Assessing the Impact of Zero Tillage on Agrochemical Transport

土壤是地球上最复杂的生物材料，但我们对其形态如何影响其功能的了解仍然很少。这是因为我们无法观察到地下正在发生的事情，因为土壤是不透明的。然而，使用X射线计算机断层成像等工具对土壤系统进行成像的新方法现在提供了一种探索这种隐藏的地下世界的方法。土壤是地球上最大的陆地碳库。农业土壤管理的变化可能会影响它们在全球碳循环中作为源或汇的作用，以及它们温室气体排放的规模和组成。保护性农业方法，如减少种植的方法，正在全球范围内得到越来越多的采用。越来越多的证据表明，通过减少或停止耕作(即免耕)，土壤结构随着时间的推移而演变，从而在保持作物产量的同时改善土壤健康/质量。最近的数据表明，在减少温室气体排放和加强碳封存方面也有好处。虽然免耕在北美和南美洲的采用很快，但欧洲，特别是英国，反应较慢，目前在最少耕作下只有约50%，在免耕下约有10%。迫切需要概述英国采用免耕的影响的证据。迫切需要新的证据来概述英国采用免耕的影响。一个尚未评估的关键领域是耕作对土壤应用农用化学品的生物性能的影响，尽管来自田间的经验证据表明，产品性能确实受到了影响。免耕大大增加了容重，进而降低了土壤孔隙度，从而对水和溶质(包括农用化学品)的渗透产生了不利影响。然而，保持土壤不受干扰的影响是随着时间的推移，在土壤动物的推动下，土壤结构的发展。这种结构与耕作土壤相比孔隙度降低，但具有与之相当的孔隙连通性，这是土壤水力功能最重要的特性。主要目的是说明免耕条件下获得的土壤结构如何以及在什么时间尺度上对农用化学品产品性能产生影响。与先正达公司合作，并结合实地和实验室工作，这一令人兴奋的博士项目将评估的关键问题包括：i)免耕施加的土壤结构对土壤中农用化学品的分布和移动有什么影响；ii)不同土壤类型之间的差异在多大程度上持续存在；iii)土壤结构的差异如何影响农用化学品的生物性能；iv)在从传统耕作转变为免耕的过程中，土壤水力特性在什么情况下有利于土壤中农用化学品的最佳有效性。

Soil is the most complex biomaterial on earth, yet our understanding of how its form influences its function is still poorly understood. This is large due to our inability to observe what is happening underground as soil is opaque. However, new methods to image soil systems, using tools such as X-ray Computed Tomography now provide a means to explore this hidden underworld. Soil is the largest land-based reservoir of carbon on Earth. Changes in the management of agricultural soils can affect their role as a source or sink in the global carbon cycle, and the scale and composition of their greenhouse gas emissions. Conservation Agriculture approaches such as those that reduce cultivation are gathering pace in adoption globally. There is increasing evidence that by reducing or ceasing to plough (i.e. zero tillage), a soil structure evolves, over time, which improves soil health/quality whilst maintaining crop yield. Recent data has shown there are also advantages in terms of reduced greenhouse gas emissions and enhanced carbon sequestration. While the adoption of zero tillage in N. & S. America has been rapid, Europe, and in particular, the UK, has been slower to respond with currently only c. 50% under min tillage and around 10% under zero tillage. Evidence that outlines the implications for the adoption of zero tillage in the UK is urgently needed. New evidence that outlines the implications for the adoption of zero tillage in the UK is urgently needed.A key area not yet assessed is the impact of tillage on the bio-performance of soil applied agrochemicals despite empirical evidence from the field indicating product performance is indeed affected. Zero tillage substantially increases bulk density and subsequently decreases soil porosity which impacts negatively on the infiltration of water and solutes, including agrochemicals. However, the impact of leaving the soil undisturbed is the development of a soil structure, over time, driven by the soil fauna. This structure has a reduced porosity compared to ploughed soil but a comparable pore connectivity which is the most important property for soil hydraulic function.The overarching aim is to illustrate how, and over what time scales, soil structure obtained under zero tillage impacts on agrochemical product performance. In partnership with Syngenta, and using a combination of field and laboratory work, key questions that this exciting PhD project will assess include: i) What is the impact of the soil structure imposed by zero tillage on the distribution and movement of agrochemicals in soil; ii) To what extent are differences persistent across soil types; iii) How do differences in soil structure affect the bio-performance of agrochemicals and iv) At what point, if any, in the conversion from conventional to zero tillage do soil hydraulic properties favour optimum availability of agrochemicals in soils.