Nitrogen retention and plant uptake on a highly weathered central Amazonian Ferralsol amended with compost and charcoal

Leaching losses of N are a major limitation of crop production on permeable soils and under heavy rainfalls as in the humid tropics. We established a field trial in the central Amazon (near Manaus, Brazil) in order to study the influence of charcoal and compost on the retention of N. Fifteen months after organic‐matter admixing (0–0.1 m soil depth), we added ¹⁵N‐labeled (NH₄)₂SO₄ (27.5 kg N ha^–1 at 10 atom% excess). The tracer was measured in top soil (0–0.1 m) and plant samples taken at two successive sorghum (Sorghum bicolor L. Moench) harvests. The N recovery in biomass was significantly higher when the soil contained compost (14.7% of applied N) in comparison to only mineral‐fertilized plots (5.7%) due to significantly higher crop production during the first growth period. After the second harvest, the retention in soil was significantly higher in the charcoal‐amended plots (15.6%) in comparison to only mineral‐fertilized plots (9.7%) due to higher retention in soil. The total N recovery in soil, crop residues, and grains was significantly (p < 0.05) higher on compost (16.5%), charcoal (18.1%), and charcoal‐plus‐compost treatments (17.4%) in comparison to only mineral‐fertilized plots (10.9%). Organic amendments increased the retention of applied fertilizer N. One process in this retention was found to be the recycling of N taken up by the crop. The relevance of immobilization, reduced N leaching, and gaseous losses as well as other potential processes for increasing N retention should be unraveled in future studies.     

Effects of pulsation rate and viscosity on pulsation-induced taste enhancement: new insights into texture-taste interactions

Oral stimulation with high-tastant concentrations that are alternared with low-tastant concentrations or water rinses (pulsatile stimulation) results in taste intensity ratings that are higher than continuous stimulation with the same average tastant concentration. This study tested the combined effects of taste pulsation rate and viscosity on pulsation-induced taste enhancement in apple juice. According to a tastant-kinetics hypothesis, less pulsation-induced taste enhancement is expected at enhanced pulsation rates in the high-viscous proximal stimulus compared to lower viscous stimuli. High-concentration sucrose apple juice pulses and low-concentration sucrose apple juice intervals were alternated at different pulsation periods (pulse + interval in seconds) every 2.5 s (period length = 5 s) or every 1.25 s (period length = 2.5 s). Pulsed stimuli were presented at two viscosity levels by the addition of pectin (0 and 10 g/L). Sweetness intensities of pulsed stimuli were compared to a continuous reference of the same net but nonalternating sucrose concentration. Sweetness ratings were higher for pulsatile stimuli than for continuous stimuli. In low-viscous stimuli, enhancement depended on the pulsation period and peaked at 5 s periods. In high-viscous stimuli, the same enhancement was observed for both pulsation periods. These results contradict a tastant-kinetics hypothesis of viscosity-induced taste suppression because impaired tastant kinetics by viscosity would predict the opposite: lower pulsation-induced taste enhancement for viscous stimuli, especially at higher pulsation rates. Instead, these observations favor an explanation based on perceptual texture-taste interactions, which predict the observed independence between viscosity and pulsation rate.     

Microbial community responses to disease management soil treatments used in flower bulb cultivation

Biology and Fertility of Soils - A number of management practices, such as soil fumigation and flooding, have been employed in efforts to control diseases and weeds in the cultivation of ornamental...     

Growth measurements of saprotrophic fungi and bacteria reveal differences between canopy and forest floor soils

Canopy-held organic matter develops into a distinct soil system separate from the forest floor in wet temperate coniferous forests, creating a natural microcosm. We distinguished between fungal and bacterial components of the decomposer community in one site with Maple (Acer macrophyllum) and one site with Alder (Alnus rubra) by using direct measurements of growth; acetate incorporation into ergosterol, and leucine incorporation for fungi and bacteria, respectively. The higher organic matter content of the canopy soils correlated with higher fungal growth. The relative importance of fungi, indicated by fungal:bacterial growth ratio, was higher in the canopy soil of the Maple site, while there was no difference in the Alder site. The high C:N ratio of the Maple canopy soil likely contributed to this difference. These results demonstrate a divergence between canopy and forest floor that should be explored to gain insights in decomposer ecology using the natural microcosms that the canopy soils provide.     

Species concepts and systematics of domesticated cereals

Summary Cultivated cereals are domesticated grasses. Wild progenitors of domestic cereals are aggressive natural colonizers and often become weedy in man disturbed habitats. Hybridization between cultivated cereals and their close wild relatives gives rise to mimetic cereal weeds that often accompany the domestic species well beyond its natural range. Similar weeds may also evolve from abandoned cultivars as a result of mutations that restore their ability for natural seed dispersal. Cultivated complexes of domestic species are typically variable. Man selects and isolates phenotypes to suit his fancies, with the result that different phenotypes of a cereal are often grown for different uses in the same village, and adjacent villages often grow different phenotypes for similar uses. Conventional species concepts do not hold for domestic species. It is proposed that wild, weed and cultivated complexes of individual domestic species be recognized respectively as subspecies. Major discontinuities in variation within the weed or cultivated subspecies are then identified as races without formal taxonomic recognition.

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Artbegriff und Systematik bei domestizierten Getreiden

Zusammenfassung Kultivierte Getreide sind domestizierte Gräser. Die wilden Vorfahren der domestizierten Getreide sind aggressive natürliche Besiedler und werden oft zu Unkräutern in vom Menschen beeinflußten Standorten. Bastardierung zwischen kultivierten Getreiden und ihren wilden Verwandten läßt mimetische Getreideunkräuter entstehen, die oft die domestizierten Arten außerhalb ihres natürlichen Verbreitungsgebietes begleiten. Ähnliche Unkräuter können sich auch aus aufgegebenen Sorten entwickeln als ein Ergebnis von Mutationen, die ihre Fähigkeit zur natürlichen Samenausstreuung wiederherstellen. Kultivierte Komplexe domestizierter Arten sind in typischer Weise variabel. Der Mensch selektiert und isoliert Phänotypen nach seinen Vorstellungen mit dem Ergebnis, daß verschiedene Phänotypen eines Getreides oft zu verschiedenen Zwecken im selben Dorf angebaut werden, und benachbarte Dörfer oft verschiedene Phänotypen für ähnliche Zwecke kultivieren. Der herkömmliche Artbegriff bewährt sich nicht bei domestizierten Arten. Es wird vorgeschlagen, daß Wild-, Unkraut- und Kulturformen einer domestizierten Art als entsprechende Unterarten angesehen werden. Größere Gruppen innerhalb der Unkraut- oder Kultur-Unterart sollten als Rassen ohne formale taxonomische Bezeichnung gehandhabt werden.

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Hydrological parameterization of piping in loess‐rich soils in the Bergisches Land,Nordrhein‐Westfalen,Germany

Pedohydrological properties were investigated on a piped slope in the Bergisches Land in the Rhenish Slate Mountains (Nordrhein‐Westfalen, Germany). The study confirmed that genesis and development of pipes decisively depend on hydrological conditions in the soils. Vertical water permeability of saturated samples was very high. This promoted fast seepage. Many macropores produced by earthworms also caused high transport capacity for soil water. Even more efficient were the burrows of moles and mice, enabling immediate infiltration and direct vertical and lateral water movement. On the contrary, the horizontal saturated permeability was low indicating no correlation with piping. Porosity of piped soils was not different to that of other soils of the region without pipes.     

Assessment of genetic relationships between <Emphasis Type="Italic">Rhus</Emphasis> L. species using RAPD markers

Genetic diversity of seven Rhus L. species was assessed using random amplified polymorphic DNA (RAPDs) markers. Initially, 90 primers were screened, of which 25 produced reproducible amplification products. These primers generated a total of 296 bands, with an average of 11.8 bands per primer. Out of 296 bands scored, 236 (80%) were polymorphic and 62 (20%) were monomorphic. Primers OPC-05 and OPD-05 generated 100% polymorphic bands. The resolving power of primers ranged from 9.4 to 26.8. Similarity matrix values ranged from 0.45 to 0.63. The dendrogram generated using Unweighted Pair Group Method using Arithmetic Averages (UPGMA) grouped all the species of Rhus in one major group with two sister groups, whilst R. pyroides Burch. and R. dentata Thunb. were outliers. R. gerrardii (Harv. ex Engl.) Diels, R. glauca Thunb. and R. pentheri Zahlbr. constituted one sister group, while R. natalensis Bernh. ex C. Krauss and R. gueinzii Sond. were included in the other. The degree of genetic diversity observed between seven species of Rhus with RAPD markers suggest that this approach could be used for studying the phylogeny of the genus.     

Toxicological and analytical investigations of noni (Morinda citrifolia) fruit juice

Morinda citrifolia (noni) is known to contain genotoxic anthraquinones in the roots. Because of the widespread use of noni juice, the possible genotoxic risk was examined through a battery of short-term tests. Noni juice was also chemically analyzed for the possible presence of anthraquinones. Noni juice extract in the Salmonella microsome assay showed a slight mutagenic effect in strain TA1537, due to the presence of flavonoids. No mutagenicity was observed in the mammalian mutagenicity test with V79 Chinese hamster fibroblasts. Rats treated with a noni juice concentrate did not show DNA repair synthesis (UDS) in primary rat hepatocytes, nor could DNA adducts or DNA strand breaks be observed. HPLC analysis of noni juice for anthraquinones was negative, with a sensitivity of <1 ppm. In summary, chemical analysis and genotoxicity tests reveal that noni juice does not have a genotoxic potential and that genotoxic anthraquinones do not exist in noni juice.