Resources

Coordinated Site Network for Studying the Impacts of 4R Nutrient Management on Crop Production and Nutrient Loss

Crops: Corn for grain Corn for silage
4R Practices: Source Rate Time Place

Lead Researcher:

Dr. Matt Helmers

Professor

Iowa State University

Start Date: 2017

End Date: 2021

Collaborating scientists and universities

  • Dr. Sylvie Brouder, Professor Purdue University
  • Dr. Laura Christianson, Assistant Professor University of Illinois
  • Dr. Cameron Pittelkow, Assistant Professor, University of Illinois
  • Dr. Kelly Nelson, Professor University of Missouri
  • Dr. Dan Jaynes, Soil Scientist USDA-ARS National Laboratory for Agriculture and the Environment
  • Dr. John Kovar, Soil Scientist USDA-ARS National Laboratory for Agriculture and the Environment
  • Lowell Gentry, Research Scientist University of Illinois
  • Dr. Craig Drury, Research Scientist Agriculture and Agri-Food Canada
  • Dr. Fabian Fernandez, Assistant Professor University of Minnesota
  • Dr. Alison Eagle, Scientist, Sustainable Agriculture, Ecosystems Program, Environmental Defense Fund
  • Dr. Jeffrey Volenec, Professor Purdue University

Matching Funds

  • Foundation for Food and Agriculture Research

Project Summary

Currently, there is a concerted effort from industry, universities, and state and federal action agencies to promote the 4R nutrient management approach on-farm– considering the Right source, Right rate, Right time, and Right place– for managing nutrient additions from commercial fertilizer and organic materials. With its massive acreage and intensive nutrient use, corn production systems are an important focus of the 4R program. To convince farmers to adopt the 4R approach, and to ensure that production, soil health, and environmental goals are realized, there is a critical need for field research that measures responses to 4R management systems across a range of soils and agro-ecosystems within the main corn producing areas of North America. Limited research data linking agronomic and environmental performance of 4R practices across a wide variety of conditions is a critical research gap leading to high uncertainty regarding practice efficacy for both farmers and environmental program and policy decision makers. Along with production and soil health effects, full accounting of the multiple forms and pathways of nitrogen (N) and phosphorus (P) is essential to understand the environmental consequences of current and advanced best nutrient practices. A thorough accounting of the N balance could also serve as an early warning for practices that are improving or reducing soil carbon and thus soil health because soil carbon-nitrogen interactions dramatically impact soil organic matter accumulation and carbon sequestration. Further, potassium (K) nutrition of crops has attracted renewed attention, and although not of environmental concern, K requirements of crops are nearly the same as those of N, and cannot be ignored. We propose the creation of a coordinated field site network strategically distributed across the cornbelt with unique infrastructure that would collect similar agronomic and environmental measures thereby enabling for the first time knowledge synthesis across varied soils, climates, and management systems. Quantification of the impacts of 4R management on crop yield, P, K, and nitrate (NO3) losses in water, N losses to the atmosphere, and changes in soil health at the same location under a range of management practices is severely lacking. In addition, we are aware of no studies explicitly aimed at understanding the interactions between 4R management strategies and soil health.

Project Goals:

  • Quantify the impact of 4R Nutrient Stewardship on crop yield, soil health, nutrient use efficiencies, nutrient losses with leaching, and gaseous nitrogen losses across a network of coordinated studies in the major corn producing area of North America.

Project Results:

  • Preliminary nitrogen balance assessments indicated a -15 to -17 lb N/ac balance while optimizing corn yields when injecting N fertilizer for one study year averaged across all sites.
  • Corn-soybean rotations in the study resulted in a 10 to 24 lb N/ac lower nitrogen balance than a continuous corn system.
  • Conventional tillage resulted in greater corn yield with a reduced nitrogen balance of 4 to 7 lb N/ac compared to reduced tillage, however, the amount of nitrate loss in tile drainage was 9 to 13 lb N/ac greater with more intensive tillage.

Annual Reports

2017

Publications

Spatial and Temporal N Management for Irrigated Vegetable Production Systems

Crops: Apples Broccoli Cauliflower Celery Lettuce
4R Practices: Rate Time Place

Lead Researcher:

Dr. Charles Sanchez

Professor

University of Arizona

Start Date: 2019

End Date: 2022

Collaborating scientists and universities

  • Dr. Pedro Andrade-Sanchez, University of Arizona

Project Summary

Intensive vegetable production in the desert receives large annual applications of nitrogen (N) fertilizers. Soils in the southwestern United States are generally low in organic matter and amounts of N applied range from 200 to 400 kg/ha. Crop recoveries are less than 50%. There are numerous possible fates of fertilizer applied N in addition to the desired outcome of crop uptake. Over the past 15 years, researchers with the University of California and University of Arizona have developed strategies for efficient nutrient management. For N, these practices include fertilizer timing, pre-side dress plant and soil testing, and improved irrigation management. However, these guidelines have been applied to uniform management schemes in spite of the fact that fields often show considerable variation in soil properties. In-field soil textural variation is a significant factor affecting the mobility and availability of N. The prospect of variable rate (VRT) pre-plant and in-season N fertilizer application has not been evaluated in desert vegetable cropping systems. Certainly, varying N fertilizer applications by soil management zone makes sense. Further, emerging optical sensor technologies expand opportunities for in-season N management. We have evaluated VRT for pre-plant P fertilization in the desert. However, data exploring the potential for using VRT for N management is limited.

Studies conducted within Bard Water District, Yuma County Water Users Association, and Yuma Irrigation District in 2019-2020.

Project Goals:

  • Develop economically viable and effective sampling protocols to generate prescription maps for the variable rate pre-plant and in-season application of N comparing soil and plant sampling.
  • Compare variable rate N application to current methods and evaluate alternative economic outcomes.
  • Evaluate and test methods to augment zone-based management with optical sensors.

Project Results:

  • In the first year of this study, broccoli and iceberg lettuce yields were optimized with variable rate technology using soil-based zones.
  • Utilizing variable rate side-dress nitrogen applications, broccoli and iceberg lettuce yield per pound of nitrogen applied was optimized.

Annual Reports

Evaluating the 4R Nutrient Stewardship Concept and Certification Program in the Western Lake Erie Basin

Crops: Corn for grain Corn for silage Soybeans
4R Practices: Source Rate Time Place

Evaluating the 4R Nutrient Stewardship Concept and Certification Program in the Western Lake Erie Basin

Lead Researcher:

Dr. Kevin King

Research Soil Scientist

USDA-ARS Soil Drainage Research Unit

Start Date: 2014

End Date: 2019

Collaborating scientists and universities

  • Dr. Thomas Bruulsema, Plant Nutrition Canada
  • Dr. Remegio Confesor Jr., Heidelberg University
  • Dr. Joseph DePinto, LimnoTech
  • Dr. Laura Johnson, Heidelberg University
  • Gregory LaBarge, Ohio State University
  • Dr. Brian Roe, Ohio State University
  • Dr. Douglas Smith, USDA-ARS Soil Erosion Research Laboratory
  • Carrie Vollmer-Sanders, The Nature Conservancy
  • Dr. Mark Williams, USDA-ARS Soil Drainage Research Unit
  • Dr. Robyn Wilson, Ohio State University

Matching Funds

  • USDA-NRCS Conservation Innovation Grant
  • Ohio Farm Bureau Federation
  • Ohio Corn and Wheat Growers Association
  • Ohio Soybean Association
  • USDA-NRCS Mississippi River Basin Initiative
  • The Nature Conservancy
  • USDA-NRCS Cooperative Conservation Partnership Initiative
  • Ohio State University
  • Heidelberg University
  • USDA Conservation Effects Assessment Project

Project Summary

Lake Erie is part of the Great Lakes System, which contains 20% of the surface freshwater in  the world. Annually, tourism associated with Lake Erie generates more than $7.4 billion in direct  sales, while Lake Erie seaports generate approximately $1 billion in revenue (USDA-NRCS,  2005). Sport fishing within Lake Erie has also been estimated to generate hundreds of millions of dollars annually. Unfortunately, over the past five years there has been an increased incidence of  algal blooms and proliferation of aquatic weeds. Not only are algal blooms aesthetically unappealing, but they also can cause the formation of hypoxic zones in stratified waters. In some instances, algal blooms contain toxins that are harmful to humans and aquatic life. The increase in nuisance and harmful algal blooms (HABs) in Lake Erie has led to greater water treatment costs, reductions in fish populations, and poor water quality that has negatively impacted fishing and tourism industries within the Great Lakes region. 

The primary cause of water quality impairment and algal blooms within Lake Erie is the input of excess nutrients, such as nitrogen (N) and phosphorus (P), often transported from agricultural lands. Many growers have accepted responsibility and are taking action to improve soil health and reduce nutrient losses from their fields. However, there are still additional opportunities through scientific and technological advancements to help growers keep nutrients in their fields to benefit both crop growth and watershed health. 4R Nutrient Stewardship is an innovative approach to nutrient management that considers the economic, social, and environmental dimensions of nutrient management. Although the concept is relatively simple (apply the right source of nutrient, at the right rate, at the right time and in the right place), following the 4R principles has the potential to significantly reduce the amount of nutrients transported to Lake Erie as well as increase crop nutrient use efficiency. 

One way to encourage adoption of the 4R principles is to first define key actions that characterize nutrient and water stewardship and to recognize good stewardship through a credible certification program. The 4R Certification Program Advisory Committee, led by members of the agricultural industry, grower representatives, and supported by The Ohio State University, state government, and facilitated by The Nature Conservancy, have been meeting since the spring of 2012 to create a program that identifies best management practices (BMPs) and encourages nutrient service providers (e.g., agricultural retailers, crop advisers) to adopt the 4R Nutrient Stewardship concept. The 4R Certification Program will help these nutrient service providers tailor 4R principles to each grower’s unique needs, while minimizing nutrient losses and maximizing crop uptake. This program represents an effort by the agricultural industry to actively embrace a scientific-based approach to nutrient management and sustainable crop production. Such an effort diminishes the need for and the likelihood of public regulations that might otherwise be implemented to decrease nutrient loading to surface waters. 

Project Goals:

  • To monitor the impacts of 4R Nutrient Stewardship practices and the 4R Certification Program on crop productivity, nutrient losses, and biotic integrity from select fields, streams, and watersheds in the WLEB. 
  • To model the environmental benefits in Lake Erie (turbidity and HABs) following various levels of implementation of 4R Nutrient Stewardship practices and the 4R Certification Program in three WLEB agricultural watersheds. 
  • To determine the behavioral impact of 4R educational efforts and the 4R Certification Program on the knowledge, beliefs, and management practices of crop growers and nutrient service providers in the WLEB.
  • To conduct a triple bottom line evaluation of the economic, social, and environmental performance of the 4R Nutrient Stewardship Program in the WLEB. 
  • To integrate information from all the above to develop indicators for continued public reporting of progress and guide the 4R Nutrient Stewardship Certification Program. 

Project Results:

  • Sub-surface placement and incorporating phosphorus fertilizer with tillage, as compared to surface application with no incorporation, reduced dissolved phosphorus concentration in tile discharge by 66% and 75%, respectively. Incorporation of phosphorus fertilizer through sub-surface injection or tillage also reduced particulate phosphorus losses compared to surface application with no incorporation.
  • Injecting phosphorus fertilizer or incorporating in the soil with tillage mitigates phosphorus losses during large precipitation events, reducing seasonal and annual losses.
  • Soil legacy phosphorus has a persistent impact on hydrologic phosphorus losses. Annual phosphorus applications only represented ~3% of the annual phosphorus inputs, indicating legacy phosphorus had a large effect.
  • No-till systems increased drainage dissolved phosphorus loads 72 to 75% compared to conventional tillage. The interaction of management practices and individual site characteristics explained variability in nitrogen and phosphorus losses.
  • Soil-test phosphorus is a good preliminary screening indicator for hydrologic losses, but upland management, edge-of-field practices, and in-stream approaches are required to reduce dissolved-reactive phosphorus losses.

Annual Reports

2015

2016

2017

2018

Publications

Minimizing Phosphorus Loss with 4R Stewardship and Cover Crops

Crops: Corn for grain Corn for silage Soybeans
4R Practices: Time Place

Minimizing Phosphorus Loss with 4R Nutrient Stewardship and Cover Crops

Lead Researcher:

Dr. Nathan Nelson

Professor

Kansas State University

Start Date: 2014

End Date: 2019

Collaborating scientists and universities

  • Dr. Kraig L Roozeboom, Kansas State University
  • Dr. Peter Tomlinson, Kansas State University
  • Dr. Phil L. Barnes, Kansas State University
  • Dr. Jeffery R. Williams, Kansas State University
  • Dr. Gerard J. Kluitenberg, Kansas State University

Project Summary

Fertilizer timing and placement can have large impacts on P loss. Currently recommended BMPs have focused on sub‐surface fertilizer placement as the recommended method for reducing P loss. In contrast, economic and farm management factors may encourage producers to use surface‐broadcast P applications in the fall. Weather patterns typical of the Great Plains indicate that a shift to fall applications may also reduce P loss from surface applied P fertilizer compared to spring surface applications. We need field-scale data comparing P loss from fall surface applied P fertilizer to sub‐surface spring‐applied P fertilizer so we can make accurate recommendations for the right timing and placement combinations to minimize P loss.

Furthermore, cover crop use may protect against potential increased P loss associated with fall surface‐applied fertilizers, thereby allowing producers wider flexibility in fertilizer management while maintaining minimal P loss. However, we need more information about the effects of cover crops on P loss and the interaction between cover crops and P fertilizer management. Because cover crops can also impact crop yields, we need comprehensive analysis that includes cover crop and fertilizer management impact on multiple agronomic, environmental, and economic factors, including grain yield, N uptake and use, and P uptake and use, input costs, gross return, net return, N and P loss, sediment loss, and runoff volume. Producers and fertilizer dealers recognize the value in this information.

Project Goals:

  • Determine the agronomic, environmental, and economic impacts of fall surface‐applied P fertilizer compared to currently recommended BMPs for P fertilizer (spring injected P) and no P fertilizer application in corn‐soybean rotations.
  • Determine the agronomic, environmental, and economic effects of winter cover crops in corn‐soybean rotations.
  • Determine the interaction of fertilizer management and cover crop use on agronomic, environmental, and economic measures in corn‐soybean rotations.

Project Results:

  • Spring subsurface placement of P fertilizer maintains lower dissolved P concentrations in runoff water compared to fall broadcast fertilizer application and resulted in lower total P concentrations.
  • Changing P fertilizer management, transitioning from surface broadcast to sub-surface placement, was the most economical methods of reducing P loss.
  • Cover crops in a no-till corn-soybean rotation reduce annual sediment loss by 60 to 70%.
  • Cover crops increased annual average dissolved and total P losses by 28%, varying greatly by runoff year.

Annual Reports

2014

2015

2016

2017

2020

Publications

Supplemental Late-vegetative N Applications for High-yield Corn: Agronomic, Economic, and Environmental Implications with Modern versus Older Hybrids

Crops: Corn for grain
4R Practices: Place

Supplemental Late-vegetative N Applications for High-yield Corn: Agronomic, Economic, and Environmental Implications with Modern versus Older Hybrids

Lead Researcher:

Dr. Tony Vyn

Department of Agronomy, Henry A. Wallace Chair in Crop Sciences

Purdue University

Start Date: 2014

End Date: 2017

Collaborating scientists and universities

  • Dr. Sarah Mueller, Purdue University

Matching Funds

  • USDA-National Institute for Food and Agriculture
  • Corteva Agriscience – Pioneer Hi-Bred

Project Summary

Modern corn hybrids have a “functional stay green” capacity whereby their leaves not only stay green longer during the grain filling period, but also maintain their photosynthetic capacity until much later in the grain filling period. Modern hybrids also yield more than hybrids of earlier decades because of their improved stress tolerance to plant density and other stress factors (whether pest-related factors or abiotic challenges). Therefore, one of the major corn management questions of our time is whether corn hybrids take up more of their total plant N during the reproductive period and, if they do, whether modern hybrids are more responsive to intentionally very late vegetative stage N fertilizer applications. We know that part of the positive response of modern corn hybrids to higher N rates is that total plant and grain uptake of other nutrients like P and Zn also increase.

Perhaps one of the more difficult negative environmental consequences to monitor with corn production systems is that of management consequences on greenhouse gas emissions. The cropping systems group at Purdue University has also done extensive work on monitoring greenhouse gases in corn production systems over the last 10 years, as the largest single pathway to reduce N2O losses to the atmosphere is to increase the N uptake by corn plants itself. This can be addressed by focusing on enhancing crop yield and total plant N uptake while minimizing N2O emissions.  

Project Goals:

  • To determine the extent to which modern hybrids are likely to be more yield-responsive to late-vegetative N applications than hybrids of 20 years ago, and the physiological reasons for those differences if, indeed, modern hybrids are more responsive. 
  • To evaluate the opportunity for split N applications involving an intentionally late vegetative N application to reduce season-long and cumulative N2O emissions relative to a single early side-dress N application strategy. 
  • To use a partial budget approach to determine the economic implications of late-season N applications (whether supplemental N is applied, or whether a normally recommended N rate is side-dress applied both early and late) in high-yield corn production systems relative to a single-time, side-dress N application. 

Project Results:

  • New Era genotypes increased the proportion of the total plant N at maturity accumulated post-silking (percent PostN) as N stress levels at R1 increased—demonstrating improved adaptability to low N environments.
  • New Era hybrids maintained similar GY on a per plant basis under both low and high N stress at R1 despite being subject to much higher population stress.
  • PostN is more strongly correlated to GY (both eras combined) when under severe R1 N stress than under less acute N stress at R1.
  • The New Era accumulated more total N (an increase of 30 kg N ha−1) and higher %PostN (an increase from 30% in Old to 36% in New Era).
  • The change in stover dry weight from silking to physiological maturity (ΔStover) has a positive, linear relationship with PostN in the Old Era but less so in the New Era.

Annual Reports

2015

Publications

Assessing the Effects of Conservation Practices and Fertilizer Application Methods on Nitrogen and Phosphorus Loss from Farm Fields – A Meta-Analysis

Crops: Corn for grain Corn for silage Cotton Hay Potato Rice Rye Ryegrass Sorghum Soybeans Sugar beets Sugarcane Winter wheat Wheat
4R Practices: Metadata Project

Assessing the Effects of Conservation Practices and Fertilizer Application Methods on Nitrogen and Phosphorus Loss from Farm Fields – A Meta-Analysis

Lead Researcher:

Dr. Song Qian

Associate Professor

University of Toledo

Start Date: 2014

End Date: 2016

Collaborating scientists and universities

  • Dr. R. Daren Harmel, USDA-ARS

Matching Funds

  • University of Toledo Research Council

Project Summary

The project augments an existing database by (1) revising studies included in the existing database to update information about fertilizer application methods, as well as additional variables, and (2) updating the database with recent studies. The project documents the use of the propensity score method and the multilevel modeling approach in the context of meta-analysis. Results are applicable for improved assessment of agricultural practices and their effects on the environment and can be used for providing realistic parameter values for watershed-scale modeling.

Project Goals:

  • Compile a large cross-sectional database to document existing studies on agriculture management practices
  • Document the use of two statistical methods for meta-analyses, as well as the effects of various conservation practices and fertilizer application methods in reducing nitrogen and phosphorus loss from farm fields.

Project Results:

  • Updated the MANAGE database and is in the process of achieving the objective of finding the effects of the two noted agricultural practices on nutrient loss.
  • Significant reductions in total phosphorus loads leaving a field when conservation practices were implemented.
  • 70 percent reduction in the amount of total phosphorus leaving a field using the 2007 version of MANAGE while current analysis of the October 2014 edition showed a 54 percent reduction in total phosphorus leaving the field.
  • The application conservation practices to a field reduce the amount of nutrient loss leaving a field.

Annual Reports

2015

2016

Publications

Impacts of 4R Nitrogen Management on Crop Production and Nitrate-Nitrogen Loss in Tile Drainage

Crops: Corn for grain Soybeans
4R Practices: Source Rate Time Place

Impacts of 4R Nitrogen Management on Crop Production and Nitrate-Nitrogen Loss in Tile Drainage

Lead Researcher:

Dr. Matthew Helmers

Director, Iowa Nutrient Research Center and Dean’s Professorship in the College of Agriculture and Life Sciences

Iowa State University

Start Date: 2014

End Date: 2017

Collaborating scientists and universities

  • Dr. John Sawyer, Iowa State University
  • Mr. Carl Peterson, Iowa State University
  • Mr. Chad Huffman, Iowa State University
  • Mr. Terry Tuttle, Iowa State University

Matching Funds

  • The Northwest Research Farm Association

Project Summary

Corn and soybean producers in Iowa and throughout much of the U.S. Corn Belt are increasingly challenged to maximize crop production to supply feed, fiber, and more recently biofuels (especially ethanol from corn) while at the same time managing soils by utilizing fertilizers and animal manures efficiently and minimizing negative impacts on water quality. In particular, there is concern about nutrient export from subsurface drainage and surface water runoff to water systems in Iowa and the Gulf of Mexico. In addition to local impacts on receiving waters, nitrogen (N) and phosphorous (P) loads from U.S. Corn Belt are suspected as primary drivers of hypoxia in the Gulf of Mexico. The EPA SAB’s 2007 hypoxia reassessment identified both N and P as major contributors to Gulf hypoxia and the 2008 Action Plan called for a dual nutrient strategy of 45% reductions in both N and P loads. Relative to N loss, nitrate‐N is the predominant form in many agricultural watersheds due to subsurface drainage or shallow subsurface flow. Nitrate‐N loading from the Mississippi River is suspected to be a main contributor to the hypoxic zone in the Gulf of Mexico, and the main source of nitrate‐N in the Mississippi River Basin has been linked to subsurface drainage in the Midwest. Based on the need for nitrate‐N reductions to meet water quality goals, new management practices are needed that have the potential to significantly reduce nitrate‐N losses at minimal cost and/or provide economic benefits. Practices are needed that will address the right source at the right rate in the right place. In addition, there is a need to quantify the water quality and crop yield impacts of some traditionally recommended best nutrient management practices such as timing of N application The Iowa Nutrient Reduction Strategy Science Assessment has indicated nitrate‐N loss improvement with certain practices, such as time of application (spring versus fall) and nitrification inhibitor. However, the published data available for the science assessment was limited for those practices, especially from Iowa research. Also, the practice of split or in‐season application had indication of limited benefit to tile drainage nitrate‐N reduction. Among other practices, the Iowa Nutrient Reduction Strategy specifically identified in‐season sensor‐based nitrogen application and nitrogen inhibitors needing of future research that would concurrently document crop production and water quality (nitrate‐N loss) effects.

Project Goals:

  • Determine the effects of N fertilizer application and N fertilizer application timing on nitrate-N leaching losses along with potential impacts on crop yield.
  • Determine the effects of N fertilizer application and N fertilizer application timing on crop yield.
  • Disseminate project findings through peer-reviewed journal articles, Extension fact sheets, Extension presentations, and other outlets as appropriate; and provide needed scientific information for on-going review and adjustment of the Nutrient Reduction Strategy Science Assessment.

Project Results:

  • Annual variability in precipitation and drainage losses greatly affects nitrogen loads removed from corn and soybean fields.
  • Nitrogen surplus (N inputs minus N outputs) relates to drainage nitrate concentration, but the effect of flow impairs the relationship between nitrogen surplus and nitrate loading from tile drainage.
  • Hydrology of crop land soils and nutrient management need to be considered for a comprehensive assessment of potential nitrogen loss from corn and soybean rotations.

Annual Reports

2014

2015

2016

2017

Publications

Nitrogen Losses: A Meta-analysis of 4R Nutrient Management in U.S. Corn-Based Systems

Crops: Corn for grain
4R Practices: Metadata Project

Nitrogen Losses: A Meta‐analysis of 4R Nutrient Management in U.S. Corn‐Based Systems

Lead Researcher:

Dr. Alison Eagle

Scientist

Environmental Defense Fund

Start Date: 2014

End Date: 2014

Collaborating scientists and universities

  • Dr. Lydia Olander, Duke University
  • Dr. Katie Locklier, Duke University
  • Dr. James Heffernan, Duke University
  • Dr. Emily Bernhardt, Duke University

Project Summary

Modern fertilization practices have fed the world, but unfortunately, they also contribute to serious environmental consequences – coastal dead zones and fish kills, acid rain, climate change, and stratospheric ozone destruction. These result most notably from nitrate (NO3) leaching and runoff, and nitrous oxide (N20) emissions coming from nitrogen (N) not taken up by crops. Improved fertilizer management is vital to efforts that seek to increase cropping efficiency and minimize these nutrient losses. Such improvements can enhance both farm profitability and environmental sustainability. Many studies have evaluated responses of yield to varying fertilization rates, some have measured losses of NO3 and a few have included N20 , but rarely have they considered these all together, and not in a way that accounts for multiple aspects of proper nutrient management or how these relationships vary with soil, climate, or crop type. A meta‐analysis of existing research would allow evaluation of many of these relationships and significantly enhance our understanding of what is controlling N use efficiency (NUE) and N loss pathways.

Answering these questions in a comprehensive and integrating manner will provide novel, region‐specific information that can be used to 1) estimate the magnitude of reduced fertilizer needs and reduced excess N under different scenarios of 4R management, 2) estimate the magnitude of NO3 and N2O losses under different scenarios of 4R management, 3) invest limited research dollars more strategically and 4) implement N management in ways that maintain or improve yields while minimizing environmental costs. 

Project Goals:

  • How do crop yield, NO3 leaching, and N20 emissions respond to N fertilizer application rate, timing, type, and placement? 
  • How do these effects of fertilization practices depend on climate and soil factors?

Project Results:

  • Field research on N2O and NO3 losses in corn-based systems in North America points to potential system improvements and reduced losses with a selection of 4R nutrient management practices.
  • If the standard practices tested in the field data from this meta-analysis appropriately represent those in production agriculture, nitrification inhibitors could reduce average N2O emissions by 36%, and side-dressing fertilizer instead of applying at or before planting could reduce emissions by 50%. In addition, where aqueous ammonia fertilizer is in use, average NO3 leaching reductions of 18 kg N/ha may be achieved by using UAN or urea fertilizer instead.
  • Cross-site comparisons are needed to capture both N2O and NO3 loss potential and how they relate to each other in varying regions and with different management.

Annual Reports

2015

2016

Publications