Exploiting root exudation of organic acids and phytases to enhance plant utilisation of soil phosphorus

磷（P）是一种不可再生资源，对作物生产至关重要。矿物磷供应的不确定性，加上对粮食安全和磷对沃茨的环境影响的关注，都需要在土壤中磷形态范围的合理知识的基础上提高农学磷效率。本研究与以往的土壤有机磷回收方法不同，它主要研究有机磷（Po）组分，并利用不同植物根系分泌物的新组合来溶解有机磷，使其以无机正磷酸盐的形式被生物利用。与植物利用土壤有机磷相关的两个基本问题是，大部分有机磷强烈附着在土壤颗粒上，因此植物无法利用，第二，即使不牢固地附着在土壤颗粒上，它的存在形式也不容易被植物吸收。一些植物具有可以帮助获得土壤中有机磷的特性;首先，一些植物可以从它们的根部产生有机酸，这可以释放附着在土壤颗粒上的P，其次，一些植物可以释放磷酸酶（例如植酸酶），它可以将有机P水解成植物可以吸收的形式。然而，作物植物通常不具备这两种性状，因此需要植物的组合，每种植物都发挥不同的作用。依靠三叶草下播到谷类作物中为当前作物提供氮（N），作为越冬绿色肥料，并为后续作物提供N的系统在有机农业企业中相当常见。我们有三叶草品系，可以产生矿化有机磷所需的植酸酶，而一些大麦品系已被证明可以释放有机酸，使有机磷可用于矿化。我们将调查一个三叶草/大麦双作系统作为一个示范可持续的替代密集应用的P和N肥料，从而可能使耕地系统更有效的经济和环境。因此，我们将测试的总体假设，即：种植系统的根系分泌有机酸阴离子和植酸酶可以促进更可持续的农业生产，通过访问土壤有机磷的形式。具体而言，我们建议调查和了解的作用，有机酸和磷酸酶在植物混合物中的肌醇磷酸盐池访问的有机磷。然后，我们将探讨这些有机磷形式在土壤和根际发生了什么，并检查它们的潜力（或以其他方式）从土壤中浸出到表面沃茨，在那里它们可能导致富营养化。将进行一系列的实验，以确定潜在的合适的大麦和三叶草的菌株，这样一个系统，然后通过实验将这些菌株的不同组合，生长在土壤中，以评估什么样的组合可以最有效地获得不同形式的有机磷，同时最大限度地减少沥滤损失。通过增加土壤中储存的磷的利用量，我们可以减少对无机肥料的依赖，提高农业的可持续性，并提高我们在未来几十年提供粮食安全的能力。

Phosphorus (P) is a non-renewable resource, essential for crop production. Uncertainties over mineral P supplies coupled with concerns for food security and environmental impact of P on waters all necessitate an improvement in agronomic P efficiencies, based on sound knowledge of the range of P forms in soils. Our research is different to previous approaches to recover P from soils in that it focuses on the organic P (Po) components and uses a novel combination of root exudates from different plants to solubilise organic P and make it bioavailable as inorganic orthophosphate.The two fundamental problems associated with the use of soil organic P by plants are that much of it is strongly attached to soil particles and therefore inaccessible to plants, and secondly, even when not firmly attached to soil particles, the forms in which it exists are not readily available for plant uptake. Some plants possess traits that can help access organic P in soils; firstly some plants can produce organic acids from their roots, which can release the P attached to soil particles, and secondly some can release phosphatases (e.g. phytase), which can hydrolyse the organic P into forms which plants can take-up. However, crop plants generally do not possess both these traits and so combinations of plants are required, each carrying out a different role. Systems that rely on clover undersown into cereal crops to provide nitrogen (N) to the current crop, act as an overwinter green manure, and to provide N to following crops are fairly common in organic farming enterprises. We have clover lines which can produce phytase required to mineralize organic P, while some strains of barley have been shown to release organic acids, making the organic P available for mineralisation. We will investigate a clover/barley bi-cropping system as an exemplar sustainable alternative to intensive applications of P and N fertilizers, thus potentially making the arable system more efficient both economically and environmentally. Thus we shall test the overarching hypothesis that: Cropping systems with roots exuding both organic acid anions and phytase can facilitate more sustainable agricultural production by accessing soil organic P forms. Specifically, we propose to investigate and understand the role of organic acids and phosphatases in plant mixtures in accessing the organic P from the inositol phosphate pool. We shall then explore what happens to these organic P forms in the soils and the rhizosphere and examine their potential (or otherwise) for leaching from the soil to surface waters where they may cause eutrophication. A range of experiments will be carried out to identify potentially suitable strains of barley and clover for such a system, followed by experiments incorporating different combinations of these strains, grown in soil, to assess what combinations can most efficiently access different forms of organic P, while minimizing leaching losses. By increasing the amount of P utilized from the P stored in soils we can reduce the reliance on inorganic fertilisers, increasing agricultural sustainability and improving our ability to deliver food security in coming decades.