Effect of Freeze-thaw Cycles on Soil Properties and Phosphorus Dynamics in Southern Ontario Agricultural Soils

Abstract

Agricultural phosphorus (P) inputs to surface waters are a primary driver of surface water eutrophication. In agroecosystems that experience significant winters, P loss primarily occurs during the non-growing season (NGS). As air temperatures continue to warm, NGS hydrology is expected to change, leading to diminished snowpacks and soils being exposed to fluctuating temperatures, leading to an increase in soil freeze-thaw cycles (FTCs). This thesis aimed to investigate the effects of FTCs on soil P dynamics and transport and the soil physical properties that regulate soil P processes across three dominant agricultural soil textures in southern Ontario. The results suggest the effects of FTCs on soil properties and P processes are most notable in silt-textured soils, reducing soil aggregate stability and promoting the quantity of labile P. These changes in soil P processes did not promote dissolved reactive P (DRP) loading in subsurface discharge but may promote total P (TP) loading.