Resources

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

• Tuttle, T., Sawyer, J , Helmers, M , Pederson, C & Waring, E . (2020) “Impact of 4R Management on Crop Production and Nitrate-Nitrogen Loss in Tile Drainage”, Iowa State University Research and Demonstration Farms Progress Reports. 2019(1). Read More
• Helmers, M., Pederson, C., Sawyer, J., & Tuttle, T. (2018). Impact of 4R Management on Crop Production and Nitrate-Nitrogen Loss in Tile Drainage. Farm Progress Reports, 2017(1), 91. Read More

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

• Qian, S. S., & Harmel, R. D. (2016). Applying Statistical Causal Analyses to Agricultural Conservation: A Case Study Examining P Loss Impacts. Journal of the American Water Resources Association, 52(1), 198–208. Read More
• Christianson, L.E., Harmel, R.D., Smith, D., Williams, M.R. and King, K. (2016), Assessment and Synthesis of 50 Years of Published Drainage Phosphorus Losses. J. Environ. Qual., 45: 1467-1477. Read More
• Christianson, L.E. and Harmel, R.D. (2015), 4R Water Quality Impacts: An Assessment and Synthesis of Forty Years of Drainage Nitrogen Losses. J. Environ. Qual., 44: 1852-1860. Read More
• Christianson, L. E., & Harmel, R. D. (2015). The MANAGE Drain Load database: Review and compilation of more than fifty years of North American drainage nutrient studies. Agricultural Water Management, 159, 277-289. Read More

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

• Mueller, S.M, and T.J. Vyn. 2016. Maize plant resilience to N stress and post-silking N capacity changes over time: A review. Frontiers Plant Sci. 7:1-14. Read More
• Omonode, R. A., & Vyn, T. J. (2019). Tillage and Nitrogen Source Impacts on Relationships between Nitrous Oxide Emission and Nitrogen Recovery Efficiency in Corn. Journal of Environmental Quality, 48(2), 421–429. Read More
• Omonode RA, Halvorson AD, Gagnon B and Vyn TJ (2017) Achieving Lower Nitrogen Balance and Higher Nitrogen Recovery Efficiency Reduces Nitrous Oxide Emissions in North America’s Maize Cropping Systems. Front. Plant Sci. 8:1080.
• van Hoose, N. 2016. Modern corn hybrids more resilient to nitrogen stress, crowded planting conditions. Purdue Agricultural News. Mar. 7, 2016. Read More