Buffer strips to protect the Venice Lagoon from non point source pollution From: Proceeding of the International conference on buffer zones, their processes and potential in water protection Heythrop (UK), august-september 1996 by Daniel Franco , Marino Perelli & Mario Scattolin Agricultural cropped fields were recognised as an important source of nitrogen pollution affecting the Venice Lagoon ecosystem. Till the sixties the agricultural management of this area was characterised by a large diffusion of hedgerow system and vegetated strips. Most of them were pulled out in the last decades to create a "modern" agricultural cropping system. Venetian Municipality is developing several actions to control lagoon pollution, including the planting of windbreaks and hedgerows. These are reintroduced by means of particular landscape planning model, accounting for the needing of local agriculture (Franco et al., 1995b, 1996). There was a lack of knowledge about the effect of the buffer strips in pollution control in Northern Italy environment (Franco et al., 1995a). To assess the non-point source pollution functionality in the planning system, a filed test was established. This test was a part of a more complex experimentation on non-point pollution in the area of Venice Lagoon (Perelli et al., 1993), including control of manure utilisation and the implementation of the "Dafne® 1 " approach to animal manure utilisation (Perelli and Franco, 1994a, 1994b). Methods Grain corn (Zea mais L.) was grown in 1995 and in 1996 on a calcareous clay-loam soil. A multistoried one-line shelterbelt was planted on half length of the border line of a field, using plant material suitable for producing effective results in the first years of the project (e.g. 2-3 m trees, 1.5 m shrubs). The hedgerow was realised with several experimental structure scheme using local species selected for their high capacity to control nutrients leaching: • White poplar (Pupulus alba L.) • European ash (Fraxinus excelsior L.) • White willow (Salix alba L.) • Black alder (Alnus glutinosa L.) • Cranberry bush (Viburnum opolus L.) The nutrient losses were monitored by means of piezometric wells and traps for run off. Sampling was made every ten days for groundwater and after every runoff event for the traps. For a better understanding of the data exposed in the figures of this paper, the nitrite nitrogen (which was lower then 1,5% of N-NO3) was included in the nitric nitrogen