Does Drainage Duration Affect Wetland and Ditch Soil Properties? a Case Study from Southeast Saskatchewan.

Increased precipitation and associated flooding of agricultural land in regions of the Canadian Prairies has led to an increase in surface agricultural drainage. Drainage is used to expand the productive land base, reduce costs associated with manoeuvring equipment around wetlands, allow for earlier seeding and improve growing conditions. Given that low-lying areas tend to have higher nutrient and organic matter concentrations than the surrounding uplands, drainage may create some of the best agricultural land. However, these benefits have not been quantified in the semi-arid to sub-humid Canadian Prairies, and furthermore, there is no information regarding the duration of any associated benefits. Do soil benefits persist after 10 years of drainage? After 50 years? Nor is there any information about the soil properties and processes in the ditches themselves, which could have potential downstream water quality implications. Do ditch soils change over time? The aim of this study is to quantify the effects of surface agricultural drainage on selected soil properties and processes as a function of drainage duration. Forty-two wetlands and thirty-two ditch segments were selected in the Prairie Pothole Region in the Black soil zone of southeast Saskatchewan. The drainage age of wetlands ranged from 0 (undrained) to >50 years.  A corresponding midslope was sampled with each wetland and each ditch (ditch-slope). Intact cores were collected to a depth of 60 cm for analysis of bulk density, aggregate stability, macronutrients (including N mineralization and nitrification and P sorption/desorption) and organic matter quantity and quality. This study will contribute to a better understanding of how drainage affects key soil fertility related properties in order to determine if drainage is a suitable management practice for long term soil quality, including whether beneficial management practices need to be modified over time to reflect changing soil properties.