Nutrient cycling in organic field crops in Canada and the United States

Authors: CARR, PATRICK - Montana State University; Cavigelli, Michel; DARBY, HEATHER - University Of Vermont; DELATE, KATHLEEN - Iowa State University; EBERLY, JED - Montana State University; GRAMIG, GRETA - North Dakota State University; HECKMAN, JOSEPH - Rutgers University; MALLORY, ELLEN - University Of Maine; REEVE, JENNIFER - Utah State University; SILVA, ERIN - University Of Wisconsin; SUCHOFF, DAVID - North Carolina State University; WOODLEY, ALEX - North Carolina State University

Submitted to: Agronomy Journal
Publication Type: Review Article
Publication Acceptance Date: 6/25/2019
Publication Date: 9/5/2019
Citation: Carr, P.M., Cavigelli, M.A., Darby, H., Delate, K., Eberly, J.O., Gramig, G.G., Heckman, J.R., Mallory, E., Reeve, J.R., Silva, E.M., Suchoff, D.H., Woodley, A.L. 2019. Nutrient cycling in organic field crops in Canada and the United States. Agronomy Journal. 111:1-17.

Interpretive Summary: Organic farmers have identified soil fertility and weed management as the two highest priority areas for research. This review provides the first comprehensive review of soil fertility management on organic farms across North America. While soil types, climate, cropping systems and other factors vary by region, there are several broad and consistent principles that govern organic nutrient management across North America and elsewhere: integrated use of legume cover crops and animal byproducts can help balance nutrient inputs with outputs, soil organic matter plays a critical role in regulating nutrient cycling and availabilities, and a deeper understanding of soil biology and factors controlling rates of biological transformations is crucial to improving nutrient management in organic systems. Future research should be conducted at sites managed organically rather than conventionally, so that results reflect the cropping practices (e.g., diverse crop rotations) that are generally used by organic farmers. These results will be of interest to organic farmers, organizations that support organic farmers, and scientists studying organic farming systems.

Technical Abstract: Organic farmers have identified soil fertility and weed management as the two highest priority areas for research. Research on crop nutrient management in organic systems has occurred in Canada and the USA, but little attempt has been made to coordinate these efforts across or, in some cases, within regions. Similarly, no effort has been made to review the literature about organic nutrient management across North America. Our objective was to complete a comprehensive review of soil fertility management on organic farms across the continent that could be used to guide future research efforts. It is acknowledged that environmental differences and other factors may limit interregional applications of research results in some instances, but there are several broad and consistent principles which govern organic nutrient management across North America and elsewhere. Moreover, knowledge can be gained by evaluating research results even when regions differ markedly in climate or otherwise (e.g., the Mid-Atlantic compared to the Great Plains and Intermountain West Regions). Results of this review indicate that while research has been conducted on soil fertility management in organic environments in North America, much work is still needed. Specifically, future research must be done in environments managed organically rather than conventionally, so that results reflect the cropping practices (e.g., diverse crop rotations) that are generally used by organic farmers.