Rotary zone tillage improves corn establishment in a kura clover living mulch

Authors: DOBBRATZ, M - University Of Minnesota; Baker, John; GROSSMAN, JULIE - University Of Minnesota; WELLS, M.SCOTT - University Of Minnesota; GINAKES, PEYTON - University Of Minnesota

Submitted to: Soil & Tillage Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/5/2019
Publication Date: 6/1/2019
Citation: Dobbratz, M., Baker, J.M., Grossman, J., Wells, M., Ginakes, P. 2019. Rotary zone tillage improves corn establishment in a kura clover living mulch. Soil & Tillage Research. 189(6):229-235. https://doi.org/10.1016/j.still.2019.02.007.
DOI: https://doi.org/10.1016/j.still.2019.02.007

Interpretive Summary: Perennial living mulches are farming systems that provide the environmental benefits of cover crops in row crop agriculture, including reductions of erosion and chemical runoff, without the need to replant each year. One plant that is commonly used as a living mulch is kura clover, a long-lived legume that spreads by rhizomes. Strip tillage can be used to establish rows in it for planting corn or soybeans, but yields are often reduced compared to conventional production. We hypothesized that one reason for yield reduction might be early season competition for light, water, and nutrients, and that this could be ameliorated by creating a wider tilled zone. To test this hypothesis, we employed a novel rotary zone tillage unit (RZT) that uses rotary tines to create a wide (30 cm) cleared zone for each row. This system was compared against a traditional shank-based strip tillage unit (ST) for corn production over two growing seasons. We measured early season temperature and water content within the rows, biomass production of both corn and kura clover, and corn yield in both systems. In both years, corn emerged earlier and developed faster in the RZT plots. There was no significant difference in yield in the first season between the systems, but in the second season there was a substantial benefit to the rotary zone tillage system, which produced 4.0 Mg ha-1 in grain and 3.5 Mg ha-1 more stover, with no significant impact of kura clover biomass production. We conclude that the RZT system improves the likelihood for successful corn production in perennial living mulch systems, which should improve the adoption rate of this promising new farming system.

Technical Abstract: Kura clover (Trifolium ambiguum Bieb.) perennial living mulch is a farming practice designed to pair water quality services and row crop production. In this system, rows are mechanically or chemically killed within a perennial kura clover stand to create a suitable environment for planting a cash crop. However, yields are often reduced relative to conventional, fully-tilled systems, likely due to early season competition between the row crop and the clover. This hypothesis was tested by using a novel rotary zone tillage unit (RZT) that creates 30 cm wide tilled strips for each row, with rows spaced 76 cm apart. We compared RZT to two row preparation strategies that have been commonly used in living mulch systems: herbicide band kill (BK), and shank tillage (ST), also known as strip tillage. We monitored kura clover health, soil moisture & temperature, corn emergence, corn development, and corn yield in all three row preparation strategies over two growing seasons, but the primary objective was to compare the novel RZT with the traditional shank-based strip tillage unit. In 2015, corn grown in RZT plots emerged and developed faster than corn grown in ST plots, but this did not lead to a difference in grain or stover yield. However, in 2016, corn grown in RZT plots not only emerged and developed faster, but also produced 4.0 Mg ha-1 more grain and 3.5 Mg ha-1 more stover biomass than corn grown in ST plots. Kura clover biomass was not affected by treatment in either year. We conclude that rotary zone tillage is a promising row preparation strategy in kura clover living mulch for corn production with minimal herbicide use.