Infiltration within native prairie vegetative strips embedded in row crop fields across Iowa

Abstract

The integration of native prairie vegetative strips into row crop agriculture is a promising conservation strategy that has gained momentum in adoption rates throughout the US Midwest. Previous studies have shown that prairie strip establishment can lead to several positive soil and water quality outcomes, such as reductions in surface runoff and nutrient and sediment exports. However, the impacts of prairie strips on soil infiltration are not well known. In this study, the Cornell Sprinkle Infiltrometer system was used to measure differences in field-saturated infiltration rate between prairie strip and row crop treatments at six sites across Iowa after five to seven years since prairie strip establishment. Additionally, approximate sorptivity was calculated to compare trends in early infiltration between the two treatments at each site. Measurements were taken over a two-year span during summer and fall testing periods. Further, at two additional prairie strips sites, a separate approach using the tension infiltrometer generated hydraulic conductivity data for prairie strip and row crop treatments at 3, 4, and 14 years since prairie strip establishment. Differences between prairie strip and row crop were mostly undetected across nearly all sites in field-saturated infiltration rate and saturated hydraulic conductivity at 5 to 7 and 14 years after prairie strip establishment, respectively. However, at one site, saturated hydraulic conductivity was significantly greater within prairie strip than row crop, and at another, field-saturated infiltration rate was 3.6 times greater in prairie strip than row crop. Therefore, considering trends from both prairie strip age and infiltration testing method groups, differences in saturated infiltration capacity between prairie strip and row crop appear to be related to site-specific characteristics like soil texture, row crop tillage, and soil organic matter, especially at earlier stages of prairie strip establishment. Comparing trends in sorptivity approximations between the two treatments determined that prairie strips had 26% and 38% greater early infiltration than row crops during fall testing periods, but no treatment difference was found in the summer testing period. Since significant results were mostly limited to the fall, a combination of initial soil moisture and surface roughness disparities between treatments likely explain the observed treatment differences in approximate sorptivity. Within prairie strips, greater early infiltration relative to row crops delays and limits surface runoff generation. Therefore, this study suggests that a row crop field containing prairie strips will generate less surface runoff than a comparable 100% row crop field during a given rainfall event at the end and potentially beginning of the annual corn ( Zea mays L.) and soybean ( Glycine max [L.] Merr.) growing season in Iowa. By improving early infiltration and subsequently limiting runoff generation and sediment transport, prairie strips can be a valuable soil and water conservation tool.