Improving herbicide degradation studies: maintaining soil structure, microbial functioning and rhizosphere effects to reflect natural conditions

改进除草剂降解研究：维持土壤结构、微生物功能和根际影响以反映自然条件

• 批准号: 2618477
• 金额: --
• 依托单位: CRANFIELD UNIVERSITY
• 依托单位国家: 英国
• 项目类别: Studentship
• 财政年份: 2021
• 资助国家: 英国
• 起止时间: 2021 至 无数据
• 项目状态: 未结题
• 来源: https://gtr.ukri.org/projects?ref=studentship-2618477
• 关键词: Improving; herbicide; degradation; studies; maintaining

Rationale: An essential component of achieving food security is the continuing need for modern, safe agrochemicals available to reduce losses due to weeds, pests and diseases. This requires the best possible understanding of their behaviour and degradation in agricultural ecosystems. The field and laboratory testing under the current regulatory framework fall short on delivering this understanding as they are conducted under controlled conditions that deviate from natural field conditions. Such testing systems predate our current understanding of the complex nature of soil, and notably the influence of environmental perturbations, soil structure, microbial diversity and the rhizosphere. Aim: To develop a deeper understanding of the role of soil structure, the rhizosphere and microbial diversity on herbicide degradation rates, and to apply this knowledge to the design of test systems for use in predicting optimal application and environmental impact. Background: There are significant limitations to current test guidelines (OECD 307) for evaluation of the transformation of potential crop protection chemicals. Firstly, OECD 307 specifies that soil should be sieved (2 mm) prior to incubation studies; the resulting disintegration of structure influences the size, activity and composition of microbial communities through a number of mechanisms: (i) dehydration of cells previously inside water-filled aggregates but now exposed to air; (ii) rupture of macroaggregate-binding fungal hyphae; (iii) altered bioavailability of microbial substrates, e.g. soil organic carbon previously occluded within aggregates; and (iv) spatial reorganisation of microbial populations and the altered connectedness of water- and air-filled pathways. A second significant shortcoming is the absence of crops. Recent work by Syngenta using a 14C labelled herbicide (prometryn) showed that inclusion of viable crop root systems resulted in faster decline of the herbicide (50% of DT50), higher formation of non-extractable residues, and minimal uptake by the plants. There is a significant knowledge gap in the relative magnitude and interaction of these different processes, and a need to incorporate more realistic scenarios into herbicide dissipation studies. Objectives and approachObjective 1. Quantify key physical and biological pathways and drivers of transformation of Crop Protection Products (CPP) in test systems and fields. Under this objective, experiments will examine the effect of soil physical disturbance, soil type, and CPP chemistry on CPP biotransformation and the soil microbial (community size, composition, activity), biochemical (e.g. available carbon co-substrates) and biophysical characteristics (e.g. connected air and water ways; diffusion). Objective 2. Develop methods which maintain or recreate key soil physical properties that retain functional diversity in soil microbial communities, so that degradation rates more closely reflect field measurements. Building upon our experience in characterising soils with X-ray CT and recreating soil structure in microcosms, we will focus on identifying methods to control pore-solid interfaces and diffusive pathways. Objective 3. to quantify the relative importance of the biophysical (soil structure), biochemical (rhizodeposition) and microbial (rhizosphere) effects on microbial communities brought about by the processes in the rhizosphere that contribute to driving differing CPP behaviour in planted versus non-planted soil.Cover Crops (selected based on our BBSRC work 'using roots to bio-engineer soils') will be grown in the Agri-Tech Soil Health Facilities to create realistic test systems (1 m3) each under controlled soil and environmental conditions. At an initial stage we test specific hypotheses using root surrogates to supply different sources of Carbon.

理由：实现粮食安全的一个重要组成部分是继续需要现代、安全的农用化学品，以减少杂草、病虫害造成的损失。这就需要尽可能了解它们在农业生态系统中的行为和退化。当前监管框架下的现场和实验室测试无法提供这种理解，因为它们是在偏离自然现场条件的受控条件下进行的。这样的测试系统早于我们目前对土壤复杂性质的理解，特别是环境扰动、土壤结构、微生物多样性和根际的影响。目的：深入了解土壤结构、根际和微生物多样性对除草剂降解率的作用，并将这些知识应用于测试系统的设计，用于预测最佳施用和环境影响。背景：目前用于评估潜在作物保护化学品转化的测试指南（OECD 307）存在显著的局限性。首先，经合组织307规定，在进行孵化研究之前，应筛选土壤（2毫米）；由此产生的结构解体通过若干机制影响微生物群落的大小、活动和组成：(i)以前在充满水的聚集体内但现在暴露于空气中的细胞脱水；（ii）结合大聚集体的真菌菌丝破裂；（iii）微生物基质的生物利用度发生改变，例如，以前被封闭在团聚体中的土壤有机碳；微生物种群的空间重组以及充满水和空气的路径的连通性的改变。第二个重大缺点是没有农作物。先正达公司最近使用一种14C标记的除草剂（prometryn）进行的研究表明，纳入有活力的作物根系会导致除草剂更快地下降（50%的DT50），形成更多的不可提取残留物，并且植物吸收最少。在这些不同过程的相对量级和相互作用方面存在显著的知识差距，需要将更现实的情景纳入除草剂耗散研究中。目标和方法量化测试系统和田间作物保护产品（CPP）转化的关键物理和生物途径和驱动因素。在这一目标下，实验将研究土壤物理干扰、土壤类型和CPP化学对CPP生物转化和土壤微生物（群落规模、组成、活性）、生化（如有效碳共基质）和生物物理特征（如空气和水的连接方式；扩散）的影响。目标2。发展维持或重建关键土壤物理特性的方法，以保持土壤微生物群落的功能多样性，使降解率更接近地反映实地测量结果。基于我们在x射线CT表征土壤和重建微观土壤结构方面的经验，我们将专注于确定控制孔-固界面和扩散途径的方法。目标3。量化根际过程对微生物群落的生物物理（土壤结构）、生物化学（根沉积）和微生物（根际）影响的相对重要性，这些影响有助于驱动种植与非种植土壤中不同的CPP行为。覆盖作物（根据我们的BBSRC工作“使用根对土壤进行生物工程”选择）将在Agri-Tech土壤健康设施中种植，以在受控的土壤和环境条件下创建实际的测试系统（每个1立方米）。在初始阶段，我们使用根替代物来测试特定的假设，以提供不同的碳源。