A comparison of soil properties observed in farmed, restored and natural closed depressions on the Des Moines Lobe of Iowa

Abstract

Extensive artificial soil drainage systems, including subsurface tiles and surface ditches, have been installed throughout the agricultural Midwest to remove excess water from perennially wet soils. Factors of soil formation, such as soil climate and biota, have been substantially altered by artificial drainage and the associated land use change. Efforts to restore wetlands are ongoing but success has been limited in some cases. The objectives of this study were to 1) quantify alterations of wetland soils due to artificial drainage in the recently glaciated, Des Moines Lobe region of north-central Iowa; and 2) compare physical and chemical soil properties of farmed (artificially drained) wetlands to those undergoing restoration efforts and those considered natural (undrained). Wetlands in thirteen Des Moines Lobe closed depressions were sampled during this study representing three distinct populations: farmed, restored and natural soils. There were distinct visual differences in soil morphological properties between farmed and restored wetlands and farmed depressions had significantly higher soil nutrients (NO3, P and K). Fewer differences were noted between restored and natural wetlands, implying that restoration of wetlands was returning soils to a more natural state in a relatively short time (15-20years) compared to the time since they were initially drained (50-100years). Study results suggest soil alteration due to artificial drainage and provide important context for establishing realistic timeframes for wetland soil restoration in closed depressions located on the Des Moines Lobe.