Phosphate fixation and the response of maize to fertilizer phosphate in Kenyan soils

In tropical soils, plant growth is often limited by a low P availability. In addition, these soils often have high P-fixation capacities due to high amounts of iron and aluminum oxyhydroxides. Furthermore, small-scale farming systems in which subsistence crops are produced for local markets are common in the tropics. Such conditions exit in South West Kenya, in the Kish area, where this study was carried out.The overall aim of the study was to improve our understanding of fertilizer P - soil - maize crop interactions and, thereby, to increase the yield response and improve the P recovery and utilization in plants. Initial and residual yield responses to fertilizer P applications; P uptake in plants, as well as P distribution and utilization within the plants; apparent fertilizer P recovery; and dissolution, transport and sorption of fertilizer P in the soils were studied under field conditions during three successive growing seasons. This was done within the concept of the low-input strategy, whereby the high-input strategy was used as a reference.The soils were classified as Ultisols and Mollisols, or as Nitisols and Luvic Phaeozems. They were low in available native P (P-Olsen 1.6 to 3.2 mg/kg) and had medium to high P sorption capacities (445 to 870 mg/kg) measured under laboratory conditions. Total P ranged from 490 to 1,035 mg/kg. Triple superphosphate was used as P fertilizer and hybrid maize as test crop.Good initial and residual yield responses were found in all soils even at low P application rates. The concept of P-fixation, as defined in this study, was not appropriate for the soils in the Kisii area. The second 'slow' phase of the fixation process was shown to proceed at a very slow rate under field conditions. Thus, P fixation is much less of a problem for farmers than expected. When P limited grain yield, the relationship between grain yield (z) and P in plant (y) could be described by the equation: z=620(y-0.50). The efficiency of utilization increased with P application to about 550 kg/kg at P rates of 22 to 131 kg/ha and decreased at higher rates due to a luxurious P uptake. Granular fertilizer residues with P in the form of Fluorapatite, Brushite and an amorphous P compound could be recovered in the soil until the end of the trials, about 600 days after application. Fertilizer P was retained in the soil immediately surrounding the residual fertilizer granules to total P values up to>8,000 mg/kg, which was much higher than predicted from the P-sorption studies in the laboratory. Available P levels (P-Olsen) in the P-enriched soil volume were high, up to>800 mg/kg. The available fertilizer P fraction (ΔP-Olsen/ΔP total) remained fairly constant with time. It was suggested that the number of roots, i.e. root surface area, present in the small P-enriched volume was the limiting factor in fertilizer P uptake. As a result, the apparent P recoveries per crop were low. They were about 10 % each growing season at a P rate of 22 kg/ha.Subseed placement at the start of each growing season is recommended, either placed alone or together with small amounts of cow dung. Then, plants benefit highly from both the startereffect of freshly-applied fertilizer and the residual effect of previously-applied (residual) fertilizer. P application rates of 20 to 40 kg/ha (in P 2 O 5 : 45 to 90 kg/ha) are advised for maize. At these rates, slightly more P is applied than plants require for producing maximum grain yields and the P availability of the soils will gradually increase by enlarging the soil volume enriched with fertilizer P. This repeated subseed placement fits in well with the low-input strategy and is probably easily adaptable in tropical small-scale farming systems

Notes on determinations of nitrate in plant material.

The determination of nitrate in extracts of plants including grass, maize, sugarbeet leaves, lucerne, peas, cucumber, radish and lettuce by 3 different methods was tested. The methods based on nitration of O'-xylenol and dialysis of plant extracts and reduction of nitrate to nitrite ions by a Cu-Cd reductor were equally satisfactory. No influence of the extraction ratio was found. Extraction of plant material with water or electrolyte solution gave comparable results. Direct potentiometry gave too high results at lower nitrate ion levels. This phenomenon depends on the nature of plant material analysed and is apparently caused by organic anions. For spinach, the electrode can be used when the nitrate content is about 300 mmol nitrate/kg DM or higher. (Abstract retrieved from CAB Abstracts by CABI’s permission

Performance evaluation of a rapid molecular diagnostic, MultiCode based, sample-to-answer assay for the simultaneous detection of Influenza A, B and respiratory syncytial viruses

AbstractBackgroundClinical signs and symptoms of different airway pathogens are generally indistinguishable, making laboratory tests essential for clinical decisions regarding isolation and antiviral therapy. Immunochromatographic tests (ICT) and direct immunofluorescence assays (DFA) have lower sensitivities and specificities than molecular assays, but have the advantage of quick turnaround times and ease-of-use.ObjectiveTo evaluate the performance of a rapid molecular assay, ARIES FluA/B & RSV, using laboratory developed RT-PCR assays (LDA), ICT (BinaxNOW) and DFA.MethodsAnalytical and clinical performance were evaluated in a retrospective study arm (stored respiratory samples obtained between 2006–2015) and a prospective study arm (unselected fresh clinical samples obtained between December 2015 and March 2016 tested in parallel with LDAs).ResultsGenotype inclusivity and analytical specificity was 100%. However, ARIES was 0.5 log, 1–2logs and 2.5logs less sensitive for fluA, RSV and fluB respectively, compared to LDA. In total, 447 clinical samples were included, of which 15.4% tested positive for fluA, 9.2% for fluB and 26.0% for RSV, in both LDA and ARIES. ARIES clinical sensitivity compared to LDA was 98.6% (fluA), 93.3% (fluB) and 95.1% (RSV). Clinical specificity was 100% for all targets. ARIES detected 10.6% (4 fluA, 8 fluB, 11 RSV) and 26.9% (7 fluA, 3 fluB, 22 RSV) more samples compared to DFA and ICT, all confirmed by LDA.ConclusionAlthough analytically ARIES is less sensitive than LDA, the clinical performance of the assay in our tertiary care setting was comparable, and significantly better than that of the established rapid assays

Workshop: Praktijklessen uit de Krimpenerwaard Triade : adviezen voor de verdere ontwikkeling en toepassing van de Triade als methode voor locatiespecifieke ecologische risicobeoordeling van bodemverontreiniging

De Triade geldt als een geaccepteerd instrument om de effecten van bodemverontreiniging op het bodemecosysteem te meten. In dit rapport zijn adviezen verwoord voor de verdere ontwikkeling en toepassing van de Triade, als methode om ecologische risico's van bodemverontreiniging te bepalen. Zij zijn gebaseerd op de ervaringen uit het Krimpenerwaard project en de discussies gevoerd in de workshop "Praktijkervaringen met de Krimpenerwaard Triade" op 12 september 200

Empathy in multiple sclerosis-correlates with cognitive, psychological and occupational functioning

Background Recent studies report deficits in social cognition in individuals with multiple sclerosis (MS). Social cognitive skills such as empathy are important for adequate social and occupational functioning. Our objectives are: (1) to examine whether empathy differs between individuals with MS and healthy controls, (2) to examine relations between empathy and cognitive, psychological and occupational functioning. Methods 278 individuals with MS (relapsing-remitting subtype) and 128 healthy controls from the MS@Work study participated in this investigation. The participants completed questionnaires about demographics, cognitive, psychological and occupational functioning, and underwent neurological and neuropsychological examinations. Mann-Whitney U-tests were used to examine group differences in empathy. Pearson and Spearman rank correlation analyses were used to examine relations between empathy and the other measures. Results Empathy did not differ between individuals with MS and healthy controls. In individuals with MS, higher empathy was correlated with a higher educational level (X2(df) = 13.2(2), p = 0.001), better verbal learning (r = 0.20, p = 0.001), less symptoms of depression (r=−0.21, p = 0.001), higher extraversion (r = 0.25, p ≤ 0.001), agreeableness (r = 0.55, p ≤ 0.001) and conscientiousness (r = 0.27, p ≤ 0.001) and better occupational functioning in terms of work scheduling and output demands (r = 0.23, p = 0.002) and less cognitive/psychological work barriers (r = −0.21, p = 0.001). In healthy controls, higher empathy was correlated with less symptoms of depression (r = −0.34, p ≤ 0.001), less fatigue (r = −0.37, p ≤ 0.001), higher agreeableness (r = 0.59, p ≤ 0.001) and better occupational functioning in terms of work ability as compared to lifetime best (r = 0.28, p = 0.001) and less cognitive/psychological work barriers (r = −0.34, p ≤ 0.001). Empathy did not differ between unemployed and employed individuals with MS or healthy controls. Conclusion Empathy did not differ between individuals with MS and healthy controls. Within both investigated groups, higher empathy was weakly to moderately correlated with less symptoms of depression, higher agreeableness and better occupational functioning. We also found unique correlations for empathy within the investigated groups. Longitudinal studies are needed to further examine social cognition in relation to cognitive, psychological and occupational functioning in both individuals with MS and healthy controls. It would be particularly interesting to concurrently examine changes in the brain network involved with social cognition

Aggressive therapy in patients with early arthritis results in similar outcome compared with conventional care: the STREAM randomized trial

Objective. To compare the effects of aggressive tight control therapy and conventional care on radiographic progression and disease activity in patients with early mild inflammatory arthritis

External Quality Assessment on Molecular Tumor Profiling with Circulating Tumor DNA-Based Methodologies Routinely Used in Clinical Pathology within the COIN Consortium

BackgroundIdentification of tumor-derived variants in circulating tumor DNA (ctDNA) has potential as a sensitive and reliable surrogate for tumor tissue-based routine diagnostic testing. However, variations in pre(analytical) procedures affect the efficiency of ctDNA recovery. Here, an external quality assessment (EQA) was performed to determine the performance of ctDNA mutation detection work flows that are used in current diagnostic settings across laboratories within the Dutch COIN consortium (ctDNA on the road to implementation in The Netherlands).MethodsAliquots of 3 high-volume diagnostic leukapheresis (DLA) plasma samples and 3 artificial reference plasma samples with predetermined mutations were distributed among 16 Dutch laboratories. Participating laboratories were requested to perform ctDNA analysis for BRAF exon 15, EGFR exon 18–21, and KRAS exon 2–3 using their regular circulating cell-free DNA (ccfDNA) analysis work flow. Laboratories were assessed based on adherence to the study protocol, overall detection rate, and overall genotyping performance.ResultsA broad range of preanalytical conditions (e.g., plasma volume, elution volume, and extraction methods) and analytical methodologies (e.g., droplet digital PCR [ddPCR], small-panel PCR assays, and next-generation sequencing [NGS]) were used. Six laboratories (38%) had a performance score of >0.90; all other laboratories scored between 0.26 and 0.80. Although 13 laboratories (81%) reached a 100% overall detection rate, the therapeutically relevant EGFR p.(S752_I759del) (69%), EGFR p.(N771_H773dup) (50%), and KRAS p.(G12C) (48%) mutations were frequently not genotyped accurately.ConclusionsDivergent (pre)analytical protocols could lead to discrepant clinical outcomes when using the same plasma samples. Standardization of (pre)analytical work flows can facilitate the implementation of reproducible liquid biopsy testing in the clinical routine