Semester of Graduation

Spring

Degree

Master of Science (MS)

Department

School of Plant, Environmental Management and Soil Science

Document Type

Thesis

Abstract

The use of biological soil amendments of animal origin (BSAAOs), such as raw poultry litter (PL) and cow manure (CM) is a common practice for improving soil fertility and crop productivity. However, the potential for microbial contamination raises concerns about food safety. This study evaluated the effects of PL, CM, and chemical fertilizer control on soil health, crop yields, and food safety risks in radish and bell pepper production over two years. Additionally, the impact of manure application methods (tilled vs. surface-applied) was assessed.

Field trials were conducted at the Louisiana State University Agricultural Center Burden Botanical Gardens using a completely randomized design with six treatment combinations: PL (tilled and surface-applied), CM (tilled and surface-applied), and a chemical fertilizer control (tilled and surface-applied). Soil and produce samples were analyzed for nutrient content, organic matter, pH, microbial contamination (Escherichia coli and total coliforms), and organisms die-off rates.

Results indicated that manure amendments increased soil phosphorus, potassium, and magnesium levels, with PL exhibiting higher nutrient retention but leading to soil pH declines over time. Short-term manure application did not significantly alter soil organic matter content. While BSAAO treatments did not significantly affect bell pepper yields, radish yields were notably higher in PL-treated plots, especially when tilled. However, excessive PL applications led to plant burning caused by high ammonia content in the manure. Bacterial wilt reduced bell pepper yields in the second year.

Microbial analysis revealed that radishes grown in PL-treated plots had higher E. coli levels than those in CM or control plots, indicating increased contamination risks. Bell peppers exhibited lower microbial contamination, and E. coli was undetectable after 13 weeks, supporting the USDA National Organic Program 90-day waiting period for trellised crops. While plastic mulch reduced E. coli risks, total coliforms persisted, suggesting additional mitigation strategies are needed.

This study highlights the need for optimized manure management practices that balance soil fertility benefits with mitigating food safety risks. Findings highlight the importance of application methods, environmental conditions, and regulatory compliance in ensuring sustainable and safe vegetable production systems.

Date

4-1-2025

Committee Chair

Fontenot, Kathryn

Download

Available for download on Friday, March 31, 2028

Share

COinS