Degree

Doctor of Philosophy (PhD)

Department

School of plant, environment and soil sciences

Document Type

Dissertation

Abstract

The adoption of cover crops in Louisiana is lower than the national average, underscoring the need for region-specific research to address environmental challenges and demonstrate the short-term benefits of these practices within existing production systems. This research evaluated the integration of cover crops (CC) in energy cane (Saccharum spp.) and no-till cotton systems, focusing on their effects on soil health, nitrogen (N) management, and biomass production. Soil health indicators (SHIs), including enzymatic activities (β-glucosidase, β-glucosaminidase, and urease), protein N, inorganic N concentrations (nitrate and ammonium), soil organic matter (SOM), and microbial community composition assessed through ester-linked fatty acid methyl esters (EL-FAME), were monitored. Additionally, precision agriculture tools, such as vegetation indices (normalized difference vegetation index -NDVI and normalized difference red-edge index -NDRE) and Real-Time Kinematic GPS (RTK GPS)-derived Digital Elevation Models (DEMs), were used to quantify cover crop benefits. The first study explored a rotation system integrating sweet sorghum (Sorghum bicolor (L.) Moench) during energy cane fallow periods, alongside winter cover crops and residue management strategies. The results indicated that integrating sweet sorghum with full residue retention from energy cane substantially enhanced total biomass feedstock. Conversely, the complete removal of residues notably decreased the total biomass feedstock. Although winter cover crops suppressed weed infestation in clay soils, they did not affect energy cane yields or SHIs, indicating limited short-term impacts on soil health. The second study assessed cover crops in no-till cotton (Gossypium spp.) systems under different N application rates. CCs showed no significant short-term effects on cotton yield, SHIs, or microbial communities. However, mix treatment -crimson clover (Trifolium incarnatum) + cereal rye (Secale cereale) achieved the lowest optimal N fertilization rate (EONR) at 98.05 kg N ha⁻¹. Crimson clover treatment produced high yields with a moderate N fertilization rate (140 kg N ha⁻¹), and the fallow treatment achieved the highest yield but required significantly higher N inputs (211 kg N ha⁻¹) than other CC treatments, indicating lower N efficiency and highlighting the potential N value of CC to reduce synthetic fertilizer reliance. The third study DEMs effectively monitored seedbed-furrow height as a proxy for soil erosion, while NDVI and NDRE correlated with CC biomass accumulation at specific days after planting. These findings highlight the potential of cover crops and advanced technologies to enhance agricultural sustainability and support broader adoption of these practices in Louisiana.

Date

12-9-2025

Committee Chair

Tubana, Brenda

Available for download on Friday, January 09, 2026

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