Navigation

P1-182 Effect of Top-dressing Compost and Heat-treated Poultry Litter Pellets on Survival of E. coli in Dairy Manure Compost-amended Soils

Sunday, July 26, 2015
Exhibit Hall (Oregon Convention Center)
Patricia Millner , U.S. Department of Agriculture ARS EMFSL , Beltsville , MD
Kathryn White , U.S. Department of Agriculture-ARS , Beltsville , MD
Lorna Graham , University of Maryland Eastern Shore , Princess Anne , MD
Nancy (Tong) Liu , University of Maryland-College Park , College Park , MD
Jaime Coffie
Richard Stonebraker , University of Maryland Eastern Shore , Princess Anne , MD
David Clark
Fawzy Hashem , University of Maryland Eastern Shore , Princess Anne , MD
Manan Sharma , U.S. Department of Agriculture ARS EMFSL , Beltsville , MD
Introduction: Animal manure composts (biological soil amendments, BSAs) are used to maintain quality and fertility of soils. When produced by validated processes, composts are approved for use by USDA-National Organic Program rules and current FDA Produce Safety rules. Likewise, heat-treated poultry litter pellets (htPLP) produced by a validated process are approved BSAs. Nutrient-rich, microbiologically unbuffered htPLP top-dressed on compost-amended soil poses a potential risk of rapid colonization and survival by pathogenic bacteria inadvertently introduced to BSAs and then subsequently transferred to crops.

Purpose: A randomized complete block (n = 4) field experiment conducted in Beltsville, MD, examined survival of non-pathogenic E. coli (gEc) and attenuated E. coli O157:H7 (attO157) in soil amended with and without composted dairy manure solids (CDM), and top-dressed with or without either CDM, htPLP, or fertilizer.

Methods: Plots (2 m2) surface-amended with CDM or not were spray-inoculated with a multi-strain cocktail of rifampicin-resistant gEc and attO157 (~4.92 log CFU/ml) prior to tillage incorporation at USDA-ARS-BARC. Plots were seeded to spinach 1 day post-inoculation (dpi) and top-dressed with either CDM, htPLP, or fertilizer according to nitrogen requirements 35 dpi. Soil samples (n = 160) were collected/analyzed 0 - 62 dpi by direct plating and MPN procedures to determine survival of E. coli populations.

Results: The attO157 populations declined from ~2.0 to ≤ 0.02 log MPN/gdw in CDM-amended plots by day 3 in the fall and did not recover after top-dressing with CDM, htPLP, or fertilizer. Populations of gEc survived better in all BSA treatments than attO157 populations (P < 0.05). Rainfall during 1 - 29dpi sustained gEc populations to 2.5 - 3.8 log MPN/gdw, but after top-dressing, rainfall, and below freezing temperatures, populations ranged 0.95 (htPLP only) - 1.7(CDM only) log MPN/gdw on 62 dpi.

Significance: These results indicate that attO157 populations decline more rapidly than gEc populations in soil amended at agronomic rates with quality CDM even with adequate soil moisture and subsequent top-dressing with CDM, htPLP, or fertilizer.

Back to: Poster Session 1 – Laboratory and Detection Methods, Low-water Activity; Retail and Food Service Safety; Seafood; Communication Outreach and Education; Produce; Food Toxicology; Non-microbial Food Safety; Food Defense; Microbial Food Spoilage
<< Previous Abstract | Next Abstract >>