Real-time in situ sensing of soil nitrogen status to promote enhanced nitrogen use efficiency in agricultural systems

氮素(N)对作物生产力至关重要，然而，通常情况下，我们添加到农田中的氮素有一半会流失到环境中。这浪费了资源，对空气、水、土壤、人类健康和生物多样性构成威胁，并产生有害的温室气体(GHG)排放。这些环境问题在很大程度上是因为我们无法在空间和时间上将化肥投入与田间作物需求准确匹配。如果要克服这些问题，我们需要彻底改变目前耕地和草地生产系统中的氮素管理技术。一种潜在的解决方案是，使用可以“感知”土壤中植物有效氮量的技术，并结合可以报告作物冠层氮素状况的传感器。这些传感器本身可以为农民提供有关土壤/作物氮素状况的有用信息。然而，如果它们随后被用来为化肥管理决策提供信息，它们就需要提炼。这是因为气候变量(如温度、降雨量、日照时数)和土壤因素(如质地、有机质含量)可对土壤过程和植物生长产生重大影响，而与土壤氮素状况无关。因此，这些传感器需要与其他数据和改进的土壤-作物生长模型相结合，才能更准确地报告土壤N如何与任何给定时间点的作物N需求有关。在这个项目中，我们演示了如何采用精准农业技术(以土壤硝酸盐传感器的形式)来提高农田(小麦、油菜)和草地系统的氮素利用效率。虽然我们专注于土壤硝酸盐，因为它可以说是土壤N与生产力和环境相关的关键形式，但我们所采取的方法也很容易适用于目前正在开发传感器的其他养分(例如，铵、磷、钾)。我们根据BBSRC-SARIC计划的战略目标和英国政府最近制定的战略目标设计了我们的研究计划，以促进可持续集约化战略的实施。为了最大限度地发挥技术开发、商业化和采用的潜力，我们正在整个计划中与一系列行业合作伙伴密切合作。总体而言，我们的目标是(I)展示新型氮素传感器用于实时测量土壤氮素状况；(Ii)使用地质统计学方法优化这些现场传感器的部署；(Iii)建立新的机械数学模型，以准确预测作物氮素需求；(Iv)从氮素使用和经济角度验证这些传感器和模型在典型草原和农田系统中的好处；以及(V)探索这些新技术如何通过增强的以行业为中心的决策支持工具来改进当前的化肥管理和指导方针。最终，这种技术转变可以通过降低成本、最大限度地提高产量和最大限度地减少对环境的破坏，为农民带来大量节省。例如，如果我们的技术将英国施有化肥的农田(820万公顷草地和耕作作物)的氮素利用效率提高10%，我们估计将节省10万吨氮肥(相当于每年为农民节省6900万GB)。当考虑到硝酸盐污染的直接和间接成本(例如，从饮用水中去除硝酸盐估计每年要花费英国水务公司&GT；GB 2000万英镑)，并考虑到制造和使用10万吨氮肥减少的直接和间接温室气体排放，采用经过验证的精准农业方法的好处是显而易见的。

Nitrogen (N) is vital for crop productivity, however, typically half of the N we add to agricultural land is usually lost to the environment. This wastes the resource and produces threats to air, water, soil, human health and biodiversity, and generates harmful greenhouse gas (GHG) emissions. These environmental problems largely result from our inability to accurately match fertiliser inputs to crop demand in both space and time in the field. If these problems are to be overcome, we need a radical step change in current N management techniques in both arable and grassland production systems. One potential solution to this is the use of technologies that can 'sense' the amount of plant-available N present in the soil combined with sensors that can report on the N status of the crop canopy. On their own, these sensors can provide useful information on soil/crop N status to the farmer. However, they need refining if they are then to be used to inform fertiliser management decisions. This is because climate variables (e.g., temperature, rainfall, sunlight hours) and soil factors (e.g., texture, organic matter content) can have a major influence on soil processes and plant growth, independent of soil N status. These sensors therefore need to be combined with other data and improved soil-crop growth models to provide a more accurate report of how soil N relates to crop N demand at any given point in time. In this project, we are demonstrating how adoption of precision agriculture techniques (in the form of soil nitrate sensors) can be used to improve N use efficiency in both arable (wheat, oilseed rape) and grassland systems. While we are focusing on soil nitrate, as it arguably represents the key form of soil N associated with productivity and the environment, the approaches we are taking are also readily applicable to other nutrients for which sensors are currently being developed (e.g., ammonium, phosphate, potassium).We have designed our research programme in accordance with the strategic objectives of the BBSRC-SARIC programme and those recently produced by HM Government to facilitate delivery of sustainable intensification strategies. To maximise the potential for technology development, commercialisation and adoption we are working closely with a range of industry partners throughout the programme. Overall, we aim to (i) demonstrate the use of novel N sensors for the real-time measurement of soil N status; (ii) use geo-statistical methods to optimise the deployment of these in situ sensors; (iii) produce new mechanistic mathematical models which allow accurate prediction of crop N demand; (iv) validate the benefits of these sensors and models in representative grassland and arable systems from a N use and economic standpoint; and (v) explore how these new technologies can improve current fertiliser management and guidelines through enhanced industry-focused decision support tools.Ultimately, this technology shift could result in substantial savings to the farmer by both reducing costs, maximising yields and minimising damage to the environment. For example, if our technology improves N use efficiency by 10% in agricultural land where fertiliser is applied in the UK (8.2 million hectares of grassland and tilled crops), we estimate it would save 100 thousand tons of N fertiliser (equivalent to a saving of £69 million per annum to farmers). When the direct and indirect costs of nitrate pollution are considered (e.g., removing nitrate from drinking water is estimated to cost UK water companies >£20 million annually), and the reduction in direct and indirect greenhouse gas emissions from manufacture and use of 100 thousand tons of N fertiliser are accounted for, the benefits of adopting a validated precision agriculture approach are clear.