Impacts of riparian buffer vegetation on soil quality physical parameters, 20-23 years after initial riparian buffer establishment

Abstract

Multispecies riparian buffers (MRBs) are a conservation practice that protects water quality and prevents soil erosion by improving soil quality including aggregate stability, particulate organic matter (POM), and water infiltration. USDA Conservation Reserve Program MRB contracts last 10-15 years; evidence shows MRB soil quality may improve within 3-7 years, but there is little data on how MRB soils perform after contracts typically expire. Slaked soil aggregate stability was measured in a 20-21 year-old MRB in central Iowa at the surface (0-15 cm) and used to calculate the indices mean weight diameter (MWD), geometric mean diameter (GMD), and percent water-stable macroaggregates (%WSA). The MRB contained zones of switchgrass (Panicum virgatum L. ‘Cave-inRock’), hybrid poplar (Populus spp.), and cool-season grass; results were compared with an adjacent crop field, a formerly grazed pasture, and a natural riparian forest. Bulk density, total soil carbon, and POM were also measured. A Cornell sprinkle infiltrometer was used to measure infiltration in a 10-year old tree and cool-season grass MRB, and in the switchgrass, cool-season grass and silver maple zones of the MRB used in the soil aggregate study. MRBs were compared with trafficked and non-trafficked crop interrows in a nearby crop field. Perennial vegetation had greater MWD, GMD, %WSA, and total SOC compared to the crop field. Data collected in 1997 showed no significant differences in %WSA or MWD between switchgrass and crop field, but did between cool-season grasses and crop field. However, %WSA and MWD under switchgrass increased 45.8% and 120.5%,