Date of Award
8-2026
Document Type
Dissertation
Degree Name
Doctor of Philosophy (PhD)
Department
Plant and Environmental Science
Committee Chair/Advisor
Sruthi Narayanan
Committee Member
Rongzhong Ye
Committee Member
Michael W. Marshall
Committee Member
William C. Bridges
Abstract
Cover crop interseeding offers a potential strategy to increase plant diversity and make better use of above- and belowground resource niches within organic corn production systems. Interseeded cover crops can support agroecosystem sustainability through aboveground biomass production as well as belowground processes mediated by roots, including soil structural improvement, nutrient cycling, biological activity, and carbon storage. However, the success of interseeding depends on selecting cover crop species and management practices that provide these benefits without competing with the crop for water, nutrients, and light. Research studies were conducted to evaluate the effects of interseeded cover crop species, seeding rate, and tillage on corn performance, soil moisture, soil carbon- and nitrogen-cycling indicators, microbial functional gene abundance, and corn root development in organic corn systems in South Carolina. Field experiments were conducted across four site-years at Clemson and Florence, South Carolina: Clemson in 2023 and 2024, and Florence in 2022 and 2024. Buckwheat (Fagopyrum esculentum Moench), pigeonpea (Cajanus cajan [L.] Millsp.), white clover (Trifolium repens L.), and their mixture were interseeded at recommended, low (1.5 times < recommended), and high (1.5 times > recommended) seeding rates under conventional and reduced tillage. Buckwheat established most consistently and produced greater biomass than the other cover crops in most site-years. Pigeonpea produced moderate but less consistent growth, whereas white clover failed to establish either as a single species or in the mixture. The mixture was mainly composed of buckwheat and pigeonpea. Compared with the no-cover-crop control, interseeded buckwheat, pigeonpea, and the mixture did not reduce corn biomass, grain yield, or soil moisture across seeding rates and tillage systems tested. Belowground responses were treatment dependent. Permanganate oxidizable carbon increased by 34–46% under conventional tillage with pigeonpea at all seeding rates, buckwheat at the high rate, and the mixture at the high rate, and by 27% under reduced tillage with pigeonpea at the low rate. Under reduced tillage, buckwheat increased the ammonia-oxidizing archaea:ammonia-oxidizing bacteria (AOA:AOB) ratio 2.77-fold relative to the no-cover-crop control. Cover crop interseeding also increased corn root length, root surface area, and root diameter by 56, 62, and 46%, respectively, under reduced tillage. Overall, interseeding maintained organic corn performance and soil moisture, caused selective rather than broad changes in soil carbon- and nitrogen-cycling indicators, and showed potential complementarity with corn root growth under reduced tillage. These results indicate that cover crop interseeding can be integrated into organic corn production in South Carolina when adapted species and appropriate management practices are used.
Recommended Citation
Madrid, Luvina B., "Evaluating the Responses of Organic Corn Systems to Interseeded Cover Crops, Seeding Rate, and Tillage" (2026). All Dissertations. 4291.
https://open.clemson.edu/all_dissertations/4291
Author ORCID Identifier
0009-0007-9362-6019