Laboratory-Measured Soil Organic Carbon Mineralization in Soil Samples from Six Long-Term Crop Rotations in Alberta as a Function of Sample Disturbance

  • Author / Creator
    Kipps, Kyle W
  • Soil organic carbon (SOC) plays a dual role in soil; as a key compound determining the function and performance of agricultural soils and as the main terrestrial pool of carbon. The carbon content of cultivated soils has been found to depend on management practices. This laboratory incubation serves to quantify the effect of different long-term crop rotations and type of physical disturbance on the amount of potentially mineralizable carbon. Potentially mineralizable carbon was measured by the amount of CO2 respired from the soil under laboratory conditions for a defined period, in this case 182 days. Soil samples were collected from the University of Alberta Breton Plots and Agriculture and Agri-Food Canada’s Lethbridge Research Centre. Headspace samples from the incubation chambers were taken on a decreasing frequency over the course of 182 days and analyzed using gas chromatography. Mineralized carbon proved to be dependent on the interaction of the sample location (Breton or Lethbridge), crop rotation and disturbance treatment applied. Generally, crop rotations with higher light fraction (LF) contents resulted in higher potentially mineralizable carbon. Increasing physical disturbance was found to decrease the LF content and increase the C:N ratio of the remaining LF both of which reduced the potentially mineralizable carbon. The total SOC content was not found to decrease with physical disturbance suggesting that the carbon formerly in the LF, which was mineralizable, was transferred within the soil and retained. The results suggest that in addition to crop rotation, particle size of crop residue returned to the soil may offer management options for control of SOC dynamics in tilled soils. Understanding the mechanisms controlling SOC dynamics of these soils is beneficial for improved management of SOC and greenhouse gas emissions in cultivated soils.

  • Subjects / Keywords
  • Graduation date
    Fall 2015
  • Type of Item
  • Degree
    Master of Science
  • DOI
  • License
    This thesis is made available by the University of Alberta Libraries with permission of the copyright owner solely for non-commercial purposes. This thesis, or any portion thereof, may not otherwise be copied or reproduced without the written consent of the copyright owner, except to the extent permitted by Canadian copyright law.