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

氮（N）对作物生产力至关重要，然而，通常我们添加到农业用地的氮的一半通常会损失到环境中。这浪费了资源，对空气、水、土壤、人类健康和生物多样性造成威胁，并产生有害的温室气体排放。这些环境问题很大程度上是由于我们无法在田间的空间和时间上准确地将肥料投入与作物需求相匹配。如果要克服这些问题，我们需要在耕地和草地生产系统中对目前的氮管理技术进行根本性的改变。一个潜在的解决方案是使用可以“感知”土壤中植物有效氮含量的技术，结合可以报告作物冠层氮状况的传感器。这些传感器本身可以为农民提供有关土壤/作物氮状况的有用信息。然而，如果要将其用于指导化肥管理决策，则需要对其进行改进。这是因为气候变量（例如，温度、降雨量、日照时数）和土壤因素（例如，质地、有机质含量）对土壤过程和植物生长有重要影响，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，以提供更准确的报告，说明土壤氮与作物氮需求在任何给定时间点的关系。在这个项目中，我们正在展示如何采用精准农业技术（以土壤硝酸盐传感器的形式）可以用来提高耕地（小麦，油菜）和草地系统的氮利用效率。虽然我们关注的是土壤硝酸盐，因为它可以说代表了与生产力和环境相关的土壤氮的主要形式，但我们采取的方法也很容易适用于目前正在开发传感器的其他营养素（例如，我们根据BBSRC-SARIC方案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方案，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，我们在整个项目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）展示使用新型氮传感器实时测量土壤氮素状况;（ii）使用地质统计方法优化这些原位传感器的部署;（iii）产生新的机械数学模型，可以准确预测作物氮素需求;（iv）从氮素利用和经济角度验证这些传感器和模型在代表性草地和耕地系统中的效益;以及（v）探讨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善当前的肥料管理和指导方针。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，为农民节省大量资金。例如，如果我们的技术在英国使用化肥的农业土地（820万公顷草地和耕作作物）中将氮的利用效率提高10%，我们估计将节省10万吨氮肥（相当于每年为农民节省6900万英镑）。当考虑硝酸盐污染的直接和间接成本时（例如，从饮用水中去除硝酸盐估计每年花费英国水务公司> 2000万英镑），并且考虑到制造和使用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.