Resources

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

Phosphorus Fertilizer Placement and Tillage Interaction for Corn and Soybean in the U.S.

Crops: Corn for grain Corn for silage Soybeans
4R Practices: Metadata Project

Meta-analysis of Phosphorus Fertilizer Placement and Tillage Interaction for Corn and Soybean in the U.S.

Lead Researcher:

Dr. Dorivar Ruiz Diaz

Professor

Kansas State University

Start Date: 2014

End Date: 2015

Collaborating scientists and universities

  • Dr. David Mengel, Kansas State University
  • Dr. Cristie Preston, Senior Agronomist, Nutrien

Matching Funds

  • Kansas Soybean Commission
  • Kansas Corn Commission
  • USDA-NRCS
  • Kansas Agricultural Experiment Station
  • Kansas State University Department of Agronomy

Project Summary

Phosphorus placement and interactions with tillage has been evaluated extensively for corn and soybean in the US. Results suggest that placement of P fertilizer can play an important role in early P plant uptake and yield as well as potential P loses to surface water for some soils and tillage conditions. The rate of P uptake per unit of root in corn decreases throughout the vegetative growth phase; and therefore early season P fertilizer applications and placement can be particularly important for optimum plant growth. Broadcast application can result in a more uniform distribution and likely affecting more soil volume. Crops have shown a response for various levels of soil test, including low soil test P (STP) conditions and medium to high STP. However, accumulation of P near the soil surface may result in higher lost potential with runoff; and possible decreased P availability due to increased soil-fertilizer interaction in soils with high P sorption capacity. Broadcast application may be more practical for some producers and suitable for some soils and tillage conditions. However, soils and tillage conditions and the interaction with P application methods should be evaluated with larger datasets and across different soils and environments. Potential P loses with water runoff can be affected significantly by phosphorus placement and tillage. Many studies in the US evaluated water runoff and P loses as affected by tillage and fertilizer. However studies often show different results, which may be due to differences in soils, rainfall amounts and intensities, slope, moisture content, and infiltration rate. Evaluation and summary of the existing literature can help to identify factors contributing to potential P loses in addition to tillage and fertilizer placement. Crop response and P loss potential can be affected by the interaction between soil and tillage factors with P fertilizer placement. Accurate evaluation of these interactions would require large dataset that comprise a variety of soils, tillage and placement combinations.

Project Goals:

  • Analyze and summarize published and unpublished field-based data on corn and soybean response to P placement and the interaction with tillage.
  • Complete a data review on yield response and phosphorus loses with surface runoff as affected by P placement and tillage interaction.
  • Include data review of estimated P use efficiency with placement and tillage interactions; and estimate the economic return associated with different systems.

Project Results:

  • Very limited amount of work is available on the long-term effect of specific management systems used by producers for tillage and/or placement on potential P loses to surface water.
  • Some states in the US have limited amount of published data on the overall topic of tillage by P placement interaction for both agronomic and environmental implications.
  • Results of all evidence analysis show higher corn yield means with broadcast applications in soils with soil-test P below <20 ppm phosphorus.
  • Higher corn yields were also observed with conventional tillage in soils with high STP.
  • Analysis of direct evidence shows generally lower corn yields in no-till systems with little difference between placements.
  • Band P fertilizer applications yielded highest in high STP and may provide a yield increase only if the rates are limiting (< 19 lb P ac-1).

Annual Reports

2015

2016

A ‘Manage’ ed approach for 4R nutrient stewardship on drained land

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

A “MANAGE”ed Approach to 4R Nutrient Stewardship on Drained Land

Lead Researcher:

Dr. Laura Christianson

Assistant Professor

University of Illinois

Collaborating scientists and universities

  • Dr. R. Daren Harmel, USDA-ARS

Start Date: 2014

End Date: 2015

Matching Funds

  • Texas State Soil and Water Conservation Resource Board

Project Summary

As agriculture in the 21st century is faced with increasing pressure to reduce negative environmental impacts while continuing to efficiently produce food, fiber, and fuel, it becomes ever more important to reflect upon more than half a century of drainage water quality research to identify future paths towards increased sustainability. This work provided a quantitative review of the water quality and crop yield impacts of artificially drained agronomic systems across North America by compiling data from drainage nutrient studies into the “Measured Annual Nutrient loads from Agricultural Environments” (MANAGE) database. Of the nearly 400 studies reviewed, 91 individual journal publications and 1279 site-years were included in the new MANAGE Drain Load table with data from 1961 to 2012.

Project Goals:

  • The MANAGE Drain Load database: Review and compilation of more than fifty years of drainage nutrient studies.
  • 4Rs water quality impacts: A review and synthesis of forty years of drainage nitrogen losses.
  • A quantitative review and synthesis of fifty years of drainage phosphorus losses.

Project Results:

  • Increasing nitrogen application rates both improved crop yields and increased dissolved nitrogen loads in drainage. “Fine-tuning” these rates is clearly important from economic and environmental standpoints, but it would be short-sighted and unrealistic to focus solely on this practice.
  • The order of magnitude difference between agronomic phosphorus application rates and phosphorus loadings that can cause ecological damage presents a serious environmental challenge, especially compared to nitrogen. Across the literature, generally less than 2% of applied phosphorus was lost in drainage in a given site year.
  • Practices such as applying at planting or side-dressing had lowest median nitrogen losses (not significant).
  • Adherence to 4Rs strategies is vital regardless of the nutrient source, and accurate implementation of the 4Rs approach will require site-specific knowledge.

Annual Reports

2015

Publications

Enhanced Efficiency Fertilizer in Corn Systems in the Midwest

Crops: Corn for grain Corn for silage
4R Practices: Metadata Project

Meta-analysis of Enhanced Efficiency Fertilizers in Corn Systems in the Midwest

Lead Researcher:

Dr. Rachel Cook

Assistant Professor

North Carolina State University

Start Date: 2014

End Date: 2015

Matching Funds

  • Dow AgroSciences

Project Summary

The 4R approach to nutrient stewardship has helped develop a better context for driving best management practices in production agriculture. As the agricultural community becomes more involved in exploring the three aspects of sustainability, including the economic, social, and environmental triple bottom line, the 4Rs (right source, right rate, right time, and right place) provide a framework for better management of fertilizer applications.

The exceedingly large number of possible combinations of source, rate, time, and place, even within one cropping system, can make it difficult to compare results from studies located in different regions, with different climate, soils, and accepted management practices. To prevent needless duplication of study parameters and suggest future study directions, the soil fertility and fertilizer community needs to systematically compile what we know in order to move forward in the most efficient manner possible.

Project Goals:

  • Compile a database that will characterize environmental variables (latitude and longitude, precipitation, soil texture, soil organic matter, and plot size).
  • Meta-analysis will re-evaluate the current literature on nitrapyrin, and expand the analysis to include other nitrification inhibitors, urease inhibitors, and controlled release fertilizers will create a more useful and broader-scoped analysis of the environmental and agronomic benefits of these management practices in Midwestern corn production.

Project Results:

  • Application timing and nitrogen rate had a greater effect than nitrogen source with enhanced efficiency properties for management and environmental factors for this specific meta-analysis.
  • A need for an additional assessment that coverages greater regions and specific systems that are susceptible to losses is clear.
  • Nitrate leaching and water-quality information reported with measures of variability are the biggest information gap at this time for both tile-drained and non-tile-drained systems.

Annual Reports

2014

2015