In-soil trophic interactions between plants, rhizosphere bacteria and nematodes: improving availability of soil phosphorus

磷化肥是农业生产的重要组成部分，但全球磷矿供应有限且受地理限制；因此，更好地利用磷供应至关重要。许多农业土壤含有大量的磷，但大多是有机形式(特别是植酸盐)，通常被认为是植物所不能利用的。一些植物既可以分泌有机酸，也可以分泌酶，这两种物质结合在一起可能会活化和降解土壤中的有机磷。然而，这些过程在许多土壤中的有效性有限，开发利用这些有机磷储备的系统是全球农业可持续集约化的一个重要挑战。当接种某些土壤微生物时，植物对植酸盐中磷的利用得到提高。此外，已有研究表明，草地线虫对地下根的捕食促进了养分通量，并影响了根际微生物群落的组成。同样，最近的研究表明，当线虫的细菌放牧促进了有机磷的释放时，松树幼苗对有机磷的植物利用得到了改善。为了设计未来的可持续农业系统，了解可耕作作物下这些土壤营养相互作用的重要性对粮食安全非常重要。我们的目标是：1)在从琼脂到土壤的一系列复杂系统中，根际线虫和细菌之间的营养相互作用是否增加了植物对P的利用；以及2)植物和土壤细菌衍生的酶和有机酸的功能作用及其与线虫放牧的相对相互作用，以提高对有机P的利用。为了实现这一点，项目最初将包括a)受控环境实验，在琼脂中种植各种形式的P(PI、植酸盐和糖磷酸盐)，并添加细菌(自然土壤群落和特定的解磷菌)和线虫(自然土壤群落、细菌放牧和真菌放牧)的全要素组合；B)从Balruddery可持续发展平台(可持续与常规)的两个处理中采集的土壤-土壤中日益复杂的实验将被消毒，并重新接种一系列日益复杂的处理。这将包括对线虫和细菌群落结构组合的评估，以及对有机磷库的测量；c)对线虫和细菌组合的评估，以及对Rothamsted LTE现有处理方法和档案中适当样本中有机磷库的测量；d)在苏格兰政府部门咨询秘书处的实习，以深入了解政策和研究如何相互作用。

Phosphorus (P) fertiliser is an important component for agricultural production, but global supplies of rock phosphate are finite and geographically restricted; hence better use of P supplies is vital. Many agricultural soils contain large amounts of P, but mostly in organic forms (especially phytate), which are generally considered unavailable to plants. Some plants can exude both organic acids and enzymes, which together can potentially mobilise and hydrolyse soil organic P. However, the effectiveness of these processes is limited in many soils, and developing systems to utilise these organic P reserves is an important challenge in global sustainable intensification of agriculture. Plant utilisation of P from phytate is improved when inoculated with certain soil micro-organisms. Additionally, it has been demonstrated that below-ground root herbivory by nematodes in grasslands promoted nutrient flux and influenced the composition of the rhizospheric microbial community. Similarly, recent research has shown improved plant utilisation of organic P by pine seedlings when bacterial grazing by nematodes facilitated the release of P from organic sources. Understanding the importance of these soil trophic interactions under arable crops in order to design future sustainable agricultural systems is important for food security. We aim to establish 1) whether trophic interactions between rhizospheric nematode and bacteria increases plant utilisation of P in systems of a range of complexity from agar to soil; and 2) the functional role of plant- and soil bacteria derived enzymes and organic acids and their relative interaction with nematode grazing for enhanced utilisation of organic P.To achieve this the project will initially include a) controlled environment experiments, growing a range of plants in agar with P supplied in various forms (Pi, phytate and sugar phosphates) with addition of a full factorial combination of bacteria (natural soil community and specific phosphate solubilising bacteria) and nematodes (natural soil community, bacterial grazers and fungal grazers); b) experiments of increasing complexity in soil - soils taken from both treatments of the Balruddery Sustainability Platform (Sustainable vs Conventional) will be sterilised and re-inoculated with an additive range of treatments of increasing complexity. This will include an assessment of the nematode and bacterial community structure assemblages alongside measurement of organic P pools ; c) an assessment of the nematode and bacteria assemblages, alongside measurements of organic P pools in existing treatments of the Rothamsted LTEs and in appropriate samples taken from the archive; d) an internship with the Scottish Government Department Advisory Secretariat to gain an insight into how policy and research interface.