Einfluss von organischer N-Düngung auf die Entwicklung von Leguminosen-Nachsaaten

Im Dauergrünland werden sowohl organische (z.B. Gülle) als auch mineralische N-Dünger eingesetzt, wobei deren Wirkung auf Leguminosen oder Leguminosen-Mischbestände teilweise unterschiedlich bewertet wird. Für den Ökolandbau hat die organische N-Düngung eine besondere Relevanz, denn eine mineralische N-Düngung ist nicht zulässig. Bislang ungeklärt war, ob und in welchem Maße eine organische N-Düngung (Gülle) eine Nachsaat von Leguminosen negativ beeinflusst. Ein mehrfaktorieller Versuch mit drei Leguminosen Nachsaat-Varianten im Dauergrünland, zwei N-Düngearten und zwei N-Düngeniveaus wurde über den Zeitraum von 3 Jahren beobachtet. Zur Vergleichbarkeit mit anderen Studien wurden mineralische N-Düngervarianten in die Studie mit einbezogen. Der Leguminosen-Anteil von Rotklee und Weißklee wurde durch erhöhte organische N-Düngerraten reduziert. Eine Reduktion war schon bei einer N-Gabe von 85 kg ha-1 messbar. Durch eine erhöhte N-Gabe erhöhte sich der Trockenmasse-Ertrag in der Kontrolle (keine Nachsaat), aber nicht in den Klee-nachgesäten Varianten. Klee-nach- gesäte Varianten hatten auch ohne N-Düngung gleiche oder erhöhte Trockenmasse-Erträge im Vergleich zur N-gedüngten Kontrolle

The Influence of Nitrogen Applications and Low Rainfall Conditions on Yield of Mixed Grass-Legume Grassland for 2 Years

Mixed-species grassland containing legumes were suggested to increase yield compared to monocultures. Furthermore, some legumes were suggested to be able to sustain growth, even under drought conditions. The first aim of the current study was to measure if multispecies grassland with legumes is also more productive when their N input due to symbiotic N2 fixation is taken into account. Our second aim was to determine the benefit of grass–legume mixtures in terms of dry matter production under naturally occurring drought conditions. Mixed-species grasslands, consisting of monocultures and variable mixtures of (a) Trifolium pratense, (b) Trifolium. repens, (c) Lolium perenne, and (d) a mixture of drought-tolerant grasses (GSWT based), were assessed for their dry matter production over two years with contrasting weather patterns. The legume–grass seeding mixtures received either a fixed (180 kg N ha−1) or adapted N-fertilizer application (0–180 kg N ha−1), with the latter taking the assumed symbiotic N2 fixation by legumes into account. Mixed-species grassland showed improved yield compared to monocultures both in comparably humid and drought-affected years. The benefits of multispecies grass–legume mixtures were considerably more obvious under a fixed but still measurable under an adapted N-fertilizer regime. The species diversity effect appears to be significantly dependent on the additional N supply enabled by legumes’ symbiotic N2-fixation. Legumes and drought-tolerant grasses yielded equally well under drought conditions, although legumes showed major advantages during moderate drought and humid conditions. White and red clover, although both legumes, differed significantly in their persistence under elevated-N and their dry matter production under low-N fertilizer application, but were equal in their tolerance towards drought

The beneficial and detrimental effects of sewage sludge applications in South Australia / Karin M. Weggler-Beaton.

Bibliography: leaves 256-275.xx, 275 leaves : ill., map ; 30 cm.Thesis (Ph.D.)--University of Adelaide, Dept. of Plant Science, 199

Development of Legumes After Reseeding in Permanent Grassland, as Affected by Nitrogen Fertilizer Applications

Legumes in grassland can increase locally grown protein in fodder while reducing the nitrogen (N)-fertilizer requirements. Although the benefits of forage legumes are known, there was a decline in their use in the past due to inexpensive N-fertilizer, soya products from abroad, and variable legume persistence. In recent years, mounting environmental concern has sparked new interest in legumes. To quantify the effect of legume reseeding and N-application on permanent grassland on crude protein (CP) and dry matter yield (DM), a multifactorial trial was set up. Factors considered were clover species (red clover, white clover), N-application rate (0–170 kg N ha−1), N-fertilizer type (mineral-N, organic-N), and cutting management (3, 5-cut). Legume percentages were scored, and DM- and CP-yield was measured for three years. Crude-protein gains after legume reseeding were considerable and between 2.5–3.4 after red clover and 0.4–1.7 t CP ha−1 3 years−1 after white clover-reseeding even when compared to the control-high-N treatment. Legume percentages were negatively correlated to N-rates down to rates as low as 42 or 85 kg N ha−1 for a three- or five-cut management, respectively. Nitrogen-applications increased the yield (DM, CP) of control plots, whereas for legume-reseeded plots yield remained unchanged or was reduced. Differences due to N-fertilizer type were small or non-existent. Reseeding of clover was shown to be a viable method to increase crude protein in permanent grassland for about three years (red clover) and possibly beyond (white clover)

Nest predation in Reed Buntings Emberiza schoeniclus: an experimental study

Predation is a major cause of nest failure in many bird species. High levels of nest loss may be a consequence of habitat fragmentation, leading to increased amounts of edge habitat. Yet the evidence for generally high nest predation rates along edges in fragmented landscapes is ambiguous. Using real nests of Reed Buntings Emberiza schoeniclus in which artificial Reed Bunting and real Japanese Quail Coturnix japonica eggs were placed, we experimentally tested for edge effects on nest predation in highly fragmented reed Phragmites sp. habitats in the Swiss lowlands. We also examined seasonal patterns of predation and the impacts of nest visits by observers. We found evidence for an edge effect at the water-sided reed edge, with nests located closer to the water being more likely to be predated than those further away. Predation probability increased from early to late season, suggesting that nest predation may be density dependent. Probability of nest predation was only weakly influenced by whether or not a nest was visited. Our results suggest that the intensive reed management currently applied in Swiss nature reserves may result in unnaturally high levels of nest losses in the Reed Bunting, because reed bands are not wide enough to allow nest placement at a safe distance from reed edges