Clay addition to sandy soil - effect of clay concentration and ped size on microbial biomass and nutrient dynamics after addition of low C/N ratio residue

Addition of clay-rich subsoil to sandy soil has been shown to increase crop production on sandy soils. The added clay is present as peds ranging in size from a millimetre to several centimetre. In thisexperiment clay soil (73% clay) was added to sandy soil (3% clay) at 10 and 20% clay w/w as 1, 3 and 5 mm peds. Shoots of young Kikuyu grass (C/N 20) were ground and added at 10g kg-1, and soils were incubated for 45 days at 80% of water holding capacity.The study confirmed that clay addition to sandy soil increased soil organic carbon retention but decreased cumulative respiration and available P compared to sandy soil alone. Ped size had little effect on respiration and nutrient availability. Over the course of 45 days peds broke down and organic C was bound to the < 53 μm fraction. The greatest proportion of peds and total organic carbon (54-67%) was in the initially added ped size. The TOC content of < 53 μm fraction of initially added peds was 0.38% and at the end of the experiment (after 45 days) the TOC had increased by 24, 19 and 10% in 1, 3 and 5 mm peds respectively.Shermeen Tahir and Petra Marschne

Compost effects on microbial biomass and soil P pools as affected by particle size and soil properties

Previous studies have shown that finer composts release nutrients more quickly than coarse composts, but little is known about the nutrient release from different size fractions of a compost. To assess if compost size fractions differ in their effect on microbial biomass and soil P pools, a compost from garden waste was separated by sieving into different particle size fractions (> 5 mm, 3-5 mm and 5 mm fraction and in microbial biomass C and P with the < 3 mm fraction. The size of the P pools was mainly affected by soil type, the compost fractions had similar effects on soil P pools except for a greater increase in available P concentration by the finest fraction compared to the coarser size fractions. Soil A with the highest organic matter content had the highest concentrations of Fe/Al associated P (NaOH-P) and organic P whereas Ca-associated P (HCl-P) dominated in the alkaline soil C. The size of most P pools, even the so-called stable P pools changed over time in amended and non-amended soils. It can be concluded that the size of P pools is more strongly affected by soil properties such as organic matter content, texture and pH than by the compost fractionsS. Lata Verma, P. Marschne

Effect of incorporated or mulched compost on leaf nutrient concentrations and performance of Vitis vinifera cv. Merlot

Compost can reduce evaporation and increase nutrient uptake by plants, but it is not clear if it can increase soil water holding capacity or stimulate leaf gas exchange, water use efficiency and yield of vines. To study these effects, compost from garden and food waste was incorporated or mulched in a vineyard at a rate of 100 m3 ha-1, three months before the measurements. The vineyard received irrigation during spring and summer. Soil water content was monitored regularly with a capacitance probe. Photosynthesis, transpiration, stem water potential and leaf area index were measured several times during the vegetation period. At harvest, yield, berry weight and quality as well as chlorophyll, N, P and K concentrations in leaves were determined. Only mulched compost increased soil water content at 10 cm depth, but the water content in the deeper layers was not affected by compost addition. Compost also did not affect transpiration rate and stomatal conductance during the vegetation period, but mulched compost increased the photosynthesis per plant at flowering, pea size and maturity periods. Compost amendment, particularly mulching, increased yield, specific berry weight, and leaf N and P concentrations, and reduced the number of chlorotic leaves at harvest. Berry quality was not affected by compost amendment. It can be concluded that mulched compost has a positive effect on grapevine yield and can be an alternative fertiliser source for vines with no adverse effect on berry quality.T.-T. Nguyen, S. Fuentes, P. Marschne

Genotypic variation in phosphorus efficiency between wheat cultivars grown under greenhouse and field conditions

Phosphorus (P) efficiency (relative growth), which is described as the ratio of shoot dry matter or grain yield at deficient P supply to that obtained under adequate P supply, was compared in 25 winter wheat cultivars grown under greenhouse and field conditions with low and adequate P levels in a P-deficient calcareous soil. Adequate P supply resulted in significant increases in shoot dry weight and grain yield under both experimental conditions. In the greenhouse experiment, the increases in shoot dry weight under adequate P supply (80 mg kg(-1)) were from 0% (cv: C-1252) to 34% (cv: Dagdas). Under field conditions, the cultivars showed much greater variation in their response to adequate P supply (60 kg ha(-1)): the increases in shoot dry weight and grain yield with adequate P supply were between -2% (cv: Sivas-111/33) and 25% (cv: Kirac-66) for shoot dry matter production at the heading stage and between 0% (cv: Kirkpinar-79) and 76% (cv: Kate A-1) for grain yield at maturity. Almost all cultivars behaved totally different in their response to P deficiency under greenhouse and field conditions. Phosphorus efficiency ratios (relative growth) under greenhouse conditions did not correlate with the P efficiency ratios under field conditions. In general, durum wheat cultivars were found to be more P efficient compared with bread wheat cultivars. The results of this study indicated that there is wide variation in tolerance to P deficiency among wheat cultivars that can be exploited in breeding new wheat cultivars for high P deficiency tolerance. The results also demonstrated that P efficiency was expressed differently among the wheat cultivars when grown under greenhouse and field conditions and, therefore, special attention should be paid to growth conditions in screening wheat for P efficiency

Sorption and fractionation of dissolved organic matter and associated phosphorus in agricultural soil

Molibility of dissolved organic matter (DOM) strongly affects the export of nitrogen (N) and phosphorus (P) from oils to surface waters. To study the sorption an mobility of dissolved organic C and P (DOC, DOP) in soil, the pH-dependent sorption of DOM to samples from Ap, EB, and Bt horizons from a Danish agircultural Humic Hapludult was investigated and a kinetic model applicable in field-scale model tested. Sorption experiments of 1 to 72 h duration were conducted at two pH levels (pH 5.0 and 7.0) and six initial DOC concentrtions (0-4.7 mmol L-1). Most sorption/desorption occurred during the first few hours. Dissolved organic carbon and DOP sorption decreased strongly with increased pH and desorption dominated at pH 7, especially for DOC. Due to fractionation during DOM sorption/desorption at DOC concentrations up to 2 mmol L-1, the solution fraction of DOM was enriched in P indicating preferred leaching of DOP. The kinetics of sorption was expressed as a function of how far the solution DOC or DOP concentrations deviate from "equilibrium". The model was able to simulate the kinetics of DOC and DOP sorption/desorption at all concentrations investigated and at both pH levels making it useful for incorporation in field-scale models for quantifying DOC and DOP dynamics

Vanadium (β-(Dimethylamino)ethyl)cyclopentadienyl Complexes with Diphenylacetylene Ligands

Reduction of the V(III) (β-(dimethylamino)ethyl)cyclopentadienyl dichloride complex [η5:η1-C5H4(CH2)2NMe2]VCl2(PMe3) with 1 equiv of Na/Hg yielded the V(II) dimer {[η5:η1-C5H4(CH2)2NMe2]V(µ-Cl)}2 (2). This compound reacted with diphenylacetylene in THF to give the V(II) alkyne adduct [η5:η1-C5H4(CH2)2NMe2]VCl(η2-PhC≡CPh). Further reduction of 2 with Mg in the presence of diphenylacetylene resulted in oxidative coupling of two diphenylacetylene groups to yield the diamagnetic, formally V(V), bent metallacyclopentatriene complex [η5:η1-C5H4(CH2)2NMe2]V(C4Ph4).

Quantitative trait loci conferring grain mineral nutrient concentrations in durum wheat 3 wild emmer wheat RIL population

Mineral nutrient malnutrition, and particularly deficiency in zinc and iron, afflicts over 3 billion people worldwide. Wild emmer wheat, Triticum turgidum ssp. dicoccoides, genepool harbors a rich allelic repertoire for mineral nutrients in the grain. The genetic and physiological basis of grain protein, micronutrients (zinc, iron, copper and manganese) and macronutrients (calcium, magnesium, potassium, phosphorus and sulfur) concentration was studied in tetraploid wheat population of 152 recombinant inbred lines (RILs), derived from a cross between durum wheat (cv. Langdon) and wild emmer (accession G18-16). Wide genetic variation was found among the RILs for all grain minerals, with considerable transgressive effect. A total of 82 QTLs were mapped for 10 minerals with LOD score range of 3.2–16.7. Most QTLs were in favor of the wild allele (50 QTLs). Fourteen pairs of QTLs for the same trait were mapped to seemingly homoeologous positions, reflecting synteny between the A and B genomes. Significant positive correlation was found between grain protein concentration (GPC), Zn, Fe and Cu, which was supported by significant overlap between the respective QTLs, suggesting common physiological and/or genetic factors controlling the concentrations of these mineral nutrients. Few genomic regions (chromosomes 2A, 5A, 6B and 7A) were found to harbor clusters of QTLs for GPC and other nutrients. These identified QTLs may facilitate the use of wild alleles for improving grain nutritional quality of elite wheat cultivars, especially in terms of protein, Zn and Fe

Estimating the number needed to treat from continuous outcomes in randomised controlled trials: methodological challenges and worked example using data from the UK Back Pain Exercise and Manipulation (BEAM) trial

Background Reporting numbers needed to treat (NNT) improves interpretability of trial results. It is unusual that continuous outcomes are converted to numbers of individual responders to treatment (i.e., those who reach a particular threshold of change); and deteriorations prevented are only rarely considered. We consider how numbers needed to treat can be derived from continuous outcomes; illustrated with a worked example showing the methods and challenges. Methods We used data from the UK BEAM trial (n = 1, 334) of physical treatments for back pain; originally reported as showing, at best, small to moderate benefits. Participants were randomised to receive 'best care' in general practice, the comparator treatment, or one of three manual and/or exercise treatments: 'best care' plus manipulation, exercise, or manipulation followed by exercise. We used established consensus thresholds for improvement in Roland-Morris disability questionnaire scores at three and twelve months to derive NNTs for improvements and for benefits (improvements gained+deteriorations prevented). Results At three months, NNT estimates ranged from 5.1 (95% CI 3.4 to 10.7) to 9.0 (5.0 to 45.5) for exercise, 5.0 (3.4 to 9.8) to 5.4 (3.8 to 9.9) for manipulation, and 3.3 (2.5 to 4.9) to 4.8 (3.5 to 7.8) for manipulation followed by exercise. Corresponding between-group mean differences in the Roland-Morris disability questionnaire were 1.6 (0.8 to 2.3), 1.4 (0.6 to 2.1), and 1.9 (1.2 to 2.6) points. Conclusion In contrast to small mean differences originally reported, NNTs were small and could be attractive to clinicians, patients, and purchasers. NNTs can aid the interpretation of results of trials using continuous outcomes. Where possible, these should be reported alongside mean differences. Challenges remain in calculating NNTs for some continuous outcomes

Oral capecitabine as an alternative to i.v. 5-fluorouracil-based adjuvant therapy for colon cancer: safety results of a randomized, phase III trial

Background: Oral capecitabine achieves a superior response rate with an improved safety profile compared with bolus 5-fluorouracil-leucovorin (5-FU/LV) as first-line treatment for patients with metastatic colorectal cancer. We report here the results of a large phase III trial investigating adjuvant oral capecitabine compared with 5-FU/LV (Mayo Clinic regimen) in Dukes' C colon cancer. Patients and methods: Patients aged 18-75 years with resected Dukes' C colon carcinoma were randomized to receive 24 weeks of treatment with either oral capecitabine 1250 mg/m2 twice daily, days 1-14 every 21 days (n = 993), or i.v. bolus 5-FU 425 mg/m2 with i.v. leucovorin 20 mg/m2 on days 1-5, repeated every 28 days (n = 974). Results: Patients receiving capecitabine experienced significantly (P <0.001) less diarrhea, stomatitis, nausea/vomiting, alopecia and neutropenia, but more hand-foot syndrome than those receiving 5-FU/LV. Fewer patients receiving capecitabine experienced grade 3 or 4 neutropenia, febrile neutropenia/sepsis and stomatitis (P <0.001), although more experienced grade 3 hand-foot syndrome than those treated with 5-FU/LV (P <0.001). Capecitabine demonstrates a similar, favorable safety profile in patients aged <65 years or ≥65 years old. Conclusions: Based on its improved safety profile, capecitabine has the potential to replace 5-FU/LV as standard adjuvant treatment for patients with colon cancer. Efficacy results are expected to be available in 2004. Keywords: Adjuvant treatment, capecitabine, chemotherapy, colorectal cance

Phytoscreening and phytoextraction of heavy metals at Danish polluted sites using willow and poplar trees

The main purpose of this study was to determine typical concentrations of heavy metals (HM) in wood from willows and poplars, in order to test the feasibility of phytoscreening and phytoextraction of HM. Samples were taken from one strongly, one moderately, and one slightly polluted site and from three reference sites. Wood from both tree species had similar background concentrations at 0.5 mg kg(−1) for cadmium (Cd), 1.6 mg kg(−1) for copper (Cu), 0.3 mg kg(−1) for nickel (Ni), and 25 mg kg(−1) for zinc (Zn). Concentrations of chromium (Cr) and lead (Pb) were below or close to detection limit. Concentrations in wood from the highly polluted site were significantly elevated, compared to references, in particular for willow. The conclusion from these results is that tree coring could be used successfully to identify strongly heavy metal-polluted soil for Cd, Cu, Ni, Zn, and that willow trees were superior to poplars, except when screening for Ni. Phytoextraction of HMs was quantified from measured concentration in wood at the most polluted site. Extraction efficiencies were best for willows and Cd, but below 0.5 % over 10 years, and below 1 ‰ in 10 years for all other HMs. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (doi:10.1007/s11356-013-2085-z) contains supplementary material, which is available to authorized users