Investigating carbon and nitrogen cycling during the transition to organic agriculture with a laboratory incubation study

Estimating how carbon and nitrogen pools respond during the transition from conventional to organic management is critical for ensuring overall system sustainability. Organic crop production, characterized by its restricted use of synthetic inputs and focus on resources present in the agro-ecosystem, is widely considered a sustainable alternative to conventional crop production. However, one of the most challenging aspects of organic crop production in western Canada is its reliance on the practice of tillage for weed and nutrient management, which can elicit significant process responses for both carbon and nitrogen. A proposed alternative to intensive tillage is to integrate crops and livestock in order to promote improved nutrient cycling. While both are considered effective management techniques, their impact on carbon and nitrogen cycling during the organic transition period from no-till conventional practices remains poorly understood. This research aims to examine how the introduction of tillage and an integrated crop-livestock system alter edaphic conditions which govern nutrient dynamics in soil.

A field research project comparing intensive tillage and integrated crop-livestock during the organic transition period is currently underway in a humid continental climate in western Canada. Intact soil cores were collected in the third growing season of the trial and underwent a laboratory incubation experiment which analysed carbon dioxide (CO₂) and nitrous oxide (N₂O) fluxes. Following the incubation, soil cores were analysed with a hydraulic property analyser, and available nitrogen and dissolved organic carbon were determined. In combination, these measurements provide a comprehensive understanding of nutrient pool responses to variable soil conditions created by contrasting management techniques.

Results suggest that the intensive tillage system exhibited higher losses in the form of N₂O and CO₂ emissions (p <0.05), as a consequence of higher nutrient concentrations (p <0.05) and water-filled pore space (p<0.05). Since N₂O and CO₂ are potent greenhouse gasses, increased emissions under intensive tillage highlight important climate implications of soil management choices. Additionally, greater nutrient losses reduce the pool of nitrogen available for crops, potentially undermining soil fertility during the transition to organic production. These findings underscore how strongly management practices shape nutrient availability during this critical transition period.