stimuli. The present experiment assessed the hypothesis that this affect‐Startle effect increases as pictures are judged to be more arousing. Eyeblinks elicited by startle probes of three different intensities were recorded while subjects viewed pictures varying in both pleasure (pleasant, neutral, and unpleasant) and arousal (low, moderate, and high). Both blink potentiation during unpleasant content and blink diminution during pleasant content were clearly strongest for picture contents high in arousal. The effect was present for all probe intensities tested.
Tracking early and late stages of information processing: Contributions of startle eyeblink reflex modification
Authors: Jennings Penny D. , Schell Anne M. , Filion Diane L. , Dawson Michael E.
Published: February 2007

Startle eyeblink modification was examined as a measure of information processing. College students were presented with tones of 5 and 7 s duration of either high or low pitch, followed by startle‐eliciting stimuli at lead intervals of 120, 2.000, 4,500, or 6,000ms. Attention to tones was manipulated by instructing the task group to count the longer tones of either pitch. The no‐task group had no instructed task. Startle eyeblink was inhibited at the short lead interval and facilitated at the long lead intervals in both groups. The task group showed greater inhibition and facilitation during attended than during ignored tones, indicating that early and late controlled processing was occurring. In the task group, I he degree of facilitation appeared to reflect the degree of cognitive demands of the task. Startle eyeblink modification may provide a sensitive measure of the nature and timing of stapes of processing in active and passive attentional conditions.
Reproducibility of blood pressure and heart rate reactivity: A meta‐analysis
Authors: Swain Annette , Suls Jerky
Published: February 2007

Reproducibilities of blood pressure and heart rule (HR) reactivity reported in studies assessing responses to the same laboratory stressors across occasions were reviewed with meta‐analytic techniques. Changes in HR had the greatest reproducibility (r =.555), followed by systolic blood pressure (SBP) (.407) and diastolic blood pressure (DBF) (.348), Both SBP and HR response reproducibility was higher at shorter lest‐retest intervals, whereas DBP values varied unsystematically with length of test‐retest interval Older samples exhibited higher SBP and DBP reproducibility to stressors. SBP and DBP reproducibilities were better for tasks that did not make speech demands. The reliability of reactivity assessment was higher when based on three or more measurements, On the basis of able evidence, the drop in stress reproducibility, as test‐retest interval increases, places limits on the viability of BP reactivity as a strong marker or risk factor for coronary heart disease.
Event‐related brain potentials in a varied‐set memory search task: A reconsideration
Authors: KOTCHOUBEY B. I. , JORDAN J. S. , GRÖZINGER B. , WESTPHAL K. P. , KORNHUBER H. H.
Published: February 2007

Event‐related potentials (ERPs) were recorded in 19 healthy subjects as they completed two Sternberg (1969, American Scientist, 57, 421–457) memory tests. In separate sessions, either single digits (i.e., 0–9) or 10 abstract figures were used as stimuli. In both sessions, memory set sizes were 1 (M1), 2 (M2), or 4 (M4). The amplitude and latency of the parietal P400 and the frontocentral negativity preceding P400 varied significantly with set size, but only between M1 and M2, whereas reaction time increased dramatically from M1 to M2 and from M2 to M4. These findings challenge previous assertions that the ERPs reflect aspects of the exhaustive serial search proposed by Sternberg. A late parietal positivity (P620), which failed to vary with set size, was larger in response to figures than to digits and may represent the search for, or utilization of, semantic traces of the stimuli.
Perceptual factors affecting age‐related differences in focused attention: Performance and psychophysiological analyses
Authors: ZEEF ELLY J. , SONKE CORINE J. , KOK ALBERT , BUITEN MEREL M. , KENEMANS J. LEON
Published: February 2007

In this study, the impact of two perceptual factors, feature similarity and spacing, on age‐related differences in performance and psychophysiological measures were investigated within a focused attention paradigm. Young and old subjects performed an Eriksen letter identification task, in which centrally presented targets were flanked by response‐compatible or response‐incompatible letters. In feature similarity conditions, targets and flankers had a low or high amount of feature overlap. In spacing conditions, flankers were presented at four different lateral positions from the target. In the condition with high feature overlap and shortest target‐flanker distance, old subjects showed greater interference by incompatible flankers than young subjects. Feature similarity was of little influence on age‐related differences. However, spacing turned out to be of critical importance. Age‐related interference effects disappeared when the target‐flanker distance increased. This appears to be due to a decrease in response competition.
Brain activation, affect, and aerobic exercise: An examination of both state‐independent and state‐dependent relationships
Authors: PETRUZZELLO STEVEN J. , TATE ANDREW K.
Published: February 2007

Resting electroencephalograph (EEG) asymmetry is a biological marker of the propensity to respond affectively to, and a measure of change in affect associated with, acute aerobic exercise. This study examined the EEG‐affect–exercise relationship. Twenty participants performed each of three randomly assigned 30‐min conditions: (a) a nonexercise control, (b) a cycling exercise at 55% VO2max, and (c) a cycling exercise at 70% VO2max. EEG and affect were assessed pre‐ and 0, 5, 10, 20, and 30 min postcondition. No significant results were seen in the control or 55% conditions. In the 70% exercise condition, greater relative left frontal activation preexercise predicted increased positive affect and reduced state anxiety postexercise. Participants (n= 7) with extreme relative left frontal activation post‐exercise reported concomitant decreases in anxiety, whereas participants (n= 7) with extreme relative right frontal activation postexercise reported increases in anxiety. These findings (a) replicate prior work, (b) suggest a dose‐response intensity effect, and (c) support the idea that exercise is an emotion‐eliciting event. Affective responses seem to be mediated in part by differential resting levels of activation in the anterior brain regions. Ongoing anterior brain activation reflected concurrent postexercise affect.
Assessment of posture and motion by multichannel piezoresistive accelerometer recordings
Authors: FAHRENBERG JOCHEN , FOERSTER FRIEDRICH , SMEJA MANFRED , MÜLLER WOLFGANG
Published: February 2007

Modern assessment of posture and motion involves the use of wide bandwidth piezoresistive accelerometers. The direct current (DC) component allows for assessment of slow motion and change in position referring to the gravitational axis; the alternating current (AC) component, calibrated in g, represents acceleration along the sensitive axis of the device. A method study was designed to evaluate the division in DC and AC components, reliabilities, discrimination between conditions, and detection of types of physical activities. Recordings were made in 26 student participants for eight conditions: sitting, standing, lying supine, sitting and typing on a PC keyboard, walking, climbing stairs, walking downstairs, and cycling. This procedure was repeated in reversed order. A classification of physical activities according to the eight conditions (first trial) and based on four parameters, that is DC components trunk, thigh, and lower leg and AC component trunk, was correct in almost 100% of patterns, when applied to the second trial.
An in vivo comparison of two circumferential penile strain gauges: The introduction of a new calibration method
Authors: JANSSEN ERICK , VISSENBERG MARIETTE , VISSER SAMBHAVO , EVERAERD WALTER
Published: February 2007

This study assessed the comparability of two types of penile strain gauges using both a circular and a newly developed oval calibration device. A group of 25 sexually functional participants places both an electromechanical and an indium/gallium‐in‐rubber strain gauge on the penis and viewed an erotic film. The electromechanical gauge as calibrated on the circular device resulted in greater penile circumference changes than the indium/gallium‐in‐rubber gauge. Mean circumference changes were not different for the two strain gauges when the oval calibration device was used. The use of an oval calibration device improves ecological validity of calibration of penile strain gauges. Standard inclusion of this method in studies on male sexual response will increase comparability of research findings.
The effect of unconditional stimulus modality and intensity on blink startle and electrodermal responses
Authors: SIDDLE DAVID A. T. , LIPP OTTMAR V. , DALL PATRICIA J.
Published: February 2007

Attentional accounts of blink facilitation during Pavlovian conditioning predict enhanced reflexes if reflex and unconditional stimuli (US) are from the same modality. Emotional accounts emphasize the importance of US intensity. In Experiment 1, we crossed US modality (tone vs. shock) and intensity in a 2 × 2 between‐subjects design. US intensity but not US modality affected blink facilitation. In Experiment 2, we demonstrated that the results from Experiment I were not due to the motor task requirements employed. In Experiment 3, we used a within‐subjects design to investigate the effects of US modality and intensity. Contrary to predictions derived from an attentional account, blink facilitation was larger during conditional stimuli that preceded shock than during those that preceded tones. The present results are not consistent with an attentional account of blink facilitation during Pavlovian conditioning in humans.
Cerebral processing of words and the development of chronic pain
Authors: KNOST BÄRBEL , FLOR HERTA , BRAUN CHRISTOPH , BIRBAUMER NIELS
Published: February 2007

The processing of pain‐related, body‐related, and neutral words was assessed in individuals with prechronic pain and matched healthy controls. Integrated surface electromyogram, heart rate, skin conductance level, and visual event‐related potentials from 11 electrode sites were recorded during the presentation of three word types at perception threshold. Startle responses were recorded from words presented above perception threshold. The patient and control groups did not differ in recognition performance. Pain‐related words evoked an enhanced early component (N100) of the visual event‐related potential only in the prechronic pain group. In both groups the late slow wave and the startle response were enhanced for body‐ and pain‐related words compared with those for neutral words. All word types elicited larger late positivities in the prechronic pain group and in the right compared with the left hemisphere. These data suggest differential cortical processing of pain‐related material in persons at a prechronic pain stage.
Autonomic patterns during respiratory suspensions: Possible markers of Transcendental Consciousness
Authors: TRAVIS FREDERICK , WALLACE R. KEITH
Published: February 2007

In two experiments, we investigated physiological correlates of transcendental consciousness during Transcendental Meditation® sessions. In the first, experimenter‐initiated bells, based on observed physiological patterns, marked three phases during a Transcendental Meditation session in 16 individuals. Interrater reliability between participant and experimenter classification of experiences at each bell was quite good. During phases including transcendental consciousness experiences, skin conductance responses and heart rate deceleration occurred at the onset of respiratory suspensions or reductions in breath volume. In the second experiment, this autonomic pattern was compared with that during forced breath holding. Phasic autonomic activity was significantly higher at respiratory suspension onset than at breath holding onset. These easily measured markers could help focus research on the existence and characteristics of transcendental consciousness.
Management of difficult soils for intensive winter cereals in central England: a farm case study
Authors: Pidgeon J.D. , Thorogood P.J.
Published: February 2007

Abstract. After satisfactory results during the mid‐1970s, winter cereal yields and profitability were disappointing during 1979–81 on a Buckinghamshire farm with Ragdale series stagnogley soil. Poor soil physical conditions were diagnosed and then improved by soil loosening and mole drainage. Other inputs and management remained intensive but essentially constant. Three‐year average winter wheat and barley yields rose from 5.6 and 4.9 t ha for 1979–81 to 7.4 and 6.8 t ha respectively for 1982–84. A large part of this increase could be attributed to improved soil management. The observations were made as a farm case study and not as a replicated field trial. They may nevertheless be of interest to others and of national relevance as similar soils occupy some 30% of the cereal area in England.
The effect of preplanting soil preparation and soil management on soil physical parameters in an apple orchard
Authors: Atkinson D. , Herbert R. F. , Gurung R. P.
Published: February 2007

Abstract. Effects on soil physical properties in a trial which compared establishing an apple orchard on grassed and cultivated soil and of maintaining soil with or without a vegetative cover post‐planting are discussed. On a fine sandy loam soil (Fyfield series) prone to erosion, bulk density, water filled porosity and soil erosion, measured at intervals after the establishment year, were all unaffected by the use of grass. Infiltration rate was much higher on grassed than on herbicide treated soil as was the apparent ability to accept heavy rainfall.
Examples of erosion on brickearth soils in east Kent
Authors: Boardman J. , Hazelden J.
Published: February 2007

Abstract. High rates of erosion are reported from three sites on brickearth (loess) soils in east Kent. Problems are acute where soils are used for intensive production of vegetables and salad crops. Erosion appears to be the result of structural instability, lack of crop cover for much of the year, and certain managment practices, such as ridging the soil for the crop. In the autumn of 1984, about 120 tonnes of soil was lost from rills in a field of onions: an erosion rate of about 15 t ha−1. A large field under winter cereals also eroded and this resulted in damage to property. Conservation techniques are recommended.
Effects of gypsum‐slotting on infiltration rates and moisture storage in a swelling clay soil
Authors: Jayawardane N.S. , Blackwell J.
Published: February 2007

Abstract. Previous studies have shown marked increases in wheat yields on a swelling clay soil due to gypsumslotting compared to no‐gypsum and surface gypsum applications, largely through improved aeration in the surface layers. In the present study, steady infiltration rates indicated 2‐fold increases due to surface gypsum applications and 4‐ to 6‐fold increases due to slotted gypsum. This should provide increased moisture storage and reduced soil erosion hazards during prolonged heavy rainfall periods, provided that a crust does not form under the impact of raindrops. However, gypsum‐slotted lands should not be used in crop rotations which include ponded rice, due to increased potential water use and risk of rising watertables and salinization.

The effect of the ‘throttle’ in the upper B horizon which restricts moisture storage in the lower soil layers during short‐term and prolonged ponding was reduced, but not eliminated, by surface and slotted gypsum applications. Thus the moisture contents of the lower depths in both the non‐ameliorated and ameliorated soils were less than the moisture content at saturation or at ‐10 kPa potential even after flooding for 11 days.
Use of soil and climatic data to predict hydraulic loading behaviour of Irish soils
Authors: Gardiner M. J.
Published: February 2007

Abstract. The purpose of this study was to try to estimate from soil and climate data both absolute and temporal individual soil hydraulic loading limits under Irish conditions. The two concepts cumulative soil moisture deficit (CSMD) and winter rain acceptance potential were used.

Cumulative soil moisture deficit (1956–75) ranged from 116 mm in the southeast to 2 mm in the northwest. Four regions were delineated with mean cumulative maximum deficits (mm) of 105.3, 57.7, 20.0, and 2.0 respectively. Consequently, except for Region 4, hydraulic overloading is unlikely to occur under normal farm practices during soil moisture deficit period. Soil moisture deficit was present in Region 1 from early April through October, in Region 2 from early May through September, in Region 3 from early May through August and in Region 4, only in July.

The concept of winter rain acceptance potential (WRAP) has been used to assess the possibilities for farm effluent disposal outside of the SMD period. Some 49% of Irish soils have a very high to moderate WRAP, 36% have a low to very low WRAP. These latter categories are likely to exhibit problems if effluents are applied outside of the SMD period.

Regional farm slurry storage duration requirements have been estimated from SMD and WRAP data. These are 11.3, 14.0, 16.7 and 20.0 weeks respectively for regions 1, 2, 3 and 4.
Salt‐affected soils in England and Wales
Authors: Loveland P.J. , Hazelden J. , Sturdy R.G. , Hodgson J.M.
Published: February 2007

Abstract. Soils mainly in alluvial marine sediments around the coast of England and Wales, occupy about 6% of the agricultural land. The extent of salt‐affected soils within these parent materials is unknown, but is believed to be significant from the evidence of existing soil surveys.

The principal salt is sodium chloride, and the degree of salinity depends on depth to saline groundwater, the intensity of leaching, and the frequency and severity of past marine flooding. Evidence suggests that while the effects of the flooding are obvious and immediate, long‐term salinity owes more to groundwater behaviour and chemistry.

The amount of sodium in these soils, particularly the heavier‐textured ones, makes them structurally unstable, especially when wet. The instability in turn makes them difficult to drain. Ameliorative treatments are possible, but are expensive and slow to take effect.

In their natural or semi‐natural state these soils form large areas of wetland or unimproved grassland, often of interest to conservationists. In spite of this, and their generally unfavourable properties for cultivation, extensive areas have become arable in recent years.

Structural stability, salt content, and exchangeable sodium percentage are intimately linked and can be measured during soil survey, which then aids rational decisions about land use. Such a survey of the North Kent Marshes is presented as a case study.
Soil water management in the rain‐fed farming systems of the Mediterranean region
Authors: Cooper P.J.M. , Gregory P.J.
Published: February 2007

Abstract. This paper summarizes the essential features of the Mediterranean climate and its associated soils and farming systems. Rain falls mainly during the winter so that crops must usually rely on stored soil moisture when they are growing most rapidly. Water use efficiency of dry matter production can be increased in three ways but chiefly by decreasing evaporation from the soil surface. Soil and crop management techniques used to increase water use efficiency are reviewed.
Temporal and spatial patterns of nitrate losses from an agricultural catchment
Authors: Burt T.P. , Arkell B.P.
Published: February 2007

Abstract. Nitrate losses from a small catchment of mixed land use in south Devon, England, are described. The temporal pattern of leaching is dominated by major losses through the winter months when both streamflow and nitrate concentration are large. Storm runoff is generated mainly by subsurface stormflow, and nitrate losses are particularly important at such times. The spatial pattern of nitrate loss from the catchment is controlled both by land use and by topography.
Herbicide treatment on winter oilseed rape and its implication for increasing soil erosion risk in marginal cropping areas of the United Kingdom
Authors: Wright G.G.
Published: February 2007

Abstract . A combination of crop photography and crop radiance (near‐infrared and red) values are used to measure ground cover establishment (leaf area). The high correlation between the green leaf area and near‐infrared/red ratio (NIR/R) can provide a non‐destructive method for monitoring crop growth. Using this relationship the effects of pre‐ and post‐emergence herbicide treatments (Metazachlor) on winter oilseed rape were studied. It is shown that pre‐emergence spraying reduces germination and autumn and spring growth rates. One management aspect of pre‐emergence spraying is the delay in achieving ground cover. For marginal crops on soils with a high risk of erosion critical ground cover may be delayed by as much as two weeks.
Forestry and soil erosion in Britain – a review
Authors: Moffat A.J.
Published: February 2007

Abstract.Research on soil erosion under forest in Britain is reviewed. Erosion can increase as a result of afforestation in the uplands, sometimes with undesirable consequences for surface water quality. Published rates of erosion are usually close to ‘natural’ ones, at around 500 kg ha−1yr−1. Of the forest operations that can lead to erosion ploughing is the most important. Clearfelling may also increase erosion, but little is known of its long‐term effects. New developments in forestry may do much to reduce the risk of soil erosion, particularly the replacement of ploughing by subsoiling and the control of drain gradients.
Comparison of the macropore structure of a sandy loam surface soil horizon subjected to two tillage treatments
Authors: Moran C.J. , Koppi A.J. , Murphy B.W. , McBratney A.B.
Published: February 2007

Abstract. Erosion and excessive runoff from a crusting and hard‐setting red‐brown earth may he ameliorated with suitable management. A field trial, near Cowra, New South Wales, to assess the long‐term effect of different tillage systems was used to compare the effect of direct drilling with conventional district cultivation practices under continuous wheat. The soil was sampled in the eighth year for assessment of the soil macropore structure, measurement of bulk density and hydraulic conductivity under tension. Vertical faces were prepared from resin impregnated blocks and the macropore structure described mathematically and visually using digital images and data generated from these images. Infiltration, bulk density and image analysis data all lead to the same conclusions about changes in pore structure. Under direct drilling no crust was evident, and there was greater macroporosity (> 0.175 mm diameter in section). The treatment effects appeared to be significant to about 30 to 35 mm depth at the time of sampling. Greater root and faunal activity were observed under direct drilling.
The principles of fertilizer use for sports turf
Authors: Lawson D.M.
Published: February 2007

Abstract. Fertilizer application to sports turf has a significant effect on the playing characteristics of the surface as well as its aesthetic appearance. Nutrient availability affects leaf and root density, infestation by weed species, resistance to fungal pathogens, tolerance to wear, drought and cold in the turf grasses and surface hardness. The increasing use of high sand content, free‐draining root zones for sports areas is leading to a larger demand for nitrogen and also to an increased interest in the use of slow‐release nitrogen fertilizers. The optimum nutrient application rates are examined, particularly for nitrogen and the direction in which research on fertilization practice should take is considered.
Nitrogen mineralization in loamy arable soils after increasing the ploughing depth and ploughing grasslands
Authors: Richter G.M. , Hoffmann A. , Nieder R. , Richter J.
Published: February 2007

Abstract.Increasing the ploughing depth and ploughing in grassland has been common in Germany during the past 20 years. Incubation studies were conducted with topsoils from luvisols and gleysols at different times after change of management in order to assess its influence on nitrogen mineralization and its kinetic parameters.

The results show that deep ploughing slows the mineralization of nitrogen. The difference between earlier (1967–72) and more recently (1980–82) deepened topsoil has become smaller after a further three years of cultivation, however. The preceding crops (wheat or sugar beet), the amount of N fertilizer as well as clay and nitrogen contents cause a variation in N mineralization. The results indicate a continuing approach of an‘equilibrium’organic matter and nitrogen content. The enrichment capacity of intensively managed soils may be replenished within 10 years.

Gleysols formerly under grass mineralize more nitrogen than‘traditionally’ploughed soils, even 27 years after the ploughing‐in. While nitrogen from easily decomposable materials decreases within the first 10 years, the resistant fraction is a long‐lasting determinant for N mineralization. Both processes need to be considered when applying fertilizer to minimize nitrate leaching.
Properties of soil aggregates as influenced by tillage practices
Authors: Mbagwu J.S.C. , Bazzoffi P.
Published: February 2007

Abstract. Changes in aggregate stability, density, and porosity as well as the water retention and nutrient contents of different aggregate size fractions due to intensive tillage were investigated. Three soils from Vicarello, Fagna and Gambassi in North Central Italy which had been under permanent vegetation, minimum or conventional tillage for more than seven years were studied. The aggregates on conventionally tilled plots were slightly denser and less porous than those on the untilled or minimum‐tilled plots. The aggregates were less stable under conventional tillage on all soils. Conventional tillage reduced the proportion or macro‐aggregates by 22% at Vicarello and 35% at Gambassi. There were no differences in macro‐aggregate proportions between minimum‐ and conventionally tilled plots at Fagna. The potential of the dry aggregates to distintegrate upon contact with water was greatest in the conventionally tilled and least in the untilled treatments. The proportions of dry macro‐aggregates (> 0.25 mm) in the untilled and tilled plots were 90 and 71%, respectively. The soil of the tilled plots contained less carbon and nitrogen than that of the untilled plots in all aggregate size fractions. The silt‐plus‐clay contents of the aggregates accounted for between 65 and 93% of variability in the water they retained at small potentials while organic carbon contents accounted for between 71 and 90% of variability in the stability of the aggregates irrespective of the tillage treatments.
Mechanized relay‐cropping in an irrigated red‐brown earth in south‐eastern Australia
Authors: Tisdall J.M. , Adem H.H.
Published: February 2007

Abstract. Machinery was designed specifically for relay‐cropping on permanent raised beds (150 mm high and 1.5 m wide) in northern Victoria. This machinery enabled maize (Zea mays) to be successfully sown at 2, 4 and 5 weeks before harvest, and 1 day after harvest (Control), of wheat (Triticum aestivum). The sowing equipment consisted of a four‐row cultivator, behind which were four precision seeders. The wheels (250 mm in diameter) were spaced at 1.5 m to track along the base of the furrows. In one pass on each bed, the sowing equipment tilled two strips (each 50 mm wide, 30 mm deep and 50 mm from the outer row of wheat) and sowed maize, with little damage to the wheat crop. We extended the axle of the trailed harvester so that the wheels (250 mm in diameter) were 3 m apart, and moved the drawbar 300 mm to one side so that all wheels ran along the base of the furrows. There were no significant differences between treatments in yield (mean 2.9 t ha‐1) of dryland wheat, in final emergence percentage (mean 89%) or in early growth of irrigated maize. The maize yielded significantly less grain in the treatment sown at 5 weeks (9.6 t ha‐1), but not 2 or 4 weeks (mean 10.6 t ha‐1) before the wheat was harvested, than in the Control (10.8 t ha‐1). The wheat and maize yielded more grain than those grown traditionally as sole crops in northern Victoria.
Atmospheric ammonia in relation to grassland agriculture and livestock production
Authors: Whitehead D.C.
Published: February 2007

Abstract. Farm livestock typically retain 5–23% of dietary nitrogen, and consequently excrete large amounts of nitrogen, mainly in urine. Areas affected by cattle urine may receive the equivalent of several hundred kg nitrogen per hectare. Urea is usually hydrolysed to ammonium carbonate within a few days. This increases the soil pH and thereby assists volatilization of ammonia. Volatilization is also increased by soil warmth and by small soil cation exchange capacities. Over the grazing season in lowland UK about 15% of the nitrogen in urine is likely to be volatilized as ammonia, but only 1–5% of the nitrogen in dung is lost in this way.

Substantial volatilization of ammonia probably occurs from animal houses and after spreading of slurry in the field. About 3–4% of fertilizer nitrogen used in the UK is lost as gaseous ammonia. Cut grass herbage also loses ammonia by volatilization, if allowed to remain in the field in wet conditions. Total annual emissions of nitrogen as ammonia from grassland and livestock in UK are probably 320 000–420 000 tonnes.
Fixation and transfer of nitrogen by white clover to ryegrass
Authors: McNeill A.M. , Wood M.
Published: February 2007

Abstract. 15N2 was used in a sealed controlled environment chamber to investigate the transfer of fixed nitrogen from white clover to perennial ryegrass growing in soil in pots. There was no difference in the 15N content of roots and shoots of clover plants after exposure to 15N. No labelled fixed nitrogen was detected in ryegrass plants growing with the clover plants for a period of 129 days. There was therefore no evidence of rapid direct transfer (excretion) of fixed nitrogen from clover to ryegrass.
Rapid methods for diagnosis of soil‐borne plant pathogens
Authors: Fox R.T.V.
Published: February 2007

Abstract. Root diseases are often hard to identify or quantify visually, particularly by the inexperienced, so several modern methods of diagnosis from other branches of biology have been modified for soil‐borne plant pathogens. Though very sensitive, most of these techniques are slower and more laborious than the routine inspection of plants for disease symptoms, yet they need less expertise and are consistently accurate. Apart from immunology, most laboratory diagnostic procedures have so far proved ill‐suited for field use, as they are neither sufficiently flexible nor portable. Despite the rapid detection and identification of numerous viruses by routine enzyme‐linked immunosorbent assays (ELISA), there have been until recently few suitable protocols adapted for fungi. DNA hybridization forms the basis of another group of fairly rapid diagnostic techniques which will probably be restricted to the laboratory for some while yet. Nevertheless, DNA techniques have proved valuable in various investigations, such as unravelling the phylogeny of some species of soil‐borne pathogens. For the foreseeable future methods based on antibodies and DNA probes are likely to extend their domination of detection and diagnosis techniques. By making recognition easier, these techniques play complementary roles in expanding our understanding of the biology, taxonomy and ecology of soil‐borne pathogens.
Simulating nitrogen dynamics in soils using a deterministic model
Authors: Hutson J.L. , Wagenet R.J.
Published: February 2007

Abstract. LEACHN is a deterministic model for simulating nitrogen dynamics in soil. Transport processes are based upon numerical solutions to the Richards equation for water flow and the convection‐dispersion equation for solute transport. Transformations of urea, ammonium, nitrate and three organic pools are included, and the influence of water content and temperature can be reflected. Lack of measured input data sometimes limits the more general use of models such as these. Approaches to estimating data values using soil survey information and a limited number of measured data are discussed. Simple model sensitivity studies and a limited number of field measurements can guide the choice of input data values and lead to simulations that reflect the main features of the field soil nitrogen regime. Such an approach provides initial values for a modelling exercise, and improves intuition regarding the relative importance of processes and interactions in the field nitrogen cycle.