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Wageningen, Netherlands

van Eekeren N.,Louis Bolk Institute | Bos M.,Louis Bolk Institute | de Wit J.,Louis Bolk Institute | Keidel H.,Blgg | Bloem J.,Wageningen University
Applied Soil Ecology

For the purpose of feeding value, drought resistance and nitrogen utilization, other grasses (e.g. Festuca arundinacea and Dactylis glomerata) than the currently widely used perennial rye grass (Lolium perenne) are introduced in dairy farming, either as a monoculture or in a mixture. To study the effect of these grasses on yield and soil chemical and biological quality, the three species were sown in a field experiment in monoculture and in two mixtures. Within two growing seasons, the grass species tested under high soil fertility conditions did not show significant effects on most of the tested soil biological parameters. Only for the mixture of L. perenne and D. glomerata a higher soil NO3 - and mineral N content were most probably related to a higher bacterial activity, possibly induced by dying roots of L. perenne. This was the likely cause of the high aboveground dry matter yield of this mixture. The N-efficiencies of the monocultures of L. perenne, F. arundinacea and D. glomerata were not different when only considering the aboveground biomass. In L. perenne and F. arundinacea the total N in root biomass was higher while under D. glomerata the NO3 - in the soil was higher. The lower fraction of mineral N to total N for L. perenne, F. arundinacea and the mixture of the two suggests that their organic matter build-up/mineralization ratio was higher than for D. glomerata. Furthermore, the mixture of L. perenne and F. arundinacea showed significantly lower soil mineral N levels than the monocultures of each. We conclude that grassland systems with a mixture of L. perenne and F. arundinacea are more sustainable than the monocultures of each, in terms of reduction of nitrogen losses and the build-up of soil organic matter. D. glomerata should only be used in a mixture in which the companion grass(es) are maintained. © 2010 Elsevier B.V. Source

Garbeva P.,Netherlands Institute of Ecology | Hol W.H.G.,Netherlands Institute of Ecology | Termorshuizen A.J.,Blgg | Kowalchuk G.A.,Netherlands Institute of Ecology | And 2 more authors.
Soil Biology and Biochemistry

In most soils, fungal propagules are restricted to a certain extent in their ability to grow or germinate. This phenomenon, known as soil fungistasis, has received considerable attention for more than five decades, mostly due to its association with the general suppression of soil-borne fungal diseases. Here, we review major breakthroughs in understanding the mechanisms of fungistasis. Integration of older fungistasis research and more recent findings from different biological and chemical disciplines has lead to the consensus opinion that fungistasis is most likely caused by a combination of microbial activities, namely withdrawal of nutrients from fungal propagules and production of fungistatic compounds. In addition, recent findings indicate that there are mechanistic links between these activities leading towards an integrated theory of fungistasis. Among the potentially fungistatic compounds volatiles have received particular attention. Whereas it has long been assumed that fungistasis is the result of the metabolic activity of the total soil microbial biomass, more recent research points at the importance of activities of specific components of the microbial community. These insights into fungistasis have also formed the basis for strategies to increase general soil suppression. Besides these basic and practical aspects of fungistasis, its impact on fungal ecology, in particular on fungal exploration strategies, is discussed. Finally, we take a closer look at plant-soil feedback experiments to demonstrate the occurrence of fungistasis-like phenomena and to suggest that fungistasis may be part of a much wider phenomenon: general soil biostasis. © 2010 Elsevier Ltd. Source

Hol W.H.G.,Netherlands Institute of Ecology | de Boer W.,Netherlands Institute of Ecology | Termorshuizen A.J.,Blgg | Meyer K.M.,University of Gottingen | And 6 more authors.
Ecology Letters

Rare species are assumed to have little impact on community interactions and ecosystem processes. However, very few studies have actually attempted to quantify the role of rare species in ecosystems. Here we compare effects of soil community assemblages on plant-herbivore interactions and show that reduction of rare soil microbes increases both plant biomass and plant nutritional quality. Two crop plant species growing in soil where rare microbes were reduced, had tissues of higher nutritional quality, which theoretically makes them more susceptible to pest organisms such as shoot-feeding aphids and root-feeding nematodes. Reduction of rare microbes increased aphid body size in the absence of nematodes; nematodes always reduced aphid body size independent of the soil microbial community. This study is the first to show that rare soil microbes are not redundant but may play a role in crop protection by enhancing aboveground and belowground plant defence. It remains to be tested whether these are direct effects of rare soil microbes on plants and herbivores, or indirect effects via shifts in the microbial soil community assemblages. © 2010 Blackwell Publishing Ltd/CNRS. Source

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