Biogenic silicon in agricultural landscapes (BiSiAL): Quantification, qualitative characterization, and importance for Si balances of agricultural biogeosystems

尽管硅（Si）通常被认为是植物非必需的，但植物中Si积累的许多益处是已知的，例如，增加的植物生长和对非生物（例如，缺水）以及生物胁迫（例如，真菌感染）。然而，一些因素限制了土壤中植物有效硅的含量。因此，详细分析农业生态系统土壤中植物有效硅的含量及其影响具有重要意义。几种生物利用溶解的Si（Si（OH）4）合成（=生物硅化）生物硅质（BSi）结构（SiO2 x nH 2 O）。由于其相对较高的溶解度相比，矿物硅BSi是一个重要的来源，植物有效硅在土壤中。基于现代显微镜和光谱学方法（共聚焦激光扫描显微镜、显微FTIR光谱学）的组合，将在所要求的项目中实现单个BSi池的量化和BSi结构的物理化学表面性质的分析，这些目标无法通过已建立的碱提取方法来实现。主要是由于通过收割和增加侵蚀的硅出口引起的，农业土壤中植物有效硅的量会减少（=人为脱硅）。由于收割，每年从农业生态系统中出口的硅公顷约达100公斤。然而，尽管有这样的知识，只有零碎的经验研究结果的主题硅平衡（现状，硅投入，硅输出）的农业生态系统。因此，所请求项目的目标如下：一）农业生态系统的全面硅平衡;二）查明影响硅平衡的因素（侵蚀程度、生物硅库等）。农业景观研究中心（ZALF）提供了关于实验基础设施的全球独特要求，（仪器化田间实验CarboZALF-D和长期田间实验V140）来实现这些目标。所要求的项目的结果应该有助于从根本上了解人为脱硅作用及其对农业生态系统的影响。此外，以实践为导向的建议，限制或防止人为脱硅可以从这些结果。

Despite the fact that silicon (Si) is generally considered as non-essential for plants, many benefits of Si-accumulation in plants are known, e.g., increased plant growth and resistance against abiotic (e.g., water deficiency) as well as biotic stresses (e.g., fungal infections). However, several factors limit the plant available Si fraction in soils. In this context, it is of fundamental importance to analyze the size of the plant available Si fraction and corresponding influences in soils of agricultural biogeosystems in detail. Several organisms use dissolved Si (Si(OH)4) for synthesis (= biosilicification) of biogenic siliceous (BSi) structures (SiO2 x nH2O). Due to its relatively high solubility compared to minerogenic Si BSi is an important source of plant available Si in soils. Based on a combination of modern microscopic and spectroscopic methods (confocal laser scanning microscopy, micro-FTIR-spectroscopy) the quantification of single BSi pools and analyses of physicochemical surface properties of BSi structures will be realized in the requested project, objectives that cannot be obtained with established alkaline extraction methods.In general, humankind actively influences Si cycling due to intensified land use. Induced mainly by Si exports through harvesting and increased erosion the amount of plant available Si can decrease in agricultural soils (= anthropogenic desilicification). Caused by harvesting approximately up to 100 kg Si ha-1 are exported from agricultural biogeosystems every year. However, despite this knowledge, there are only fragmentary empirical findings on the subject of Si balances (status quo, Si inputs, Si outputs) of agricultural biogeosystems. Thus, the objectives of the requested project are as follows:i) Comprehensive Si balancing of agricultural biogeosystems.ii) Identification of factors that influence Si balances (degree of erosion, BSi pools, etc.).iii) Analyses of temporal developments of the plant available Si fraction and BSi pools in soils of agricultural biogeosystems.iv) Quantification of BSi pools and qualitative characterization of BSi structures in agricultural biogeosystems.The Centre for Agricultural Landscape Research (ZALF) provides worldwide unique requirements regarding the experimental infrastructure (instrumented field experiment CarboZALF-D and long-term field experiment V140) to achieve these objectives. The results of the requested project are supposed to contribute to a fundamental understanding of anthropogenic desilicification and its impacts on agricultural biogeosystems. Furthermore, practice-oriented recommendations for restriction or prevention of anthropogenic desilicification can be derived from these results.