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Available P (available + p)
Selected AbstractsOrganic phosphorus speciation and pedogenesis: analysis by solution 31P nuclear magnetic resonance spectroscopyEUROPEAN JOURNAL OF SOIL SCIENCE, Issue 6 2007R. W. McDowell Summary Changes in phosphorus (P) during soil development are central to the understanding of labile P for plant productivity and soil P management. We used NaOH-EDTA extraction with 31P nuclear magnetic resonance spectroscopy (31P NMR), sequential P fractionation, and general soil chemical characterization to better our understanding of P dynamics within two chronosequences (Manawatu and Reefton) and one Basalt maturity sequence under original native vegetation. With time, orthophosphate and orthophosphate monoesters tended to increase with organic C to a maximum of about two-thirds of NaOH-EDTA-extractable P in young soils (16 000 years in the Reefton chronosequence), but gradually declined thereafter to about one-third of NaOH-EDTA-extractable P in the oldest soils (130 000 years old). This coincided with a depletion of P from primary minerals (e.g. apatite) and readily available P for plant production. This depletion of inorganic P resulted in a greater reliance on organic P cycling via mineralization, hence the depletion of the normally recalcitrant monoester-P pool. Concomitantly, the build-up of labile P species (diesters and pyrophosphate) and scyllo - over myo -inositol hexakisphosphate occurred as soils developed, and might be attributed to microbial activity, including scavenging for P. This work highlights the importance of organic P cycling during pedogenesis. [source] Effects of different dietary phytase activities on the concentration of antioxidants in the liver of growing broilersJOURNAL OF ANIMAL PHYSIOLOGY AND NUTRITION, Issue 4 2010F. Karadas Summary One-hundred and fifty male chickens were used to evaluate the effects of different activities (0, 250, 500, 12 500 FTU/kg) of phytase on their performance and antioxidant concentration in the liver. The chicks were housed in 30 cages and were allocated to six replicates of five dietary treatments. All diets were formulated to be adequate in energy and protein (12.90 MJ/kg metabolizable energy, 214 g/kg crude protein), however, the negative control (NC) was lower in available P compared with the positive control (PC) (2.5 vs. 4.5 g/kg diet). The other three diets were the NC supplemented with phytase at 250, 500 and 12 500 FTU/kg (NC + 250, NC + 500 and NC + 12 500 FTU respectively). The concentration of antioxidants in the liver of the birds was determined using HPLC at 21 days of age. Low P diets (NC) reduced weight gain, however, supplementation with phytase improved weight gain to the extent that it was better than the PC at the 12 500 FTU treatment (p < 0.05). Feed conversion ratio was also improved by the high level of phytase supplement more than other treatments (p < 0.05). Feed consumption was not affected either by dietary phosphorus concentration or by different phytase supplementation. The antioxidant data showed that the unsupplemented diet with low phosphorus (NC) decreased the concentration of coenzyme Q10 and retinol-linoleate in the liver compared with that of birds on the adequate phosphorus treatment (PC). Phytase supplementation, especially at the higher doses (500 and 12 500 FTU) increased the level of coenzyme Q10 to the same level as the PC treatment. In addition, the highest dose (12 500 FTU) of phytase increased retinol concentration in the liver of chickens compared with those on the NC treatment. The highest inclusion level of phytase increased the ,-tocopherol level in the liver compared with the lower levels of phytase (NC + 250 and NC + 500 FTU). [source] Phosphorus status on Canadian organic farmsJOURNAL OF THE SCIENCE OF FOOD AND AGRICULTURE, Issue 15 2007Ralph C Martin Abstract In eastern North America, many conventional livestock farms, especially dairy farms with high inputs of feed and fertiliser have excess soil phosphorus levels and an annual phosphorus surplus. However, a Canadian dairy farm in transition to organic, without fertiliser inputs reduced its farm P surplus to a marginal level. On long-term organic dairy farms in Ontario, most soils tested low to very low in available P as measured by a standard soil test. Canadian Prairie organic grain farms also consistently demonstrate deficiencies in available soil P. Organic producers have few viable alternatives for P management. Phosphate rock can be acceptable to organic standards (provided they are low in heavy metals, and not processed synthetically), but the P in these becomes available slowly, especially in high pH soils common on most organic farms in Canada. An alternative is to increase soil P availability. Enhanced microbial activity in organically managed soils may make P more available. Livestock manures are rich sources of available phosphorus, but a majority of organic farmers in Canada do not keep livestock. Off-farm manure sources are subject to organic regulations and hauling costs, both of which may be prohibitive. Furthermore, manure from conventional farms in Canada may be contaminated by genetically modified material from corn and soybean feed. Additional research is required to improve short-term availability of soil P and long-term replacement. Copyright © 2007 Society of Chemical Industry [source] Relationship between soil nutrient availability and plant species richness in a tropical semi-arid environmentJOURNAL OF VEGETATION SCIENCE, Issue 6 2006Yareni Perroni-Ventura Abstract Question: What is the relationship between soil fertility and plant species richness in the ,fertile islands' occurring beneath two species of legume (Cercidium praecox and Prosopis laevigata)? Location: Tehuacán-Cuicatlán region, central Mexico. Methods: Plant richness was measured in three micro-environments (below canopies of C. praecox, below canopies of P. laevigata and in areas without canopies). The concentration of soil nutrients (C, N and P), C and N in the microbiota, and processes of ecosystem functioning (net C mineralization rate and N mineralization) were measured. The relationship between soil variables and plant richness were assessed with ANCOVAs. Results: Soil nutrients and species richness increases markedly under fertility islands. There were higher concentrations of C and N in the soil, faster rates of C mineralization, and higher species richness under P. laevigata canopies. The relationship between soil fertility and species richness was always positive except for total N, ammonium and net C mineralization rate under C. praecox, and for available P under P. laevigata. Conclusions: The sign of the relationship between soil fertility and species richness varies according to the nutrient and the micro-environment. Positive relationships could result from between species complementarity and facilitation. Negative relationships could be explained by a specific limitation threshold for some soil resources (P and N for plants and C for the soil microbiota) which eliminate the possibilities of between species complementarity and facilitation above that threshold. As in all observational studies, these relationships should be considered only correlational. [source] Effect of land use on some soil properties related to the risk of loss of soil phosphorusLAND DEGRADATION AND DEVELOPMENT, Issue 1 2008F. Troitiño Abstract Although land use clearly modifies soil properties, the intensity of the modifications depends on the management procedures and also on the soil properties themselves. To enable construction of models that describe soil nutrient losses, extensive databases corresponding to soils under different land use must be made available. Analysis of 404 samples of soils (from Galicia, NW Spain), under different types of use revealed that most of the soil properties underwent changes in the following order: forest use (least modified) - grassland - arable (most modified). Decreases in the contents of organic matter, extractable oxides and P-adsorption capacity followed the same order, as did increases in the contents of available P (total, inorganic and organic), P desorbed with distilled water, and degree of P saturation. In general, in all of the soils, independently of their use, the amount of P desorbed (whether total P, molybdate reactive P or particulate P) was more closely related to the degree of P saturation than to the levels of P extracted with bicarbonate. Copyright © 2007 John Wiley & Sons, Ltd. [source] Increased N affects P uptake of eight grassland species: the role of root surface phosphatase activityOIKOS, Issue 10 2010Yuki Fujita Increased N deposition may change species composition in grassland communities by shifting them to P limitation. Interspecific differences in P uptake traits might be a crucial yet poorly understood factor in determining the N effects. To test the effects of increased N supply (relative to P), we conducted two greenhouse fertilization experiments with eight species from two functional groups (grasses, herbs), including those common in P and N limited grasslands. We investigated plant growth and P uptake from two P sources, orthophosphate and not-readily available P (bound-P), under different N supply levels. Furthermore, to test if the N effects on P uptake was due to N availability alone or altered N:P ratio, we examined several uptake traits (root-surface phosphatase activity, specific root length (SRL), root mass ratio (RMR)) under varying N:P supply ratios. Only a few species (M. caerulea, A. capillaris, S. pratensis) could take up a similar amount of P from bound-P to that from orthophosphate. These species had neither higher SRL, RMR, phosphatase activity per unit root (Paseroot), nor higher total phosphatase activity (Pasetot: Paseroot times root mass), but higher relative phosphatase activity (Paserel: Pasetot divided by biomass) than other species. The species common from P-limited grasslands had high Paserel. P uptake from bound-P was positively correlated with Pasetot for grasses. High N supply stimulated phosphatase activity but decreased RMR and SRL, resulting in no increase in P uptake from bound-P. Paseroot was influenced by N:P supply ratio, rather than by only N or P level, whereas SRL and RMR was not dominantly influenced by N:P ratio. We conclude that increased N stimulates phosphatase activity via N:P stoichiometry effects, which potentially increases plant P uptake in a species-specific way. N deposition, therefore, may alter plant community structure not only by enhancing productivity, but also by favouring species with traits that enable them to persist better under P limited conditions. [source] Determining the important environmental variables controlling plant species community composition in mesotrophic grasslands in Great BritainAPPLIED VEGETATION SCIENCE, Issue 4 2009Veronika Kalusová Abstract Question: What is the relative importance of local site effects and selected important environmental variables in determining plant species composition? How do species respond to these environmental variables? Location: Ten mesotrophic grassland sites of high conservation value in southern England. Methods: Species cover was assessed in between 10 and 25 randomly selected 1-m2 quadrats at each site. At each quadrat degree of waterlogging (W), soil Olsen extractable phosphorus (P) and soil pH were measured. Variation partitioning was used to separate site and soil effects, and HOF (Huisman, Olff & Fresco) modelling was used to produce response curves for the major species on soil gradients, based on coenoclines derived from partial canonical correspondence analysis (pCCA). Results: Variation partitioning identified Site as the most important environmental variable (34.6%). Only 18.7% was accounted for by the three soil variables together; W (degree of waterlogging), P and pH accounted for 11.1%, 5.7% and 4.3%, respectively in raw form with 2.4% shared. However, when Site and the other soil variables were removed the variation explained reduced to 2.3% for W, 1.1% for P and 1.0% for pH. The species responses to each of these soil environmental factors could be separated into four types on each gradient. Most species were abundant at low W, low soil P and intermediate pH. Conclusions: Site-based factors were more important than the three soil variables, which were assumed to be directly or indirectly associated with productivity. This implies that each site has unique properties that are more important than the soil variables. The three soil factors were, however, significant and the groups of the most common species, based on significant response curves, can be used as a first approximation of indicators of environmental conditions in British mesotrophic grasslands for conservation. However, W accounted for most variation, and the current reliance on soil available P and soil pH for assessing conservation/restoration potential should be viewed with caution. [source] Microphase-Separated Poly(vinylpyridine) Block Copolymer Prepared with a Novel Bifunctional InitiatorMACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 7 2009Masami Shoji Abstract A vinylpyridine block copolymer was prepared by stepwise controlled/living radical polymerization with a novel bifunctional initiator, 4-(2-bromopropanoyloxy)- N -(p -methylbenzyloxy)-2,2,6,6-tetramethylpiperidine. The initiator was synthesized in a facile manner using commercially available p -xylene and 4-hydroxy-2,2,6,6-tetramethylpiperidine-1-oxyl (4-hydroxy TEMPO). Through stepwise atom transfer radical polymerization (ATRP) of methyl methacrylate (MMA) and nitroxide-mediated radical polymerization (NMRP) of 4-vinylpyridine (4VP), the PMMA- b- P4VP copolymer was prepared with a wide range of the copolymer compositions. Microphase-separation was demonstrated in cross sectional TEM images of self-standing block copolymer membranes. [source] Estimating the redshift distribution of photometric galaxy samples , II.MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 4 2009Applications, tests of a new method ABSTRACT In Lima et al. we presented a new method for estimating the redshift distribution, N(z), of a photometric galaxy sample, using photometric observables and weighted sampling from a spectroscopic subsample of the data. In this paper, we extend this method and explore various applications of it, using both simulations and real data from the Sloan Digital Sky Survey (SDSS). In addition to estimating the redshift distribution for an entire sample, the weighting method enables accurate estimates of the redshift probability distribution, p(z), for each galaxy in a photometric sample. Use of p(z) in cosmological analyses can substantially reduce biases associated with traditional photometric redshifts, in which a single redshift estimate is associated with each galaxy. The weighting procedure also naturally indicates which galaxies in the photometric sample are expected to have accurate redshift estimates, namely those that lie in regions of photometric-observable space that are well sampled by the spectroscopic subsample. In addition to providing a method that has some advantages over standard photo- z estimates, the weights method can also be used in conjunction with photo- z estimates e.g. by providing improved estimation of N(z) via deconvolution of N(zphot) and improved estimates of photo- z scatter and bias. We present a publicly available p(z) catalogue for ,78 million SDSS DR7 galaxies. [source] | |||||||||||||