Using Critical Zone Science to Enhance Soil Fertility and Improve Ecosystem Services for Peri-Urban Agriculture in China

Lead Research Organisation: University of Leeds
Department Name: School of Earth and Environment


This research project focuses on sustainable intensification of agriculture in highly productive peri-urban farming areas in China. This agricultural base is essential to meet China's increasing food production demands but is under pressure from urban pollution inputs, soil and water pollution from farming practices - particularly extensive use of mineral fertilisers and pesticides, and urbanisation. We will quantify the benefits and risks of a substantial step-increase in organic fertiliser application as a means to reduce the use of mineral fertiliser.

Our approach is to study the role of soil as a central control point in Earth's Critical Zone (CZ), the thin outer layer of our planet that determines most life-sustaining resources. Our Critical Zone Observatory (CZO) site is the Zhangxi catchment within Ningbo city, a pilot city of rapid urbanization in the Yangtze delta. We will combine controlled manipulation experiments of increased organic fertiliser loading with determination of soil process rates and flux determinations for water, nutrients, contaminants, and greenhouse gas (GHG) emissions across the flux boundaries where the soil profile interfaces with and influences the wider CZ; surface waters and aquifers, vegetation, and the atmosphere. To guide the research design we have identified 3 detailed scientific hypotheses.

1. Replacement of mineral fertiliser use by organic fertiliser will shift the soil food web for N/C cycling from one dominated by bacterial heterotrophic decomposition of soil organic matter (SOM) and bacterial nitrification to produce plant available N and loss of soluble nitrate to drainage waters, to one dominated by heterotrophic fungal decomposition of complex, more persistent forms of OM to low molecular weight organic N forms that are plant available. This change in N source will increase SOM content and improve soil structure through soil aggregate formation.
2. Increased use of organic fertiliser from pig slurry (PS), and wastewater sludge (WS) will lead to increased environmental occurrence of emerging contaminants, particularly antibiotics and growth hormones. Environmental transport, fate and exposure must be determined to quantify development of microbial antibiotic resistance and other environmental and food safety risk, and develop soil and water management practices for risk mitigation.
3. Decreased use of mineral fertilisers and increased use of organic fertilisers will reduce environmental and food safety risks from metals contamination; this is due to lower metal mobility and bioavailability from redox transformations, reduced soil acidification and increased metal complexation on soil organic matter.

Our programme of research will conduct the manipulation experiments across nested scales of observation with idealised laboratory microcosm systems, controlled manipulation experiments in field mesocosms, pilot testing of grass buffer strips to reduce the transport of emerging contaminants from the soil to surface waters, and field (~1ha) manipulation experiments. Mechanistic soil process models will be tested, further developed to test the specific hypotheses, and applied to quantify process rates that mediate the landscape scale CZ fluxes as a measure of ecosystem service flows. GIS modelling methods include data from characterisation of a subset of soil properties and process rates at a wider set of locations in the catchment, together with catchment surface water and groundwater monitoring for water and solute flux balances. The GIS model that is developed will identify the geospatial variation in nutrient, contaminant, and GHG sources and sinks and will be used to quantify fluxes at the catchment scale. These results will determine the current baseline of ecosystem service flows and will evaluate scenarios for how these measures of ecosystem services will change with a transition to widespread of organic fertilisers through the farming area of the catchment.

Planned Impact

This project develops a closely integrated project between research teams in the UK and China that directly addresses the following sustainable development challenges of China.

1. Economic development through innovation in agricultural practices
2. Food security through improved agricultural yields on existing productive land
3. Food safety through decreases in plant available soil contaminants
4. Water quality protection and improvement through reduced soil pollution
5. Wellbeing of urban inhabitants through peri-urban land management
6. Ecological resilience of agricultural production to environmental change
7. Meeting environmental commitments through reduced greenhouse gas emissions from land
8. Agricultural nutrient resource recovery from animal and human food consumption
9. The environmental impacts of urbanisation

The project addresses the challenges effectively by linking the research activities with innovation in farming practices through field manipulation experiments that act as testbeds and demonstrations for the use of organic fertilisers. The project addresses the challenges efficiently by focusing on the role of soil as a central control point within the integrated Critical Zone (CZ) system where positive changes in managing soil fertility can influence multiple beneficial outcomes to the development challenges. Efficiency of research investment is gained by drawing on the current investment in staff and infrastructure by the principal China partner (IUE) at the site and through collaboration with the Zhejiang Academy of Sciences Agricultural Institute in Ningbo city. The programme of impact activities includes strong UK and China stakeholders and performance metrics for immediate and long-term impact are defined. UK strengths in novel, high throughput molecular tools for soil food web dynamics will be applied with the Chinese investigators at the Ningbo CZO. This will provide the scientific evidence on how in organic fertiliser application will impact the soil N-cycle and can be pro-actively managed to improve yields and long-term soil fertility for food security. UK strengths in novel isotope biogeochemistry will be carried out jointly with the Chinese partners and will provide the scientific evidence to optimise soil management practices that reduce toxic metals uptake to food crops, to improve food safety. UK strengths for in situ quantitative analysis of emerging contaminants will develop novel biosensor technology and deploy it in the manipulation experiments in China. This will provide the scientific evidence for soil management practices to reduce the flux of contaminants to surface and groundwater. This will protect and improve water quality and help reduce the occurrence of environmental antibiotic resistance. UK strengths in mechanistic soil process modelling that is integrated with CZ flux determinations will be applied to interpret the results of the field manipulation experiments. The modelling will provide the scientific evidence to guide practice in organic fertiliser use to potentially benefit: crop yields, soil and water quality, ecological resilience to atmospheric deposition of urban contaminants, and reduced greenhouse gas emissions from land. Additional impacts include the potential for improved yields to help livelihoods and reduce poverty in farming communities. Joint design and delivery of manipulation experiments with farmers will support early identification and adoption of improved soil management practices. Organic fertilisers increase soil organic matter content which improves soil pore structure through aggregate formation. This increases plant-available water-holding capacity for drought resilience, and increases interaggregate water drainage for flood resilience. Reduced mineral fertiliser use will cut the life-cycle costs of the carbon footprint of manufacturing, greenhouse gas emissions from land, and increased water pollution from nutrient leaching.


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Banwart S (2019) Soil Functions: Connecting Earth's Critical Zone in Annual Review of Earth and Planetary Sciences

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NE/N007514/1 04/01/2016 30/03/2016 £303,516
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Description The project team has been assessing the potential to recycle organic carbon, nitrogen, phosphorous and potassium from organic waste streams back to agricultural use through the production of organic fertiliser products to support agricultural production in China. The fieldwork considered manure and urban wastewater as nutrient sources but this can be extended to recover nutrients from food processing waste and vegetation green waste. If this approach is successful and can be scaled up geographically, it has the potential to reduce substantially the demand for mineral N fertiliser, which has a very high carbon footprint from the energy demand of fertiliser manufacturing. Reduce mineral fertiliser use helps address key environmental policy aims of China to reduce agricultural runoff pollution and help meet China's international obligations to reduce national greenhouse gas emissions. The project identified potential risks as well, particularly the occurrence of medical and veterinary pharmaceutical compounds in manure and wastewater sludges and the potential for these compounds to select for antimicrobial resistance genes (ARGs) in soil and water microorganisms. One of the principle outcomes of the project has been the first every assessment of the global environmental loading of ARGs from humans and domestic livestock showing livestock offers ARG loadings that are similar to that of the human population. The results suggest that displacing mineral fertiliser with organic streams may results in elevated exposure of environmental organisms such as those of the soil microbiome to ARGs from the human and livestock gut [Science, 357(6356), 1099-1100)]. This demonstrates that the relative risks and benefits of reducing mineral fertiliser use need to be quantified as evidence to inform policy on fertiliser use and on agricultural practices to minimise risk from elevated ARG levels compared to background soil and water levels.
Exploitation Route These key ODA results highlight both the enormous potential benefits but also some risks that need to be assessed, in order for China to better decarbonise food production, while achieving food security objectives and improving rural livelihoods for farming communities. The project is directly contributing to solutions that simultaneously address SDG 2 Zero Hunger, SDG 13 Climate Action, SDG 14 Life below Water and SDG 15 Life on Land. If proven as a solution to reduce mineral fertiliser use in China, the use of organic fertilisers would offer the potential of similar economic development benefits throughout E Asia and in other agrarian economies in DAC Low and Middle Income Countries.
Sectors Agriculture, Food and Drink,Environment,Healthcare

Description Substantial new data sets are now available for application to the Phase 2 UK-China Critical Zone Observatory Programme which is funded to maximise impact. The data sets allow application and further development for decision support tools on land management for soil and water resources protection and sustainable development in China. Further catchment data has been compiled from the site for economic valuation of the ecosystems services that are provided by Earth's critical zone within the study area, which supports the impact agenda for policy in Phase 2. The following Sustainable Development Goals are addressed in the objectives of the project: No Poverty; Zero Hunger; Good Health and Well-Being; Clean Water and Sanitation; Sustainable Cities and Communities; Responsible Consumption and Production; Climate Action; Life below Water; Life on Land; Partnerships The Phase 2 Funding Award is the following. NE/S009124/1 MIDST-CZ: Maximising Impact by Decision Support Tools for sustainable soil and water through UK-China Critical Zone science PI: Professor S. Banwart Duration: 1 Jan 2019 - 31 Mar 2021 Award: £96,464 (Total Award to consortium: £1.1million, led by University of Aberdeen)
Sector Environment
Title Elemental analysis of soil in the Ningbo watershed, China 
Description Elemental analysis of 80 soil samples taken in the Ningbo Watershed, in the Zhangxi catchment, Eastern China. Variables measured include As, Cd, Cr, Cu, Ni, P, Pb, and lead isotope ratios along with concentrations of Zn, Ca and K. Data was collected in March 2016 and analysed at Queens Belfast University. The data was collected and analysed as part of a NERC NSFC funded multi project research programme UK- China Critical Zone Observation Programme. 
Type Of Material Database/Collection of data 
Year Produced 2019 
Provided To Others? Yes  
Description Dual PhD Programme in Critical Zone Science Nanjing University and University of Leeds 
Organisation Nanjing University (NJU)
Country China 
Sector Academic/University 
PI Contribution University of Leeds hosts students starting in Nanjing University for the final 2 years of the 4 year dual PhD programme and hosts the first 2 years of students starting at University of Leeds, before they complete the final 2 years at Nanjing University. The first students will be enrolled on the dual PhD programme at Nanjing University in autumn 2021. University of Leeds contributes primary supervision to students starting at University of Leeds and co-supervision of students starting at Nanjing University.
Collaborator Contribution Nanjing University hosts students starting at University of Leeds for the final 2 years of the 4 year dual PhD programme and hosts the first 2 years of students starting at Nanjing University, before they complete the final 2 years at University of Leeds. Nanjing University. The first students will be enrolled on the dual PhD programme at Nanjing University in autumn 2021. Nanjing University contributes primary supervision to students starting at Nanjing University and co-supervision of students starting at University of Leeds.
Impact Block award of 4 24-month PhD scholarships per year from the Chinese Scholarship Council to cover living expenses for Chinese students during the final 2 years of the programme when they are based at University of Leeds.
Start Year 2021
Description Joint International Research Centre for Critical Zone Science 
Organisation Nanjing University (NJU)
Country China 
Sector Academic/University 
PI Contribution £15,000 in support for academic and research staff exchanges and PhD academic visits. Access to laboratory and field research facilities.
Collaborator Contribution Nanjing University (NJU) was a core partner on the Peri-Urban CZO project. During that project in Phase 1 of the UK-China critical zone observatory prgramme, and during the MIDST-CZ project which is funded during Phase 2 of the UK-China programme, NJU continues to provide financial support and laboratory and field research facilities in China for academic and research staff exchanges and PhD student visits with University of Leeds. NJU also acts as liaison with regional business and government collaborators in Jiangsu province for the Midst-CZ project.
Impact Prof. Hongyan GUO, Nanjing University was awarded a Chinese Scholarschip Council 12-month fellowship for an academic visit to University of Leeds starting in March 2018.
Start Year 2017