Improving Nitrogen Use for Crop and Environmental Health

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Project 1: Reducing N2O Emissions from Anhydrous Ammonia
Project 2: Gaps in Understanding the Benefits of 4R Practices to Direct and Indirect Emissions of N2O in the Canadian Prairies
Project 3: Enhancing N2O Emissions Modelling with 4R Practices
Project 4: Eastern Canada
Project 5: 4R Adoption Scenario Modelling for Canada
Dr. Xiaopeng Gao

Research Program Synopsis

Intensifying food production to meet the needs of the growing world population requires the use of nitrogen (N) fertilizers to grow more food on current cropland. Unfortunately, N fertilizer can also be a major contributor of N losses to groundwater supplies and to the atmosphere. Soil microbes convert N fertilizers into nitrous oxide (N2O), a potent greenhouse gas. The sustainability of crop production is dependent upon reducing these losses. This Industrial Research Chair (IRC) will advance 4R nutrient stewardship, an innovative approach developed by the fertilizer industry, to apply the Right fertilizer at the Right rate, at the Right time and in the Right place, to enhance production goals, farm profitability and environmental sustainability.

The Western Grains Research Foundation, a farmer-funded non-profit supporting agricultural research in Canada, and Fertilizer Canada, an association of manufacturers and distributors of fertilizers in Canada, support building capacity in 4R nutrient stewardship in Canada. The Senior Chairholder, Dr. Mario Tenuta, is an accomplished and well-respected researcher in soil N management, N2O emissions and 4R N practices.

This chair program fills important gaps in knowledge, training and adoption of 4R practices by:

  1. Evaluating how nitrification inhibitors stabilize fertilizers and reduce N2O emissions and N losses;
  2. Initiating long-term studies to contrast the benefit of 4R practices on direct N2O emissions and indirect emissions as NH3 and leaching N losses on different soils;
  3. Improving models of N2O emissions to include 4R practices;
  4. Summarizing farm survey information to gauge current use of 4R practices; and
  5. Synthesizing findings of this IRC and other studies to forecast the extent by which the adoption of 4R practices can help Canada achieve greenhouse emission reduction commitments.

The IRC will be at the forefront of nutrient stewardship research and training and will offer leadership in 4R practice implementation to advance Canada as a leader in 4R nutrient stewardship. The knowledge and infrastructure capacity created will enrich industry and research collaborations, to serve as a critical expertise hub to advance N use efficiency and environmental health.

Project 1: Reducing N2O Emissions from Anhydrous Ammonia

Fall application of N fertilizer prior to the growing season is a common practice of farmers on the Canadian Prairies. There are many reports of fall addition of N fertilizer resulting in transformations and loss of NO3 when soils are warm and moist. Thus, farmers often add a greater amount of N fertilizer in fall than they would in spring.

Previous research by the Applied Soil Ecology Lab has evaluated commercially available enhanced efficiency N products to reduce N2O emissions in field trials and concluded that certain controlled release products and granular urea mixed with nitrification inhibitors reduced N2O emissions by 30-60%. However, the addition of a nitrification inhibitor to the condensate of anhydrous ammonia prior to injection did not slow nitrification or reduce N2O emissions. The finding is important because anhydrous ammonia is a fertilizer source of choice by about a third of farmers in the Eastern Prairies, thus it is important to find a nitrification inhibitor that works to reduce N2O emissions.

IRC Project 1 will use two new nitrification inhibitors applied in conjunction with anhydrous ammonia to determine their efficacy for reducing direct N2O emissions.

Applied Soil Ecology Lab and U of M Department of Soil Science personnel applying Anhydrous Ammonia to a field site. Also visible are several static-vented chambers used to sample gas emissions. ©Mario Tenuta

Project 2: Gaps in Understanding the Benefits of 4R Practices to Direct and Indirect Emissions of N2O in the Canadian Prairies

In 2005, the micrometeorological system at the Trace Gas Manitoba (TGAS-MAN) long-term agricultural field site began acquiring continuous field-scale fluxes of both N2O and CO2 using a flux-gradient micrometeorological technique. The site is managed using practices, equipment, and rotations that farmers in the area use. It has allowed researchers to determine the long-term influence of annual weather variation, crop rotations, and management on N2O and CO2 emissions. Continuous field-scale flux determinations over the course of each day of the year have captured the intense but short fluxes of N2O and CO2 lasting days to a couple of weeks during spring thaw and after fertilizer N addition. As a result, TGAS-MAN has contributed greatly to the understanding of GHG emissions and mitigation from agricultural fields and stands as one of the most important field research facilities of the University of Manitoba.

One of four micrometeorological stations at the long-term agricultural field site, TGAS-MAN.
Project 2.1: Benefits of 4R Practices on Light Soil – Direct N2O Emissions

Data from TGAS-MAN has revealed that fertilizer-based N2O emissions are much greater than the IPCC Tier II emission factor for the Black Soil zone of the Canadian Prairie Region. The TGAS-MAN site has high clay and a relatively high organic carbon content typical of the Red River Valley, which Dr. Tenuta believes results in higher than expected N2O emissions. It is possible that N2O emissions are also grossly underestimated for Prairie soils not in the Black Soil zone, which haven’t been examined using long-term field-scale monitoring approaches.

IRC Project 2.1 will establish TGAS-WESTMAN, a new long-term research site that replicates the activities of TGAS-MAN but in western Manitoba on sand soil. This will allow calculation of direct N2O emissions from light soil, which can then be contrasted with emissions from the clay soil at TGAS-MAN.

Project 2.2: Benefits of 4R Practices – Indirect Emissions of N2O through Ammonia Emissions

A glaring gap in our understanding of how 4R practices reduce N2O emissions in Canada is their effect on the emissions of ammonia (NH3), which is reactive and can produce N2O. Determinations of NH3 emissions from cropped fields in the Canadian Prairies has not been conducted before.

IRC Project 2.2 will use TGAS-MAN and TGAS-WESTMAN to determine ammonia emissions with varying 4R practices, and contrast emissions from clay and sand soils.

Project 2.3: Benefits of 4R Practices – Indirect Emissions of N2O through Nitrate Leaching

Most research investigating the efficacy of 4R practices to reduce N2O emissions have focused on direct pathways; little research has been conducted to study indirect emissions such as leaching of nitrate (NO3).

IRC Project 2.3 will take advantage of the newly established TGAS-WESTMAN field site to investigate the benefit of 4R practices on indirection emissions of N2O from leaching losses of NO3.

A Drain Gauge G3 passive-capillary lysimeter is used to determine the volume of water and chemicals draining from the root zone into groundwater. Leachate samples can be easily collected for analysis.

Project 3: Enhancing N2O Emissions Modelling with 4R Practices

Canada currently uses Intergovernmental Panel on Climate Change (IPCC) Tier II methodology for reporting greenhouse gas emissions from agricultural fields, but will eventually move to Tier III. Such methodology involves estimating N2O emissions for individual fields in relation to weather and management; this will require biophyisical models capable of determining field-specific N2O emissions. In addition, Canada’s current version of the DeNitrification-DeComposition (DNDC) model includes only the following N management practices: N application rate, timing, and some sources.

IRC Project 3 will use data from TGAS-MAN, TGAS-WESTMAN, and the University of Guelph Elora long-term field study sites to update Canada’s DNDC model to better handle 4R practices that farmers use. It will be modified to include placement depth, surface band placement, urease inhibitors, and nitrification inhibitors.

Project 4: Eastern Canada

Project 4.1: Eastern Canada Fertilizer Survey

The annual Canadian Fertilizer Use Survey is a wealth of information as to the current state of adoption and use of 4R practices for N, P, and K management for grain crops across Canada. However, the survey data has not been summarized for use by industry and policymakers in publication format or online. Project 4.1 will analyze the survey results for Eastern Canada, publish the findings, and make the data accessible online to other researchers and policymakers.

Project 4.2: Meta-analysis of 4R Practices in Eastern Canada

The Nitrous Oxide Emission Reduction Protocol (NERP) tries to capture N2O emission reductions with increasing intensiveness of 4R practices to manage N. Because of the lack of available 4R studies ten years ago,
when the NERP was developed, conservative reduction factor values had to be used. Project 4.2 will include a meta-analysis of 4R studies for Eastern Canada and similar climates and production systems globally to
base new NERP 4R emission reduction factors on actual field observations.

Project 5: 4R Adoption Scenario Modelling for Canada

IRC Project 5 will use two approaches to assess the impact of 4R N management adoption scenarios in Canada on N2O emissions:

(1) Empirical approach: IPCC Tier II methodology for N2O emissions in Canada will be applied to agricultural ecodistrics across the country. A baseline emission will be calculated using emission factors based on meta-analysis of N2O reductions for 4R practices, adoption of 4R practices by farmers from the Canadian Fertilizer Use Survey, and fertilizer N use by ecodistrict across Canada. This baseline will be compared to emissions scenarios generated by varying adoption levels of various 4R practices by ecodistrict.

(2) Mechanistic approach: This approach will use results from Project 3, 4.1, and 4.2. The AAFC Management Factor Tool will be used to provide climate and soil input values by ecodistrict for Canada to the Canadian DNDC model adopted for 4R practices. Similarly, the Canadian Fertilizer Use Survey results will be summarized by ecodistrict and the Management Factor Tool used to provide N rates, sources, placement, and timing practices to DNDC to establish a current baseline in N2O emissions. As with the empirical approach, scenarios of adoption levels of various 4R practices by ecodistrict will generate emissions scenarios to compare to the baseline.

Sensitivity analysis for response in emissions to individual 4R practices using both modelling approaches will identify those practices with the greatest potential to reduce N2O emissions in Canada.

Dr. Xiaopeng Gao

A key component of NSERC’s Industrial Research Chair program is increasing the University of Manitoba’s research capacity in the area of 4R® Nutrient Management. To that end, Dr. Xiaopeng Gao joined the Department of Soil Science as Assistant Professor in Soil Fertility and Agronomy in September of 2020.

Dr. Gao received his BSc in Soil Chemistry and MSc in Plant Nutrition in China, and his PhD in Soil Science in the Netherlands. He worked as a project coordinator for Agriculture and Agri-Food Canada before joining the Applied Soil Ecology Lab as a research associate, where he focused on the development of modelling of 4R® Management strategies to reduce N2O emissions from agricultural systems.

Dr. Gao’s research focuses on understanding the fate of nutrients, and the development and application of best management practices to improve soil fertility and nutrient management in agroecosystems. As part of the Industrial Research Chair program, he intends to develop a research program in optimizing and advancing soil fertility and nutrient management in sustainable cropping systems to achieve agronomic, environmental, and social benefits.

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