bluuebunny/crossref_metadata_2025 huggingface dataset:
Baroreceptor stimulation alters cortical activity
Authors: RAU HARALD , PAULI PAUL , BRODY STUART , ELBERT THOMAS , BIRBAUMER NIELS
Published: February 2007

The arterial baroreceptors constitute an essential sensory link for the short‐term regulation of blood pressure and may also influence higher cortical function. The present study was undertaken to evaluate previous reports of such a cortical influence under conditions of psychologically controlled, mechanical baroreceplor stimulation. This control was achieved by use of PRES (phase‐related external suction), a modified neck suction technique. PRES applies short suction bursts that have a different impact on baroreceptors depending on their timing within the cardiac cycle and has the advantage that subjects cannot easily discriminate between conditions of stimulation and inhibition. Electroencephalograms were recorded from 22 subjects during PRES manipulations. A surface‐negative shift of about 10 μV developed during the cuff manipulations. Over frontal‐central regions, this shift was smaller during baroreceptor stimulation than during inhibition. These data provide support for the proposal that baroreceptor activation influences cortical activity.
Parametric manipulations of auditory stimuli differentially affect P3 amplitude in schizophrenics and controls
Authors: SALISBURY DEAN F. , O'DONNELL BRIAN F. , McCARLEY ROBERT W. , NESTOR PAUL G. , FAUX STEVEN F. , SMITH R. SCOTT
Published: February 2007

Schizophrenics show P3 amplitude reduction and topographic asymmetries. It is unclear whether the underlying cause of these deficits is primarily functional or structural. This study examined the effect of stimulus discrimi‐nability and task instruction on behavioral performance and P3 in schizophrenics and normal control subjects. Stimulus discriminability was manipulated by varying the overall loudness and pitch disparity of the two tones in an auditory oddball paradigm. Instructions emphasized either speed or accuracy of response. Instructions had no significant effects on reaction time, perceptual sensitivity, response bias, or P3. With increased discriminability, however, both groups improved in mean reaction time to targets and perceptual sensitivity. In controls, P3 became earlier and larger with increased stimulus discriminability and was consistently larger over left temporal areas than over right temporal areas. In schizophrenics, P3 latency was related to stimulus discriminability, but amplitude was not; P3 amplitude did not increase with improvement of perceptual sensitivity and reaction time. Unlike normal controls, schizophrenics had a P3 asymmetry at temporal sites, with reduced left‐sided voltages. The results are not consistent with a primarily functional cause of P3 aberrations in schizophrenia and are compatible with the hypothesis that P3 amplitude deficits in schizophrenia are related to underlying pathophysiology of temporal lobe generator sites.
Social neuroscience: Autonomic, neuroendocrine, and immune responses to stress
Authors: CACIOPPO JOHN T.
Published: February 2007

The immune system is influenced by central nervous system processes that are shaped by social and psychological factors. Considerations of social factors, intrapersonal processes, and autonomic psychophysiology therefore may contribute to a fuller understanding of both immune and brain function. Research reviewed here (a) examines the socioemotional factors that contribute to, or moderate, responses to brief and chronic stressors, (b) determines whether or not stable individual differences in heart rate reactivity predict neuroendocrine and immune responses to a brief psychological stressor and to an influenza virus vaccine, and (c) investigates the autonomic origins of individual differences in low and high heart rate reactivity and their relationship to neuroendocrine and immune responses to chronic and acute stressors. Among our findings are: (a) acute psychological stressors activate the sympathetic adrenomedullary system across individuals and affect immune function; and (b) individuals characterized by high sympathetic cardiac reactivity to acute psychological stressors also show a relative activation of the hypothalamic pituitary adrenocortical system and altered immune function.
Autonomic cardiac control. I. Estimation and validation from pharmacological blockades
Authors: BERNTSON GARY G. , CACIOPPO JOHN T. , QUIGLEY KAREN S.
Published: February 2007

Pharmacological blockades have been used to estimate the relative contributions of the autonomic branches to cardiac chronotropic control. Systematic biases in these estimates, however, can arise from both methodological and physiological factors. Selective blockades can be interpreted by two inferential models, and a single blockade condition can yield estimates of autonomic control for both autonomic branches. The residual autonomic control of the heart after blockade of a single division provides an index of the functional contribution of the unblocked branch. In contrast, the change in chronotropic state of the heart after blockade of the same division reflects the subtractive loss of that branch and thus provides an index of the normal contribution of the blocked branch. We demonstrate that the systematic biases that can arise in blockade studies introduce distortions of the subtractive and residual estimates that are of equal magnitude but opposite sign. Consequently, the discrepancy between the subtractive and residual‐model estimates provides a measure of bias in blockade studies and permits the derivation of validity indices that can facilitate interpretations of blockade data.
Individual differences in the autonomic origins of heart rate reactivity: The psychometrics of respiratory sinus arrhythmia and preejection period
Authors: CACIOPPO JOHN T. , UCHINO BERT N. , BERNTSON GARY G.
Published: February 2007

Heart rate reactivity has been conceptualized, at least implicitly, as a unidimensional construct ranging from low to high, reflecting individual differences in adrenergic reactivity to daily stressors. However, an individual's classification as high in heart rate reactivity ignores possible individual differences in the autonomic origins of this reactivity. Sixty‐eight women were exposed to orthostatic and speech stressors to determine the psychometric properties (postural stability, convergent and discriminant validity) of heart rate, preejection period, and respiratory sinus arrhythmia. Results revealed that (a) basal, stress, simple reactivity (stress — baseline), and residualized change indices of heart rate, prejection period, and respiratory sinus arrhythmia were stable across postures and (b) heart rate reactivity was significantly reatated to preejection period and respiratory sinus arrhythmia reactivity, whereas the latter two measures were unrelated. Reactivity classifications may therefore be significantly improved by attention to concurrent estimates of the activity of both autonomic branches.
Working memory and preparation elicit different patterns of slow wave event‐related brain potentials
Authors: RUCHKIN DANIEL S. , CANOUNE HOWARD L. , JOHNSON RAY , RITTER WALTER
Published: February 2007

Some event‐related brain potential (ERP) studies of working memory have used delayed match‐to‐sample designs in which a stimulus (S1) is held in memory for comparison with a subsequent stimulus (S2). During the S1‐S2 interval, ERP slow negativities varied with both the type and amount of material held in working memory. One interpretation is that these slow waves index working memory operations. An alternative explanation is that they only reflect general preparatory processing for the response to S2. To decide between these explanations, we used two visual processing tasks that required similar preparation for S2. In one task, visual memory rehearsal operations were required. During the S1‐S2 interval, there were clear differences between the amplitudes, topographies, and the effect of information load on the slow waves in the two tasks, thus ruling out preparation only as an explanation.
Effects of anger/hostility, defensiveness, gender, and family history of hypertension on cardiovascular reactivity
Authors: SHAPIRO DAVID , GOLDSTEIN IRIS B. , JAMNER LARRY D.
Published: February 2007

In this study, we examined the combined effects of anger/hostility and defensiveness on reactivity to three stressors (math, handgrip, cold pressor) and how these effects are moderated by gender and family history of hypertension. The subjects were 209 college students. Low compared with high Spielberger anger‐out scores were associated with greater diastolic blood pressure (DBP) reactivity in low‐but not high‐defensive women with a negative family history. High compared with low hostility scores were associated with greater heart rate reactivity in low‐defensive men with an opposite effect in high‐defensive men. Gender, family history, and defensiveness each affected differential DBP reactivity to the three tasks. Combined study of biological factors and coping styles can improve our understanding of cardiovascular reactivity and disease.
Circadian distribution of motor activity and immobility in narcolepsy: Assessment with continuous motor activity monitoring
Authors: MIDDELKOOP HUUB A. M. , LAMMERS GERT JAN , VAN HILTEN BOB J. , RUWHOF CINDY , PIJL HANNO , KAMPHUISEN HILBERT A. C.
Published: February 2007

The circadian distribution of motor activity and immobility of 14 unmedicated narcoleptics and matched controls was evaluated by monitoring continuous wrist motor activity 5 successive days and nights at home. Sleep was also assessed by sleep logs. The amplitude of the circadian rhythm of motor activity and immobility was significantly lower in narcoleptics than in controls. The variables that best distinguish narcoleptics from controls were the diurnal and nocturnal mean duration of uninterrupted immobility, which can be explained by excessive daytime sleepiness and frequent nocturnal awakenings, respectively. Thus, measures of diurnal and nocturnal motor activity and immobility appear useful for the objective assessment of some of the sleep‐wakefulness manifestations of narcolepsy.
Visual event‐related potentials in first‐episode psychotic patients and their relatives
Authors: KATSANIS JOANNA , IACONO WILLIAM G. , BEISER MORTON
Published: February 2007

We conducted a comprehensive examination of the sensory visual event‐related potential (ERP) of psychiatric patients and their relatives using a methodology that improves upon those used previously by other investigators. One hundred thirty‐five patients at the onset of their first psychotic episode, 146 first‐degree relatives of these patients, and 113 normal controls were exposed to light flashes of four different intensities while their ERPs were recorded from three central scalp sites. For most analyses, various ERP amplitude measures did not discriminate the different psychiatric groups or their relatives either from one another or from the normal controls. These findings indicate that patients with schizophrenia, schizophreniform disorder, and affective disorder at the early stage of their illness do not display significant deficits in the processing and regulation of simple sensory visual stimulation.
Distinct early and late subcomponents of the photic blink reflex: Response characteristics in patients with retrogeniculate lesions
Authors: HACKLEY STEVEN A. , JOHNSON LENWORTH N.
Published: February 2007

To assess cortical contributions to the photic blink reflex, signal averaged electromyograms (EMG) were compared for responses to strobe flashes presented within the blind and sighted hemifields of 13 patients with occipital lobe lesions. Reflexes evoked by flashes within the scotoma were virtually identical to those evoked by flashes within the intact visual field. This suggests that both the early and late components of this reflex (R50 and R80, respectively) are mediated by subcortical structures that do not require, or benefit from, conscious visual processing. Additional findings included larger R80s at the eyelid contralateral to the lesion, regardless of stimulated hemifield. This presumably reflects the loss of a tonic descending influence of visual cortex onto the motor limb of the reflex arc. The R80 was also larger for stimuli activating the crossed (temporal hemifield) rather than the uncrossed (nasal hemifield) afferent pathway.
The circadian variation of cardiovascular stress levels and reactivity: Relationships to individual differences in morningness/eveningness
Authors: NEBEL LINDA E. , HOWELL ROBERT H. , KRANTZ DAVID S. , FALCONER JENNIFER J. , GOTTDIENER JOHN S. , GABBAY FRANCES H.
Published: February 2007

Two studies assessed the circadian variation of cardiovascular responses to stress in healthy and coronary artery disease (CAD) populations. In within‐subjects designs, stressors were administered to healthy male subjects and male CAD patients both in the morning and afternoon, and subjects were classified as either morning or evening types using the Morningness‐Eveningness Questionnaire (Horne & Östberg, 1976, International Journal of Chronobiology, 4, 97–110). No consistent circadian variation in blood pressure or heart rate responses was observed in the aggregate sample of either healthy subjects or CAD patients. However, there were significant interactions between circadian type and time of day. In both populations, morning, subjects exhibited higher cardiovascular levels during the morning session, and evening subjects exhibited higher levels during the afternoon session. Analyses of cardiovascular reactivity revealed less consistent evidence for this interaction. Self‐reports of stress revealed interactions between time of day and and morningness/eveningness only in CAD sample. In CAD patients, preliminary analysis of myocardial wall function, an index of myocardial ischemia, did not reveal a significant interaction between morningness/eveningness and time of day, perhaps due to small sample size. The presence of differing circadian patterns in stress response based on individual differences in morningness/eveningness is discussed in teerms of its methodological implications for psychophysiological research and in terms of the role of stress as an acute trigger of CAD.
Mental and physical countermeasures reduce the accuracy of the concealed knowledge test
Authors: Honts Charles R. , Devitt Mary K. , Winbush Marcus , Kircher John C.
Published: February 2007

The effects of a physical (pressing the toes to the floor) and a mental (counting backward by sevens) countermeasure on the concealed knowledge test (CKT) were examined in a mock crime experiment with 40 subjects. Some knowledgeable subjects were informed about the nature of the CKT and were trained in the use of a countermeasure, whereas others remained uninformed. All subjects were offered a monetary reward if they could produce a truthful outcome. Subjects were tested using standard field techniques and instrumentation. The physical and, to a lesser extent, the mental countermeasures reduced the accuracy of the CKT. These results clearly demonstrate that the CKT has no special immunity to the effects of countermeasures.
Ventilatory responses to imagined exercise
Authors: GALLEGO JORGE , DENOT‐LEDUNOIS SONJA , VARDON GUY , PERRUCHET P.
Published: February 2007

We studied whether the ventilatory responses to imagined exercise are influenced by automatic processes. Twenty‐nine athletes produced mental images of a sport event with successive focus on the environment, the preparation, and the exercise. Mean breathing frequency increased from 15 to 22 breaths/min. Five participants reported having voluntarily controlled breathing, two of them during preparation. Twenty participants reported that their breathing pattern changed during the experiment: 11 participants were unable to correctly report on the direction of changes in frequency, and 13 incorrectly reported changes in amplitude. This finding suggests that these changes were not voluntary in most participants and may therefore reveal automatic forebrain influences on exercise hyperpnea. However, these changes may also reflect nonspecific processes (e.g., arousal) different from those occurring during actual exercise.
ERP repetition effects in indirect and direct tasks: Effects of age and interitem lag
Authors: RUGG MICHAEL D. , MARK RUTH E. , GILCHRIST JUNE , ROBERTS RICHARD C.
Published: February 2007

Event‐related potentials (ERPs) were recorded for visually presented words in young and older participants while they performed two tasks. In the indirect task, participants responded to occasional target words. Some of the nontarget words were repeated after a single intervening trial, and others were repeated after a mean of 10 trials. In the direct task participants responded to every item, discriminating between words presented for the first and the second times. Compared with ERPs to unrepeated words, those to words repeated in the indirect task after either lag were more positive in both participant groups. For the short lag, this effect was larger among the older participants. In the direct task, words repeated after either lag elicited a positive shift in the ERPs of the young participants. In the older participants, short lag repeats elicited a repetition effect, but smaller than the equivalent effect among the young participants. Long lag repeats failed to elicit a repetition effect in the direct task in the older participants. The findings show that word repetition in these tasks reflects the modulation of two ERP components, which differ in their sensitivity to age‐related changes in memory function.
Ten‐year stability of cardiovascular responses to laboratory stressors
Authors: SHERWOOD ANDREW , GIRDLER SUSAN S. , BRAGDON EDITH E. , WEST SHEILA G. , BROWNLEY KIMBERLY A. , HINDERLITER ALAN L. , LIGHT KATHLEEN C.
Published: February 2007

In this study we examined test‐retest stability of cardiovascular stress responses over a decade of the life span. Participants were 55 male college undergraduates. 19 years of age at initial testing, and 29 years of age at follow‐up testing Stressors were a foot cold pressor and an aversive reaction time task. Cardiovascular measures included systolic and diastolic blood pressure, heart rate, and preejection period. For cold pressor, the magnitude and pattern of cardiovascular responses remained unchanged at the 10‐year follow‐up. For the reaction time task, the characteristic cardiovascular response patterns was preserved but with significant attenuation of magnitude. The present findings are consistent with previous observations of temporal stability but over a substantially longer test‐retest interval. The long‐term stability of stress responses is discussed in the context of stress test methodology, behavioral response demands, and maturation of the physiological systems involved in cardiovascular response expression.
The effects of recent food, alcohol, and tobacco intake and the temporal scheduling of testing on cardiovascular activity at rest and during psychological stress
Authors: SHEFFIELD DAVID , DAVEY SMITH GEORGE , CARROLL DOUGLAS , SHIPLEY MARTIN J. , MARMOT MICHAEL G.
Published: February 2007

Participants in cardiovascular psychophysiological studies receive various instructions regarding restraints on alcohol, food, and tobacco intake prior to testing. Further, although the hour of testing is frequently a concern, little attention is paid to month of the year. In the present study, we examined cardiovascular activity at rest and in response to a laboratory stress task in 1,272 men in terms of these variables. Alcohol consumption among alcohol users and food intake within 4 hr of testing were associated with higher baseline diastolic blood pressure (BP) but lower baseline heart rate (HR). Tobacco use in smokers within 1 hr of testing was associated with elevated baseline BP and HR. Hour of testing was related to baseline HR, whereas month of the year was associated with baseline BP. In contrast to these baseline effects, cardiovascular reactions to the laboratory stress task were largely immune to these contextual influences.
Suppression of sleepiness in drivers: Combination of caffeine with a short nap
Authors: Reyner Luise A. , Horne James A.
Published: February 2007

Previous research has shown that caffeine and a<15‐min nap effectively and separately reduce sleepiness in drivers for I hr. In the present study, we examined in 12 sleepy individuals the treatments combined, taken during a 30‐min break, prior to a longer (2 hr) continuous monotonous afternoon drive in a car simulator. Nonnap comparisons were 200 mg caffeine only and placebo. For placebo, driving incidents. Subjective and electroencephalographic measures of sleepiness all reflected a mid‐afternoon peak'. This peak was significantly reduced by caffeine and eliminated by the combined treatment, which reduced incidents to 9% of placebo levels versus 34% of placebo levels for caffeine alone. Naps comprising “nonsleep dozing” were still effective.
Attentional selection and attentional gradients: An alternative method for studying transient visual‐spatial attention
Authors: EIMER MARTIN
Published: February 2007

In two experiments, I employed an alternative method for studying transient visual‐spatial attention. Instead of using precuse, attention was manipulated by presenting most stimuli sequentially at predictable locations. In Experiment 1, most stimuli appeared in a regular clockwise or counterclockwise order, but some were separated by one or both visual meridians from the expected location. In Experiment 2, most stimuli were presented succesively along the horizontal meridian, and some stimuli were separated by one, two, or three positions from the expected location. Faster response times and larger posterior P1 and N1 components as well as enhanced negativities at midline electrodes were found for expected‐location than for unexpected‐location stimuli. These effects were partially modulated by the distance of unexpected stimuli from the current focus of attention, suggesting the existence of attentional gradients. Moreover, the data suggest that the direction of previous attentional shifts and the visual meridians play an important role for spatial attention.
Effects of source and amount of fertilizer nitrogen and nitrification inhibitors on the yield and nitrate concentration of glasshouse lettuce
Authors: Vaughan J.
Published: February 2007

Abstract. Urea and ammonium were compared with and without nitrification inhibitors (nitrapyrin and dicyandiamide) as a possible means of reducing the nitrate concentration in winter lettuce grown in the glasshouse. Neither inhibitor had a significant effect on nitrate concentrations at the lower rate of applied nitrogen (138 kg ha−1 N). At the higher rate of urea (414 kg ha−1 N) dicyandiamide significantly reduced the nitrate concentration but this was accompanied by an unacceptable loss in yield and quality thought to be due to phytotoxic effects of the high level of residual ammonium. Nitrapyrin had no effect on the nitrate concentrations in lettuce.
Farmers' judgement of land evaluation in the Welsh marches
Authors: Fisher P. F. , John D. T. , Williams D. P.
Published: February 2007

Abstract. An interview survey of farmers' assessment of the overall capacity of land, as well as its suitability for specific uses is compared with the judgement of the Soil Survey of England and Wales. The results are interpreted as showing that in a general evaluation the farmers are accurately aware of the quality of their land, but they are less well informed as to its true suitability for specific uses. The comparison shows the potential importance of land suitability analysis to the farmers, especially at a time of changing economic pressures.
Practical aspects of sportsfield drainage
Authors: Adams W.A.
Published: February 2007

Abstract. The use of sportsfields in winter results in drastic changes in the physical properties of most soils. In consequence adequate sportsfield drainage demands much greater attention to the transmission of incident rainfall to the underdrain system than is normally necessary in agricultural drainage. Solutions to the problem differ in concept and cost, and range from complete profile construction to bypass drainage systems, causing minimal soil disturbance. Specific requirements are examined and practical solutions illustrated and discussed.
Computer programs to assist the automation of soil description
Authors: Fisher P.F. , Pearson M.D. , Clarke S.R. , Ragg J.M.
Published: February 2007

Abstract. Computer‐compatible proformas have been designed to incorporate soil descriptions into automated soil information systems. This paper presents two systems designed to replace proformas by enabling the direct entry of soil descriptions into computers. One, CASTS (Computer Aided Soil Thin Section description), is in essence a computerized glossary of the terms used to describe soil thin sections. The terms are organized into menus that are presented to the user in a fixed, logical sequence. The system runs on an Apple microcomputer or VAX minicomputer. The other, SPR (Soil Profile Recorder), is for use in the field on the Husky Hunter lap computer. The program enables descriptions from soil auger‐borings to be recorded, and has facilities to manipulate entries and transmit them to a central information system. These computer systems are compared with the proformas, and recommendations are made for incorporating improvements in future versions.
A critical state soil mechanics model for agricultural soils
Authors: Hettiaratchi D.R.P.
Published: February 2007

Abstract. The paper presents the experimentally derived state boundary surfaces of critical state theory for a sand, a loam and a clay soil. Orderly changes to these surfaces with moisture content and two soil micro‐structural states have been identified. These findings are used as the basis for the formulation of a fairly simple universal model of the geometry of critical state space for unsaturated soils. Examples are given of how this model can be used to explain known soil behaviour in many practical situations. The indications are that this model can provide the theoretical framework for a fundamental comprehension of the many complex processes involved in soil loosening and compaction. There is, as yet, no simple experimental technique for measuring the critical state boundaries of field soils and this is a major impedement to the development of the model as a practical soil management tool.
The effects of shelter for cereal crops in an exposed area of Cleveland, North‐East England
Authors: Hough M.N. , Cooper F.B.
Published: February 2007

Abstract. Plots of spring barley, winter wheat and winter barley were sheltered with netting in a coastal area of North‐East England. Crop height, yield components and grain yield were measured and compared with unsheltered crops receiving the same agronomic treatments. Plant height, ears m‐2, 1000 grain weight and grain yield were increased by shelter in seasons with windy, dry weather during the tillering and stem extension phases. Negligible response was found in a wet season. One experiment suggests that greater applications of nitrogen fertilizer can counteract the effects of exposure.
A regression model for nitrate leaching in Northern Ireland
Authors: Smith R.V. , Stewart D.A.
Published: February 2007

Abstract. A model has been developed based on multiple regression which explains 95% of the variation in nitrate loading of the major rivers in the 4453 km2 Lough Neagh catchment for the years 1971–1987. The model relates loading of nitrate in the hydrological year to fertilizer usage, previous summer rainfall, summer temperature of the current year and December‐May flow. It indicates that there is an increase in nitrate loading associated with fertilizer usage, and that the equivalent of 13% of nitrogen fertilizer that is lost as leachate comprises 50% of the river loadings.
Soil physical conditions of the root zone layer and the performance of winter games' pitches
Authors: Baker S.W.
Published: February 2007

Abstract. The performances of 16 different sand and sand‐soil root zone constructions were examined during three seasons of simulated football‐type wear. Water infiltration rates were controlled mainly by the percentage of sand in the rooting matrix although the type of sand also had a strong effect in the pure sand root zones. Even mixes with 91% sand had poor infiltration after two seasons of wear and suffered from occasional ponding after heavy rain. Pure sand root zones and high‐specification sand‐soil mixes had better grass retention and a firmer surface in wet weather than root zone material with sand contents < 90%. Traction values for the different root zone materials were similar, except for a pure sand construction based on a coarse 0.25–1.0 mm diameter sand. However, pure sand constructions can become unstable, particularly in dry conditions if the ground cover is less than 20%. Strategies for the use of sand amelioration and pure sand root zones are discussed in relation to the demands of particular user groups.
Approaches to measuring the contribution of nematodes and protozoa to nitrogen mineralization in the rhizosphere
Authors: Griffiths B.S.
Published: February 2007

Abstract. Nematodes and protozoa assist nitrogen mineralization by consuming bacteria, and this may increase the amount of nitrogen taken up by plants so that it exceeds the amount lost by root exudation. One of the methods used to determine bacterial consumption by protozoan grazers in aquatic ecosystems, namely progressive dilution of the grazing pressure, was tested in a sandy soil. The result suggests that a basic assumption of the technique, that grazing is directly proportional to the dilution factor, is untrue for soils, possibly because the increase in moisture content with increasing dilution enhances grazer activity.
Epidemiology of fungally‐transmitted viruses
Authors: Adams M.J.
Published: February 2007

Abstract. The recent spread of sugar‐beet rhizomania and barley yellow mosaic virus in Europe has stimulated fresh interest in plant viruses with soil‐borne fungal vectors. Although there are at least 20 such viruses, most of which cause diseases of important field crops, there are many gaps in our knowledge of their epidemiology because much research has concentrated exclusively on the viruses. The vectors are lower fungi that are obligate parasites of plant roots and are therefore difficult to study experimentally. Resting spores containing virus can survive indefinitely in soils but effects of rotation have not been greatly studied. There is no quantitative information relating inoculum levels of fungus and virus to disease development. Only limited information is available about inoculum distribution in soil and factors affecting its potency. The diseases are mostly dispersed by soil movement during agricultural operations but some features of disease distribution in infested fields await adequate explanation. Little is known about interactions with other micro‐organisms.
Forestry and soil protection in the UK
Authors: Moffat A.J.
Published: February 2007

Abstract. Protection of soil against common threats to its function are discussed in relation to UK forestry practice. British forestry uses very little fertilizer and pesticides, so the effect of their use on forest soil is minimal. Some soil acidification often accompanies forestry, but there is as yet no evidence that UK forest condition or yield have suffered as a consequence. Proper management of forest operations can control the severity of soil compaction and erosion, and though there is no evidence that either is widespread, more information is required on their occurrence.
Soil nitrate sources and nitrate leaching losses, Slapton, South Devon
Authors: Trudgill S. T. , Burt T. P. , Heathwaite A. L. , Arkell B. P.
Published: February 2007

Abstract. Concentrations of soil nitrate were measured in areas of different land use within a small drainage basin. From previous work on nitrate losses from subcatchments, soil nitrate levels were expected in the order arable > grassland > woodland. Although differences were detected, they were not consistent and seasonal variations in soil nitrate for the same land use were greater than those between land uses. Seasonal fluctuations in stream nitrate loads were not strongly related to the seasonal differences in soil nitrate levels but were more closely related to stream discharge and antecedent climatic conditions. Losses of nitrate from the catchment seemed to be transport limited and independent of variations in soil nitrate supply; the implication is that water quality control by land use manipulation will only be successful in supply limited situations when leaching losses are sensitive to variations in soil nitrate supply.
Influence of land use on soil properties in a forest region of Southern Nigeria
Authors: Ogunkunle A. O. , Eghaghara O. O.
Published: February 2007

Abstract. To assess the effect of different land uses on soil properties, five land use types (fallow, Gmelina, arable, secondary forest and cocoa plots) on a sandy loam Alfisol (Typic Kandiudalf) were compared in terms of surface (0–15 cm) soil pH, exchangeable acidity, K, Ca and Mg, extractable P, total N, organic matter, gravimetric moisture, temperature and bulk density. There were significant differences (P≤ 0.05‐P≤ 0.001) between the land use types for all the properties except exchangeable acidity and moisture. All the land use types differed significantly from each other in at least four properties. Fallow and secondary forest differed in nine properties, fallow and cocoa in seven and fallow and Gmelina in six. In terms of the number of properties with high variability (CV ≥ 35%), the order was arable, secondary forest and cocoa (4) > Gmelina (3) > fallow (1).
Erosion rates on bare loamy sand soils in east Shropshire, UK
Authors: Fullen M. A.
Published: February 2007

Abstract. Results from over seven years of monitoring of erosion rates on bare arable loamy sand soils at the Hilton experimental site, Shropshire, UK, are reported. On bare plots, rates are very variable; erosion during one summer convectional storm exceeded that recorded during six individual years of plot measurement. Exposure of erodible arable soils to convectional storms puts them at risk of excessive erosion. Plot erosion rates were frequently high, with rates up to 67.4 t/ha occurring during an individual storm. Rates were influenced by rainfall erosivity, slope steepness and soil organic content. Mean soil organic content on the bare plots decreased over five years by 0.08%/yr.
Soil conservation options in the UK
Authors: Morgan R. P. C.
Published: February 2007

Abstract. Soil erosion occurs with sufficient frequency and severity on arable land in the UK to warrant erosion control measures. The main justification is to decrease the off‐farm damages resulting from sedimentation and pollution. The grassing of valley floors, the creation of riparian buffer zones and the use of winter cover crops are recommended as suitable measures. These have additional benefits in terms of wildlife habitats and decrease of nitrate leaching. Financial incentives targeted at farmers in erosion‐sensitive areas are proposed as the main method of implementation.
Effects of rainfall intensity and antecedent moisture on the steady‐state infiltration rate in a semi‐arid region
Authors: Bowyer‐Bower T. A. S.
Published: February 2007

Abstract. The infiltration and runoff responses of degraded and non‐degraded semi‐arid land surfaces were investigated by rainfall simulation in the Lowveld of Swaziland. The hydrological response of the soil was controlled by changes in the properties of the soil surface, the nature of which was dependent upon rainfall intensity and antecedent moisture, as well as upon soil type and condition. Rather than there being one final steady‐state infiltration rate for a given soil type and condition (i.e. a constant of soil response), the final rates achieved were variable for each soil type and condition, and depended upon rainfall intensity and antecedent moisture. The implications of this for soil use and management in terms of infiltration measurement and runoff assessment are considered.
Scope for more efficient use of fertilizer nitrogen
Authors: Sylvester‐Bradley R.
Published: February 2007

Abstract. About 1.6 million tonnes of fertilizer N are applied to UK crops each year. In net terms, 10–60% of this is not taken up by the crop to which it was applied. Fertilizer N commonly doubles crop yield, but in the short term at least more than 90% of current production would be possible with only half normal use of N. However, costs of crop production other than fertilizer N are a large proportion of gross returns, so profits are sensitive to adjustments in N use and controls on N use could affect land values. Survey data show that compliance with current recommendations is good; recent improvements have come through restricting the use of N applications in autumn. Further improvements are possible by adjusting N use more fully for the extent to which past N applications have exceeded crop removal, and by better targeting the N used to improve protein concentrations of wheat grain. Research now in progress may provide insights into minimizing the crop N necessary for yield formation and the crop N left in the field at harvest, specifying the growing conditions which result in efficient N uptake from soil.
Influence of cattle trampling on soil porosity under alternate dry and ponded conditions
Authors: Taboada M. A. , Lavado R. S.
Published: February 2007

Abstract. The impact of cattle trampling on the porosity of a representative soil (Typic Natraquoll) of the flooding Pampa of Argentina was studied from 1984 to 1987. Water content, total porosity (TP), macroporosity (> 30 μm) and mean weight diameter of water‐stable aggregates (MWD) were determined in undisturbed topsoil samples taken from adjacent continuously grazed (1.0 animal unit/ha/yr) and ungrazed (since 1976) areas. It was expected that trampling would decrease macroporosity when the soil was ponded, and that the damaged macropores would regenerate during the subsequent soil drying. This was only partly verified. The soil varied in TP from 58 to 64% in the ungrazed area, and from 53 to 78% in the grazed area. This variation resulted mainly from shrink‐swell processes. Trampling decreased soil macroporosity (mainly >60 μm) from 8 to 5% and decreased MWD from 5.35 to 4.58 mm under dry soil conditions. The damaged soil pores regenerated and aggregate stability recovered during the subsequent period of surface water ponding, when soil swelling increased macropores in the grazed area but not in the ungrazed area. There was no evidence of poaching damage in this soil.
The effect of different post‐restoration cropping regimes on some physical properties of a restored soil
Authors: Davies R. , Younger A.
Published: February 2007

Abstract. The aggregate stabilities of a soil restored after opencast mining and an undisturbed soil were measured over a complete cropping year from the time of ploughing a grass ley in autumn. This was to examine the effects of various post‐restoration cropping regimes on soil aggregate stability and soil porosity. A wet sieving technique and a mild dispersion method were used to determine indices of soil macro‐ and micro‐aggregate stability, respectively. Air filled porosity at field capacity and crumb porosity were also determined. Removal, storage and restoration decreased macro‐ and micro‐aggregate stability. After restoration, the different grass managements i.e. cutting for silage and grazing, had similar effects on soil aggregate stability and maintained greater aggregate stability than the arable regimes. The pattern of fluctuation in soil macro‐aggregate stability over the year was similar under all crops at both sites, but at the restored site there was a decline in stability, and differences in the air filled porosity at field capacity developed between cropping regimes. Micro‐aggregate stability was less at the restored than at the undisturbed site and showed no seasonal variation or difference between cropping regimes. However, a difference in crumb porosity between cropping regimes did develop.
Maintaining soil fertility under increasing land use pressure in the Middle Mountains of Nepal
Authors: Schreier H. , Shah P.B. , Lavkulich L.M. , Brown S.
Published: February 2007

Abstract.Nepal is facing a serious problem of being unable to maintain soil fertility in agriculture and forestry. Land use practices initiated over the past 10–15 years have resulted in insufficient nutrient inputs, while biomass use and production have increased. Changes in forest soil fertility have resulted from intensive use of forest biomass for animal feed and collection of forest litter for use in agriculture. The agricultural fertility changes have resulted from intensifying annual crop rotations from 1.5 to 2.5 crops and insufficient inputs. The removal of biomass from the forest has curtailed the natural organic cycle by virtually eliminating nutrient inputs.

The soils are very acidic and have little C, N, P and exchangeable bases, but have large amounts of active iron. Basic nutrients are not sustained in agriculture and differences in inputs and management between irrigated and rainfed agricultural systems are becoming visible. Irrigated fields show the largest cation content because of input from irrigation water. Rainfed agricultural sites, which receive the most nutrients (fertilizers and manure), have the highest pH values and C and N contents. All soil fertility conditions are marginal and put into question the long‐term sustainability of current levels of production. Alterations in the cropping intensity are needed and the introduction of nitrogen fixing trees and crops seems to be the most viable option towards sustainability.
The carbon content of soil and its geographical distribution in Great Britain
Authors: Howard P.J.A. , Loveland P.J. , Bradley R.I. , Dry F.T. , Howard D.M. , Howard D.C.
Published: February 2007

Abstract. England and Wales have 155 314 1 × 1 km squares, of which 140049 have more than 50% soil cover. The total soil organic carbon content, based on the dominant soil series and dominant land cover type, is estimated to be 2773 × 106 t C. Scotland has 84929 1 × 1 km squares, of which 82 420 have a nominated dominant soil series. The total soil organic carbon content is estimated to be 19011 × 106 t C, 6.85 times the total organic carbon content of the soil of England and Wales. The total organic carbon content of the soil of Great Britain is estimated to be 21 784 × 106 t C, of which 87% is in Scottish soils and 75% is in Scottish peats.

A map of the mean soil organic carbon content of 10 × 10 km squares of the National Grid using classes of equal range illustrates the narrow range of organic carbon contents of the soils of England and Wales and the dominance of organic carbon in Scottish soils. A map using the same data, but with classes of unequal ranges increasing in size with increasing carbon content, is better for showing detailed differences within England and Wales.
Desert reclamation using Yellow River irrigation water in Ningxia, China
Authors: Fullen M.A. , Fearnehough W. , Mitchell D.J. , Trueman I.C.
Published: February 2007

Abstract. The effects of silt‐laden Yellow River irrigation water on the properties of reclaimed dune sands were investigated at the Shapotou Research Station in Ningxia Autonomous Region, China. The practice resulted in distinct and rapid improvements in the physical and chemical properties of reclaimed desert soils. Irrigation led to the development of sandy loam topsoils, with up to 39 cm accumulating over 25 years of treatment. These topsoils had improved structure, greater soil organic matter contents and smaller bulk densities than buried desert sands. Geochemical analyses suggested river silt and sheep manure were making distinctive contributions to the improved soil fertility, with older topsoils having progressively greater concentrations of Ca, Mg, K, P, S, Fe, Mn and Zn. Soil Cr concentrations are increasing and it seems appropriate that changes in heavy metal concentrations in irrigated soils are monitored.
A risk assessment of sulphur deficiency in cereals using soil and atmospheric deposition data
Authors: McGrath S.P. , Zhao F.J.
Published: February 2007

Abstract. A qualitative model was used to assess the risk of S deficiency in cereals in Britain. A risk index was generated for each of 6301 soil data points by considering the inputs of S from atmospheric deposition, the content of soil organic matter, and factors influencing the potential leaching of sulphate, i.e. soil type, texture, pH and annual rainfall. The results show that currently 11% of the British land area is at high risk of S deficiency, and a further 22% at medium risk. The high risk areas are in south‐east Scotland, the Scottish Borders, East Anglia, the Welsh Borders and south‐west England. These agree well with the distribution of reported incidences of S deficiency in cereals. If the UK target for reduction in SO2 emissions by the year 2003 is met, the model predicts that the high and medium risk areas will increase to 23 and 27%, respectively. Thus, agricultural use of S‐containing fertilizers is likely to increase in importance in the near future.
Soil structural improvements with the addition of Lantana camara biomass in rice‐wheat cropping
Authors: Sharma P.K. , Verma T.S. , Bhagat R.M.
Published: February 2007

Abstract. A long‐term field experiment was initiated in June 1988 in a silty clay loam soil to investigate the potential of Lantana camara, an obnoxious weed, for improving structural properties and productivity of soil in rice‐wheat cropping. Lantana was incorporated into the soil 10–15 days before puddling at 10, 20 and 30 t/ha (fresh weight).

At the end of the sixth cropping season, Lantana additions increased the organic carbon (OC) of the 0–15 cm soil layer by 11–24%, and of water‐stable aggregates (WSA, 0.50–8.0 mm diameter) by 10–21%; OC of WSA <0.50 mm diameter remained unaffected. About 17–25% of the applied OC was retained in the soil. The OC increase resulted in a decrease in bulk density of the plough layer (0–15 cm) by 7%, a decrease in aggregates of 2–8 mm diameter and of clods by 4% and 6%, respectively. There was an increase in water‐stable aggregates and aggregate porosity, and a decrease in clod‐breaking strength from 420 to 216 kPa. Soil cracking at the surface changed from wide, deep cracks in hexagonal pattern to a close‐spaced network of fine cracks. Lantana additions increased <5mm wide cracks at the expense of 10–20 mm wide cracks; 5–10 mm wide cracks remained unchanged. Total volume of cracks decreased by 36% and surface area of cracks by 55% compared with the control plots.