Effects of Intensive Zone Tillage on Soil Quality in an Organic Kura Clover Living Mulch.

Perennial legume mulches in row crop systems present a cover cropping approach that can maintain long-term ground cover as well as build soil quality through continuous rhizodeposition.  In spring, narrow zones for cash crop planting are created using tillage, leaving living cover between tilled rows.  Organic growers are interested in zone tillage living mulch approaches, but are prohibited from using herbicides that inhibit legume regrowth.  This leads to reductions in cash crop yields when living mulches recover too quickly and compete for resources at crop establishment.  We designed an intensive zone tillage method using a novel rotary zone tiller to examine competition between organic field corn and a kura clover (Trifolium ambiguum) living mulch, as well as soil quality parameters.  We investigated the impact of zone tillage in a well-established stand of kura clover in Rosemount, MN in 2015 and for two spatially distinct regions: in the cash crop row where the clover is tilled and between rows where clover has been left undisturbed for nearly a decade.  To determine how undisturbed belowground root systems contribute to soil quality in comparison to aboveground plant matter incorporations, particulate organic matter (POM) carbon and nitrogen and permanganate oxidizable carbon (POX) were measured.  Average POX values were typically greater between rows after spring tillage and planting than in the crops rows, and ranged from 606.94 mg kg soil^-1 to 846.61 mg kg soil^-1.  The same trend held true for average POM values, which ranged from 70,225.92 mg POM-C kg soil^-1 to 150,873.94 mg POM-C kg soil^-1, and 6,212.88 mg POM-N kg soil^-1 to 14,370.81 mg POM-N kg soil^-1.