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Importance of Soil Amendments: Survival of Bacterial Pathogens in Manure and Compost Used as Organic Fertilizers, Page 1 of 2
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Biological soil amendments (BSAs), including manure, compost, and compost teas (CTs), play an important role in conventional and organic agriculture. The use of these amendments can provide nutrients to soils, improving soil fertility and crop production. However, recent outbreaks of bacterial, viral, and parasitic infections associated with produce commodities over the past decade have focused more attention on agricultural inputs used to grow fresh fruits and vegetables. In response to these outbreaks, proposed rules from the U.S. Food and Drug Administration (FDA) have been issued, titled “Standards for the Growing, Harvesting, Packing and Holding of Produce for Human Consumption” Supplemental to the Proposed Rule ( 1 ). As part of these standards, the FDA has proposed specific rules and guidelines for how several BSAs can be applied to soils and fields intended to grow produce for human consumption.
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(A) The survival of a three-strain (TVS 353, 354, and 355), nonpathogenic (generic) E. coli inoculum in either poultry litter–amended (gEC PL), horse manure–amended (gEC HM), or unamended (gEC uA) soils over 98 days in southern Pennsylvania (Southeastern Agricultural Research and Extension Center, Pennsylvania State University, Landisville, PA). Amendments were surface applied (no till). (B) The moisture content of PL-amended soils [PL Hi(s)], HM-amended soils [HM Hi(c)], and uA soils [uA Hi(s)]. (C) The air temperature throughout the study. Values below the x-axis indicate the number of days of the study. Dashed lines indicate days when changes in E. coli populations occurred, potentially attributed to changes in either soil moisture content or temperature. The first dashed line indicates that an increase in air temperature (graph C) from days 0 to 5 corresponded to an increase in all E. coli populations in graph A; the second dashed line indicates that an increase in soil moisture content (graph B) from day 7 to day 14 corresponded to an increase in all E. coli populations; the third dashed line indicates that a decline in soil moisture content of PL Hi(s) from day 14 to day 28 resulted in a decline of E. coli populations in gEc PL. These graphs show that air temperature and soil moisture content can affect E. coli populations in soils amended with surface-applied manures more than E. coli populations in tilled in soils ( Fig. 2 ).
(A) The survival of a three-strain (TVS 353, 354, and 355), nonpathogenic (generic) E. coli inoculum in either poultry litter–amended (gEC PL), horse manure–amended (gEC HM), or unamended (gEC uA) over 98 days in soils at the Southeastern Agricultural Research and Extension Center. Amendments were tilled into soils. (B) The moisture content of tilled PL-amended [PL Hi(c)], HM-amended [HM Hi(c)], and uA soils ]uA Hi(c)]. (C) The air temperature throughout the study. Values below the x-axis indicate the number of days of the study. Dashed lines indicate days where changes in E. coli populations occurred, potentially attributed to changes in either soil moisture content or temperature. The first dashed line indicates that all E. coli populations (graph A) increased on day 5 with an increase in all soil moisture contents (graph B) from day 3 to day 5. On day 7 (no dashed line), the decline in E. coli populations between days 5 and 7 was associated with a fall in the soil moisture content of all soils. The second dashed line indicates an increase in gEC HM and gEC uA populations from day 14 to day 28, which corresponds to an increase in HM Hi(c), and uA Hi(c) soil moisture contents (no increase in gEC PL was observed). The figure illustrates that E. coli populations in tilled soils amended with manure may be less responsive to changes in air temperature and more responsive to changes in soil moisture content than E. coli in surface manure-amended soils ( Fig. 1 ).
Guidance and proposed rules by organizations and federal agencies in the United States on the application of biological soil amendments to agricultural fields intended to grow selected fruit and vegetable crops
Change in inoculated E. coli populations in manure-amended soils in large pots in a greenhouse environment after weekly irrigation events