Understanding soil quality and resilience: effects of perturbations and natural variations on nitrous oxide emission water retention and structure

该项目涉及农业土壤的质量。根需要水、溶解的养分和氧气，而优质的土壤可以运输所有这些。良好的土壤对于可持续农业/特别是在不破坏土壤或周围环境的情况下生产草或作物非常重要。拖拉机车轮或耕作造成的压实会破坏土壤结构。此外，如果含硝酸盐的土壤变得积水，它会散发出一氧化二氮（笑气）。一氧化二氮是一种导致全球变暖的强效温室气体，也加剧了平流层臭氧层的破坏。如果土壤是有弹性的，那么即使它变得紧实或积水，它也可以恢复。该项目的目的是了解更多关于土壤的结构和过程，以便我们可以提高土壤质量和恢复力，并尽量减少一氧化二氮的排放。我们打算使用四种新的，或新改进的实验方法，基于英国各地不同的研究中心。它们是X射线计算机断层扫描（类似于医院使用的CAT扫描），一种用于测量土壤仅通过重力排水时的持水能力的设备，一种能够监测12个实验室样本排放的一氧化二氮的设备，以及一种“蒸渗仪”，它测量硝酸盐在模拟降雨下分布和通过土壤的精确方式。土壤是一种非常复杂的材料，到目前为止，大多数研究都是将它们的性质联系起来，而没有完全了解它们。为了超越这一点，我们求助于一种名为“孔隙-核心”的计算机模型，它模拟了土壤的多孔结构。我们打算通过在较大的结构中引入紧密排列的小孔阵列，使模型更加先进，就像真实的土壤中发生的那样。计算机程序不仅将所有不同的属性关联起来，它还将结果显示在虚拟现实环境中，这样我们就可以爬进土壤内部，看看发生了什么。该模型将使我们能够了解较小孔隙相对于较大孔隙的几何排列，一氧化二氮产生和排放的孔隙环境，硝酸盐如何在土壤中分布以喂养一氧化二氮诱导细菌，以及压实和饱和度如何影响发生的过程。该模型还将推动实验向前发展，因为它需要准确的数据，并能够预测在其他条件下和不同土壤系统中的一氧化二氮排放。一氧化二氮的排放受其他因素的影响，这些因素将不会被测量或模拟，例如温度和风速。它还因土壤管理/特别是施肥量、耕作和放牧或种植制度而异。然而，所有这些影响的基础是基本结构和过程，更好地了解和预测这些将有助于为土地管理政策提供信息，以实现最佳土壤质量和恢复力，并将一氧化二氮排放量降至最低。

This project concerns the quality of agricultural soil. Roots need water, dissolved nutrients and oxygen, and good quality soil can transport all of these. Good soil is important for sustainable agriculture / specifically the production of grass or crops without damage to the soil or surrounding environment. The structure of soil can be damaged by compaction caused by tractor wheels or tillage. Also, if nitrate-containing soil becomes waterlogged, it exudes nitrous oxide (laughing gas). Nitrous oxide is a potent greenhouse gas causing global warming, and also adds to the destruction of the stratospheric ozone layer. If a soil is resilient, then even if it does become compacted or water-logged, it can recover. The aim of this project is to learn more about the structure and processes within soil, so that we can promote soil quality and resilience, and minimise emission of nitrous oxide. We intend to use four new, or newly improved, experimental methods, based at different research centres across the UK. These are X-ray computed tomography (similar to the CAT-scans used in hospitals), a device for measuring the water-holding ability of soil when it is being drained by gravity only, an apparatus capable of monitoring the nitrous oxide emitted from twelve laboratory samples, and a 'lysimeter' which measures the precise way nitrate is distributed and leashes through the soil under simulated rainfall. Soil is a very complicated material, and up until now studies have mostly correlated their properties without completely understanding them. To move beyond that, we enlist the help of a computer model called 'Pore-Cor' which simulates the porous structure of soil. We intend to make the model even more advanced by introducing arrays of closely packed smaller pores within the larger structure, as occur in real soil. Not only does the computer program correlate all the different properties, it also displays its results in a Virtual Reality environment / so we can climb inside the soil and see what is going on. The model will allow us to understand the geometric arrangements of the smaller pores relative to the larger, the pore environments in which the nitrous oxide is generated and vented, how nitrate distributes through the soil to feed the nitrous oxide-inducing bacteria, and how compaction and saturation affect the processes occurring. The model will also drive the experimentation forward because of its need for accurate data, and enable predictions to be made for nitrous oxide emission under other conditions and in varying soil systems. The emission of nitrous oxide is affected by other factors which will not be measured or modelled, for example temperature and wind speed. It also varies according to soil management / in particular the amount of fertiliser added, tillage, and the grazing or cropping regime. However, underlying all these effects are the fundamental structures and processes, and better understanding and prediction of these will help inform policy on land management to achieve optimum soil quality and resilience, and minimum nitrous oxide emission.