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).
 
 

 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.)

 Fertilization was made with mineral fertiliser (urea, mono-ammonium phosphate and potassium muriate), compared with liquid animal manure, both to supply 300 kg/ha of nitrogen, 120 kg/ ha of phosphorus (P2O5) and 120 kg/ ha of potassium (K2O)
 
 

Figure 1. Nutrient abetement

The control (with an efficiency of about 50%) was very effective for nitrate, the most dangerous pollutant in water quality assessment. The control of ammonium and organic nitrogen was less effective, but we have to consider that these compounds are less mobile in the soil and generally less dangerous for water quality.

 The mean control efficiency of total nitrogen was higher than 30% and this may be considered a good result. Phosphorus control was less effective (16.1%), but its content in water was very low (Table 1). Pollutant control was very strong for runoff: the hedgerow stops more than 85% of solids, and consequently there is a good control of total phosphorus (Table 2).
 
 

 The good abatement of runoff is probably due to a very rapid growing of a permanent vegetated bank above the multistoried one-line shelterbelt. The minor control of buffer strips, instead, is probably linked to the reduced activity in the first year after planting. For a quicker effect in pollutant abatement, in this experiment older plant material, which suffers of heavier planting stress, was used instead of seedlings.
 
 

As show in figure 3, in fact, the control efficiency of all groundwater pollutants is increasing with the hedgerow taking roots: this is more clear taking in account plant growing season, which in Mediterranean climate is reduced during all winter and in full summer.

Especially nitrogen and N-NH4 have a contrasting seasonal evolution, and phosphorous seems to have slower evolution trend than N-NO3. These behaviours are probably linked to the soil and rizosphere biological activity, as it will be possible to state in further experiment phases.
 
 

• Franco D., Scattolin M.. 1995a. Le funzioni delle siepi nell'ecosistema. agrario. L'Informatore Agrario. 12 (51): 75-78.
• Franco D., Destro F., Bassato V. 1995b. Riqualificazione produttivo-ambientale del paesaggio rurale. L'Informatore Agrario. 39 (51): 27-33
• Franco D., Scattolin M., Chiozzotto E. 1996 Un parco rurale nel territorio comunale di Venezia sulla base di una procedura innovativa per l'analisi e la progettazione paesistica. Genio Rurale. in litteris.
• Perelli M. e D. Franco. 1994a. «Dafne 1»: una nuova metodologia per la razionalizzazione dell'impiego dei liquami zootecnici. L'informatore agrario, 50(32):46-53.
• Perelli M. e D. Franco. 1994b. A new approach to animal manure utilization. p. 828-829 In: Proceeding of the third congress of the European Society of Agronomy. Abano-Padova, settembre 1994.
• Perelli M., D. Franco e D. Barbin. 1993. I reflui delle attività zootecniche nel territorio del Comune di Venezia. Arsenale editrice, Venezia. pp. 72.