Sustainable land management practices in the low-lying Venetian plain: relationship to soil ecosystem services

Sustainable land management (SLM) practices, as conservation agriculture (CA) and conventional tillage with cover crops (CC), aimed at balancing competitive agricultural production and environmental protection, have been encouraged throughout the EU through policy and subsidisation. Adoption of SLM practices that regulate biogeochemical cycles, however, requires further study, especially given the effects of local pedo-climatic variability and because middle and long-term effects are not fully understood and may differ from short-term outcomes. For these reasons, in this work, field experiments were conducted in three farms in the low-lying venetian plain, characterized by loamy soils, where CA and CC were compared to conventional intensive tillage system (CV) on trials established since 2010. The first objective of the thesis was to evaluate, by integrating experimental field results with model predictions, the potential ecosystem services provided by CA and CC practices on SOC dynamic, air quality and climate regulation, nutrition biomass and regulating of water conditions. In this experiment, CA and CC results contrasted according to the soil functions, the ecosystem service category and evaluation time span. The former was more effective in providing regulating services in the short term, and less consistent in the long term, at least for GHG mitigation. GHG control is only one of the numerous ecosystem services provided by conservation practices (e.g. reduction of erosion and P particulate loss). Many of these depend on the C content which are strongly affected by the C stratification processes. Cover crop adoption, on the contrary, showed promise in the long term, whereas short-term outcomes (two-year experiment) were negatively affected by poor cover crop growth. The second objective aimed to assess the SOC stock variation due to the adoption of CA and CC in comparison to CV within a large sample (i.e., 240) of 0-50-cm soil profiles, comparing two expansive soil sampling operations conducted in 2011 and 2017. The study showed that CA enhances SOC stratification rather than SOC accumulation, with high topsoil SOC that may have partly counteracted soil surface compaction. However, a comparison with previous SOC stock quantifications between CA and CV after three years of the experiment suggests that some SOC stock increase occurred, even at 50 cm, despite being not significant. The burial of fresh biomass-C with cover crops in arable systems (CC) enhanced SOC stock depletion most likely due to priming effects, suggesting that C input management is pivotal for its accumulation in agroecosystems with low soil fertility and low SOC protection capacity.