A perennial living mulch substantially increases infiltration in row crop systems

Abstract

Poor infiltration in annual row crop systems can cause a range of problems, including sediment and nutrient loss in runoff, diminished trafficability, anaerobic soil conditions, and reduced precipitation use efficiency. Soils covered by perennial vegetation generally sustain much higher infiltration rates, and consequently are less prone to these problems. Kura clover (Trifolium ambiguum Bieb.) living mulch (KCLM) is a management system that seeks these environmental benefits of perenniality, while allowing continued production of annual row crops like maize (Zea mays L.) and soybean (Glycine max [L.] Merr.). This is done by planting them into tilled or killed strips within a perennial stand of kura clover. Our objective was to compare the hydrologic performance of long-term KCLM systems (in place for at least five years) against adjacent fields or plots in conventional row crop production on the same soil types. Measured variables included field-saturated hydraulic conductivity (K_fs), moisture release curves, and bulk density. K_fs was measured with a constant head single ring infiltrometer, and moisture release curves were determined with the evaporation method. Bulk density was measured on 5 cm diameter cores extracted from the surface horizon of each treatment. None of the long-term sites contained appreciable sloped land, so supporting runoff measurements were made on a third field in Minnesota where the KCLM had only been in place for two years, using lined plots with flumes and tipping buckets. Results revealed substantial and significant differences in K_fs at the long-term sites. At one site the mean value was 11 times greater in the living mulch than in the conventional fields, while at the other site it was 19 times greater. The runoff plots showed a 93% reduction in sediment loss for the KCLM relative to conventional production over the course of a year that included 10 runoff-inducing storms. These results suggest that KCLM may confer similar hydrologic benefits to prairie strips if strategically placed in fields or watersheds.