On the occasion of its twenty-fifth anniversary, in 1985, the Netherlands Society for Grassland and Fodder Crops (NVWV) agreed to organize an International Symposium on a topic related to intensive grass and fodder production systems. The theme selected was "Animal manure on grassland and fodder crops: Fertilizer or waste?" This Symposium was organized under the auspices of the European Grassland Federation and held at the International Agricultural Centre in Wageningen from 31 August to 3 September 1987. The problems connected with the disposal of animal waste have received much attention in recent years, especially in regions with intensive animal of animal manure per hectare agricul­ husbandry. Whereas the production tural land increased strongly, the need for it decreased because of the introduction of cheap inorganic fertilizers which are easier to handle and have a more reliable effect on crop growth. As a consequence, many farmers dispose of animal manure as cheaply as possible, whilst avoiding damage to grassland and crops and paying little attention to effective use of the plants nutrients contained in the manure. Present practices of manure handling and application often lead to environmental problems. The rise in awareness of these problems renewed interest in possibilities to improve the utilization of nutrients from animal manure in crop production. Research on this topic has been stimulated in many countries during the last decade and the aim of this Symposium was to review and assess present-day knowledge.

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Invited papers.- Value of animal manures: changes in perception.- Effects of herbage composition and supplement feeding on the excretion of nitrogen in dung and urine by grazing dairy cows.- Manure as a source of nitrogen and phosphorus in soils.- Utilization of nitrogen from injected and surface-spread cattle slurry applied to grassland.- The influence of different processing methods for slurry upon its fertiliser value on grassland.- Utilisation of phosphorus and potassium from animal manures on grassland and forage crops.- Distribution of excreted nitrogen by grazing cattle and its effects on sward quality, herbage production and utilization.- Negative effects of animal manure on grassland due to surface spreading and injection.- Cattle slurry and farmyard manure as fertilizers for forage maize.- Utilization of nitrogen from slurry applied to fodder crops. Research report from the Nordic countries, Denmark, Finland and Sweden.- Extent, effects and tackling of a regional manure surplus: a case-study for a Dutch region.- Nitrogen losses from animal manures: from grazed pastures and from applied slurry.- Phosphorus and heavy metals: accumulation and consequences.- The use of additives in livestock slurries to improve their flow properties, conserve nitrogen and reduce odours.- Economic aspects of the use of animal manures.- The future of animal manures as fertilizer or waste.- Short communications.- Utilization of stored, aerated or anaerobically digested dairy cattle and pig slurries on sown grassland.- Utilization of nitrogen from slurry applied to permanent grassland.- The effectiveness of high doses of cattle slurry as pasture fertilizer in a submontane region.- Yield of hay from grassland treated with mineral fertilizers and slurry.- Yields from swards of varying botanical composition fertilized with cattle slurry.- Mid-season application of organic manures - a waste of resources?.- Long term effects of slurry on grassland.- The utilization of slurry on light land.- Effects of organic fertilizer application on hay meadow quality in the French Northern Alps.- The effect of regular application of cattle slurry on grassland during the growing season on grass yield and daily milk production.- Trials on slurry application techniques for grassland.- Injector design for minimum grass sward damage.- Investigations of the fertilizer value of sheep excrements left on pasture.- The characterization of cattle slurry and the response of a range of crop plants to slurry application.- Scorching of Lolium perenne caused by cattle slurry.- The effect of cattle slurry on clover in grass/clover swards.- Factors controlling vegetation dynamics in hay meadows under high levels of organic fertilizer in the French Northern Alps.- Effect of cattle dung on the spread of couch grass (Elymus repens L.) in intensive grassland.- Comparative responses to applied fertilizer phosphorus on manured and unmanured soils.- Effect of animal manure on phosphorus and potassium content of herbage.- Utilization of potassium excreted by grazing cattle.- The effect of cattle slurry on the mineral content of pastures and blood serum in dairy cows.- Ammonia volatilization from urine patches in grassland.- Limitations for slurry application to peat grassland.- Effect of treated pig slurry on herbage and groundwater quality.- Nitrate in soil water at different depths during the growing season on permanent pasture (comparison of mineral fertilizer and liquid manure).- The effect of a nitrification inhibitor on the utilization of nitrogen by grass from injected and surface-applied pig slurry.- The influence of ground superphosphate on the pH value and the ammonia release from slurry.- Separation of pig slurry by sedimentation.