Effects of agricultural management on Si cycling in Italian paddy fields

Silicon (Si) is a beneficial nutrient for rice plants; it improves their resistance against biotic and abiotic stresses. Recent research showed that Si availability in soils is, on a large geographic scale, determined by stocks of weatherable silicate minerals. However, also on the smaller regional scale, pronounced differences in Si uptake of rice plants were observed. The reasons for these differences are not yet clear. They might include effects of agricultural management, such as crop residue recycling and irrigation. Here, we test the long-term effects of four different agricultural management practices in Vercelli (Northwest Italy), where one rice crop per year is cultivated from May to September. The experimental platform was installed in 2003 on a Haplic Gleysol known to be under continuous rice cultivation for the last 30 years and having low plant-available Si concentration. The following management practices were considered (i) tillage and crop residue incorporation in spring (ii) post-harvest rice straw burning and tillage in spring, (iii) tillage and crop residue incorporation in autumn, and (iv) tillage and crop residue incorporation in spring followed by dry seeding and delayed flooding. After seven years, in 2010, topsoil and plants were sampled at five points of time during the cropping season. We will examine plant-available Si concentrations in soil and Si uptake by rice. Results will be presented at the conference; they will reveal whether farmers are able to actively improve Si supply to rice plants by their agricultural management

Hidden paleosols on a high-elevation Alpine plateau (NW Italy): Evidence for Lateglacial Nunatak?

Alpine soils can provide valuable paleo-environmental information, representing a powerful tool for paleoclimate reconstruction. However, since Pleistocene glaciations and erosion-related processes erased most of the pre-existing landforms and soils, reconstructing soil and landscape development in high-mountain areas can be a difficult task. In particular, a relevant lack of information exists on the transition between the Last Glacial Maximum (LGM ~21,000 yr BP) and the Holocene (~11,700 yr BP), with this climatic shift that plays a crucial role for environmental thresholds identification. The present study aims at reconstructing the history and origin of hidden paleosols inside periglacial blockstreams and blockfields on a high-elevation Alpine plateau (Stolenberg Plateau) above 3000 m a.s.l., in the Northwestern Italian Alps. The results indicate that these soils recorded the main warming climatic phases occurred from the end of the LGM until the Late Holocene ~4000 yr BP. Our reconstructions, together with the high carbon stocks of these paleosols, suggest that during warming phases the environmental conditions on the Plateau were suitable for plant life and pedogenesis, already since 22,000–21,000 yr BP. These paleosols reasonably evidence the existence of a Lateglacial Nunatak representing, to our knowledge, one of the first documented relict non-glacial surfaces in the high-elevated European Alps. Thus, the Stolenberg Plateau provides important information about past climate and surface processes since the end of LGM, suggesting new perspectives on the long-term landscape evolution of the high European Alps