University of Manitoba: Natural Systems Agriculture: Cover Crops and Nutrient Aquisition
University of Manitoba Faculty of Agricultural and Food Sciences Department of Plant Science

Effect of Organic and Conventional Management on Soil Health

By Sarah Braman, M.Sc. student

Seeding in the Glenlea Long-Term Rotation in spring 2011.

Organic and conventional management practices have direct consequences on soil health. Physical and biological soil properties are affected by crop rotation, fertilizer source and chemical use. It is important to evaluate the effect of management practices on soil health to ensure agricultural land will be fertile for the future.

One method for measuring soil health is the microbial respiration quotient (qCO2), and microbial C, N and P. Microbial activity in the soil characterizes the effect of agricultural management on metabolic efficiency, carbon cycling, nutrient sustainability and mineralization-immobilization-turnover.

Soil microbial activity immobilizes then mineralizes organic residues from above ground plant biomass and below ground root excretions, dead roots, manure and fertilizer. Immobilization ties up residues and fertilizer while mineralization completes decomposition and turns over plant available nutrients. Microbial metabolic activity releases nutrients like nitrogen and phosphorous and respires CO2 into the atmosphere. Detritus from microbial decomposition contributes to soil organic matter (SOM) pools. High carbon contents of organic matter supplies food for other microbes. While it is important to build SOM, its potential for energy can only be realized through decomposition with carbon lost as a byproduct (Janzen, 2005). The efficiency of microbial metabolic activity characterizes nutrient cycling and quality in soil (Chen, 2003).

The objective of this study is to assess the microbial respiration quotient and microbial C, N and P in the Glenlea Long-Term Rotation, established in 1992 at Glenlea MB. This project is part of the Organic Science Cluster created by the Canadian Agri-Science Cluster Initiative as part of Canada’s Growing Forward Policy Framework. The goal of Organic Science Cluster research is to compile information for organic stakeholders to increase organic product quantity and quality. Environmental stewardship is a high priority and an essential component of this initiative to investigate the environmental sustainability of different agricultural management practices.


Chen, G., Honglong, Z., Zhang, Y. 2003. Soil microbial activities and carbon and nitrogen fixation. Research in Microbiology. 154:393-398.

Janzen, H.H. 2005. The soil carbon dilemma: Shall we hoard it or use it?. Soil Biology & Biochemistry. Elsevier Ltd. 38:419-424.


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This page created June 2011.