Principles and processes in conserving and restoring cultivated organic soils: promising avenues

This paper discusses the primary processes involved in the degradation of cultivated organic soils (Histosols) in Canada: decomposition, subsidence, formation of a compacted horizon limiting drainage and last, but not least, wind erosion. The content is organized as follows: (i) description and quantification of the different mechanisms, (ii) overview of the different solutions for conserving and restoring these soils, and (iii) technical and economical assessments of the value of implementing soil conservation strategies for the benefits of future generations. At the annual scale, wind erosion, decomposition, and subsidence contribute nearly equally to organic soil losses. Overall, our investigations indicate that cultivated organic soils are losing about 2.1 to 2.4 cm per year. On top of that, drainage is gradually impaired due to the increasing development of compacted soil layers. As a result, biomass addition is needed to compensate for decomposition and wind erosion losses and to improve aeration of top layer. Drainage also needs to be improved by increasing tile drain density, digging trenches or growing permanent crops with deep rooting systems. Financial simulations suggest that cultivated organic soils will have improved productivity and return on investment on the long haul by implementing soil conservation and restoration practices.