RESUMO
Grassland-based ruminant production systems are integral to sustainable food production in Europe, converting plant materials indigestible to humans into nutritious food, while providing a range of environmental and cultural benefits. Climate change poses significant challenges for such systems, their productivity and the wider benefits they supply. In this context, grassland models have an important role in predicting and understanding the impacts of climate change on grassland systems, and assessing the efficacy of potential adaptation and mitigation strategies. In order to identify the key challenges for European grassland modelling under climate change, modellers and researchers from across Europe were consulted via workshop and questionnaire. Participants identified fifteen challenges and considered the current state of modelling and priorities for future research in relation to each. A review of literature was undertaken to corroborate and enrich the information provided during the horizon scanning activities. Challenges were in four categories relating to: 1) the direct and indirect effects of climate change on the sward 2) climate change effects on grassland systems outputs 3) mediation of climate change impacts by site, system and management and 4) cross-cutting methodological issues. While research priorities differed between challenges, an underlying theme was the need for accessible, shared inventories of models, approaches and data, as a resource for stakeholders and to stimulate new research. Developing grassland models to effectively support efforts to tackle climate change impacts, while increasing productivity and enhancing ecosystem services, will require engagement with stakeholders and policy-makers, as well as modellers and experimental researchers across many disciplines. The challenges and priorities identified are intended to be a resource 1) for grassland modellers and experimental researchers, to stimulate the development of new research directions and collaborative opportunities, and 2) for policy-makers involved in shaping the research agenda for European grassland modelling under climate change.
RESUMO
High soil P contents in agricultural soils in the Netherlands cause excessive losses of P to surface waters. The reductions in P application rates in the present manure policy are not sufficient to reach surface water quality standards resulting from the European Water Framework Directive in 2015. Accordingly, additional measures are necessary to reduce P loading to surface water. Greenhouse experiments showed that a rapid reduction in soluble P and readily available soil P can be obtained by zero P application. However, field data confirming these findings are scarce. In 2002 a phytoextraction experiment started on four grasslands sites on sand, peat, and clay soils. The phytoextraction (mining) plots receive no P and 300 kg N ha(-1) yr(-1) and the grass is removed by mowing. The experiment showed that zero P application, over a period of 5 yr, led to a strong (30-90%) reduction in P concentrations in soil solution in the upper soil layer (0-0.05 m). The reduction in concentrations declined with depth. Mining also resulted in a decline in P pools in the soil solid phase. The largest decline (10-60%) was found in weakly bound P pools (water extractable P; P(w), and ammonium lactate extractable P; P-AL), whereas reductions in more strongly bound P forms were relatively small. It may be concluded that phytoextraction appears an effective method of reducing soil P concentrations in the uppermost soil layers in a couple of years and prolonged mining may thus be effective in reducing leaching and runoff of P.
