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Aims: To use national surveillance data in Canada to describe gender differences in the pattern of farm fatalities and severe injuries (those requiring hospitalisation). Methods: Data from the Canadian Agricultural [...]

Some previously described environmental associations for atopic eczema may be due to reverse causation. We explored the role of reverse causation by comparing individual- and school-level results for multiple atopic eczema risk factors. The International Study of Asthma and Allergies in Childhood (i.e, ISAAC) Phase Three surveyed children in schools (the sampling unit) regarding atopic eczema symptoms and potential risk factors. We assessed the effect of these risk factors on atopic eczema symptoms using mixed-effect logistic regression models, first with individual-level exposure data and second with school-level exposure prevalence. Overall, 546,348 children from 53 countries were included. At ages 6–7 years, the strongest individual-level associations were with current paracetamol use (odds ratio [OR] = 1.45, 95% confidence interval [CI] = 1.37–1.54), which persisted at school-level (OR = 1.55, 95% CI = 1.10–2.21), early-life antibiotics (OR = 1.41, 95% CI = 1.34–1.48), and early-life paracetamol use (OR = 1.28, 95% CI = 1.21–1.36), with the former persisting at the school level, whereas the latter was no longer observed (OR = 1.35, 95% CI = 1.00–1.82 and OR = 0.94, 95% CI = 0.69–1.28, respectively). At ages 13–14 years, the strongest associations at the individual level were with current paracetamol use (OR = 1.57, 95% CI = 1.51–1.63) and open-fire cooking (OR = 1.46, 95% CI = 1.33–1.62); both were stronger at the school level (OR = 2.57, 95% CI = 1.84–3.59 and OR = 2.38, 95% CI = 1.52–3.73, respectively). Association with exposure to heavy traffic (OR = 1.31, 95% CI = 1.27–1.36) also persisted at the school level (OR = 1.40, 95% CI = 1.07–1.82). Most individual- and school-level effects were consistent, tending to exclude reverse causation.

It has recently been suggested that lycra garments are helpful for children with cerebral palsy (CP). Twelve children, with athetosis, ataxia, and spasticity, were fitted with lycra garments (Kendall-Camp UK Ltd). Scores on the Paediatric Evaluation of Disability Inventory (PEDI) scales were determined before and after wearing the garment for at least 6 hours a day for 6 weeks. Five children with motor problems representative of the whole group were investigated during a reach-and-grasp task by kinematic motion analysis; reflective markers were used with and without the garment. Carers were given a questionnaire concerning the practicalities of using the garments. All 12 children made improvements in at least one of the functional scales of the PEDI, and scores for the whole group showed significant gains (Wilcoxon χ2 test, self-help p<0.01; mobility p<0.5; social p<0.1). These changes were usually slight, although noticed by carers. Six children made gains of at least one scale of the caregiver assistance scores, two of the children showed losses (due to difficulties removing the garment for toileting), and four showed no change. Motion analysis indicated that (1) two children with athetosis had improved proximal stability in sitting and in smoothness of arm movements, (2) one child with ataxia had improved in proximal and distal stability, and (3) two children with spasticity had more jerky movements, although one improved in proximal stability. All children had problems in wearing the garments, including problems with toileting and incontinence of urine; the parents of only one child wanted to continue using it. Results suggest that the functional benefit of lycra garments for children with CP is mainly due to improvements in proximal stability but this should be weighed against the inconvenience and loss of independence.

It has recently been suggested that lycra garments are helpful for children with cerebral palsy (CP). Twelve children, with athetosis, ataxia, and spasticity, were fitted with lycra garments (Kendall-Camp UK Ltd). Scores on the Paediatric Evaluation of Disability Inventory (PEDI) scales were determined before and after wearing the garment for at least 6 hours a day for 6 weeks. Five children with motor problems representative of the whole group were investigated during a reach-and-grasp task by kinematic motion analysis; reflective markers were used with and without the garment. Carers were given a questionnaire concerning the practicalities of using the garments. All 12 children made improvements in at least one of the functional scales of the PEDI, and scores for the whole group showed significant gains (Wilcoxon χ2 test, self-help p<0.01; mobility p<0.5; social p<0.1). These changes were usually slight, although noticed by carers. Six children made gains of at least one scale of the caregiver assistance scores, two of the children showed losses (due to difficulties removing the garment for toileting), and four showed no change. Motion analysis indicated that (1) two children with athetosis had improved proximal stability in sitting and in smoothness of arm movements, (2) one child with ataxia had improved in proximal and distal stability, and (3) two children with spasticity had more jerky movements, although one improved in proximal stability. All children had problems in wearing the garments, including problems with toileting and incontinence of urine; the parents of only one child wanted to continue using it. Results suggest that the functional benefit of lycra garments for children with CP is mainly due to improvements in proximal stability but this should be weighed against the inconvenience and loss of independence.

A field study was conducted with the objective of determining if differences occur in soil N transformations between zero and conventional tillage systems. Tillage comparisons of 2, 4, 12, and 16 yr duration were studied at four locations on Chernozemic soils in Western Canada. Determination of mineral N levels and immobilization of 15N‐urea fertilizer indicated that only slight, periodic, transient differences occurred between tillage systems. The degree of N mineralization‐immobilization turnover, which was associated with the incorporation of crop residues and level of labile organic matter in the surface soil, was not markedly affected by tillage differences. Over the growing season, fertilizer N entering the nonmicrobial biomass organic N pool increased relative to the microbial biomass pool, suggesting that in both systems N was entering more stabilized forms of organic N over time. These results would suggest that the differences in tillage system did not cause marked changes in the soil N cycle.

In conjunction with field studies on gaseous losses of nitrogen, the transformations of fall‐applied 15N‐labelled KNO3and urea (with and without nitropyrin) were studied in black and dark brown Chernozemic (Typic Udics and Typic Haploborolls) soils during 1980–81 and 1981–82. The amount of fall‐applied N which could not be accounted for in the following spring ranged from 25 to 33% (2 sites) for KNO3and only 10 and 5% from urea without and with nitropyrin, respectively. These losses occurred during the fall (before the soil was frozen) and in the following spring (after soil thaw) and were primarily due to denitrification. Nitrification of NH+4‐N from applied urea occurred at a slow rate during the cool late fall until freeze‐up and commenced again in early spring when the soil warmed up. Application of nitrapyrin in conjunction with urea delayed nitrification as well as downward movement of fertilizer N in the soil profile and was effective in decreasing the denitrification losses. Immobilization of fertilizer N was minimum under fallow conditions (7%) but ranged from 15 to 21% and 24 to 26% of the applied N as KNO3and urea, respectively, in wheat stubble fields. Nitrapyrin did not affect the immobilization of fertilizer N or the amount of fertilizer N found in the microbial‐biomass.

A growth chamber experiment was carried out in which soil coumns that had received none or 200 kg N/ha were subjected to two differing water regimes. The δa15N (per mill 15N excess) of the NO3‐N present in the leachate of all treatments decreased initially, with maximum depletion occurring between 4 and 6 weeks. In general, during the 14‐ to 16‐week period, large increases in the δa15N of the leachate occurred. The magnitude of the decreases and subsequent increases were least for the drier water regimes receiving no fertilizer N (δa15N ranging from −2 to +7) and greatest for the high water fertilized treatment (δa15N ranging from −12 to +40). This very extensive fractionation was attributed to the preferential nitrification of 14NH4+. Isotope balance calculations based on the isotope dilution principle are included to illustrate the serious errors that can be made in estimating the fertilizer N content of selected N compartments if the NO3‐‐N is leached before the NH4+oxidation is completed.

This report consists of a re-analysis of life event and illness onset data collected in community and hospital based studies of women in Camberwell, London. Previous analyses of this data by Brown and colleagues adopted a categorical approach, with a high threshold for deciding whether severe life stress had occurred. However, further practical and theoretical advances in investigating event-illness relationships may be achieved by considering an alternative conceptualisation of life stress. This report contrasts the results obtained by the categorical approach with those from one based upon a model of adversity incorporating assumptions both of additivity between events and of decay in their stressful effect over time. The results suggest that whilst the two methods are complementary in substantive terms, they convey markedly different practical and theoretical possibilities.

The gaseous losses of N from conventional‐till (CT) and zero‐till (ZT) crop fields were 3 to 7 and 12 to 16 kg N ha−1y−1, respectively. In contrast, losses from CT and ZT fallow were severalfold higher, namely, 12 to 14 and 34 kg N ha−1, respectively. The more dense surface soil and consistently higher moisture content (lower air‐filled porosity) were identified as major factors affecting increased denitrification under ZT. The potential denitrification rates were markedly higher under ZT, and the population of denitrifiers was up to six times higher than in CT soil samples. The contribution of lower soil horizons towards gaseous N losses was found to be low on both CT and ZT fields, and this finding was confirmed from a survey carried out on three other widely differing soils. Volumetric soil moisture and air temperature were the only two of several factors that accounted for a significant portion of the variations in gaseous N fluxes under field conditions. The average mole fraction of N2O ranged from almost 100% to as low as 28% of the total gaseous products and showed a negative relationship with soil moisture.

A field study was conducted with treatments consisting of a factorial combination of N (0 or 100 kg N ha−1as (NH4)2SO4, straw (0 or 3000 kg ha−1), and two tillage treatments. Ground straw was mixed with the plow layer of soil in the conventional till (CT) plots and chopped straw was spread over the surface of the zero till (ZT) plots. Wheat (Triticum aestivumL.) was grown as the test crop. Gaseous losses of N were measured using the acetylene inhibition‐soil core technique and compared with loss estimates obtained from the imbalance in the N budget of 15N‐treated microplots located within the larger yield plots. When adequate inorganic N was present, the incorporation of straw in CT soil or the application of straw on the surface of ZT soil approximately doubled the accumulative gaseous N losses. The straw apparently increased the supply of energy material available to denitrifying organisms, and also increased surface soil moisture content (particularly during the month of June). This further stimulated denitrification in ZT soil. Unaccounted 15N on the fertilizer N balance studies agreed closely with cumulative N losses using the acetylene inhibition technique.

Linear potential sweeps and potentiostatic pulse perturbations have been employed to investigate the influence of the expander ammonium lignosulphonate, on the anodic formation of PbSO4on lead amalgam electrodes in sulphuric acid solutions at 24 °C. It was found that the expander strongly adsorbs onto the clean amalgam surface thus affecting the formation of the PbSO4film. The expander increased the charge necessary for passivation, inhibited the cathodic reduction of the film, and produced a more porous film. Evidence is given for the presence of an optimum concentration of expander. Some speculations concerning the mode of action of the expander onto the amalgam surface are presented.

Rapeseed plant tissue and composite soil samples from field fertility plots were assayed for total N and inorganic N content, respectively, and corresponding 15N abundance. Lower δa15N values were obtained for subsurface horizons containing residual fertilizer‐N in both dryland (−2.0) and irrigated (ave. −3.5) plots compared to the surface horizons (3.4 and ave. 8.6). A systematic decline in the δa15N values of the plant tissue was observed with irrigation application (20 and 30 cm) and application of N fertilizer (220 kg/ha). This was attributed in both instances to the increased contribution of fertilizer N to the plant. Calculation of the mass balance of the two isotopes in the fertilized dryland treatment indicated that no significant fractionation had occurred during N uptake by plants but the differences in the δa15N values represented changes in soil N. While this study has clearly demonstrated the potential of utilizing variations in natural 15N abundance to trace the fate of applied fertilizer N, it has also shown that it is of utmost importance to recognize the N transformations that have taken place in the soil‐plant system and the isotope effects that accompany them.

The effects of wheat straw incorporation on denitrification, immobilization of N, and C mineralization were investigated at H2O contents of 60, 90 and 120% saturation. Incorporation of increasing levels of straw consistently increased the rate of denitrification for the first 4–8 d, followed by negligible N losses thereafter. In a total period of 96 d, the addition of 1.0% straw increased N losses from 2.5 to 10.1, and from 61.6 to 83.9 μg g−1in the 60 and 120% water saturation treatments, respectively. The pattern of CO2-C evolved was practically identical to that of the denitrification rate for the initial period when sufficient was present. This study has confirmed that in flooded soils, high rates of denitrification will persist only when C is supplied by native or applied organic C sources, provided adequate is present. When was low, denitrification rates rapidly decreased, even with a sufficient supply of C. Immobilization of fertilizer N (50 μg N g−1as K15NO3) was very rapid. Around 90% of the total immobilization of applied N occurred within 4 d. Incorporation of 1.0% straw increased the immobilization of fertilizer N from 8.4 to 42.8, and from 1.0 to 7.6% in the 60 and 120% water-saturated treatments, respectively. Remineralization of recently immobilized fertilizer N was observed after 32 d in the 60% saturation treatments only. Key words: Denitrification, wheat straw, mineralization of N

Annual grain legume production has increased substantially in Western Canada over the past 15 yr but more information on the N2-fixing potential of these crops is needed. 15N isotope dilution was used to determine N2fixation of several grain legumes under dryland field conditions in Saskatchewan. Two cultivars of lentil (Lens culinarisMedik), pea (Pisum sativumL.), and fababean (Vicia fabaL.) were grown at five locations in both 1984 and 1985, with all major soil zones represented by at least one location in each year. Drought stress was moderate to severe at all sites in 1984 and at sites in the Brown and Dark Brown soil zones in 1985. Barley (Hordeum vulgareL.) and wheat (Triticum aestivumL.) were nearly identical as non-N2-fixing reference crops, but their validity as reference crops for the grain legumes included in this study was not tested. Indigenous rhizobia were incapable of supporting adequate levels of N2fixation at most sites in this study. Inoculation increased total dry matter, total N and N2fixation of all grain legume cultivars tested. Proportion of N assimilated from the atmosphere declined with increasing soil nitrate levels and increasing drought stress. Annual rates of N2fixation were as high as 75, 105 and 160 kg N ha−1for lentil, pea and fababean, respectively, at sites in the Gray and Gray-Black soil zones in 1985, but declined by an average of 5.3, 7.6 and 10.5 kg N ha−1, respectively, for every cm reduction in moisture use. Maximum rates of N2fixation in 1984 were about 80 kg ha−1. Fababean fixed the most N2under wetter conditions, while pea and lentil fixed the most under drought stressed conditions. Key words: 15N isotope dilution, dinitrogen fixation, lentil, pea, fababean, drought stress

A study was made of the effect on soil aggregation of microbial gums produced in vitroand in soil. Attention was also given to the effects of fertility treatments, kind of crop, and season on the aggregation of Spencer silt loam. The bacterial polysaccharide synthesized by Agrobacterium radiobacterin pure culture had a marked aggregating effect when added to Spencer and Miami silt loams. Addition of as little as 0.02 gm. of this gum to 100 gm. of soil caused a 50% increase in aggregates > 0.1 mm. in diameter. The gum content of numerous samples of Miami and Spencer silt loams correlated well with their respective levels of aggregation. The addition of extracted soil gum to a poorly aggregated soil increased significantly the degree of aggregation. Undecomposed pulverized plant residues added to soil increased the gum content to a maximum in six days. The maximum percentage of aggregates > 0.5 mm. in diameter was not reached until the twelfth day. In a four‐year rotation of corn, oats, and two years of alfalfa‐brome on plots which were variously limed and fertilized, increases in percentage of soil aggregates occurred at pH 6.0, 6.5, and 7.5 as compared with the aggregation level of the check plot (pH 5.5). High levels of available phosphorus and potassium as compared with low levels promoted aggregation. In general, structural deterioration began under corn and continued until the following crop of oats attained considerable growth. Thereafter improvement continued and reached a maximum during the second year of hay. Seasonal variations in soil aggregation occurred on all plots, irrespective of soil treatment or crop, and was characterized by a gradual increase in percentage of water‐stable aggregates during the spring and summer followed by a sharp decline in September.