Phosphorus status and cycling in native savanna and improved pastures on an acid low-P Colombian Oxisol

On acid low-phosphorus (P) Colombian Oxisols, improved pastures with acid-soil-tolerant grass and legume varieties have increased beef production by a factor of 10 to 15 with only modest P fertilizer inputs. This indicates that the efficiency of P fertilization could be greater than is commonly expected on such strongly P-sorbing soils. To understand the effect of improved pastures on P cycling and availability, we estimated P budgets, and characterized soil P by sequential fractionation, isotopic exchange and biological activity measurements on soil samples from unfertilized native savanna, and fertilized improved grass-only (Brachiaria decumbens cv. Basilisk) and grass-legume (B. decumbens + Pueraria phaseoloides, Kudzu) pastures established in 1978 on a medium-textured isohyperthermic, tropeptic haplustox. Comparison of calculated P budgets, based on inputs and exports, with total soil P contents showed that fertilization, as part of the improved pasture management, had resulted in a measurable increase of total P in the surface 0-20 cm soil layer of nearly 30 mg kg-1 or about 20% over the savanna level. Sequential soil P fractionation of different seasonal samplings indicated that grass-legume maintained higher organic and available inorganic P levels with less temporal variation than the two other types. The linkage of organic P and available P was also reflected in soil biological activity. Estimates of P in microbial biomass and phosphatase activity were significantly higher in grass-legume than grass-only and savanna. The improvement in soil P availability, as measured by solution P concentration, P sorption and exchangeable P, was much greater in grass-legume than in grass-only. With comparable fertilizer inputs and greater product exports, improved P availability in grass-legume cannot be due to differences in budgets but can be attributed to changes in the overall biological activity in the soil-plant system caused by the presence of legumes in the vegetation cover. Total C, organic P content and macrofaunal activity were all significantly higher in grass-legume soils. Greater turnover of organic litter in grass-legume may provide for steadier organic P inputs and, therefore, higher P cycling and availabilit

Critical evaluation of methods for determining total organic phosphorus in tropical soils

The determination of total organic phosphorus (TOP) in soils presents several methodological problems, particularly on strongly weathered and tropical soils. We reviewed the application of several methods for TOP determination to soils from different zones of the globe and evaluated the applicability of one ignition and two extraction methods to tropical soils from Brazil and Ghana. Reproducibility (coefficients of variation) was within 6% for the ignition method, and 13% for the extraction methods, due to the simplicity of the former. The two extraction methods produced results similar to each other, while the ignition method generally gave higher TOP contents. Unusually low C to organic P ratios indicate that the ignition method overestimated TOP in several soils. The Bowman extraction method, developed on weakly weathered soils, appeared also suitable for a variety of tropical soils

Randomized controlled trial on cardiovascular risk management by practice nurses supported by self-monitoring in primary care

BACKGROUND: Treatment goals for cardiovascular risk management are generally not achieved. Specialized practice nurses are increasingly facilitating the work of general practitioners and self-monitoring devices have been developed as counseling aid. The aim of this study was to compare standard treatment supported by self-monitoring with standard treatment without self-monitoring, both conducted by practice nurses, on cardiovascular risk and separate risk factors. METHODS: Men aged 50–75 years and women aged 55–75 years without a history of cardiovascular disease or diabetes, but with a SCORE 10-year risk of cardiovascular mortality ≥5% and at least one treatable risk factor (smoking, hypertension, lack of physical activity or overweight), were randomized into two groups. The control group received standard treatment according to guidelines, the intervention group additionally received pro-active counseling and self-monitoring (pedometer, weighing scale and/ or blood pressure device). After one year treatment effect on 179 participants was analyzed. RESULTS: SCORE risk assessment decreased 1.6% (95% CI 1.0–2.2) for the control group and 1.8% (1.2–2.4) for the intervention group, difference between groups was .2% (−.6–1.1). Most risk factors tended to improve in both groups. The number of visits was higher and visits took more time in the intervention group (4.9 (SD2.2) vs. 2.6 (SD1.5) visits p < .001 and 27 (P(25) –P(75):20–33) vs. 23 (P(25) –P(75):19–30) minutes/visit p = .048). CONCLUSIONS: In both groups cardiovascular risk decreased significantly after one year of treatment by practice nurses. No additional effect of basing the pro-active counseling on self-monitoring was found, despite the extra time investment. TRIAL REGISTRATION: trialregister.nl NTR218

Trehalose 6-phosphate regulates starch synthesis via posttranslational redox activation of ADP-glucose pyrophosphorylase

Trehalose is the most widespread disaccharide in nature, occurring in bacteria, fungi, insects, and plants. Its precursor, trehalose 6-phosphate (T6P), is also indispensable for the regulation of sugar utilization and growth, but the sites of action are largely unresolved. Here we use genetic and biochemical approaches to investigate whether T6P acts to regulate starch synthesis in plastids of higher plants. Feeding of trehalose to Arabidopsis leaves led to stimulation of starch synthesis within 30 min, accompanied by activation of ADP-glucose pyrophosphorylase (AGPase) via posttranslational redox modification. The response resembled sucrose but not glucose feeding and depended on the expression of SNF1-related kinase. We also analyzed transgenic Arabidopsis plants with T6P levels increased by expression of T6P synthase or decreased by expression of T6P phosphatase (TPP) in the cytosol. Compared with wild type, leaves of T6P synthase-expressing plants had increased redox activation of AGPase and increased starch, whereas TPP-expressing plants showed the opposite. Moreover, TPP expression prevented the increase in AGPase activation in response to sucrose or trehalose feeding. Incubation of intact isolated chloroplasts with 100 μM T6P significantly and specifically increased reductive activation of AGPase within 15 min. Results provide evidence that T6P is synthesized in the cytosol and acts on plastidial metabolism by promoting thioredoxin-mediated redox transfer to AGPase in response to cytosolic sugar levels, thereby allowing starch synthesis to be regulated independently of light. The discovery informs about the evolution of plant metabolism and how chloroplasts of prokaryotic origin use an intermediate of the ancient trehalose pathway to report the metabolic status of the cytosol

Numerical modelling of physical processes governing larval transport in the southern North Sea

A three-dimensional hydrodynamic model (GETM) was coupled with a particle tracking routine (GITM) to study the inter-annual variability in transport paths of particles in the North Sea and English Channel. For validation, a comparison with observed drifter trajectories is also presented here. This research investigated to what extent variability in the hydrodynamic conditions alone (reflecting passive particle transport) contributed to inter-annual variability in the transport of eggs and larvae. In this idealised study, no a priori selection of specific spawning grounds or periods was made and no active behaviour (vertical migration) or mortality was included. In this study, egg and larval development towards coastal nursery areas was based solely on sea water temperature, while settlement areas were defined by a threshold water depth. Results showed strong inter-annual variability in drift direction and distance, caused by a combination of wind speed and direction. Strong inter-annual variability was observed both in absolute amount of settlement in several coastal areas, and in the relative importance of the different areas. The effects of wind and temperature variability are minor for settlement along the western shores of the North Sea and in the English Channel, but have a very significant impact on settlement along the eastern shores of the North Sea. Years with strong south-westerly winds across the Dover Straight resulted in higher settlement figures along its eastern shores of the North Sea (standard deviation 37% of the mean annual settlement value). Settlement in the western Dutch Wadden Sea did not only show inter-annual variability, but patterns were also variable within each year and revealed seasonal changes in the origin of particles: during winter, stronger currents along with colder temperatures generally result in particles originating from further away

Investigation of the soil properties that affect Olsen P critical values in different soil types and impact on P fertiliser recommendations

Optimization of phosphorus (P) fertiliser use is desired to ensure more sustainable use of fertiliser, economic food production and reduction of eutrophication of water bodies. Presently, the Olsen P values on which fertiliser recommendations are based to achieve optimum yield are frequently the same for all soils. The aim of this study was to identify the properties of different soils that affect their critical Olsen P values in order to develop better, soil specific P fertiliser recommendations. A pot experiment using 10 soils with low available P with different P additions was carried out to investigate the impact of wide-ranging soil properties on the relationship between P addition, resultant Olsen P values and yield response of ryegrass to Olsen P values. The relationship between added P and Olsen P varied greatly between the individual soils. These relationships were affected by pH, manganese oxide, crystalline aluminium oxide and amorphous iron oxide contents of the soil. Different soils had widely varying critical Olsen P values for ryegrass. However, these could not be related to the measured soil properties. Fertiliser recommendations and critical values for optimum yield of ryegrass based on the Olsen P test should be soil specific. The complexity and lack of clarity over which combination of soil properties governs critical Olsen P values calls for further investigation with more soil types and additional soil property measurements to elucidate the different factors controlling critical Olsen P values in different soils

Climate and soil micro‐organisms drive soil phosphorus fractions in coastal dune systems

1. The importance of soil phosphorus (P) is likely to increase in coming decades due to the growing atmospheric nitrogen (N) deposition originated by industrial and agricultural activities. We currently lack a proper understanding of the main drivers of soil P pools in coastal dunes, which rank among the most valued priority conservation areas worldwide. 2. Here, we evaluated the joint effects of biotic (i.e. microbial abundance and richness, vegetation and cryptogams cover) and abiotic (i.e. pH and aridity) factors on labile, medium‐lability and recalcitrant soil P pools across a wide aridity gradient in the Atlantic coast of the Iberian Peninsula. 3. Climate determined the availability of medium‐lability, recalcitrant and total P, but had a minor net effect on labile P, which was positively and significantly related to the presence of plants, mosses and lichens. Medium‐lability P was significantly influenced by soil bacterial richness and abundance (positively and negatively, respectively). 4. Our results suggest that micro‐organisms transfer P from medium‐lability pool to more labile one. At the same time, increases in bacterial richness associated to biofilms might be involved in the thickening of the medium‐lability P pool in our climosequence. 5. These bacterial‐mediated transfers would confer resistance to the labile P pool under future climate change and uncover an important role of soil micro‐organisms as modulators of the geochemical P cycle.This project was financed by FEDER/Ministerio de Ciencia, Innovación y Universidades-Agencia Estatal de Investigación/Proyect (CGL2017-88124-R), European Research Council (ERC Grant Agreement 647038 [BIODESERT]) and the Fundaçã o para Ciência e Tecnologia (IF/00950/2014) and the FEDER, within the PT2020 Partnership Agreement and COMPETE 2020 (UID/BIA/04004/2013). F.T.M. acknowledges support from Generalitat Valenciana (CIDEGENT/2018/041). B.K.S. acknowledge research support on microbes and ecosystem functions from the Australian Research Council (DP170104634) and Research Award from the Humboldt Foundation

Effective practices of international volunteering for health : perspectives from partner organizations

Abstract: The demand for international volunteer experiences to promote global health and nutrition is increasing and numerous studies have documented the experiences of the international volunteers who travel abroad; however, little is known about effective practices from the perspective of partner organizations. This study aims to understand how variables such as the skill-level of volunteers, the duration of service, cultural and language training, and other key variables affect partner organizations’ perceptions of volunteer effectiveness at promoting healthcare and nutrition..