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


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