Influence of liming on residual soil respiration and chemical properties in a tropical no-tillage system

Because of the climate changes occurring across the planet, especially global warming, the different forms of agricultural soil use have attracted researchers´ attention. Changes in soil management may influence soil respiration and, consequently, C sequestration. The objectives of this study were to evaluate the long-term influence of liming on soil respiration and correlate it with soil chemical properties after two years of liming in a no-tillage system. A randomized complete block design was used with six replications. The experimental treatments consisted of four lime rates and a control treatment without lime. Two years after liming, soil CO2 emission was measured and the soil sampled (layers 0-5, 5-10, 10-20, and 20-30 cm). The P, Ca2+ e Mg2+ soil contents and pH and base saturation were determined. CO2 emission from soil limed at the recommended rate was 24.1 % higher, and at twice the recommended rate, 47.4 % higher than from unlimed soil. Liming improved the chemical properties, and the linear increase in soil respiration rate correlated positively with the P, Ca2+ and Mg2+ soil contents, pH and base saturation, and negatively with H + Al and Al3+ contents. The correlation coefficient between soil respiration rate and chemical properties was highest in the 10-20 cm layer.

Predictors of onset of cannabis and other drug use in male young adults: results from a longitudinal study.

BACKGROUND: The use of cannabis and other illegal drugs is particularly prevalent in male young adults and is associated with severe health problems. This longitudinal study explored variables associated with the onset of cannabis use and the onset of illegal drug use other than cannabis separately in male young adults, including demographics, religion and religiosity, health, social context, substance use, and personality. Furthermore, we explored how far the gateway hypothesis and the common liability to addiction model are in line with the resulting prediction models. METHODS: The data were gathered within the Cohort Study on Substance Use Risk Factors (C-SURF). Young men aged around 20 years provided demographic, social, health, substance use, and personality-related data at baseline. Onset of cannabis and other drug use were assessed at 15-months follow-up. Samples of 2,774 and 4,254 individuals who indicated at baseline that they have not used cannabis and other drugs, respectively, in their life and who provided follow-up data were used for the prediction models. Hierarchical logistic stepwise regressions were conducted, in order to identify predictors of the late onset of cannabis and other drug use separately. RESULTS: Not providing for oneself, having siblings, depressiveness, parental divorce, lower parental knowledge of peers and the whereabouts, peer pressure, very low nicotine dependence, and sensation seeking were positively associated with the onset of cannabis use. Practising religion was negatively associated with the onset of cannabis use. Onset of drug use other than cannabis showed a positive association with depressiveness, antisocial personality disorder, lower parental knowledge of peers and the whereabouts, psychiatric problems of peers, problematic cannabis use, and sensation seeking. CONCLUSIONS: Consideration of the predictor variables identified within this study may help to identify young male adults for whom preventive measures for cannabis or other drug use are most appropriate. The results provide evidence for both the gateway hypothesis and the common liability to addiction model and point to further variables like depressiveness or practising of religion that might influence the onset of drug use.

Suprimento de potássio em função da adubação potássica residual em um Latossolo Vermelho do Cerrado

Em alguns solos com baixos teores de potássio trocável, formas não trocáveis participam do suprimento às plantas. Há evidências de que a disponibilização do K não trocável depende mais da demanda das plantas pelo nutriente do que das propriedades do solo. O objetivo deste trabalho foi avaliar o suprimento e a exaustão de formas de K em um Latossolo Vermelho do Cerrado em decorrência da adubação potássica residual e do cultivo de Brachiaria ruziziensis (Syn. Urochloa ruziziensis). Amostras de solos foram coletadas na camada de 0-20 cm, em parcelas de um experimento de campo em que a soja vinha sendo adubada anualmente, por 10 anos, com 0, 60, 120 e 180 kg ha-1 de K2O. Em casa de vegetação, as amostras de solo receberam a aplicação de 0, 150 e 300 mg dm-3 de K e foram cultivadas com B. ruziziensis, com cinco cortes sucessivos. O suprimento de K às plantas dependeu mais do fertilizante recém-adicionado do que do efeito residual de adubações anteriores. O K não trocável foi responsável, ao longo do tempo, pela manutenção dos teores de K trocáveis e, na ausência de adubação potássica, constituiu a principal fonte de K para as plantas de B. ruziziensis. As plantas de B. ruziziensis possuem capacidade de extrair quantidade considerável de K do solo, confirmando sua importância como cultura de cobertura, na ciclagem do nutriente no solo.

Genome-wide association and longitudinal analyses reveal genetic loci linking pubertal height growth, pubertal timing and childhood adiposity.

The pubertal height growth spurt is a distinctive feature of childhood growth reflecting both the central onset of puberty and local growth factors. Although little is known about the underlying genetics, growth variability during puberty correlates with adult risks for hormone-dependent cancer and adverse cardiometabolic health. The only gene so far associated with pubertal height growth, LIN28B, pleiotropically influences childhood growth, puberty and cancer progression, pointing to shared underlying mechanisms. To discover genetic loci influencing pubertal height and growth and to place them in context of overall growth and maturation, we performed genome-wide association meta-analyses in 18 737 European samples utilizing longitudinally collected height measurements. We found significant associations (P < 1.67 × 10(-8)) at 10 loci, including LIN28B. Five loci associated with pubertal timing, all impacting multiple aspects of growth. In particular, a novel variant correlated with expression of MAPK3, and associated both with increased prepubertal growth and earlier menarche. Another variant near ADCY3-POMC associated with increased body mass index, reduced pubertal growth and earlier puberty. Whereas epidemiological correlations suggest that early puberty marks a pathway from rapid prepubertal growth to reduced final height and adult obesity, our study shows that individual loci associating with pubertal growth have variable longitudinal growth patterns that may differ from epidemiological observations. Overall, this study uncovers part of the complex genetic architecture linking pubertal height growth, the timing of puberty and childhood obesity and provides new information to pinpoint processes linking these traits.

Associations of physical activity and sport and exercise with at-risk substance use in young men: a longitudinal study.

OBJECTIVE: This study aims to measure the associations of physical activity and one of its components, sport and exercise, with at-risk substance use in a population of young men. METHOD: Baseline (2010-2012) and follow-up (2012-2013) data of 4748 young Swiss men from the Cohort Study on Substance Use Risk Factors (C-SURF) were used. Cross-sectional and prospective associations between at-risk substance use and both sport and exercise and physical activities were measured using Chi-squared tests and logistic regression models adjusting for covariates. RESULTS: At baseline, logistic regression indicated that sport and exercise is negatively associated with at-risk use of cigarettes and cannabis. A positive association was obtained between physical activity and at-risk alcohol use. At baseline, sport and exercise was negatively associated with at-risk use of cigarettes and cannabis at follow-up. Adjusted for sport and exercise, physical activity was positively associated with at-risk use of cigarettes and cannabis. CONCLUSION: Sport and exercise is cross-sectionally and longitudinally associated with a low prevalence of at-risk use of cigarettes and cannabis. This protective effect was not observed for physical activity broadly defined. Taking a substance use prevention perspective, the promotion of sport and exercise among young adults should be encouraged.

Residual effect of soil tillage on water erosion from a Typic Paleudalf under long-term no-tillage and cropping systems

Soil erosion is one of the chief causes of agricultural land degradation. Practices of conservation agriculture, such as no-tillage and cover crops, are the key strategies of soil erosion control. In a long-term experiment on a Typic Paleudalf, we evaluated the temporal changes of soil loss and water runoff rates promoted by the transition from conventional to no-tillage systems in the treatments: bare soil (BS); grassland (GL); winter fallow (WF); intercrop maize and velvet bean (M+VB); intercrop maize and jack bean (M+JB); forage radish as winter cover crop (FR); and winter cover crop consortium ryegrass - common vetch (RG+CV). Intensive soil tillage induced higher soil losses and water runoff rates; these effects persisted for up to three years after the adoption of no-tillage. The planting of cover crops resulted in a faster decrease of soil and water loss rates in the first years after conversion from conventional to no-tillage than to winter fallow. The association of no-tillage with cover crops promoted progressive soil stabilization; after three years, soil losses were similar and water runoff was lower than from grassland soil. In the treatments of cropping systems with cover crops, soil losses were reduced by 99.7 and 66.7 %, compared to bare soil and winter fallow, while the water losses were reduced by 96.8 and 71.8 % in relation to the same treatments, respectively.

Nitrogen fertilization (15NH4NO3) of palisadegrass and residual effect on subsequent no-tillage corn

Nitrogen is required in large amounts by plants and their dinamics in corn and perennial forages intercropped is little known. This study analyzed the efficiency of nitrogen fertilization (15NH4NO3) applied after corn grain harvest to palisadegrass (Brachiaria brizantha cv. Marandu) in intercrops sown at two times, as well as the N residual effect on the subsequent corn crop. The field experiment was performed in Botucatu, São Paulo State, in southeastern Brazil, on a structured Alfisol under no-tillage. The experiment was arranged in a randomized block design in a split plot scheme with four replications. The main plots consisted of two intercropping systems (corn and palisadegrass sown together and palisadegrass sown later, at corn top-dressing fertilization). The subplots consisted of four N rates (0, 30, 60, and 120 kg ha-1 N). The subplots contained microplots, in which enriched ammonium nitrate (15NH4NO3) was applied at the same rates. The time of intercrop sowing affected forage dry matter production, the amount of fertilizer-derived N in and the N use efficiency by the forage plants. Nitrogen applied in autumn to palisadegrass intercropped with corn, planted either at corn sowing or at N top-dressing fertilization, increased the forage yield up to a rate of 60 kg ha-1. The amount of fertilizer-derived N by the forage plants and the fertilizer use efficiency by palisadegrass were highest 160 days after fertilization for both intercrop sowing times, regardless of N rates. Residual N did not affect the N nutrition of corn plants grown in succession to palisadegrass, but increased grain yield at rates of 60 and 120 kg ha-1 N, when corn was grown on palisadegrass straw from the intercrop installed at corn fertilization (top-dressing). Our results indicated that the earlier intercropping allowed higher forage dry matter production. On the other hand, the later intercrop allowed a higher corn grain yield in succession to N-fertilized palisadegrass.

Molecular dynamics study of the longitudinal modes in disparate-mass binaryliquid mixtures.

A series of molecular dynamics simulations of simple liquid binary mixtures of soft spheres with disparate-mass particles were carried out to investigate the origin of the marked differences between the dynamic structure factors of some liquid binary mixtures such as the Li0.7Mg0.3 and Li0.8Pb0.2 alloys. It is shown that the facility for observing peaks associated with fast-propagating modes in the partial Li-Li dynamic structure factor of Li0.8Pb0.2 should be mainly attributed to the structure of this alloy, which is characterized by an incipient ABAB ordering as found in molten salts. The longitudinal dispersion relations at intermediate wave vectors obtained from the longitudinal current spectra are very similar for the two alloys and reflect the existence of both fast-and slow-propagating modes of kinetic character associated with light and heavy particles, respectively. The influence of the hardness of the repulsive potential cores as well as the composition of the mixture on the longitudinal collective modes is also discussed.

Guide Specification for Highway Construction Texturing Concrete Pavement for Reduced Tire/Pavement Noise using Longitudinal Tining, March 1, 2011

This document provides language that can be used by an Owner-Agency to develop materials and construction specifications with the objective of reducing tire/pavement noise. While the practices described herein are largely prescriptive, they have been demonstrated to increase the likelihood of constructing a durable, quieter concrete surface. Guidance is provided herein for texturing the concrete surface since texture geometry has a paramount effect on tire/pavement noise. Guidance for curing is also provided to improve strength and durability of the surface mortar, and thus to improve texture durability.

A systematic review of longitudinal population-based studies on the predictors of smoking cessation in adolescent and young adult smokers.

OBJECTIVE: To describe the determinants of self-initiated smoking cessation of duration of at least 6 months as identified in longitudinal population-based studies of adolescent and young adult smokers. METHODS: A systematic search of the PubMed and EMBASE databases using smoking, tobacco, cessation, quit and stop as keywords was performed. Limits included articles related to humans, in English, published between January 1984 and August 2010, and study population aged 10-29 years. A total of 4502 titles and 871 abstracts were reviewed independently by 2 and 3 reviewers, respectively. Nine articles were retained for data abstraction. Data on study location, timeframe, duration of follow-up, number of data collection points, sample size, age/grade of participants, number of quitters, smoking status at baseline, definition of cessation, covariates and analytic method were abstracted from each article. The number of studies that reported a statistically significant association between each determinant investigated and cessation were tabulated, from among all studies that assessed the determinant. RESULTS: Despite heterogeneity in methods across studies, five factors robustly predicted quitting across studies in which the factor was investigated: not having friends who smoke, not having intentions to smoke in the future, resisting peer pressure to smoke, being older at first use of cigarette and having negative beliefs about smoking. CONCLUSIONS: The literature on longitudinal predictors of cessation in adolescent and young adult smokers is not well developed. Cessation interventions for this population will remain less than optimally effective until there is a solid evidence base on which to develop interventions.