Improving soil health and nitrogen cycling through zone tilled cover cropping practices for organic production

Abstract

Zone tillage is a reduced-tillage compromise between no-till and full-width tillage that attempts to capture both the environmental advantages of year-round ground cover and the agronomic benefits of in-row tillage. This management tool is especially well-suited to the practice of cover cropping, where plants are grown between cash crops in space, time, or both. Localizing the use of tillage in cover cropped systems may preserve soil quality between crop rows where soil is not tilled, as measured by soil microbial activity and varying indicators of soil organic matter, while also making N available only in crop rows. In this dissertation, two cover cropping systems were assessed for their contributions to soil quality and crop production: 1) a perennial kura clover (KC; Trifolium ambiguum) living mulch in corn (Zea mays), where KC persists between crops rows during the growing season to maintain ground cover of between-row areas, and 2) winter annual cover crops in an organic yellow crookneck squash (Cucurbita pepo) system, where cover crops were maintained between crop rows until they were fully mature, allowing for extended ground coverage and N provisioning. In the KC system, three tillage treatments and one no-till control were tested for their ability to incorporate KC residues between rows and to minimize KC competition with the corn crop. A novel PTO-driven rotary zone till implement was found to increase in-row soil N relative to both no-till and a less disruptive zone till implement consisting of a shank with ground-driven coulters. Corn yields were higher in treatments using this novel implement. In the winter annual system, three cover crop systems were examined at early and late terminations for cover crop N content and soil quality indicators: oat (Avena sativa) + field pea (Pisum sativum), winter rye (Cereale secale) + hairy vetch (Vicia villosa), and medium red clover (Trifolium pretense). Cover crops did gain biomass between samplings, showing that additional growing time between rows was beneficial. While no differences in squash yield were detected, the clover treatment did provide N in rows while conserving it between rows, effectively preventing possible leaching.