Cover crops grown in monoculture and mixed cropping affect soils differently

Cover crops provide various benefits to agricultural soils. The legumes among cover crops may provide fixed nitrogen as nutrient. Other species show high uptake and storage capacity for nitrogen, thus preventing losses as water polluting nitrate or greenhouse effective nitrous oxide. The input of carbon by shoot and root biomass, as well as rhizodeposition and root decay after harvest or mulching increases soil quality e.g. in form of nutrient supply and organic matter buildup. Brassicaceae lack mutualism with mycorrhizal fungi and some species can reduce the number of phytopathogenic nematodes, thus affecting food web structures. However, many benefits provided by single plant species may be affected when these species grow under mixed cropping. In a pot experiment ten typical cover crop species were grown in monoculture: Phacelia tanacetifolia, Brassica rapa var. rapa, Raphanus sativus var. oleiformis, Sinapis alba, Trifolium incarnatum, Vicia villosa, Avena strigosa, Lolium multiforum, Sorghum bicolor x S. sudanense, and Fagopyrum esculentum. These were compared to six mixtures ranging in complexity from two to six species including the classics R. sativus/S. alba, R. sativus/A. strigosa, and the “Landsberger Gemenge”. Six plants per pot grew in two differently textured soils (silty loam, loamy sand) in a greenhouse for 60 days. Plant parameters measured, included shoot and root dry matter, their C and N content, root morphology, plant height as well as chlorophyll content. In the soil, the pH, C-to-N-ratio, inorganic nitrogen, microbial biomass, and abundance of microbial domains were measured. Already plant parameters indicated effects caused by mixed cropping. Height and chlorophyll content of P. tanacetifolia, S. alba, and S. bicolor were higher in monocultures than in mixtures indicating interspecific competition. Furthermore, below-ground biomass of two-species-mixtures containing R. sativus appeared to be higher than those of the corresponding monocultures. While monocultures increased soil pH differently, mixtures showed no significant difference between each other. This study aims to show that the impact on soil by different cover crop species are not necessarily realised the same way under mixed cropping

Optimierte Bestimmung der unterirdischen Pflanzenbiomasse in Theorie und Praxis

Will man den C oder N Eintrag von Pflanzen ermitteln, muss die unterirdische Pflanzenbiomasse möglichst exakt bestimmt werden. Diese besteht aus der Rhizodeposition und dem Wurzelsystem einer Pflanze. Als Rhizodeposition wird die Abgabe von organischen und anorganischen Verbindungen bezeichnet. Sie setzt sich unter anderem aus Wurzelfragmenten, Wurzelrandzellen, Wurzelexudaten und Lysaten zusammen. Auf Grund einer fehlenden Wurzelraumbegrenzung, ist die Erfassung des vollständigen Wurzelsystems einer Pflanze im Freiland problematisch. Zur Quantifizierung von Wurzelsystemen sind jedoch Freilandversuche stets Gefäßversuchen vorzuziehen, da nur so ein ungestörtes Wurzelwachstum erreicht werden kann. Als Konsequenz lassen sich unterschiedliche Wurzel-Spross-Verhältnisse in Gefäß- und Freilandversuchen feststellen. Verlagerungsprozesse innerhalb der Pflanze können zusätzlich die Berechnung der Rhizodeposition beeinflussen und so zur Über- oder Unterschätzung der unterirdischen Pflanzenbiomasse führen. Ziel war daher ein Beprobungsschema zu entwickeln, welches es ermöglicht die Wurzelbiomasse im Freiland zu erfassen und unterschiedliche Berechnungsmethoden der Rhizodeposition zu vergleichen. Hierfür wurden sowohl im Gefäß als auch im Freiland Erbsen mittels Dochtmethode mit multiplen 13C und 15N-Pulsen markiert, wodurch eine annähernd kontinuierliche Markierung simuliert wurde. Die Wurzelbiomasse der Erbse wurde im Freiland bestimmt, indem Unterproben mit einem definierten Volumen in 3 festgelegten Positionen im Bestand genommen wurden (direkt auf einer Pflanze; zwischen 2 Pflanzen in der Reihe; in der Mitte von 4 Pflanzen zwischen 2 Reihen). Durch die unterschiedliche Gewichtung der Positionen, die sich aus dem Beprobungsdurchmesser und dem Pflanze-/Reihenabstand ergaben, konnte die vollständige Wurzelbiomasse bestimmt werden. Die Rhizodeposition wurde mit einer Massenbilanz (1) und mit der Janzen und Bruinsma Methode (2) ermittelt. Zum Zeitpunkt der Blüte waren die Wurzelbiomasse und das Wurzel-Spross-Verhältnis im Feld um ein vielfaches Größer verglichen mit dem Gefäß. Bei der Berechnung nach Janzen und Bruinsma können Verlagerungsprozesse während der Blüte zur Überschätzung der Rhizodeposition führen. Erfolgt eine kontinuierliche Markierung über den gesamten Vegetationsverlauf, so kann die Rhizodeposition am Kulturende sowohl nach Janzen und Bruinsma als auch mit der Massenbilanz berechnet werden

Can the evolution of music be analyzed in a quantitative manner?

We propose a methodology to study music development by applying multivariate statistics on composers characteristics. Seven representative composers were considered in terms of eight main musical features. Grades were assigned to each characteristic and their correlations were analyzed. A bootstrap method was applied to simulate hundreds of artificial composers influenced by the seven representatives chosen. Afterwards we quantify non-numeric relations like dialectics, opposition and innovation. Composers differences on style and technique were represented as geometrical distances in the feature space, making it possible to quantify, for example, how much Bach and Stockhausen differ from other composers or how much Beethoven influenced Brahms. In addition, we compared the results with a prior investigation on philosophy. Opposition, strong on philosophy, was not remarkable on music. Supporting an observation already considered by music theorists, strong influences were identified between composers by the quantification of dialectics, implying inheritance and suggesting a stronger master-disciple evolution when compared to the philosophy analysis.Comment: 8 pages, 6 figures, added references for sections 1 and 4.C, better mathematical description on section 2. New values and interpretation, now considering a bootstrap metho

Effect of four plant species on soil 15N-access and herbage yield in temporary agricultural grasslands

Positive plant diversity-productivity relationships have been reported for experimental semi-natural grasslands (Cardinale et al. 2006; Hector et al. 1999; Tilman et al. 1996) as well as temporary agricultural grasslands (Frankow-Lindberg et al. 2009; Kirwan et al. 2007; Nyfeler et al. 2009; Picasso et al. 2008). Generally, these relationships are explained, on the one hand, by niche differentiation and facilitation (Hector et al. 2002; Tilman et al. 2002) and, on the other hand, by greater probability of including a highly productive plant species in high diversity plots (Huston 1997). Both explanations accept that diversity is significant because species differ in characteristics, such as root architecture, nutrient acquisition and water use efficiency, to name a few, resulting in composition and diversity being important for improved productivity and resource use (Naeem et al. 1994; Tilman et al. 2002). Plant diversity is generally low in temporary agricultural grasslands grown for ruminant fodder production. Grass in pure stands is common, but requires high nitrogen (N) inputs. In terms of N input, two-species grass-legume mixtures are more sustainable than grass in pure stands and consequently dominate low N input grasslands (Crews and Peoples 2004; Nyfeler et al. 2009; Nyfeler et al. 2011). In temperate grasslands, N is often the limiting factor for productivity (Whitehead 1995). Plant available soil N is generally concentrated in the upper soil layers, but may leach to deeper layers, especially in grasslands that include legumes (Scherer-Lorenzen et al. 2003) and under conditions with surplus precipitation (Thorup-Kristensen 2006). To improve soil N use efficiency in temporary grasslands, we propose the addition of deep-rooting plant species to a mixture of perennial ryegrass and white clover, which are the most widespread forage plant species in temporary grasslands in a temperate climate (Moore 2003). Perennial ryegrass and white clover possess relatively shallow root systems (Kutschera and Lichtenegger 1982; Kutschera and Lichtenegger 1992) with effective rooting depths of <0.7 m on a silt loamy site (Pollock and Mead 2008). Grassland species, such as lucerne and chicory, grow their tap-roots into deep soil layers and exploit soil nutrients and water in soil layers that the commonly grown shallow-rooting grassland species cannot reach (Braun et al. 2010; Skinner 2008). Chicory grown as a catch crop after barley reduced the inorganic soil N down to 2.5 m depth during the growing season, while perennial ryegrass affected the inorganic soil N only down to 1 m depth (Thorup-Kristensen 2006). Further, on a Wakanui silt loam in New Zealand chicory extracted water down to 1.9 m and lucerne down to 2.3 m soil depth, which resulted in greater herbage yields compared with a perennial ryegrass-white clover mixture, especially for dryland plots (Brown et al. 2005). There is little information on both the ability of deep- and shallow-rooting grassland species to access soil N from different vertical soil layers and the relation of soil N-access and herbage yield in temporary agricultural grasslands. Therefore, the objective of the present work was to test the hypotheses 1) that a mixture comprising both shallow- and deep-rooting plant species has greater herbage yields than a shallow-rooting binary mixture and pure stands, 2) that deep-rooting plant species (chicory and lucerne) are superior in accessing soil N from 1.2 m soil depth compared with shallow-rooting plant species, 3) that shallow-rooting plant species (perennial ryegrass and white clover) are superior in accessing soil N from 0.4 m soil depth compared with deep-rooting plant species, 4) that a mixture of deep- and shallow-rooting plant species has greater access to soil N from three soil layers compared with a shallow-rooting two-species mixture and that 5) the leguminous grassland plants, lucerne and white clover, have a strong impact on grassland N acquisition, because of their ability to derive N from the soil and the atmosphere

Nitrogen transfer from forage legumes to nine neighbouring plants in a multi-species grassland

Legumes play a crucial role in nitrogen supply to grass-legume mixtures for ruminant fodder. To quantify N transfer from legumes to neighbouring plants in multi-species grasslands we established a grass-legume-herb mixture on a loamy-sandy site in Denmark. White clover (Trifolium repens L.), red clover (Trifolium pratense L.) and lucerne (Medicago sativa L.) were leaf-labelled with 15N enriched urea during one growing season. N transfer to grasses (Lolium perenne L. and xfestulolium), white clover, red clover, lucerne, birdsfoot trefoil (Lotus corniculatus L.), chicory (Cichorium intybus L.), plantain (Plantago lanceolata L.), salad burnet (Sanguisorba minor L.)and caraway (Carum carvi L.) was assessed. Neighbouring plants contained greater amounts of N derived from white clover (4.8 gm-2) compared with red clover (2.2 gm-2) and lucerne (1.1 gm-2). Grasses having fibrous roots received greater amounts of N from legumes than dicotyledonous plants which generally have taproots. Slurry application mainly increased N transfer from legumes to grasses. During the growing season the three legumes transferred approximately 40 kg N ha-1 to neighbouring plants. Below-ground N transfer from legumes to neighbouring plants differed among nitrogen donors and nitrogen receivers and may depend on root characteristics and regrowth strategies of plant species in the multi-species grassland

The fossil bivalve Angulus benedeni benedeni: A potential seasonally resolved stable-isotope-based climate archive to investigate Pliocene temperatures in the southern North Sea basin

Bivalves record seasonal environmental changes in their shells, making them excellent climate archives. However, not every bivalve can be used for this end. The shells have to grow fast enough so that micrometre- to millimetre-sampling can resolve sub-annual changes. Here, we investigate whether the bivalve Angulus benedeni benedeni is suitable as a climate archive. For this, we use ca. 3-million-year-old specimens from the Piacenzian collected from a temporary outcrop in the Port of Antwerp area (Belgium). The subspecies is common in Pliocene North Sea basin deposits, but its lineage dates back to the late Oligocene and has therefore great potential as a high-resolution archive. A detailed assessment of the preservation of the shell material by micro-X-ray fluorescence, X-ray diffraction, and electron backscatter diffraction reveals that it is pristine and not affected by diagenetic processes. Oxygen isotope analysis and microscopy indicate that the species had a longevity of up to a decade or more and, importantly, that it grew fast and large enough so that seasonally resolved records across multiple years were obtainable from it. Clumped isotope analysis revealed a mean annual temperature of 13.5±3.8°C. The subspecies likely experienced slower growth during winter and thus may not have recorded temperatures year-round. This reconstructed mean annual temperature is 3.5°C warmer than the pre-industrial North Sea and in line with proxy and modelling data for this stratigraphic interval, further solidifying A. benedeni benedeni's use as a climate recorder. Our exploratory study thus reveals that Angulus benedeni benedeni fossils are indeed excellent climate archives, holding the potential to provide insight into the seasonality of several major climate events of the past ∼25 million years in northwestern Europe

Demand-Orientated Power Production from Biogas: Modeling and Simulations under Swedish Conditions

The total share of intermittent renewable electricity is increasing, intensifying the need for power balancing in future electricity systems. Demand-orientated combined heat and power (CHP) production from biogas has potential for this purpose. An agricultural biogas plant, using cattle manure and sugar beet for biogas and CHP production, was analyzed here. The model Dynamic Biogas plant Model (DyBiM) was developed and connected to the Anaerobic Digestion Model No. 1 (ADM1). Flexible scenarios were simulated and compared against a reference scenario with continuous production, to evaluate the technical requirements and economic implications of demand-orientated production. The study was set in Swedish conditions regarding electricity and heat price, and the flexibility approaches assessed were increased CHP and gas storage capacity and feeding management. The results showed that larger gas storage capacity was needed for demand-orientated CHP production but that feeding management reduced the storage requirement because of fast biogas production response to feeding. Income from electricity increased by 10%, applying simple electricity production strategies to a doubled CHP capacity. However, as a result of the currently low Swedish diurnal electricity price variation and lack of subsidies for demand-orientated electricity production, the increase in income was too low to cover the investment costs. Nevertheless, DyBiM proved to be a useful modeling tool for assessing the economic outcome of different flexibility scenarios for demand-orientated CHP production