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Long term field trials to examine corn, soybean and wheat production systems

Principal Investigators: David Hooker and Bill Deen

Research Institution: University of Guelph

Timeline: February 2013 – January 2016


  • Maintain existing long term field crop trials for current and future use.
  • Summarize long term trial results and make them more readily available as extension material.
  • Continue or complete existing project objectives that utilize the long‐term trials.
  • Continue collaborative projects with University of Guelph and other researchers and encourage others to also use these trials as field research.


  • The quantified benefits of nitrogen, tillage, and crop rotation as a systems or “big picture” approach, rather than assuming that nitrogen, tillage, and crop rotation effects are independent on each other.
  • Better crop rotation, nitrogen and tillage system decisions are more sustainable and resilient during times of water deficits with higher economic farm returns (considering the big picture or systems approach) and improved soil health and carbon sequestration.
  • Overall, since 2012, the long-term trials have produced several peer-reviewed scientific publications, a multimedia app (CashCropper), demonstration plots for graduate and undergraduate students and OMAFRA training, various extension materials and dozens of extension presentations that were given across Eastern Canada (and a few were given in the USA).

Scientific Summary:

Research is needed to determine long-term effects of crop management on the productivity, economic and environmental sustainability of cropping systems and healthy soils. Long-term trials are important to evaluate crop production system impacts that change slowly over time, on productivity, soil quality and environmental sustainability. A review of the literature on the consequences of poorly managed cropping systems include reductions of soil organic matter, aggregate stability, increased soil erosion, increased greenhouse gas emissions, N losses, decreased yield potential and increased yield instability from environmental stresses.

Currently, the spotlight is on agriculture for determining its impact or influence on mitigating climate change, emergence of a bioeconomy, etc. Therefore, it is critically important that the effects of crop rotation, crop rotation diversity, cover crops, and tillage systems can be quantified for establishing best management practices with both short-term and long-term economic and environmental consequences and benefits. Early identification of best management practices would build highly productive cropping systems, similar to investing early for compounding interest for retirement savings.

This project contributed to maintaining both long-term rotation trials at Ridgetown and Elora. These long-term rotation trials also show crop rotation systems consisting of corn-soybean and continuous soybean produced with conventional tillage produced the poorest soil health among all tillage-crop rotation systems; lower corn and soybean yields reflected soil health status. No-till is associated with improved soil health; however, tillage impact on yield and yield stability were not as pronounced as the impact of crop rotation complexity. These long-term rotation trials show that wheat in rotation with corn and soybean produce 15 bu/ac higher corn yields and 4-6 bu/ac higher soybean yields compared to a short corn-soybean rotation. Corn and soybean grain yield responses to wheat in rotation are associated with better soil structure, higher soil organic matter and higher aggregate stability compared to continuous corn or soybean, or short rotations of corn and soybean. Analysis of weather data and yields from the long-term rotation trial has shown that corn and yields in complex rotations are more resilient to stress events (i.e., water deficits) compared to continuous cropping or in short corn-soybean rotations. The rotation trial at Ridgetown demonstrated that when corn follows wheat in rotation, there is less reliance on fertilizer nitrogen for corn, especially with the use of no-till. The lower fertilizer N requirement for corn after wheat was attributed to higher soil quality parameters such as organic matter. The addition of red clover under seeded to wheat improved corn yield potential independent on nitrogen contributions by the legume. The addition of under seeded red clover enabled a reduction of the maximum economic rate of nitrogen fertilizer by approximately 70 kg N/ha.

Funding Partners:

This project is funded [in part] by the Ontario Ministry of Agriculture, Food and Rural Affairs (OMAFRA), through the Ontario Agri-Food Innovation Alliance.

Project Related Publications:

KTT activities from the long-term trials have been extensive. In 2020, the Ontario Agri-Food Innovation Alliance in collaboration with Soils at Guelph distilled four key findings about the importance of crop rotation and how it affects various on-farm outcomes including crop yield, resilience during dry years, nitrogen use efficiency and soil health into a series of key findings infographics to help crop advisors and farmers make on-farm decisions to remain competitive and sustainable. These summaries are available at:

Bittman S, Hunt D, Grant C, Deen B. 2018. Sustainable Cropping Systems. In Encyclopedia of Ecology 2nd Edition. (Ed.) Bastianoni S, Vymazal J, Martins I, Svirejeva-Hopkins A, Liu X, Fath B, Wertheim B, and Scharler U. Elsevier: ISBN: 9780444637680. 2780pp.

Congreves KA, Hooker DC, Hayes A, Verhallen EA, Van Eerd LL. 2016. Interaction of long-term nitrogen fertilizer application, crop rotation, and tillage system on soil carbon and nitrogen dynamics. Plant Soil:1-15. doi:10.1007/s11104-016-2986-y.

Congreves KA, Smith JM, Németh DD, Hooker DC, Van Eerd LL. 2015. Soil organic carbon and land use: Processes and potential in Ontario’s long-term agro-ecosystem research sites. Can J Soil Sci.: 2014; 94(3):317-336. doi:10.4141/cjss2013-094.

Deen B, Martin RC, Hooker D, Gaudin A. 2016. Crop Rotation Trends: Past, Present and Future Benefits and Drivers. In Bao-Luo Ma (Ed.), Crop Rotations: Farming Practices, Monitoring and Environmental Benefits. Nova Science Publications.

Ferrari Machado PV, Farrell RE, Deen W, Voroney P, Congreves KA, Wagner-Riddle, C. 2021. Crop residues contribute minimally to spring-thaw nitrous oxide emissions under contrasting tillage and crop rotations. Soil Biology & Biochemistry: 152:xxx-xxx.

Gaudin ACM, Tolhurst TN, Ker AP, et al. 2015. Increasing crop diversity mitigates weather variations and improves yield stability. PLoS One: 10(2): e0113261. doi:10.1371/journal.pone.0113261.

Gaudin ACM, Janovicek K, Deen B, Hooker DC. 2015. Wheat improves nitrogen use efficiency of maize and soybean-based cropping systems. Agric. Ecosyst. Environ.: 210:1-10. doi:10.1016/j.agee.2015.04.034.

He W, Grant BB, Smith WN, VanderZaag AC, Piquette S, Qian B, Jing Q, Rennie TJ, Belanger G, Jego G, Deen B. 2019. Assessing alfalfa production under historical and future climate in eastern Canada: DNDC model development and application. Environmental Modelling and Software: 122:xxx-xxx.

Jarecki M, Grant B, Smith W, et al. 2018. Long-term Trends in Corn Yields and Soil Carbon under Diversified Crop Rotations. J Environ Qual.: doi:10.2134/jeq2017.08.0317.

King AE, Congreves KA, Deen B, Dunfield K, Simpson MJ, Voroney P, Wagner-Riddle C. 2020. Crop rotations differ in soil carbon stabilization efficiency, but the response to quality of structural plant inputs is ambiguous. Plant and Soil: 1-18.

Linton NF, Ferrari Machado PV, Deen B, Wagner-Riddle C, Dunfield K. 2020. Long-term diverse rotation alters nitrogen cycling bacterial groups and nitrous oxide emissions after nitrogen fertilization. Soil Biology and Biochemistry: 149:xxx-xxx.

Munkholm LJ, Heck RJ, Deen B, Zidar T. 2016. Relationship between soil aggregate strength, shape and porosity for soils under different long-term management. Geoderma: 268:52-59. doi:10.1016/j.geoderma.2016.01.005.

Munroe JW, McCormick I, Deen B, Dunfield K. 2016. Effects of 30-years of crop rotation and tillage on bacterial and archaeal ammonia oxidizers. J Environ Qual: 948 (June 2015):1-31. doi:10.2134/jeq2015.06.0331.

Renwick LR, Bowles TM, Deen B, Gaudin ACM. 2018.  Potential of increased temporal crop diversity to improve resource use efficiencies: exploiting water and nitrogen linkages. In Agro-Ecosystem Diversity, 1st Edition:  Reconciling Contemporary Agriculture and Environmental Quality (Ed.) Lemaire G, Carvalho P, Kronberg S, Recous S. Elsevier: 474pp ISBN: 9780128110508.

Van Eerd LL, Congreves KA, Hayes A, Verhallen A, Hooker DC. 2014. Long-term tillage and crop rotation effects on soil quality, organic carbon, and total nitrogen. Can J Soil Sci.: 2014;94(3):303-315. doi:10.4141/cjss2013-093.

Winstone, BC, Heck RJ, Munkholm LJ, Deen B. 2018. Characterization of soil aggregate structure by virtual erosion of X-ray CT imagery. Soil Tillage Res. 185: 70–76. Elsevier. doi:10.1016/j.still.2018.09.001.