A perennial living mulch substantially increases infiltration in row crop systems

Authors: BAKER, JOHN; Feyereisen, Gary; ALBRECHT, KENNETH - UNIVERSITY OF WISCONSIN; Gamble, Joshua

Submitted to: Journal of Soil and Water Conservation
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/29/2021
Publication Date: 3/1/2022
Citation: Baker, J.M., Feyereisen, G.W., Albrecht, K.A., Gamble, J.D. 2022. A perennial living mulch substantially increases infiltration in row crop systems. Journal of Soil and Water Conservation. 77(2):212-220. https://doi.org/10.2489/jswc.2022.00080.
DOI: https://doi.org/10.2489/jswc.2022.00080

Interpretive Summary: Kura clover is a low-growing legume that spreads by rhizomes and persists for many years. For these reasons it has been tested in research settings as a perennial living mulch, i.e. - a crop that can be seeded once and then used for many years as a cover crop, into which annual row crops like corn and soybeans can be planted. The long-term effects of such a cropping system on soil properties are not well-known, because there are few locations where such a system has been in place for more than 2-3 years. We made a series of measurements of key soil properties on two long-term (>5 year) kura clover living mulch (KCLM) systems, in Wisconsin and Minnesota, comparing them to adjacent plots of conventional corn/soybean systems on the same soil type.There were no significant differences between the KCLM and conventional systems in cation exchange capacity, soil organic carbon, or moisture holding capacity, and only minor differences in surface layer bulk density at one site. However, there were large differences in two key hydrologic properties, saturated hydraulic conductivity (infiltration rate) and sediment loss. The KCLM systems had saturated hydraulic conductivities that were 10-20 times higher than the conventional systems, and in the measurements of runoff loss on sloped ground, which were only performed at the MN site, the KCLM system reduced sediment loss by 93%. These hydrologic benefits are similar to those reported in comparisons of restored prairie to conventional cropped fields, suggesting that the KCLM system may offer many of the benefits that have been noted for the inclusion of prairie strips, while preserving the ability to produce crops.

Technical Abstract: Kura clover is a rhizomatous perennial legume into which corn and soybeans have been successfully planted to provide the conservation benefits of cover crops without the challenge and expense of annual establishment. The long-term impacts of this form of production on soil physical and chemical properties are not well known. We conducted a suite of paired measurements at sites in MN and WI where kura clover/corn living mulch systems (KCLM) had been in place for at least five years immediately adjacent to conventionally farmed fields or plots on the same soil type. Measurements included soil organic carbon (SOC), cation exchange capacity (CEC), bulk density ('s), moisture release curves, and field-saturated hydraulic conductivity (Kfs), obtained from single-ring infiltrometer data. In a related experiment, runoff and sediment loss were measured at a single site in MN where both KCLM and conventional corn were grown on a 9% slope. There were no detectable differences between the two treatments at either site in SOC, CEC, or soil moisture contents at either field capacity (0.01 MPa) or wilting point (1.5 MPa). Effects on 's were minimal, with small reductions in the surface 5 cm for the KCLM, but no apparent differences at greater depths. There were, however, large differences in Kfs, with values 10 to 20 times higher in the KCLM than in the conventional corn. Similar large improvements were found in erosion prevention on sloped ground, where the presence of the living mulch reduced soil loss over the course of a year by 93%. The KCLM system thus may offer a way to obtain some of the benefits of perennial vegetative strips while maintaining row crop production.