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

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.

The inefficient use of nitrogen (N) within agricultural systems is almost ubiquitous with typically only 50% of the N applied to the land subsequently recovered in the crop. This gross inefficiency is largely caused by the poor spatial and temporal targeting of fertiliser N relative to crop N demand, leading to a major loss of N to freshwater, groundwater and the atmosphere (via leaching, surface runoff or gaseous emissions). This diffuse pollution has a major environmental impact as well as a producing significant social (including human health) and indirect economic cost. One of the biggest challenges facing the agricultural industry is therefore finding new ways to optimise the use of N fertiliser to both reduce costs and improve sustainability. In response to this challenge, and in direct alignment with both the strategic objectives of the SARIC programme and those of RCUK (2016), we describe a new integrated precision agriculture approach to achieve this goal. Our aim is to combine the power of new soil-based in situ N sensors with mathematical models, spatial statistics and existing canopy N sensors to develop new decision support tools to allow farmers and their advisors to decide when and where to apply N. A range of key industry partners have joined this project consortium to demonstrate how soil and canopy sensors can be deployed in arable and grassland systems for measurement of soil and crop N status. Geo-statistical methods will be used to show the optimal deployment of these sensors. This information will feed into new mechanistic models which will be used to predict crop N demand. Together with our industry partners, we will explore via workshops and outreach activities how these new technologies can improve current fertiliser management and guidelines through enhanced industry-focused decision support tools.

RCUK (2016) A vision and high-level strategy for UK animal and plant health research to 2020 and beyond. BBSRC, ESRC, NERC, HM Government.

UK agriculture uses over 0.85 million tonnes of nitrogen (N) fertiliser each year which is spread over 8.2 million hectares of tilled and grassland soil. A major proportion of this added fertiliser, however, is not taken up by the crop and is lost to the wider environment. This results in a major economic loss to farmers and can lead to pollution of water courses, groundwater and the atmosphere. As the use of synthetic fertilisers will continue to be pivotal in food production for the foreseeable future, new ways are needed to effectively target the efficient use of this resource. One of the major outputs from our research programme will be the development of new decision support tools that utilise on-farm, real-time soil data which continually update during the growing season. This represents a major advancement in current fertiliser guidance systems (e.g. RB209, Planet, Farmscoper). The outputs of our research on society can be grouped as follows:

INDUSTRY: This research proposal is directly underpinned by key industry partners. These include (i) Yara UK who are one of the leading suppliers of N fertilisers, crop nutrient sensors (e.g. Yara-N-Sensor) and fertiliser guidance; (ii) Agricultural Industries Confederation (AIC) who are the agrisupply industry's leading trade association. AIC's Fertiliser Sector represents over 95% of the UK's agricultural fertiliser supply industry, worth about £2bn; (iii) British Grassland Society is a communication forum which through events and publications promotes the profitable and sustainable use of grass and forage; (iv) Agriculture and Horticulture Development Board (AHDB) is a Levy Board which represents the cattle, sheep, pigs, milk, potatoes, cereals, oilseeds and horticultural industries. AHDB are also responsible for reviewing current UK fertiliser recommendations associated with RB209; (v) Delta-T Devices are one of the leading companies in the development and sales of soil and plant based sensors; (vi) Syngenta is one of the world's leading agricultural companies with an annual global revenue of £l0 billion; (vii) AgSpace are leading software developers producing decision support tools for precision agriculture. Our project directly aligns with the strategic priorities for all these industry organisations. All the main partners will be members of our management board, and will provide invaluable guidance throughout the project and will facilitate the dissemination of the project findings.

POLICY COMMUNITY: The results from this project will directly inform policymakers (e.g. Defra, DECC) by providing clear advice on future developments in precision agriculture including the environmental and economic costs and benefits and barriers to technology adoption. We will also provide guidance on the timelines and likely impact that adopting these technologies will have at the UK level and its potential impact on the UK N inventory. Policymakers are also central to our proposal (see WP5) ensuring dialogue throughout the programme. We will also build on our established links with Defra and Welsh Government to ensure effective dialogue.

WIDER COMMUNITY: A web page and Twitter feed from the Bangor website will provide ongoing information on the project and its results. Different aspects of the project will be used for teaching, generating student projects, and will be presented at open days at (1) the Bangor University Agricultural Extension Farm, which is one of Defra's Sustainable Intensification Platform flagship sites, and (2) by our industrial partners. We will also feature the project in School Science Week, using visualisation of nitrogen pollution to stimulate wider discussion about agriculture and the environment. See also the section of Pathways to Impact for more details.

SCIENTIFIC COMMUNITY: Our research will inform scientists working in several areas of research (see Academic Beneficiaries section for more details).