No abstract

No abstract

SummaryOne of the main concerns of the environmental scientists and policy makers is related to the environmental compatibility of current agricultural systems and, in particular, to the losses of chemical fertilizers and manure in surface and ground-waters, as a consequence of run-off and leaching phenomena. In most cases European recent agrienvironmental schemes envisaged specific measures for the reduction of fertilizer rates and the control of manure applications, in order to limit the releases of nutrients in surface and ground-waters. Substantial financial resources are invested in those measures and therefore the issue raises interest in monitoring and evaluating their effectiveness. Nutrient balance indicators are often used for quantitative assessment of the effectiveness of the measures in limiting the environmental impact of farming activities. N-surplus is one of the most commonly used indicators. The paper refers the results of a research project aimed at assessing the outcomes of agri-environmental measures implemented in the Venice Lagoon Watershed with an approach based upon the gross nitrogen balance, called "Nboxes". The results of applying the Nboxes procedure to a sample of 550 farms set are presented, evidencing the expectations of greater effectiveness in terms of nitrogen surplus reduction from the measure C.5.1.3a and C.5.1.3b (low input farming and buffer strips). Measures supporting improved irrigation systems, controlled drainage and more rational livestock nutritional programmes and technologies, showed instead only limited potential for tangible contributions to the reduction of nitrogen surplus in cultivated soils.

A methodological framework was designed to assess the effectiveness of agri-environmental policy measures adopted by the Veneto Region to reduce diffuse water pollution of agricultural origin. Two already existing methodologies were combined in a new flexible approach for policy assessment: Conceptual Modelling and Bayesian Networks (BNs). The former supported the development of a shared conceptual model (a cognitive map) of the agro-ecosystem of the study area; while the latter allowed the development of a probabilistic model coherent with the cognitive map. BNs were selected because they allow analyses with scarce data; they can be updated when further information becomes available, and are easily understandable by layperson. The paper reports the results obtained in the Venice Lagoon Watershed (VLW) case study, where the current agri-environmental measures were assessed in order to identify their effectiveness in terms of reduction of nitrogen releases in water bodies connected to the lagoon ecosystem. Preliminary results obtained by implementing expert opinions in the BN pointed out the likely limited effects of the measures on the declared objective of safeguarding the lagoon ecosystem. Final remarks are drawn about the potentials of the proposed methodology.

No abstract